Quantum Physics
New submissions
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New submissions for Fri, 26 Apr 24
- [1] arXiv:2404.16083 [pdf, other]
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Title: Constant-depth preparation of matrix product states with adaptive quantum circuitsComments: 25 pages, 5 figuresSubjects: Quantum Physics (quant-ph)
Adaptive quantum circuits, which combine local unitary gates, midcircuit measurements, and feedforward operations, have recently emerged as a promising avenue for efficient state preparation, particularly on near-term quantum devices limited to shallow-depth circuits. Matrix product states (MPS) comprise a significant class of many-body entangled states, efficiently describing the ground states of one-dimensional gapped local Hamiltonians and finding applications in a number of recent quantum algorithms. Recently, it was shown that the AKLT state -- a paradigmatic example of an MPS -- can be exactly prepared with an adaptive quantum circuit of constant-depth, an impossible feat with local unitary gates due to its nonzero correlation length [Smith et al., PRX Quantum 4, 020315 (2023)]. In this work, we broaden the scope of this approach and demonstrate that a diverse class of MPS can be exactly prepared using constant-depth adaptive quantum circuits, outperforming optimal preparation protocols that rely on unitary circuits alone. We show that this class includes short- and long-ranged entangled MPS, symmetry-protected topological (SPT) and symmetry-broken states, MPS with finite Abelian, non-Abelian, and continuous symmetries, resource states for MBQC, and families of states with tunable correlation length. Moreover, we illustrate the utility of our framework for designing constant-depth sampling protocols, such as for random MPS or for generating MPS in a particular SPT phase. We present sufficient conditions for particular MPS to be preparable in constant time, with global on-site symmetry playing a pivotal role. Altogether, this work demonstrates the immense promise of adaptive quantum circuits for efficiently preparing many-body entangled states and provides explicit algorithms that outperform known protocols to prepare an essential class of states.
- [2] arXiv:2404.16087 [pdf, other]
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Title: Statistical Mechanics of Stochastic Quantum Control: $d$-adic Rényi CircuitsComments: 14+3 pages, 13+1 figures, 3+4 tablesSubjects: Quantum Physics (quant-ph); Disordered Systems and Neural Networks (cond-mat.dis-nn); Statistical Mechanics (cond-mat.stat-mech); Chaotic Dynamics (nlin.CD)
The dynamics of quantum information in many-body systems with large onsite Hilbert space dimension admits an enlightening description in terms of effective statistical mechanics models. Motivated by this fact, we reveal a connection between three separate models: the classically chaotic $d$-adic R\'{e}nyi map with stochastic control, a quantum analog of this map for qudits, and a Potts model on a random graph. The classical model and its quantum analog share a transition between chaotic and controlled phases, driven by a randomly applied control map that attempts to order the system. In the quantum model, the control map necessitates measurements that concurrently drive a phase transition in the entanglement content of the late-time steady state. To explore the interplay of the control and entanglement transitions, we derive an effective Potts model from the quantum model and use it to probe information-theoretic quantities that witness both transitions. The entanglement transition is found to be in the bond-percolation universality class, consistent with other measurement-induced phase transitions, while the control transition is governed by a classical random walk. These two phase transitions merge as a function of model parameters, consistent with behavior observed in previous small-size numerical studies of the quantum model.
- [3] arXiv:2404.16095 [pdf, other]
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Title: Long-range multipartite entanglement near measurement-induced transitionsComments: 5+2 pages, 4+2 figuresSubjects: Quantum Physics (quant-ph); Disordered Systems and Neural Networks (cond-mat.dis-nn); Statistical Mechanics (cond-mat.stat-mech); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics - Theory (hep-th)
Measurements profoundly impact quantum systems, and can be used to create new states of matter out of equilibrium. Here, we investigate the multipartite entanglement structure that emerges in quantum circuits involving unitaries and measurements. We describe how a balance between measurements and unitary evolution can lead to multipartite entanglement spreading to distances far greater than what is found in non-monitored systems, thus evading the usual fate of entanglement. We introduce a graphical representation based on spanning graphs that allows to infer the evolution of genuine multipartite entanglement for general subregions. We exemplify our findings on circuits that realize a 1d measurement-induced dynamical phase transition, where we find genuine 3-party entanglement at all separations. The 2- and 4-party cases are also covered with examples. Finally, we discuss how our approach can provide fundamental insights regarding entanglement dynamics for a wide class of quantum circuits and architectures.
- [4] arXiv:2404.16101 [pdf, other]
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Title: Multivariate FidelitiesComments: 79 pages, 1 figureSubjects: Quantum Physics (quant-ph); Information Theory (cs.IT); Mathematical Physics (math-ph); Operator Algebras (math.OA)
The main contribution of our paper is to introduce a number of multivariate quantum fidelities and show that they satisfy several desirable properties that are natural extensions of those of the Uhlmann and Holevo fidelities. We propose three variants that reduce to the average pairwise fidelity for commuting states: average pairwise $z$-fidelities, the multivariate semi-definite programming (SDP) fidelity, and a multivariate fidelity inspired by an existing secrecy measure. The second one is obtained by extending the SDP formulation of the Uhlmann fidelity to more than two states. All three of these variants satisfy the following properties: (i) reduction to multivariate classical fidelities for commuting states, (ii) the data-processing inequality, (iii) invariance under permutations of the states, (iv) its values are in the interval $[0,1]$; they are faithful, that is, their values are equal to one if and only if all the states are equal, and they satisfy orthogonality, that is their values are equal to zero if and only if the states are mutually orthogonal to each other, (v) direct-sum property, (vi) joint concavity, and (vii) uniform continuity bounds under certain conditions. Furthermore, we establish inequalities relating these different variants, indeed clarifying that all these definitions coincide with the average pairwise fidelity for commuting states. Lastly, we introduce another multivariate fidelity called multivariate log-Euclidean fidelity, which is a quantum generalization of the Matusita multivariate fidelity. We also show that it satisfies most of the desirable properties listed above, it is a function of a multivariate log-Euclidean divergence, and has an operational interpretation in terms of quantum hypothesis testing with an arbitrarily varying null hypothesis.
- [5] arXiv:2404.16106 [pdf, other]
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Title: A robust approach for time-bin encoded photonic quantum information protocolsAuthors: Simon J. U. White, Emanuele Polino, Farzad Ghafari, Dominick J. Joch, Luis Villegas-Aguilar, Lynden K. Shalm, Varun B. Verma, Marcus Huber, Nora TischlerSubjects: Quantum Physics (quant-ph)
Quantum states encoded in the time-bin degree of freedom of photons represent a fundamental resource for quantum information protocols. Traditional methods for generating and measuring time-bin encoded quantum states face severe challenges due to optical instabilities, complex setups, and timing resolution requirements. Here, we leverage a robust approach based on Hong-Ou-Mandel interference that allows us to circumvent these issues. First, we perform high-fidelity quantum state tomographies of time-bin qubits with a short temporal separation. Then, we certify intrasystem polarization-time entanglement of single photons through a nonclassicality test. Finally, we propose a robust and scalable protocol to generate and measure high-dimensional time-bin quantum states in a single spatial mode. The protocol promises to enable access to high-dimensional states and tasks that are practically inaccessible with standard schemes, thereby advancing fundamental quantum information science and opening applications in quantum communication.
- [6] arXiv:2404.16107 [pdf, other]
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Title: Certifying nonstabilizerness in quantum processorsComments: 7+10 pages, 3+2 figures. Comments are welcome!Subjects: Quantum Physics (quant-ph)
Nonstabilizerness, also known as magic, is a crucial resource for quantum computation. The growth in complexity of quantum processing units (QPUs) demands robust and scalable techniques for characterizing this resource. We introduce the notion of set magic: a set of states has this property if at least one state in the set is a non-stabilizer state. We show that certain two-state overlap inequalities, recently introduced as witnesses of basis-independent coherence, are also witnesses of multi-qubit set magic. We also show it is possible to certify the presence of magic across multiple QPUs without the need for entanglement between them and reducing the demands on each individual QPU.
- [7] arXiv:2404.16129 [pdf, other]
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Title: Efficiently constructing a quantum uniform superposition over bit strings near a binary linear codeComments: 32 pages, 9 figuresSubjects: Quantum Physics (quant-ph)
We demonstrate that a high fidelity approximation to $| \Psi_b \rangle$, the quantum superposition over all bit strings within Hamming distance $b$ of the codewords of a dimension-$k$ linear code over $\mathbb{Z}_2^n$, can be efficiently constructed by a quantum circuit for large values of $n$, $b$ and $k$ which we characterize. We do numerical experiments at $n=1000$ which back up our claims. The achievable radius $b$ is much larger than the distance out to which known classical algorithms can efficiently find the nearest codeword. Hence, these states cannot be prepared by quantum constuctions that require uncomputing to find the codeword nearest a string. Unlike the analogous states for lattices in $\mathbb{R}^n$, $|\Psi_b \rangle$ is not a useful resource for bounded distance decoding because the relevant overlap falls off too quickly with distance and known classical algorithms do better. Furthermore the overlap calculation can be dequantized. Perhaps these states could be used to solve other code problems. The technique used to construct these states is of interest and hopefully will have applications beyond codes.
