Quantum Physics
New submissions
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New submissions for Thu, 28 Mar 24
- [1] arXiv:2403.17941 [pdf, other]
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Title: Entanglement of temporal sections as quantum histories and their quantum correlation boundsAuthors: Marcin NowakowskiComments: 8 pages, 1 figure. arXiv admin note: substantial text overlap with arXiv:2011.08437Subjects: Quantum Physics (quant-ph)
In this paper we focus on the underlying quantum structure of temporal correlations and show their peculiar nature which differentiate them from spatial quantum correlations. With a growing interest in representation of quantum states as topological objects, we consider quantum history bundles based on the temporal manifold and show the source of violation of monogamous temporal Bell-like inequalities. We introduce definitions for the mixture of quantum histories and consider their entanglement as sections over the Hilbert vector bundles. As a generalization of temporal Bell-like inequalities, we derive the quantum bound for multi-time Bell-like inequalities.
- [2] arXiv:2403.17979 [pdf, other]
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Title: Modified Multiple Sequence Alignment Algorithm on Quantum Annealers (MAQ)Authors: Melody LeeComments: 12 pages, 5 figures, initially written while at NCSSM and published in JOCSE (reformatted to fit ArXiv guidelines)Journal-ref: Journal of Computational Science Education. 14(1) 2023Subjects: Quantum Physics (quant-ph)
We propose a modified MSA algorithm on quantum annealers with applications in areas of bioinformatics and genetic sequencing. To understand the human genome, researchers compare extensive sets of these genetic sequences -- or their protein counterparts -- to identify patterns. This comparison begins with the alignment of the set of (multiple) sequences. However, this alignment problem is considered nondeterministically-polynomial time complete and, thus, current classical algorithms at best rely on brute force or heuristic methods to find solutions. Quantum annealing algorithms are able to bypass this need for sheer brute force due to their use of quantum mechanical properties. However, due to the novelty of these algorithms, many are rudimentary in nature and limited by hardware restrictions. We apply progressive alignment techniques to modify annealing algorithms, achieving a linear reduction in spin usage whilst introducing more complex heuristics to the algorithm. This opens the door for further exploration into quantum computing-based bioinformatics, potentially allowing for a deeper understanding of disease detection and monitoring.
- [3] arXiv:2403.17988 [pdf, other]
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Title: Achieving Quantum Limits of Exoplanet Detection and LocalizationComments: 30 pages, 12 figuresSubjects: Quantum Physics (quant-ph); Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Discovering exoplanets in orbit around distant stars via direct imaging is fundamentally impeded by the high dynamic range between the star and the planet. Coronagraphs strive to increase the signal-to-noise ratio of exoplanet signatures by optically rejecting light from the host star while leaving light from the exoplanet mostly unaltered. However it is unclear whether coronagraphs constitute an optimal strategy for attaining fundamental limits relevant exoplanet discovery. In this work, we report the quantum information limits of exoplanet detection and localization specified by the Quantum Chernoff Exponent (QCE) and the Quantum Fisher Information Matrix (QFIM) respectively. In view of these quantum limits, we assess and compare several high-performance coronagraph designs that theoretically achieve total rejection of an on-axis point source. We find that systems which exclusively eliminate the fundamental mode of the telescope without attenuating higher-order orthogonal modes are quantum-optimal in the regime of high star-planet contrasts. Importantly, the QFIM is shown to persist well below the diffraction-limit of the telescope, suggesting that quantum-optimal coronagraphs may further expand the domain of accessible exoplanets.
- [4] arXiv:2403.18006 [pdf, other]
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Title: Fast quantum integer multiplication with zero ancillasComments: Main text: 10 pages, 3 tables, 1 figure; appendix: 9 pages, 3 tables, 2 figuresSubjects: Quantum Physics (quant-ph)
The multiplication of superpositions of numbers is a core operation in many quantum algorithms. The standard method for multiplication (both classical and quantum) has a runtime quadratic in the size of the inputs. Quantum circuits with asymptotically fewer gates have been developed, but generally exhibit large overheads, especially in the number of ancilla qubits. In this work, we introduce a new paradigm for sub-quadratic-time quantum multiplication with zero ancilla qubits -- the only qubits involved are the input and output registers themselves. Our algorithm achieves an asymptotic gate count of $\mathcal{O}(n^{1+\epsilon})$ for any $\epsilon > 0$; with practical choices of parameters, we expect scalings as low as $\mathcal{O}(n^{1.3})$. Used as a subroutine in Shor's algorithm, our technique immediately yields a factoring circuit with $\mathcal{O}(n^{2+\epsilon})$ gates and only $2n + \mathcal{O}(\log n)$ qubits; to our knowledge, this is by far the best qubit count of any factoring circuit with a sub-cubic number of gates. Used in Regev's recent factoring algorithm, the gate count is $\mathcal{O}(n^{1.5+\epsilon})$. Finally, we demonstrate that our algorithm has the potential to outperform previous proposals at problem sizes relevant in practice, including yielding the smallest circuits we know of for classically-verifiable quantum advantage.