- [8] arXiv:2404.16135 [pdf, other]
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Title: Performant near-term quantum combinatorial optimizationComments: 5 pages, 4 figuresSubjects: Quantum Physics (quant-ph); Mathematical Physics (math-ph)
We present a variational quantum algorithm for solving combinatorial optimization problems with linear-depth circuits. Our algorithm uses an ansatz composed of Hamiltonian generators designed to control each term in the target combinatorial function, along with parameter updates following a modified version of quantum imaginary time evolution. We evaluate this ansatz in numerical simulations that target solutions to the MAXCUT problem. The state evolution is shown to closely mimic imaginary time evolution, and its optimal-solution convergence is further improved using adaptive transformations of the classical Hamiltonian spectrum, while resources are minimized by pruning optimized gates that are close to the identity. With these innovations, the algorithm consistently converges to optimal solutions, with interesting highly-entangled dynamics along the way. This performant and resource-minimal approach is a promising candidate for potential quantum computational advantages on near-term quantum computing hardware.
- [9] arXiv:2404.16156 [pdf, other]
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Title: Guardians of the Quantum GANComments: 11 pages, 10 figuresSubjects: Quantum Physics (quant-ph); Hardware Architecture (cs.AR); Cryptography and Security (cs.CR); Machine Learning (cs.LG)
Quantum Generative Adversarial Networks (qGANs) are at the forefront of image-generating quantum machine learning models. To accommodate the growing demand for Noisy Intermediate-Scale Quantum (NISQ) devices to train and infer quantum machine learning models, the number of third-party vendors offering quantum hardware as a service is expected to rise. This expansion introduces the risk of untrusted vendors potentially stealing proprietary information from the quantum machine learning models. To address this concern we propose a novel watermarking technique that exploits the noise signature embedded during the training phase of qGANs as a non-invasive watermark. The watermark is identifiable in the images generated by the qGAN allowing us to trace the specific quantum hardware used during training hence providing strong proof of ownership. To further enhance the security robustness, we propose the training of qGANs on a sequence of multiple quantum hardware, embedding a complex watermark comprising the noise signatures of all the training hardware that is difficult for adversaries to replicate. We also develop a machine learning classifier to extract this watermark robustly, thereby identifying the training hardware (or the suite of hardware) from the images generated by the qGAN validating the authenticity of the model. We note that the watermark signature is robust against inferencing on hardware different than the hardware that was used for training. We obtain watermark extraction accuracy of 100% and ~90% for training the qGAN on individual and multiple quantum hardware setups (and inferencing on different hardware), respectively. Since parameter evolution during training is strongly modulated by quantum noise, the proposed watermark can be extended to other quantum machine learning models as well.
- [10] arXiv:2404.16167 [pdf, other]
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Title: Fast photon-mediated entanglement of continuously-cooled trapped ions for quantum networkingAuthors: Jameson O'Reilly, George Toh, Isabella Goetting, Sagnik Saha, Mikhail Shalaev, Allison Carter, Andrew Risinger, Ashish Kalakuntla, Tingguang Li, Ashrit Verma, Christopher MonroeComments: 8 pages, 5 figuresSubjects: Quantum Physics (quant-ph); Atomic Physics (physics.atom-ph)
We entangle two co-trapped atomic barium ion qubits by collecting single visible photons from each ion through in-vacuo 0.8 NA objectives, interfering them through an integrated fiber-beamsplitter and detecting them in coincidence. This projects the qubits into an entangled Bell state with an observed fidelity lower bound of F > 94%. We also introduce an ytterbium ion for sympathetic cooling to remove the need for recooling interruptions and achieve a continuous entanglement rate of 250 1/s.
- [11] arXiv:2404.16203 [pdf, other]
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Title: Optimized higher-order photon state classification by machine learningSubjects: Quantum Physics (quant-ph)
The classification of higher-order photon emission becomes important with more methods being developed for deterministic multiphoton generation. The widely-used second-order correlation g(2) is not sufficient to determine the quantum purity of higher photon Fock states. Traditional characterization methods require a large amount of photon detection events which leads to increased measurement and computation time. Here, we demonstrate a Machine Learning model based on a 2D Convolutional Neural Network (CNN) for rapid classification of multiphoton Fock states up to |3> with an overall accuracy of 94%. By fitting the g(3) correlation with simulated photon detection events, the model exhibits efficient performance particularly with sparse correlation data, with 800 co-detection events to achieve an accuracy of 90%. Using the proposed experimental setup, this CNN classifier opens up the possibility for quasi real-time classification of higher photon states, which holds broad applications in quantum technologies.
- [12] arXiv:2404.16204 [pdf, other]
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Title: Entanglement-Based Artificial Topology: Neighboring Remote Network NodesSubjects: Quantum Physics (quant-ph); Networking and Internet Architecture (cs.NI)
Entanglement is unanimously recognized as the key communication resource of the Quantum Internet. Yet, the possibility of implementing novel network functionalities by exploiting the marvels of entanglement has been poorly investigated so far, by mainly restricting the attention to bipartite entanglement. Conversely, in this paper, we aim at exploiting multipartite entanglement as inter-network resource. Specifically, we consider the interconnection of different Quantum Local Area Networks (QLANs), and we show that multipartite entanglement allows to dynamically generate an inter-QLAN artificial topology, by means of local operations only, that overcomes the limitations of the physical QLAN topologies. To this aim, we first design the multipartite entangled state to be distributed within each QLAN. Then, we show how such a state can be engineered to: i) interconnect nodes belonging to different QLANs, and ii) dynamically adapt to different inter-QLAN traffic patterns. Our contribution aims at providing the network engineering community with a hands-on guideline towards the concept of artificial topology and artificial neighborhood.
- [13] arXiv:2404.16211 [pdf, other]
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Title: Verifying randomness in sets of quantum states via observablesComments: 11 pagesSubjects: Quantum Physics (quant-ph)
We present a metric, average randomness, that predicts the compatibility of a set of quantum states with the Haar-random distribution, by matching of statistical moments, through a known quantum observable. We show that Haar-randomness is connected to the Dirichlet distribution, and provide a closed-form expression, and simple bounds of the statistical moments. We generalize this metric to permutation- and unitary-equivalent observables, ensuring that if the extended average randomness is compatible with a Haar-random distribution, then the set of states is approximately Haar-random.
- [14] arXiv:2404.16227 [pdf, other]
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Title: Optimal entanglement generation in optomechanical systems via Krotov control of covariance matrix dynamicsComments: 10 pages, 5 figuresSubjects: Quantum Physics (quant-ph)
We investigated the optimal control of a continuous variable system, focusing on entanglement generation in an optomechanical system without utilizing Fock basis cutoffs. Using the Krotov algorithm to optimize the dynamics of the covariance matrix, we illustrated how to design a control objective function to manipulate the dynamics of the system to generate a desirable target state. We showed that entanglement between the macroscopic mechanical mirror and the quantum optical cavity can be reliably generated through imposing the control on the detuning of the external laser field. It has be shown that the control may be still achieved when imposing spectral constraints on the external field to restrict it to low-frequency components. In addition, we systematically studies the effects of quantum control on non-Markovian open system dynamics. We observed that memory effects can play a beneficial role in mitigating the detrimental impact of environmental noises. Specifically, the entanglement generated shows reduced decay in the presence of these memory effects.
- [15] arXiv:2404.16236 [pdf, other]
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Title: Rigorous Formalization of Orbital Functionals: Addressing the Noninteracting $v$-Representability ProblemAuthors: Neil Qiang SuSubjects: Quantum Physics (quant-ph)
Functionals that explicitly depend on occupied, unoccupied, or fractionally-occupied orbitals are rigorously formalized using Clifford algebras, and a variational principle is established that facilitates orbital (and occupation) optimization as a formal implementation method. Theoretically, these methodologies circumvent the limitations encountered in the original Kohn-Sham and related methods, particularly when the interacting system's electron density does not match that of any noninteracting reference system. This work redefines orbital (and occupation) functionals from a novel perspective, positioning them not merely as extensions of traditional density functionals, but as superior, rigorous alternatives.
- [16] arXiv:2404.16245 [pdf, ps, other]
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Title: Computationally Efficient Molecular Integrals of Solid Harmonic Gaussian Orbitals Using Quantum Entanglement of Angular MomentumSubjects: Quantum Physics (quant-ph); Chemical Physics (physics.chem-ph)
Vector-coupling and vector-uncoupling schemes in the quantum theory of angular momentum correspond to unitary Clebsch-Gordan transformations that operate on quantum angular momentum states and thereby control their degree of entanglement. The addition of quantum angular momentum from this transformation is suitable for reducing the degree of entanglement of quantum angular momentum, leading to simple and effective calculations of the molecular integrals of solid harmonic Gaussian orbitals (SHGO). Even with classical computers, the speed-up ratio in the evaluation of molecular nuclear Coulomb integrals with SHGOs can be up to four orders of magnitude for atomic orbitals with high angular momentum quantum number. Thus, the less entanglement there is for a quantum system the easier it is to simulate, and molecular integrals with SHGOs are shown to be particularly well-suited for quantum computing. High-efficiency quantum circuits previously developed for unitary and cascading Clebsch-Gordan transformations of angular momentum states can be applied to the differential and product rules of solid harmonics to efficiently compute two-electron Coulomb integrals ubiquitous in quantum chemistry. Combined with such quantum circuits and variational quantum eigensolver algorithms, the high computational efficiency of molecular integrals in solid harmonic bases unveiled in this paper may open an avenue for accelerating full quantum computing chemistry.
- [17] arXiv:2404.16279 [pdf, ps, other]
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Title: Quantum Imaginarity-Mixedness Trade-off: Characterizing Maximally Imaginary Mixed StatesComments: 14 pages, 1 figureSubjects: Quantum Physics (quant-ph)
We investigate the trade-off relations between imaginarity and mixedness in arbitrary $d$-dimensional quantum systems. For given mixedness, a quantum state with maximum imaginarity is defined to be a "maximally imaginary mixed state" (MIMS). By using the $l_{1}$ norm of imaginarity and the normalized linear entropy, we conclusively identify the MIMSs for both qubit and qutrit systems. For high-dimensional quantum systems, we present a comprehensive class of MIMSs, which also gives rise to complementarity relations between the $1$-norm of imaginarity and the $1$-norm of mixedness, as well as between the relative entropy of imaginarity and the von Neumann entropy. Furthermore, we examine the evolution of the trade-off relation for single-qubit states under four specific Markovian channels: bit flip channel, phase damping channel, depolarizing channel and amplitude damping channel.
- [18] arXiv:2404.16288 [pdf, other]
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Title: Protocol for nonlinear state discrimination in rotating condensateAuthors: Michael R. GellerSubjects: Quantum Physics (quant-ph)
Nonlinear mean field dynamics enables quantum information processing operations that are impossible in linear one-particle quantum mechanics. In this approach, a register of bosonic qubits (such as neutral atoms or polaritons) is initialized into a symmetric product state through condensation, then subsequently controlled by varying the qubit-qubit interaction. We propose an experimental implementation of quantum state discrimination, an important subroutine in quantum computation, with a toroidal Bose-Einstein condensate. The condensed bosons here are atoms, each in the same superposition of angular momenta 0 and 1, encoding a qubit. A nice feature of the protocol is that only readout of individual quantized circulation states (not superpositions) is required.
- [19] arXiv:2404.16298 [pdf, other]
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Title: The role of conjugacy in the dynamics of time of arrival operatorsComments: 21 pagesSubjects: Quantum Physics (quant-ph)
The construction of time of arrival (TOA) operators canonically conjugate to the system Hamiltonian entails finding the solution of a specific second-order partial differential equation called the time kernel equation (TKE). An expanded iterative solution of the TKE has been obtained recently in [Eur. Phys. J. Plus \textbf{138}, 153 (2023)] but is generally intractable to be useful for arbitrary nonlinear potentials. In this work, we provide an exact analytic solution of the TKE for a special class of potentials satisfying a specific separability condition. The solution enables us to investigate the time evolution of the eigenfunctions of the conjugacy-preserving TOA operators (CPTOA) by coarse graining methods and spatial confinement. We show that the eigenfunctions of the constructed operator exhibit unitary arrival at the intended arrival point at a time equal to their corresponding eigenvalue. Moreover, we examine whether there is a discernible difference in the dynamics between the TOA operators constructed by quantization and those independent of quantization for specific interaction potentials. We find that the CPTOA operator possesses better unitary dynamics over the Weyl-quantized one within numerical accuracy. This allows us determine the role of the canonical commutation relation between time and energy on the observed dynamics of time of arrival operators.
- [20] arXiv:2404.16342 [pdf, other]
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Title: Limitations in Fluorescence-Detected Entangled Two-Photon-Absorption Experiments: Exploring the Low- to High-Gain Squeezing RegimesSubjects: Quantum Physics (quant-ph)
We closely replicated and extended a recent experiment ("Spatial properties of entangled two-photon absorption," Phys. Rev. Lett. 129, 183601, 2022) that reportedly observed enhancement of two-photon absorption rates in molecular samples by using time-frequency-entangled photon pairs, and we found that in the low-flux regime, where such enhancement is theoretically predicted in-principle, the two-photon fluorescence signal is below detection threshold using current state-of-the-art methods. The results are important in the context of efforts to enable quantum-enhanced molecular spectroscopy and imaging at ultra-low optical flux. Using an optical parametric down-conversion photon-pair source that can be varied from the low-gain spontaneous regime to the high-gain squeezing regime, we observed two-photon-induced fluorescence in the high-gain regime but in the low-gain regime any fluorescence was below detection threshold. We supplemented the molecular fluorescence experiments with a study of nonlinear-optical sum-frequency generation, for which we are able to observe the low-to-high-gain crossover, thereby verifying our theoretical models and experimental techniques. The observed rates (or lack thereof) in both experiments are consistent with theoretical predictions and with our previous experiments, and indicate that time-frequency photon entanglement does not provide a practical means to enhance in-solution molecular two-photon fluorescence spectroscopy or imaging with current techniques.
- [21] arXiv:2404.16360 [pdf, other]
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Title: Preparing matrix product states via fusion: constraints and extensionsSubjects: Quantum Physics (quant-ph); Strongly Correlated Electrons (cond-mat.str-el)
In the era of noisy, intermediate-scale quantum (NISQ) devices, the efficient preparation of many-body resource states is a task of paramount importance. In this paper we focus on the deterministic preparation of matrix-product states (MPS) in constant depth by utilizing measurements and classical communication to fuse smaller states into larger ones. We place strong constraints on the MPS that can be prepared using this method, which we refer to as MPS fusion. Namely, we establish that it is necessary for the MPS to have a flat entanglement spectrum. Using the recently introduced split-index MPS (SIMPS) representation, we then introduce a family of states that belong to interesting phases of matter protected by non-onsite symmetries and serve as resources for long-range quantum teleportation, but which lie beyond the scope of ordinary MPS fusion. It is shown constructively that these states can be prepared in constant depth using a broader class of measurement-assisted protocols, which we dub SIMPS fusion. Even in cases when MPS fusion is possible, using SIMPS fusion can give rise to significantly reduced resource overhead. Our results therefore simultaneously establish the boundaries of conventional MPS fusion and push the envelope of which states can be prepared using measurement-assisted protocols.
- [22] arXiv:2404.16392 [pdf, other]
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Title: Speed limits and thermodynamic uncertainty relations for quantum systems governed by non-Hermitian HamiltonianComments: 12 pages, 2 figuresSubjects: Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech)
Non-Hermitian Hamiltonians play a crucial role in the description of open quantum systems and nonequilibrium dynamics. In this paper, we derive trade-off relations for systems governed by non-Hermitian Hamiltonians, focusing on the Margolus-Levitin and Mandelstam-Tamm bounds, which are quantum speed limits originally derived in isolated quantum dynamics. We extend these bounds to the case of non-Hermitian Hamiltonians and derive additional bounds on the ratio of the standard deviation to the mean of an observable, which take the same form as the thermodynamic uncertainty relation. As an example, we apply these bounds to the continuous measurement formalism in open quantum dynamics, where the dynamics is described by discontinuous jumps and smooth evolution induced by the non-Hermitian Hamiltonian. Our work provides a unified perspective on the quantum speed limit and thermodynamic uncertainty relations in open quantum dynamics from the viewpoint of the non-Hermitian Hamiltonian, extending the results of previous studies.
- [23] arXiv:2404.16417 [pdf, other]
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Title: Constructing Optimal Noise Channels for Enhanced Robustness in Quantum Machine LearningSubjects: Quantum Physics (quant-ph); Artificial Intelligence (cs.AI); Machine Learning (cs.LG)
With the rapid advancement of Quantum Machine Learning (QML), the critical need to enhance security measures against adversarial attacks and protect QML models becomes increasingly evident. In this work, we outline the connection between quantum noise channels and differential privacy (DP), by constructing a family of noise channels which are inherently $\epsilon$-DP: $(\alpha, \gamma)$-channels. Through this approach, we successfully replicate the $\epsilon$-DP bounds observed for depolarizing and random rotation channels, thereby affirming the broad generality of our framework. Additionally, we use a semi-definite program to construct an optimally robust channel. In a small-scale experimental evaluation, we demonstrate the benefits of using our optimal noise channel over depolarizing noise, particularly in enhancing adversarial accuracy. Moreover, we assess how the variables $\alpha$ and $\gamma$ affect the certifiable robustness and investigate how different encoding methods impact the classifier's robustness.
- [24] arXiv:2404.16445 [pdf, other]
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Title: Wavefunction collapse driven by non-Hermitian disturbanceComments: 5 pages, 4 figuresSubjects: Quantum Physics (quant-ph); Other Condensed Matter (cond-mat.other)
In the context of the measurement problem, we propose to model the interaction between a quantum particle and an "apparatus" through a non-Hermitian Hamiltonian term. We simulate the time evolution of a normalized quantum state split into two spin components (via a Stern-Gerlach experiment) and that undergoes a wave-function collapse driven by a non-Hermitian Hatano-Nelson Hamiltonian. We further analyze how the strength and other parameters of the non-Hermitian perturbation influence the time-to-collapse of the wave function obtained under a Schr\"{o}dinger-type evolution. We finally discuss a thought experiment where manipulation of the apparatus could challenge standard quantum mechanics predictions.
- [25] arXiv:2404.16454 [pdf, other]
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Title: Stabilizing quantum simulations of lattice gauge theories by dissipationComments: 7 pages, 7 figuresSubjects: Quantum Physics (quant-ph); High Energy Physics - Lattice (hep-lat)
Simulations of lattice gauge theories on noisy quantum hardware inherently suffer from violations of the gauge symmetry due to coherent and incoherent errors of the underlying physical system that implements the simulation. These gauge violations cause the simulations to become unphysical requiring the result of the simulation to be discarded. We investigate an active correction scheme that relies on detecting gauge violations locally and subsequently correcting them by dissipatively driving the system back into the physical gauge sector. We show that the correction scheme not only ensures the protection of the gauge symmetry, but it also leads to a longer validity of the simulation results even within the gauge-invariant sector. Finally, we discuss further applications of the scheme such as preparation of the many-body ground state of the simulated system.