- [5] arXiv:2403.18007 [pdf, other]
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Title: Typical thermalization of low-entanglement statesComments: 6+14 pages, one figureSubjects: Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech); Mathematical Physics (math-ph)
Proving thermalization from the unitary evolution of a closed quantum system is one of the oldest questions that is still nowadays only partially resolved. Several efforts have led to various formulations of what is called the eigenstate thermalization hypothesis. The latter, however, assume initial states which are highly concentrated around a specific energy window and, as such, cannot account for a large class of states that are of paramount importance and that are operationally accessible in natural physical settings, including many experimental schemes for testing thermalization and for quantum simulation: low-entanglement states. In this work, we prove thermalization of these states under precise conditions that have operational significance. More specifically, we define a random energy smoothing - motivated by arguments of unavoidable finite resolution - on local Hamiltonians that lead to local thermalization when the initial state has low entanglement. Finally we show that such transformation affects neither the Gibbs state locally nor, under a mild condition, the short time dynamics.
- [6] arXiv:2403.18016 [pdf, other]
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Title: Equilibration of objective observables in a dynamical model of quantum measurementsComments: 12 + 8 pages, 5 figuresSubjects: Quantum Physics (quant-ph)
The challenge of understanding quantum measurement persists as a fundamental issue in modern physics. Particularly, the abrupt and energy-non-conserving collapse of the wave function appears to contradict classical thermodynamic laws. The contradiction can be resolved by considering measurement itself to be an entropy-increasing process, driven by the second law of thermodynamics. This proposal, dubbed the Measurement-Equilibration Hypothesis, builds on the Quantum Darwinism framework derived to explain the emergence of the classical world. Measurement outcomes thus emerge objectively from unitary dynamics via closed-system equilibration. Working within this framework, we construct the set of \textit{`objectifying observables'} that best encode the measurement statistics of a system in an objective manner, and establish a measurement error bound to quantify the probability an observer will obtain an incorrect measurement outcome. Using this error bound, we show that the objectifying observables readily equilibrate on average under the set of Hamiltonians which preserve the outcome statistics on the measured system. Using a random matrix model for this set, we numerically determine the measurement error bound, finding that the error only approaches zero with increasing environment size when the environment is coarse-grained into so-called observer systems. This indicates the necessity of coarse-graining an environment for the emergence of objective measurement outcomes.
- [7] arXiv:2403.18030 [pdf, other]
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Title: EinExprs: Contraction Paths of Tensor Networks as Symbolic ExpressionsComments: 4 pages, 5 figures, submitted to JuliaCon Proceedings 2023Subjects: Quantum Physics (quant-ph); Mathematical Software (cs.MS)
Tensor Networks are graph representations of summation expressions in which vertices represent tensors and edges represent tensor indices or vector spaces. In this work, we present EinExprs.jl, a Julia package for contraction path optimization that offers state-of-art optimizers. We propose a representation of the contraction path of a Tensor Network based on symbolic expressions. Using this package the user may choose among a collection of different methods such as Greedy algorithms, or an approach based on the hypergraph partitioning problem. We benchmark this library with examples obtained from the simulation of Random Quantum Circuits (RQC), a well known example where Tensor Networks provide state-of-the-art methods.
- [8] arXiv:2403.18050 [pdf, ps, other]
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Title: Double well ground state energy splitting (or instanton flipping rate); rendering the implicit explicitAuthors: J. H. HannaySubjects: Quantum Physics (quant-ph)
A prime example of quantum tunnelling is the semiclassical 'energy splitting' of the levels of a symmetrical double well potential, or equivalently the flipping rate of an instanton. Curiously the accepted expression for the ground state energy splitting in terms of the (smooth) potential function has not been pursued to the full explicitness available from classical mechanics. This implicitness is rectified here.
- [9] arXiv:2403.18061 [pdf, other]
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Title: Efficient Hamiltonian reconstruction from equilibrium statesAuthors: Adam ArtymowiczSubjects: Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech)
We describe a novel algorithm that recovers the Hamiltonian and temperature of a quantum state in thermal equilibrium using a restricted set of measurements. The algorithm works by imposing a semidefinite constraint based on free energy minimization, which we interpret in terms of thermodynamic stability. We benchmark the algorithm on the problem of learning a nearest-neighbour Hamiltonian on a 100-qubit spin chain.