- [26] arXiv:2404.16463 [pdf, ps, other]
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Title: Quantum-assisted trustworthiness for the Quantum InternetComments: 7 pages, 5 figures, 1 table and 15 referencesSubjects: Quantum Physics (quant-ph); Networking and Internet Architecture (cs.NI)
Device redundancy is one of the most well-known mechanisms in distributed systems to increase the overall system fault tolerance and, consequently, trustworthiness. Existing algorithms in this regard aim to exchange a significant number of messages among nodes to identify and agree which communication links or nodes are faulty. This approach greatly degrades the performance of those wireless communication networks exposed to limited available bandwidth and/or energy consumption due to messages flooding. Lately, quantum-assisted mechanisms have been envisaged as an appealing alternative to improve the performance in this kind of communication networks and have been shown to obtain levels of performance close to the ones achieved in ideal conditions. The purpose of this paper is to further explore this approach by using super-additivity and superposed quantum trajectories in quantum Internet to obtain a higher system trustworthiness. More specifically, the wireless communication network that supports the permafrost telemetry service for the Antarctica together with five operational modes (three of them using classical techniques and two of them using quantum-assisted mechanisms) have been simulated. Obtained results show that the new quantum-assisted mechanisms can increase the system performance by up to a 28%.
- [27] arXiv:2404.16477 [pdf, other]
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Title: Counterfactuality, back-action, and information gain in multi-path interferometersComments: 13 pages, 3 figuresSubjects: Quantum Physics (quant-ph); History and Philosophy of Physics (physics.hist-ph); Optics (physics.optics)
The presence of an absorber in one of the paths of an interferometer changes the output statistics of that interferometer in a fundamental manner. Since the individual quantum particles detected at any of the outputs of the interferometer have not been absorbed, any non-trivial effect of the absorber on the distribution of these particles over these paths is a counterfactual effect. Here, we quantify counterfactual effects by evaluating the information about the presence or absence of the absorber obtained from the output statistics, distinguishing between classical and quantum counterfactual effects. We identify the counterfactual gain which quantifies the advantage of quantum counterfactual protocols over classical counterfactual protocols, and show that this counterfactual gain can be separated into two terms: a semi-classical term related to the amplitude blocked by the absorber, and a Kirkwood-Dirac quasiprobability assigning a joint probability to the blocked path and the output port. A negative Kirkwood-Dirac term between a path and an output port indicates that inserting the absorber into that path will have a focussing effect, increasing the probability of particles arriving at that output port, resulting in a significant enhancement of the counterfactual gain. We show that the magnitude of quantum counterfactual effects cannot be explained by a simple removal of the absorbed particles, but originates instead from a well-defined back-action effect caused by the presence of the absorber in one path, on particles in other paths.
- [28] arXiv:2404.16497 [pdf, other]
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Title: Violation of Bell inequalities in an analogue black holeSubjects: Quantum Physics (quant-ph); Quantum Gases (cond-mat.quant-gas)
Signals of entanglement and nonlocality are quantitatively evaluated at zero and finite temperature in an analogue black hole realized in the flow of a quasi one-dimensional Bose-Einstein condensate. The violation of Lorentz invariance inherent to this analog system opens the prospect to observe 3-mode quantum correlations and we study the corresponding violation of bipartite and tripartite Bell inequalities. It is shown that the long wavelength modes of the system are maximally entangled, in the sense that they realize a superposition of continuous variable versions of Greenberger-Horne-Zeilinger states whose entanglement resists partial tracing.
- [29] arXiv:2404.16515 [pdf, ps, other]
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Title: Nonclassicality in a dispersive atom-cavity field interaction in presence of an external driving fieldComments: 16 pages, 8 figures, Accepted in Int. J. Mod. Phys. BSubjects: Quantum Physics (quant-ph)
We investigate nonclassical properties of a state generated by the interaction of a three-level atom with a quantized cavity field and an external classical driving field. In this study, the fields being degenerate in frequency, are highly detuned from the atom. The atom interacts with the quantized field in a dispersive manner. The experimental set-up involves a three-level atom passing through a cavity and interacting dispersively with the cavity field mode. Simultaneously, the atom interacts with an external classical field that is in resonance with the cavity field. The three-level atom can enter the cavity in one of the bare states $\ket{e}$, $\ket{f}$ or $\ket{g}$ or in a superposition of two of these states. In this paper, we consider superposition of $\ket{e}$ and $\ket{f}$. In our analysis, we focus on the statistical properties of the cavity field after interacting with the atom. The state vector $|\psi(t)\rangle$ describes the entire atom-field system but we analyze the properties of the cavity field independently neglecting the atomic component of the system. For this the atom part is traced out from $|\psi(t)\rangle$ to acquire the cavity field state only, denoted by $\ket{\psi_{ f}(t)}$. We evaluate different nonclassical measures including photon number distribution, Mandel's $Q_M$ parameter, squeezing properties $S_x$ and $S_p$, Wigner distribution, $Q_f$ function, second-order correlation function $g^2(0)$ etc. for the obtained cavity field state.
- [30] arXiv:2404.16541 [pdf, other]
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Title: Optimal depth and a novel approach to variational quantum process tomographySubjects: Quantum Physics (quant-ph)
In this work, we present two new methods for Variational Quantum Circuit (VQC) Process Tomography onto $n$ qubits systems: PT_VQC and U-VQSVD.
Compared to the state of the art, PT_VQC halves in each run the required amount of qubits for process tomography and decreases the required state initializations from $4^{n}$ to just $2^{n}$, all while ensuring high-fidelity reconstruction of the targeted unitary channel $U$. It is worth noting that, for a fixed reconstruction accuracy, PT_VQC achieves faster convergence per iteration step compared to Quantum Deep Neural Network (QDNN) and tensor network schemes.
The novel U-VQSVD algorithm utilizes variational singular value decomposition to extract eigenvectors (up to a global phase) and their associated eigenvalues from an unknown unitary representing a general channel. We assess the performance of U-VQSVD by executing an attack on a non-unitary channel Quantum Physical Unclonable Function (QPUF). U-VQSVD outperforms an uninformed impersonation attack (using randomly generated input states) by a factor of 2 to 5, depending on the qubit dimension.
For the two presented methods, we propose a new approach to calculate the complexity of the displayed VQC, based on what we denote as optimal depth. - [31] arXiv:2404.16550 [pdf, ps, other]
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Title: Alexander S. Holevo's Researches in Quantum Information Theory in 20th CenturyAuthors: Masahito HayashiComments: This paper has been acceepted for the publication in International Journal of Quantum Information on Apr 25, 2024Subjects: Quantum Physics (quant-ph)
This paper reviews Holevo's contributions to quantum information theory during the 20 century. At that time, he mainly studied three topics, classical-quantum channel coding, quantum estimation with Cramero-Rao approach, and quantum estimation with the group covariant approach. This paper addresses these three topics.
- [32] arXiv:2404.16594 [pdf, ps, other]
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Title: Linear-optical approach to encoding qubits into harmonic-oscillator modes via quantum walksSubjects: Quantum Physics (quant-ph)
We propose a linear-optical scheme that allows encoding grid-state quantum bits (qubits) into a bosonic mode using cat state and post-selection as sources of non-Gaussianity in the encoding. As a linear-optical realization of the quantum-walk encoding scheme in [Lin {\em et al.}, Quantum Info. Processing {\bf 19}, 272 (2020)], we employ the cat state as a quantum coin that enables encoding approximate Gottesman-Kitaev-Preskill (GKP) qubits through quantum walk of a squeezed vacuum state in phase space. We show that the conditional phase-space displacement necessary for the encoding can be realized through a Mach-Zehnder interferometer (MZI) assisted with ancillary cat-state input under appropriate parameter regimes. By analyzing the fidelity of the MZI-based displacement operation, we identify the region of parameter space over which the proposed linear-optical scheme can generate grid-state qubits with high fidelity. With adequate parameter setting, our proposal should be accessible to current optical and superconducting-circuit platforms in preparing grid-state qubits for bosonic modes in the, respectively, optical and microwave domains.
- [33] arXiv:2404.16654 [pdf, other]
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Title: Two-state transfer: a generalization of pair and plus state transferSubjects: Quantum Physics (quant-ph); Combinatorics (math.CO)
In the study of quantum state transfer, one is interested in being able to transmit a quantum state with high fidelity within a quantum spin network. In most of the literature, the state of interest is taken to be associated with a standard basis vector; however, more general states have recently been considered. Here, we consider a general linear combination of two vertex states, which encompasses the definitions of pair states and plus states in connected weighted graphs. A two-state in a graph $X$ is a quantum state of the form $\mathbf{e}_u+s\mathbf{e}_v$, where $u$ and $v$ are two vertices in $X$ and $s$ is a non-zero real number. If $s=-1$ or $s=1$, then such a state is called a pair state or a plus state, respectively.
In this paper, we investigate quantum state transfer between two-states, where the Hamiltonian is taken to be the adjacency, Laplacian or signless Laplacian matrix of the graph. By analyzing the spectral properties of the Hamiltonian, we characterize strongly cospectral two-states built from strongly cospectral vertices. This allows us to characterize perfect state transfer (PST) between two-states in complete graphs, cycles and hypercubes. We also produce infinite families of graphs that admit strong cospectrality and PST between two-states that are neither pair nor plus states. Using singular values and singular vectors, we show that vertex PST in the line graph of $X$ implies PST between the plus states formed by corresponding edges in $X$. Furthermore, we provide conditions such that the converse of the previous statement holds. As an application, we characterize strong cospectrality and PST between vertices in line graphs of trees, unicyclic graphs and Cartesian products. - [34] arXiv:2404.16671 [pdf, other]
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Title: Magnetic Resonance Frequency Shift Caused by Nonuniform Field and Boundary RelaxationSubjects: Quantum Physics (quant-ph); Atomic Physics (physics.atom-ph)
Magnetic field inhomogeneity is usually detrimental to magnetic resonance (MR) experiments. It is widely recognized that a nonuniform magnetic field can lead to an increase in the resonance line width, as well as a reduction in sensitivity and spectral resolution. However, nonuniform magnetic field can also cause shift in resonance frequency, which received far less attention. In this work, we investigate the frequency shift under arbitrary nonuniform magnetic field and boundary relaxation by applying perturbation theory to the Torrey equation. Several compact frequency shift formulas are reported. We find that the frequency shift is mainly determined by $B_z$ distribution (rather than the transverse field components in previous study) and has important dependence on boundary relaxation. Furthermore, due to the difference of boundary relaxation and high order perturbation correction, this frequency shift is spin-species dependent, which implies a systematic error in many MR based precision measurements such as NMR gyroscope and comagnetometers. This insight provides a potential tool for understanding the unexplained isotope shifts in recent NMR gyroscope and new physics searching experiments that utilize comagnetometers. Finally, we propose a new tool for wall interaction research based on the frequency shift's dependency on boundary relaxation.
- [35] arXiv:2404.16693 [pdf, other]
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Title: Mutual transformations of arbitrary ternary qubit trees by Clifford gatesAuthors: Alexander Yu. VlasovComments: LaTeX 10 pages, 5 figuresSubjects: Quantum Physics (quant-ph)
It is shown that ternary qubit trees with the same number of nodes can be transformed by the naturally defined sequence of Clifford gates into each other or into standard representation as 1D chain corresponding to Jordan-Wigner transform.
- [36] arXiv:2404.16697 [pdf, other]
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Title: High-Coherence Kerr-cat qubit in 2D architectureAuthors: Ahmed Hajr, Bingcheng Qing, Ke Wang, Gerwin Koolstra, Zahra Pedramrazi, Ziqi Kang, Larry Chen, Long B. Nguyen, Christian Junger, Noah Goss, Irwin Huang, Bibek Bhandari, Nicholas E.Frattini, Shruti Puri, Justin Dressel, Andrew Jordan, David Santiago, Irfan SiddiqiSubjects: Quantum Physics (quant-ph)
The Kerr-cat qubit is a bosonic qubit in which multi-photon Schrodinger cat states are stabilized by applying a two-photon drive to an oscillator with a Kerr nonlinearity. The suppressed bit-flip rate with increasing cat size makes this qubit a promising candidate to implement quantum error correction codes tailored for noise-biased qubits. However, achieving strong light-matter interactions necessary for stabilizing and controlling this qubit has traditionally required strong microwave drives that heat the qubit and degrade its performance. In contrast, increasing the coupling to the drive port removes the need for strong drives at the expense of large Purcell decay. By integrating an effective band-block filter on-chip, we overcome this trade-off and realize a Kerr-cat qubit in a scalable 2D superconducting circuit with high coherence. This filter provides 30 dB of isolation at the qubit frequency with negligible attenuation at the frequencies required for stabilization and readout. We experimentally demonstrate quantum non-demolition readout fidelity of 99.6% for a cat with 8 photons. Also, to have high-fidelity universal control over this qubit, we combine fast Rabi oscillations with a new demonstration of the X(90) gate through phase modulation of the stabilization drive. Finally, the lifetime in this architecture is examined as a function of the cat size of up to 10 photons in the oscillator achieving a bit-flip time higher than 1 ms and only a linear decrease in the phase-flip time, in good agreement with the theoretical analysis of the circuit. Our qubit shows promise as a building block for fault-tolerant quantum processors with a small footprint.
- [37] arXiv:2404.16728 [pdf, other]
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Title: High-fidelity and Fault-tolerant Teleportation of a Logical Qubit using Transversal Gates and Lattice Surgery on a Trapped-ion Quantum ComputerAuthors: C. Ryan-Anderson, N. C. Brown, C. H. Baldwin, J. M. Dreiling, C. Foltz, J. P. Gaebler, T. M. Gatterman, N. Hewitt, C. Holliman, C. V. Horst, J. Johansen, D. Lucchetti, T. Mengle, M. Matheny, Y. Matsuoka, K. Mayer, M. Mills, S. A. Moses, B. Neyenhuis, J. Pino, P. Siegfried, R. P. Stutz, J. Walker, D. HayesSubjects: Quantum Physics (quant-ph)
Quantum state teleportation is commonly used in designs for large-scale fault-tolerant quantum computers. Using Quantinuum's H2 trapped-ion quantum processor, we implement the first demonstration of a fault-tolerant state teleportation circuit for a quantum error correction code - in particular, the planar topological [[7,1,3]] color code, or Steane code. The circuits use up to 30 trapped ions at the physical layer qubits and employ real-time quantum error correction - decoding mid-circuit measurement of syndromes and implementing corrections during the protocol. We conduct experiments on several variations of logical teleportation circuits using both transversal gates and lattice surgery protocols. Among the many measurements we report on, we measure the logical process fidelity of the transversal teleportation circuit to be 0.975(2) and the logical process fidelity of the lattice surgery teleportation circuit to be 0.851(9). Additionally, we run a teleportation circuit that is equivalent to Knill-style quantum error correction and measure the process fidelity to be 0.989(2).
- [38] arXiv:2404.16736 [pdf, other]
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Title: Lifts of quantum CSS codesAuthors: Virgile GuemardSubjects: Quantum Physics (quant-ph); Information Theory (cs.IT)
We propose a notion of lift for quantum CSS codes, inspired by the geometrical construction of Freedman and Hastings. It is based on the existence of a canonical complex associated to any CSS code, that we introduce under the name of Tanner cone-complex, and over which we generate covering spaces. As a first application, we describe the classification of lifts of hypergraph product codes (HPC) and demonstrate the equivalence with the lifted product code (LPC) of Panteleev and Kalachev, including when the linear codes, factors of the HPC, are Tanner codes. As a second application, we report several new non-product constructions of quantum CSS codes, and we apply the prescription to generate their lifts which, for certain selected covering maps, are codes with improved relative parameters compared to the initial one.
- [39] arXiv:2404.16751 [pdf, other]
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Title: Efficient unitary designs and pseudorandom unitaries from permutationsAuthors: Chi-Fang Chen, Adam Bouland, Fernando G.S.L. Brandão, Jordan Docter, Patrick Hayden, Michelle XuComments: 70 pages, 11 figuresSubjects: Quantum Physics (quant-ph); Cryptography and Security (cs.CR); Mathematical Physics (math-ph)
In this work we give an efficient construction of unitary $k$-designs using $\tilde{O}(k\cdot poly(n))$ quantum gates, as well as an efficient construction of a parallel-secure pseudorandom unitary (PRU). Both results are obtained by giving an efficient quantum algorithm that lifts random permutations over $S(N)$ to random unitaries over $U(N)$ for $N=2^n$. In particular, we show that products of exponentiated sums of $S(N)$ permutations with random phases approximately match the first $2^{\Omega(n)}$ moments of the Haar measure. By substituting either $\tilde{O}(k)$-wise independent permutations, or quantum-secure pseudorandom permutations (PRPs) in place of the random permutations, we obtain the above results. The heart of our proof is a conceptual connection between the large dimension (large-$N$) expansion in random matrix theory and the polynomial method, which allows us to prove query lower bounds at finite-$N$ by interpolating from the much simpler large-$N$ limit. The key technical step is to exhibit an orthonormal basis for irreducible representations of the partition algebra that has a low-degree large-$N$ expansion. This allows us to show that the distinguishing probability is a low-degree rational polynomial of the dimension $N$.
- [40] arXiv:2404.16753 [pdf, other]
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Title: Classifying One-Dimensional Quantum States Prepared by a Single Round of MeasurementsComments: 20 + 18 pagesSubjects: Quantum Physics (quant-ph); Strongly Correlated Electrons (cond-mat.str-el)
Measurements and feedback have emerged as a powerful resource for creating quantum states. However, a detailed understanding is restricted to fixed-point representatives of phases of matter. Here, we go beyond this and ask which types of many-body entanglement can be created from measurement. Focusing on one spatial dimension, a framework is developed for the case where a single round of measurements are the only entangling operations. We show this creates matrix product states and identify necessary and sufficient tensor conditions for preparability, which uniquely determine the preparation protocol. These conditions are then used to characterize the physical constraints on preparable quantum states. First, we find a trade-off between the richness of the preparable entanglement spectrum and correlation functions, which moreover leads to a powerful no-go theorem. Second, in a subset of cases, where undesired measurement outcomes can be independently paired up and corrected, we are able to provide a complete classification for preparable quantum states. Finally, we connect properties of the preparation protocol to the resulting phase of matter, including trivial, symmetry-breaking, and symmetry-protected topological phases -- for both uniform and modulated symmetries. This work offers a resource-theoretic perspective on preparable quantum entanglement and shows how to systematically create states of matter, away from their fixed points, in quantum devices.
- [41] arXiv:2404.16765 [pdf, other]
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Title: Threshold and frequency properties of a cold ytterbium laserSubjects: Quantum Physics (quant-ph); Atomic Physics (physics.atom-ph); Optics (physics.optics)
We investigate properties of the lasing action observed on the 1S0--3P1 intercombination transition of ytterbium atoms that are laser-cooled and -trapped inside a high-finesse cavity. The dressing of the atomic states on the 1S0--1P1 transition by the magneto-optical trap (MOT) laser light allows the coupled atom-cavity system to lase, via a two-photon transition, on the same line on which it is pumped. The observation and basic description of this phenomenon was presented earlier by Gothe et al. [Phys. Rev. A 99, 013415 (2019)]. In the current work, we focus on a detailed analysis of the lasing threshold and frequency properties and perform a comparison to our theoretical models.