- [10] arXiv:2403.18081 [pdf, other]
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Title: Antiscarring in Chaotic Quantum WellsSubjects: Quantum Physics (quant-ph)
Chaos plays a crucial role in numerous natural phenomena, but its quantum nature has remained large elusive. One intriguing quantum-chaotic phenomenon is the scarring of a single-particle wavefunction, where the quantum probability density is enhanced in the vicinity of a classical periodic orbit. These quantum scars illustrate the quantum suppression of classical chaos, offering a unique way to explore the classical-quantum relationship beyond conventional limits. In this study, we establish an ergodicity theorem for slacking a group of adjacent eigenstates, revealing the aspect of antiscarring -- the reduction of probability density along a periodic orbit generating the corresponding scars. We thereafter apply these two concepts to variational scars in a disordered quantum well, and finally discuss their broader implications, suggesting potential experimental approaches to observe this phenomenon.
- [11] arXiv:2403.18150 [pdf, other]
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Title: Band engineering and study of disorder using topology in compact high kinetic inductance cavity arraysAuthors: Vincent Jouanny, Simone Frasca, Vera Jo Weibel, Leo Peyruchat, Marco Scigliuzzo, Fabian Oppliger, Franco De Palma, Davide Sbroggio, Guillaume Beaulieu, Oded Zilberberg, Pasquale ScarlinoSubjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Superconductivity (cond-mat.supr-con)
Superconducting microwave metamaterials offer enormous potential for quantum optics and information science, enabling the development of advanced quantum technologies for sensing and amplification. In the context of circuit quantum electrodynamics, such metamaterials can be implemented as coupled cavity arrays (CCAs). In the continuous effort to miniaturize quantum devices for increasing scalability, minimizing the footprint of CCAs while preserving low disorder becomes paramount. In this work, we present a compact CCA architecture leveraging superconducting NbN thin films presenting high kinetic inductance, which enables high-impedance CCA ($\sim1.5$ k$\Omega$), while reducing the resonator footprint. We demonstrate its versatility and scalability by engineering one-dimensional CCAs with up to 100 resonators and exhibiting multiple bandgaps. Additionally, we quantitatively investigate disorder in the CCAs using symmetry-protected topological SSH modes, from which we extract a resonator frequency scattering of $0.22^{+0.04}_{-0.03}\%$. Our platform opens up exciting new prospects for analog quantum simulations of many-body physics with ultrastrongly coupled emitters.
- [12] arXiv:2403.18210 [pdf, ps, other]
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Title: A unified view of direct measurement of quantum states, processes, and measurementsComments: 11 pages, 8 figuresSubjects: Quantum Physics (quant-ph)
The dynamics of a quantum system are characterized by three components: quantum state, quantum process, and quantum measurement. The proper measurement of these components is a crucial issue in quantum information processing. Recently, direct measurement methods have been proposed and demonstrated wherein each complex matrix element of these three components is obtained separately, without the need for quantum tomography of the entire matrix. Since these direct measurement methods have been proposed independently, no theoretical framework has been presented to unify them despite the time symmetry of quantum dynamics. In this study, we propose a theoretical framework to systematically derive direct measurement methods for these three components. Following this framework and further utilizing the basis-shift unitary transformation, we have derived the most efficient direct measurement method using qubit probes. Additionally, we have experimentally demonstrated the feasibility of the direct measurement method of quantum states using optical pulse trains.
- [13] arXiv:2403.18283 [pdf, ps, other]
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Title: PT-symmetric dynamical confinement: Fermi acceleration, quantum force and Berry phaseSubjects: Quantum Physics (quant-ph); Quantum Gases (cond-mat.quant-gas)
We consider a quantum particle under the dynamical confinement caused by PT-symmetric box with a moving wall. The latter is described in terms of the time-dependent Schr\"{o}dinger equation obeying the time-dependent PT-symmetric boundary conditions. The class of the functions, describing time-dependence of the wall's position and keeping the system as PT-symmetric is found. Physically observable characteristics, such as average kinetic energy and the average quantum force are calculated as a function of time. Also, geometric phase is calculated for the harmonically oscillating wall regime. Experimental realization of the proposed model is discussed.
- [14] arXiv:2403.18299 [pdf, other]
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Title: Scaling Enhancement of Photon Blockade in Output FieldsComments: 7 pages, 4 figuresSubjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Optics (physics.optics)
Photon blockade enhancement is an exciting and promising subject that has been well studied for photons in cavities. However, whether photon blockade can be enhanced in the output fields remains largely unexplored. We show that photon blockade can be greatly enhanced in the mixing output field of a nonlinear cavity and an auxiliary (linear) cavity, where no direct coupling between the nonlinear and auxiliary cavities is needed. We uncover a biquadratic scaling relation between the second-order correlation of the photons in the output field and intracavity nonlinear interaction strength, in contrast to a quadratic scaling relation for the photons in a nonlinear cavity. We identify that this scaling enhancement of photon blockade in the output field is induced by the destructive interference between two of the paths for two photons passing through the two cavities. We then extend the theory to the experimentally feasible Jaynes-Cummings model consisting of a two-level system strongly coupled to one of the two uncoupled cavities, and also predict a biquadratic scaling law in the mixing output field. Our proposed scheme is universal and can be extended to enhance blockade in other bosonic systems.
- [15] arXiv:2403.18324 [pdf, other]
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Title: Shaping entangled photons through thick scattering media using an advanced wave beaconSubjects: Quantum Physics (quant-ph); Optics (physics.optics)
Entangled photons provide transformative new paths in the fields of communication, sensing, and computing. However, when entangled photons propagate through a complex medium such as a biological tissue or a turbulent atmosphere, their correlations are scrambled. Using wavefront shaping to compensate for the scattering and retrieve the two-photon correlations is challenging due to the low signal-to-noise ratio of the two-photon signal. While previous works partly addressed this challenge by using feedback from a strong classical laser beam that co-propagates with the entangled photons, such methods frequently depend on assumptions about the complex medium, limiting the applicability of quantum wavefront shaping. In this work, we propose and demonstrate a new feedback mechanism that is inspired by Klyshko's advanced wave picture, in which the classical laser beam counter-propagates with one of the entangled photons and co-propagates with the other. The new Klyshko feedback allows compensation of scattering in thick samples and even in situations where each photon propagates through a different scattering medium. Since the advanced wave picture applies whenever optical reciprocity is valid, such Klyshko optimization can be utilized across a wide range of configurations, offering a robust and alignment-free setup. We therefore believe this protocol will open the door for real-world applications of quantum wavefront shaping.
- [16] arXiv:2403.18395 [pdf, other]
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Title: Effective Embedding of Integer Linear Inequalities for Variational Quantum AlgorithmsSubjects: Quantum Physics (quant-ph)
In variational quantum algorithms, constraints are usually added to the problem objective via penalty terms. For linear inequality constraints, this procedure requires additional slack qubits. Those extra qubits tend to blow up the search space and complicate the parameter landscapes to be navigated by the classical optimizers. In this work, we explore approaches to model linear inequalities for quantum algorithms without these drawbacks. More concretely, our main suggestion is to omit the slack qubits completely and evaluate the inequality classically during parameter tuning. We test our methods on QAOA as well as on Trotterized adiabatic evolution, and present empirical results. As a benchmark problem, we consider different instances of the multi-knapsack problem. Our results show that removing the slack bits from the circuit Hamiltonian and considering them only for the expectation value yields better solution quality than the standard approach. The tests have been carried out using problem sizes up to 26 qubits. Our methods can in principle be applied to any problem with linear inequality constraints, and are suitable for variational as well as digitized versions of adiabatic quantum computing.
- [17] arXiv:2403.18410 [pdf, other]
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Title: Chiral Virasoro algebra from a single wavefunctionComments: 60+20 pages, 28 figuresSubjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics - Theory (hep-th)
Chiral edges of 2+1D systems can have very robust emergent conformal symmetry. When the edge is purely chiral, the Hilbert space of low-energy edge excitations can form a representation of a single Virasoro algebra. We propose a method to systematically extract the generators of the Virasoro algebra from a single ground state wavefunction, using entanglement bootstrap and an input from the edge conformal field theory. We corroborate our construction by numerically verifying the commutation relations of the generators. We also study the unitary flows generated by these operators, whose properties (such as energy and state overlap) are shown numerically to agree with our analytical predictions.