- [42] arXiv:2404.16774 [pdf, other]
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Title: Imaginary Stark Skin EffectComments: 5+9 pages 4+6 figuresSubjects: Quantum Physics (quant-ph); Quantum Gases (cond-mat.quant-gas)
The non-Hermitian skin effect (NHSE) is a unique phenomenon in non-Hermitian systems. However, studies on NHSE in systems without translational symmetry remain largely unexplored. Here, we unveil a new class of NHSE, dubbed "imaginary Stark skin effect" (ISSE), in a one-dimensional lossy lattice with a spatially increasing loss rate. The energy spectrum of this model exhibits a T-shaped feature, with approximately half of the eigenstates localized at the left boundary. These skin modes exhibit peculiar behaviors, expressed as a single stable exponential decay wave within the bulk region. We use the transfer matrix method to analyze the formation of the ISSE in this model. According to the eigen-decomposition of the transfer matrix, the wave function is divided into two parts, one of which dominates the behavior of the skin modes in the bulk. Our findings provide insights into the NHSE in systems without translational symmetry and contribute to the understanding of non-Hermitian systems in general.
- [43] arXiv:2404.16780 [pdf, other]
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Title: Rapid thermalization of dissipative many-body dynamics of commuting HamiltoniansComments: 69 pages, 7 figuresSubjects: Quantum Physics (quant-ph); Mathematical Physics (math-ph)
Quantum systems typically reach thermal equilibrium rather quickly when coupled to a thermal environment. The usual way of bounding the speed of this process is by estimating the spectral gap of the dissipative generator. However the gap, by itself, does not always yield a reasonable estimate for the thermalization time in many-body systems: without further structure, a uniform lower bound on it only constrains the thermalization time to grow polynomially with system size.
Here, instead, we show that for a large class of geometrically-2-local models of Davies generators with commuting Hamiltonians, the thermalization time is much shorter than one would na\"ively estimate from the gap: at most logarithmic in the system size. This yields the so-called rapid mixing of dissipative dynamics. The result is particularly relevant for 1D systems, for which we prove rapid thermalization with a system size independent decay rate only from a positive gap in the generator. We also prove that systems in hypercubic lattices of any dimension, and exponential graphs, such as trees, have rapid mixing at high enough temperatures. We do this by introducing a novel notion of clustering which we call "strong local indistinguishability" based on a max-relative entropy, and then proving that it implies a lower bound on the modified logarithmic Sobolev inequality (MLSI) for nearest neighbour commuting models.
This has consequences for the rate of thermalization towards Gibbs states, and also for their relevant Wasserstein distances and transportation cost inequalities. Along the way, we show that several measures of decay of correlations on Gibbs states of commuting Hamiltonians are equivalent, a result of independent interest. At the technical level, we also show a direct relation between properties of Davies and Schmidt dynamics, that allows to transfer results of thermalization between both. - [44] arXiv:2404.16783 [pdf, other]
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Title: Dual-isometric Projected Entangled Pair StatesComments: 5+7 pages, 1 figureSubjects: Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech); Strongly Correlated Electrons (cond-mat.str-el)
Efficient characterization of higher dimensional many-body physical states presents significant challenges. In this paper, we propose a new class of Project Entangled Pair State (PEPS) that incorporates two isometric conditions. This new class facilitates the efficient calculation of general local observables and certain two-point correlation functions, which have been previously shown to be intractable for general PEPS, or PEPS with only a single isometric constraint. Despite incorporating two isometric conditions, our class preserves the rich physical structure while enhancing the analytical capabilities. It features a large set of tunable parameters, with only a subleading correction compared to that of general PEPS. Furthermore, we analytically demonstrate that this class can encode universal quantum computations and can represent a transition from topological to trivial order.
- [45] arXiv:2404.16784 [pdf, other]
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Title: Harnessing Inferior Solutions For Superior Outcomes: Obtaining Robust Solutions From Quantum AlgorithmsSubjects: Quantum Physics (quant-ph); Optimization and Control (math.OC)
In the rapidly advancing domain of quantum optimization, the confluence of quantum algorithms such as Quantum Annealing (QA) and the Quantum Approximate Optimization Algorithm (QAOA) with robust optimization methodologies presents a cutting-edge frontier. Although it seems natural to apply quantum algorithms when facing uncertainty, this has barely been approached.
In this paper we adapt the aforementioned quantum optimization techniques to tackle robust optimization problems. By leveraging the inherent stochasticity of quantum annealing and adjusting the parameters and evaluation functions within QAOA, we present two innovative methods for obtaining robust optimal solutions. These heuristics are applied on two use cases within the energy sector: the unit commitment problem, which is central to the scheduling of power plant operations, and the optimization of charging electric vehicles (EVs) including electricity from photovoltaic (PV) to minimize costs. These examples highlight not only the potential of quantum optimization methods to enhance decision-making in energy management but also the practical relevance of the young field of quantum computing in general. Through careful adaptation of quantum algorithms, we lay the foundation for exploring ways to achieve more reliable and efficient solutions in complex optimization scenarios that occur in the real-world.
Cross-lists for Fri, 26 Apr 24
- [46] arXiv:2404.16088 (cross-list from cond-mat.str-el) [pdf, other]
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Title: A Generalised Haldane Map from the Matrix Product State Path Integral to the Critical Theory of the $J_1$-$J_2$ ChainComments: 4 + 7 pagesSubjects: Strongly Correlated Electrons (cond-mat.str-el); Quantum Physics (quant-ph)
We study the $J_1$-$J_2$ spin-$1/2$ chain using a path integral constructed over matrix product states (MPS). By virtue of its non-trivial entanglement structure, the MPS ansatz captures the key phases of the model even at a semi-classical, saddle-point level, and, as a variational state, is in good agreement with the field theory obtained by abelian bosonisation. Going beyond the semi-classical level, we show that the MPS ansatz facilitates a physically-motivated derivation of the field theory of the critical phase: by carefully taking the continuum limit -- a generalisation of the Haldane map -- we recover from the MPS path integral a field theory with the correct topological term and emergent $SO(4)$ symmetry, constructively linking the microscopic states and topological field-theoretic structures. Moreover, the dimerisation transition is particularly clear in the MPS formulation -- an explicit dimerisation potential becomes relevant, gapping out the magnetic fluctuations.
- [47] arXiv:2404.16098 (cross-list from hep-th) [pdf, ps, other]
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Title: Relative state-counting for semiclassical black holesComments: 5 pagesSubjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); Quantum Physics (quant-ph)
It has been shown that entropy differences between certain states of perturbative quantum gravity can be computed without specifying an ultraviolet completion. This is analogous to the situation in classical statistical mechanics, where entropy differences are defined but absolute entropy is not. Unlike in classical statistical mechanics, however, the entropy differences computed in perturbative quantum gravity do not have a clear physical interpretation. Here we construct a family of perturbative black hole states for which the entropy difference can be interpreted as a relative counting of states. Conceptually, this paper begins with the algebra of mass fluctuations around a fixed black hole background, and points out that while this is a type I algebra, it is not a factor and therefore has no canonical definition of entropy. As in previous work, coupling the mass fluctuations to quantum matter embeds the mass algebra within a type II factor, in which entropy differences (but not absolute entropies) are well defined. It is then shown that for microcanonical wavefunctions of mass fluctuation, the type II entropy difference equals the logarithm of the dimension of the extra Hilbert space that is needed to map one microcanonical window to another using gauge-invariant unitaries. The paper closes with comments on type II entropy difference in a more general class of states, where the von Neumann entropy difference does not have a physical interpretation, but "one-shot" entropy differences do.
- [48] arXiv:2404.16154 (cross-list from cs.LG) [pdf, other]
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Title: A Comparative Analysis of Adversarial Robustness for Quantum and Classical Machine Learning ModelsComments: submitted to IEEE QCE24Subjects: Machine Learning (cs.LG); Cryptography and Security (cs.CR); Quantum Physics (quant-ph)
Quantum machine learning (QML) continues to be an area of tremendous interest from research and industry. While QML models have been shown to be vulnerable to adversarial attacks much in the same manner as classical machine learning models, it is still largely unknown how to compare adversarial attacks on quantum versus classical models. In this paper, we show how to systematically investigate the similarities and differences in adversarial robustness of classical and quantum models using transfer attacks, perturbation patterns and Lipschitz bounds. More specifically, we focus on classification tasks on a handcrafted dataset that allows quantitative analysis for feature attribution. This enables us to get insight, both theoretically and experimentally, on the robustness of classification networks. We start by comparing typical QML model architectures such as amplitude and re-upload encoding circuits with variational parameters to a classical ConvNet architecture. Next, we introduce a classical approximation of QML circuits (originally obtained with Random Fourier Features sampling but adapted in this work to fit a trainable encoding) and evaluate this model, denoted Fourier network, in comparison to other architectures. Our findings show that this Fourier network can be seen as a "middle ground" on the quantum-classical boundary. While adversarial attacks successfully transfer across this boundary in both directions, we also show that regularization helps quantum networks to be more robust, which has direct impact on Lipschitz bounds and transfer attacks.
- [49] arXiv:2404.16229 (cross-list from cond-mat.mes-hall) [pdf, other]
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Title: Two qubit gate with macroscopic singlet-triplet qubits in synthetic spin-one chains in InAsP quantum dot nanowiresComments: 13 pages, 8 figuresSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Quantum Physics (quant-ph)
We present a theory of a two qubit gate with macroscopic singlet-triplet (ST) qubits in synthetic spin-one chains in InAsP quantum dot nanowires. The macroscopic topologically protected singlet-triplet qubits are built with two spin-half Haldane quasiparticles. The Haldane quasiparticles are hosted by synthetic spin-one chain realized in chains of InAsP quantum dots embedded in an InP nanowire, with four electrons each. The quantum dot nanowire is described by a Hubbard-Kanamori (HK) Hamiltonian derived from an interacting atomistic model. Using exact diagonalization and Matrix Product States (MPS) tools, we demonstrate that the low-energy behavior of the HK Hamiltonian is effectively captured by an antiferromagnetic spin-one chain Hamiltonian. Next we consider two macroscopic qubits and present a method for creating a tunable coupling between the two macroscopic qubits by inserting an intermediate control dot between the two chains. Finally, we propose and demonstrate two approaches for generating highly accurate two-ST qubit gates : (1) by controlling the length of each qubit, and (2) by employing different background magnetic fields for the two qubits.
- [50] arXiv:2404.16414 (cross-list from physics.atom-ph) [pdf, ps, other]
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Title: Validating a lutetium frequency referenceComments: 10 pagesSubjects: Atomic Physics (physics.atom-ph); Quantum Physics (quant-ph)
We review our progress in developing a frequency reference with singly ionized lutetium and give estimates of the levels of inaccuracy we expect to achieve in the near future with both the $^1S_0\leftrightarrow{}^3D_1$ and $^1S_0\leftrightarrow{}^3D_2$ transitions. Based on established experimental results, we show that inaccuracies at the low $10^{-19}$ level are readily achievable for the $^1S_0\leftrightarrow{}^3D_1$ transition, and the frequency ratio between the two transitions is limited almost entirely by the BBR shift. We argue that the frequency ratio measured within the one apparatus provides a well-defined metric to compare and establish the performance of remotely located systems. For the measurement of an in situ frequency ratio, relativistic shifts drop out and both transitions experience the same electromagnetic environment. Consequently, the uncertainty budget for the ratio is practically identical to the uncertainty budgets for the individual transitions. If the ratios for two or more systems disagree we can be certain at least one of the clock assessments is incorrect. If they agree, subsequent comparisons on one transition would only differ by relativistic effects. Since motional effects are easily assessed and typically small for a heavy ion, only the differential gravitational red-shift will significantly contribute and this can be confirmed by comparison on the second transition.
- [51] arXiv:2404.16450 (cross-list from math.NT) [pdf, ps, other]
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Title: Unconditional correctness of recent quantum algorithms for factoring and computing discrete logarithmsAuthors: Cédric PilatteComments: 22 pagesSubjects: Number Theory (math.NT); Computational Complexity (cs.CC); Quantum Physics (quant-ph)
In 1994, Shor introduced his famous quantum algorithm to factor integers and compute discrete logarithms in polynomial time. In 2023, Regev proposed a multi-dimensional version of Shor's algorithm that requires far fewer quantum gates. His algorithm relies on a number-theoretic conjecture on the elements in $(\mathbb{Z}/N\mathbb{Z})^{\times}$ that can be written as short products of very small prime numbers. We prove a version of this conjecture using tools from analytic number theory such as zero-density estimates. As a result, we obtain an unconditional proof of correctness of this improved quantum algorithm and of subsequent variants.
- [52] arXiv:2404.16470 (cross-list from cond-mat.quant-gas) [pdf, other]
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Title: A finite-time quantum Otto engine with tunnel coupled one-dimensional Bose gasesComments: 24 pages, 7 figuresSubjects: Quantum Gases (cond-mat.quant-gas); Statistical Mechanics (cond-mat.stat-mech); Quantum Physics (quant-ph)
We undertake a theoretical study of a finite-time quantum Otto engine cycle driven by inter-particle interactions in a weakly interacting one-dimensional Bose gas in the quasicondensate regime. Utilizing a $c$-field approach, we simulate the entire Otto cycle, i.e. the two work strokes and the two equilibration strokes. More specifically, the interaction-induced work strokes are modelled by treating the working fluid as an isolated quantum many-body system undergoing unitary evolution. The equilibration strokes, on the other hand, are modelled by treating the working fluid as an open quantum system tunnel-coupled to another quasicondensate which acts as either the hot or cold reservoir, albeit of finite size. We find that, unlike a uniform 1D Bose gas, a harmonically trapped quasicondensate cannot operate purely as a \emph{heat} engine; instead, the engine operation is enabled by additional \emph{chemical} work performed on the working fluid, facilitated by the inflow of particles from the hot reservoir. The microscopic treatment of dynamics during equilibration strokes enables us to evaluate the characteristic operational time scales of this Otto chemical engine, crucial for characterizing its power output, without any \emph{ad hoc} assumptions about typical thermalization timescales. We analyse the performance and quantify the figures of merit of the proposed Otto chemical engine, finding that it offers a favourable trade-off between efficiency and power output, particularly when the interaction-induced work strokes are implemented via a sudden quench. We further demonstrate that in the sudden quench regime, the engine operates with an efficiency close to the near-adiabatic (near maximum efficiency) limit, while concurrently achieving maximum power output.
- [53] arXiv:2404.16586 (cross-list from physics.chem-ph) [pdf, other]
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Title: Reduced density matrix formulation of quantum linear responseAuthors: Theo Juncker von Buchwald, Karl Michael Ziems, Erik Rosendahl Kjellgren, Stephan P. A. Sauer, Jacob Kongsted, Sonia CorianiSubjects: Chemical Physics (physics.chem-ph); Computational Physics (physics.comp-ph); Quantum Physics (quant-ph)
The prediction of spectral properties via linear response (LR) theory is an important tool in quantum chemistry for understanding photo-induced processes in molecular systems. With the advances of quantum computing, we recently adapted this method for near-term quantum hardware using a truncated active space approximation with orbital rotation, named quantum linear response (qLR). In an effort to reduce the classic cost of this hybrid approach, we here derive and implement a reduced density matrix (RDM) driven approach of qLR. This allows for the calculation of spectral properties of moderately sized molecules with much larger basis sets than so far possible. We report qLR results for benzene and $R$-methyloxirane with a cc-pVTZ basis set and study the effect of shot noise on the valence and oxygen K-edge absorption spectra of H$_2$O in the cc-pVTZ basis.
- [54] arXiv:2404.16589 (cross-list from hep-lat) [pdf, other]
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Title: Preconditioned flow as a solution to the hierarchical growth problem in the generalized Lefschetz thimble methodComments: 35 pages, 5 figuresSubjects: High Energy Physics - Lattice (hep-lat); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th); Computational Physics (physics.comp-ph); Quantum Physics (quant-ph)
The generalized Lefschetz thimble method is a promising approach that attempts to solve the sign problem in Monte Carlo methods by deforming the integration contour using the flow equation. Here we point out a general problem that occurs due to the property of the flow equation, which extends a region on the original contour exponentially to a region on the deformed contour. Since the growth rate for each eigenmode is governed by the singular values of the Hessian of the action, a huge hierarchy in the singular value spectrum, which typically appears for large systems, leads to various technical problems in numerical simulations. We solve this hierarchical growth problem by preconditioning the flow so that the growth rate becomes identical for every eigenmode. As an example, we show that the preconditioned flow enables us to investigate the real-time quantum evolution of an anharmonic oscillator with the system size that can hardly be achieved by using the original flow.
- [55] arXiv:2404.16690 (cross-list from hep-ph) [pdf, other]
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Title: Neutrino many-body flavor evolution: the full HamiltonianComments: 21 pages, 16 figuresSubjects: High Energy Physics - Phenomenology (hep-ph); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
We study neutrino flavor evolution in the quantum many-body approach using the full neutrino-neutrino Hamiltonian, including the usually neglected terms that mediate non-forward scattering processes. Working in the occupation number representation with plane waves as single-particle states, we explore the time evolution of simple initial states with up to $N=10$ neutrinos. We discuss the time evolution of the Loschmidt echo, one body flavor and kinetic observables, and the one-body entanglement entropy. For the small systems considered, we observe `thermalization' of both flavor and momentum degrees of freedom on comparable time scales, with results converging towards expectation values computed within a microcanonical ensemble. We also observe that the inclusion of non-forward processes generates a faster flavor evolution compared to the one induced by the truncated (forward) Hamiltonian.
Replacements for Fri, 26 Apr 24
- [56] arXiv:2106.05776 (replaced) [pdf, other]
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Title: Intermediate Times Dilemma for Open Quantum System: Filtered Approximation to The Refined Weak Coupling LimitComments: 15+17 pages, 8 FiguresSubjects: Quantum Physics (quant-ph)
- [57] arXiv:2108.13352 (replaced) [pdf, other]
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Title: Oxygen Vacancies in Niobium Pentoxide as a Source of Two-Level System Losses in Superconducting NiobiumSubjects: Applied Physics (physics.app-ph); Quantum Physics (quant-ph)
- [58] arXiv:2111.10409 (replaced) [pdf, other]
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Title: The Acrobatics of BQPComments: 64 pages. V2: various writing improvements. V3: minor fixes to spelling and references. V4: corrected an error in what is now Lemma 53Journal-ref: 37th Computational Complexity Conference (CCC 2022), Leibniz International Proceedings in Informatics (LIPIcs) 234, pp. 20:1-20:17 (2022)Subjects: Computational Complexity (cs.CC); Quantum Physics (quant-ph)
- [59] arXiv:2206.04524 (replaced) [pdf, other]
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Title: Activating information backflow with the assistance of quantum SWITCHComments: 10+2 pages and 4 figures, Closed to published versionJournal-ref: Journal of Physics A: Mathematical and Theoretical (2024)Subjects: Quantum Physics (quant-ph)
- [60] arXiv:2212.11743 (replaced) [pdf, other]
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Title: Amoeba Formulation of Non-Bloch Band Theory in Arbitrary DimensionsComments: 21 pages, 11 figures, 1 tableJournal-ref: Physical Review X 14, 021011 (2024)Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Quantum Gases (cond-mat.quant-gas); Mathematical Physics (math-ph); Optics (physics.optics); Quantum Physics (quant-ph)
- [61] arXiv:2212.14340 (replaced) [pdf, other]
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Title: Operational Quantum Mereology and Minimal ScramblingComments: 9+3 pages, 3 figures. Presentation improved one co-author addedSubjects: Quantum Physics (quant-ph)
- [62] arXiv:2301.06772 (replaced) [pdf, other]
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Title: Measuring Unruh radiation from accelerated electronsComments: This is an expanded version of section 3.2 of arXiv:2211.13187 which we wrote for the Multi Petawatt Prioritization (MP3) workshop. This paper has been accepted for publication in EPJCSubjects: General Relativity and Quantum Cosmology (gr-qc); Atomic Physics (physics.atom-ph); Quantum Physics (quant-ph)
- [63] arXiv:2301.08241 (replaced) [pdf, other]
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Title: A generic quantum Wielandt's inequalityComments: 25 pages, 6 figuresSubjects: Quantum Physics (quant-ph); Mathematical Physics (math-ph)
- [64] arXiv:2303.17268 (replaced) [pdf, other]
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Title: Classical-to-quantum non-signalling boxesComments: 14 pages, 3 figures, 1 table, improved presentation and more detailed proofsSubjects: Quantum Physics (quant-ph)
- [65] arXiv:2304.06768 (replaced) [pdf, other]
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Title: Improving Gradient Methods via Coordinate Transformations: Applications to Quantum Machine LearningComments: 9 pages, 10 figures, 3 tablesJournal-ref: Phys. Rev. Research 6, 023069 (2024)Subjects: Quantum Physics (quant-ph); Machine Learning (cs.LG)
- [66] arXiv:2307.15661 (replaced) [pdf, other]
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Title: Relaxations and Exact Solutions to Quantum Max Cut via the Algebraic Structure of Swap OperatorsComments: 88 pages, 6 figuresSubjects: Quantum Physics (quant-ph); Mathematical Physics (math-ph)
- [67] arXiv:2308.11215 (replaced) [pdf, ps, other]
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Title: Resonant detectors of gravitational wave in the linear and quadratic generalized uncertainty principle frameworkComments: 19 pages LATEX. Comments are welcomeJournal-ref: Eur. Phys. J. C 84 (2024) 425Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th); Quantum Physics (quant-ph)
- [68] arXiv:2309.04717 (replaced) [pdf, other]
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Title: High-fidelity detection of large-scale atom arrays in an optical latticeSubjects: Atomic Physics (physics.atom-ph); Quantum Gases (cond-mat.quant-gas); Quantum Physics (quant-ph)
- [69] arXiv:2310.04383 (replaced) [pdf, other]
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Title: Matter-wave collimation to picokelvin energies with scattering length and potential shape controlAuthors: Alexander Herbst, Timothé Estrampes, Henning Albers, Robin Corgier, Knut Stolzenberg, Sebastian Bode, Eric Charron, Ernst M. Rasel, Naceur Gaaloul, Dennis SchlippertSubjects: Atomic Physics (physics.atom-ph); Quantum Gases (cond-mat.quant-gas); Quantum Physics (quant-ph)
- [70] arXiv:2311.00338 (replaced) [pdf, ps, other]
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Title: NOON-state interference in the frequency domainComments: Main text (9 pages and 6 figures), Supplementary information (14 pages and 7 figures)Journal-ref: Light: Science & Applications, 13, 90 (2024)Subjects: Quantum Physics (quant-ph)
- [71] arXiv:2311.07086 (replaced) [pdf, other]
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Title: Inferring the arrow of time in quantum spatiotemporal correlationsComments: Close to the published version. fixed typos, Comments are welcomeJournal-ref: Phys. Rev. A 109, 032219 (2024)Subjects: Quantum Physics (quant-ph)
- [72] arXiv:2311.11028 (replaced) [pdf, ps, other]
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Title: The non-equilibrium temperature beyond local equilibrium assumptionAuthors: Zheng-Chuan WangComments: 17pages,4figuresSubjects: Statistical Mechanics (cond-mat.stat-mech); Quantum Physics (quant-ph)
- [73] arXiv:2311.11314 (replaced) [pdf, other]
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Title: Simulation of Matrix Product States to Unveil the Initial State Dependency of non-Gaussian Dynamics of Kerr NonlinearityAuthors: Souvik AgastiComments: 11 pages, 7 figures. arXiv admin note: text overlap with arXiv:2308.10667Journal-ref: J. Opt. Soc. Am. B 41, 1197-1206 (2024)Subjects: Quantum Physics (quant-ph)
- [74] arXiv:2311.15533 (replaced) [pdf, other]
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Title: Simulating Open Quantum Systems Using Hamiltonian SimulationsSubjects: Quantum Physics (quant-ph)
- [75] arXiv:2312.00862 (replaced) [pdf, ps, other]
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Title: From Spin States to Socially Integrated Ising Models: Proposed Applications of Graph States, Stabilizer States, Toric States to Opinion DynamicsAuthors: Yasuko KawahataComments: Discussion Paper:Discussion Model for Propagation of Social Opinion via Quantum Galois Noise Channels:Entanglement, SuperSpreader(2023) This paper is partially an attempt to utilize "Generative AI" and was written with educational intent. There are currently no plans for it to become a peer-reviewed paperSubjects: Physics and Society (physics.soc-ph); Quantum Physics (quant-ph)
- [76] arXiv:2312.09270 (replaced) [pdf, other]
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Title: Towards establishing a connection between two-level quantum systems and physical spacesComments: 10 pages, 2 figures, minor adjustments and a section added according to reviewer's suggestionsJournal-ref: Brazilian Journal of Physics 54, 93 (2024)Subjects: Quantum Physics (quant-ph)
- [77] arXiv:2312.09761 (replaced) [pdf, other]
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Title: Accurate and gate-efficient quantum ansätze for electronic states without adaptive optimisationAuthors: Hugh G. A. BurtonComments: 17 pages, 9 figuresSubjects: Chemical Physics (physics.chem-ph); Quantum Physics (quant-ph)
- [78] arXiv:2312.09784 (replaced) [pdf, other]
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Title: Quantum Algorithm for Solving the Advection Equation using Hamiltonian SimulationSubjects: Quantum Physics (quant-ph)
- [79] arXiv:2312.12831 (replaced) [pdf, other]
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Title: First-Order Phase Transition of the Schwinger Model with a Quantum ComputerAuthors: Takis Angelides, Pranay Naredi, Arianna Crippa, Karl Jansen, Stefan Kühn, Ivano Tavernelli, Derek S. WangComments: 21 pages, 10 figures, 1 tableSubjects: High Energy Physics - Lattice (hep-lat); Quantum Physics (quant-ph)
- [80] arXiv:2401.02251 (replaced) [pdf, other]
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Title: Nonreciprocal Unconventional Photon Blockade with Kerr MagnonsComments: 9 pages,8 figures. Accepted by Advanced Quantum TechnologiesSubjects: Quantum Physics (quant-ph)
- [81] arXiv:2401.12395 (replaced) [pdf, other]
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Title: Hybrid Quantum Repeaters with Ensemble-based Quantum Memories and Single-spin Photon TransducersAuthors: Fenglei Gu, Shankar G Menon, David Maier, Antariksha Das, Tanmoy Chakraborty, Wolfgang Tittel, Hannes Bernien, Johannes BorregaardComments: 14 pages, 7 figures in total, with 4 appendix sectionsSubjects: Quantum Physics (quant-ph)
- [82] arXiv:2401.17189 (replaced) [pdf, other]
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Title: Exceptional points and ground-state entanglement spectrum of a fermionic extension of the Swanson oscillatorComments: v1: Comments are welcome; v2: This version contains some new calculations and corrects some errors from the older versionSubjects: Quantum Physics (quant-ph); High Energy Physics - Theory (hep-th); Mathematical Physics (math-ph)
- [83] arXiv:2401.17717 (replaced) [pdf, ps, other]
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Title: On probabilities in quantum mechanicsAuthors: Inge S. HellandComments: 23 pagesSubjects: Quantum Physics (quant-ph)
- [84] arXiv:2403.11893 (replaced) [pdf, other]
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Title: Quantum Coordination Rates in Multi-Partite NetworksSubjects: Quantum Physics (quant-ph); Information Theory (cs.IT)
- [85] arXiv:2404.05410 (replaced) [pdf, other]
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Title: Solving quantum impurity problems on the L-shaped Kadanoff-Baym contourComments: 9 pages, 4 figuresSubjects: Strongly Correlated Electrons (cond-mat.str-el); Quantum Physics (quant-ph)
- [86] arXiv:2404.05998 (replaced) [pdf, other]
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Title: Efficient quantum Gibbs samplers with Kubo--Martin--Schwinger detailed balance conditionSubjects: Quantum Physics (quant-ph)
- [87] arXiv:2404.13202 (replaced) [pdf, other]
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Title: Lattice Surgery for DummiesComments: 10 pages, 13 figures, 1 tableSubjects: Quantum Physics (quant-ph)
- [88] arXiv:2404.15377 (replaced) [pdf, other]
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Title: Fourier Series Guided Design of Quantum Convolutional Neural Networks for Enhanced Time Series ForecastingAuthors: Sandra Leticia Juárez Osorio, Mayra Alejandra Rivera Ruiz, Andres Mendez-Vazquez, Eduardo Rodriguez-TelloSubjects: Quantum Physics (quant-ph); Machine Learning (cs.LG)
- [89] arXiv:2404.15477 (replaced) [pdf, ps, other]
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Title: Entanglement in Quantum Dots: Insights from Dynamic Susceptibility and Quantum Fisher InformationSubjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
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