- [18] arXiv:2403.18477 [pdf, ps, other]
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Title: Thermalization condition for non-Hermitian quantum systemsComments: 5 pages, 4 figures (main text), 3 pages (supplementary material)Subjects: Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech)
The application of the eigenstate thermalization hypothesis to non-Hermitian quantum systems has become one of the most important topics in dissipative quantum chaos, recently giving rise to intense debates. The process of thermalization is intricate, involving many time-evolution trajectories in the reduced Hilbert space of the system. By considering two different expansion forms of the density matrices adopted in the biorthogonal and right-state time evolutions, we have derived two versions of the Gorini-Kossakowski-Sudarshan-Lindblad master equations describing the non-Hermitian systems coupled to a bosonic heat bath in thermal equilibrium. By solving the equations, we have identified a sufficient condition for thermalization under both time evolutions, resulting in Boltzmann biorthogonal and right-eigenstate statistics, respectively. This finding implies that the recently proposed biorthogonal random matrix theory needs an appropriate revision. Moreover, we have exemplified the precise dynamics of thermalization and thermodynamic properties with test models.
- [19] arXiv:2403.18515 [pdf, other]
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Title: Autonomous Quantum Heat Engine Based on Non-Markovian Dynamics of an Optomechanical HamiltonianComments: Submitted to Nature Scientific ReportsSubjects: Quantum Physics (quant-ph)
We propose a recipe for demonstrating an autonomous quantum heat engine where the working fluid consists of a harmonic oscillator, the frequency of which is tuned by a driving mode. The working fluid is coupled two heat reservoirs each exhibiting a peaked power spectrum, a hot reservoir peaked at a higher frequency than the cold reservoir. Provided that the driving mode is initialized in a coherent state with a high enough amplitude and the parameters of the utilized optomechanical Hamiltonian and the reservoirs are appropriate, the driving mode induces an approximate Otto cycle for the working fluid and consequently its oscillation amplitude begins to increase in time. We build both an analytical and a non-Markovian quasiclassical model for this quantum heat engine and show that reasonably powerful coherent fields can be generated as the output of the quantum heat engine. This general theoretical proposal heralds the in-depth studies of quantum heat engines in the non-Markovian regime. Further, it paves the way for specific physical realizations, such as those in optomechanical systems, and for the subsequent experimental realization of an autonomous quantum heat engine.
- [20] arXiv:2403.18573 [pdf, ps, other]
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Title: Classifying symmetric and symmetry-broken spin chain phases with anomalous group actionsSubjects: Quantum Physics (quant-ph); Mathematical Physics (math-ph)
We consider the classification problem of quantum spin chains invariant under local decomposable group actions, covering matrix product unitaries (MPUs), using an operator algebraic approach. We focus on finite group symmetries hosting both symmetric and symmetry broken phases. The local-decomposable group actions we consider have a 3-cocycle class of the symmetry group associated to them. We derive invariants for our classification that naturally cover one-dimensional symmetry protected topological (SPT) phases. We prove that these invariants coincide with the ones of [J. Garre Rubio et al, Quantum 7, 927 (2023)] using matrix product states (MPSs) techniques, by explicitly working out the GNS representation of MPSs and MPUs, resulting in a useful dictionary between both approaches that could be of independent interest.
- [21] arXiv:2403.18581 [pdf, other]
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Title: Qubit teleportation between a memory-compatible photonic time-bin qubit and a solid-state quantum network nodeAuthors: Mariagrazia Iuliano, Marie-Christine Slater, Arian J. Stolk, Matthew J. Weaver, Tanmoy Chakraborty, Elsie Loukiantchenko, Gustavo Castro do Amaral, Nir Alfasi, Mariya O. Sholkina, Wolfgang Tittel, Ronald HansonSubjects: Quantum Physics (quant-ph)
We report on a quantum interface linking a diamond NV center quantum network node and 795nm photonic time-bin qubits compatible with Thulium and Rubidium quantum memories. The interface makes use of two-stage low-noise quantum frequency conversion and waveform shaping to match temporal and spectral photon profiles. Two-photon quantum interference shows high indistinguishability of (89.5 $\pm$ 1.9)% between converted 795nm photons and the native NV center photons. We use the interface to demonstrate quantum teleportation including real-time feedforward from an unbiased set of 795nm photonic qubit input states to the NV center spin qubit, achieving a teleportation fidelity of (75.5 $\pm$ 1.0)%. This proof-of-concept experiment shows the feasibility of interconnecting different quantum network hardware.
- [22] arXiv:2403.18585 [pdf, other]
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Title: Resonances crossing effect and quantum sensor of electric fieldsAuthors: Andrea SacchettiComments: 9 pages - 4 figures - 1 tableSubjects: Quantum Physics (quant-ph)
While the phenomenon of the exact crossing of energy levels is a rarely occurring event, in the case of quantum resonances associated with metastable states this phenomenon is much more frequent and various scenarios can occur. When there is an exact crossing of the imaginary parts of the resonances in a two-level quantum system subject to an external DC electric field, then a damped beating phenomenon occurs, which is absent if there is no such crossing. This fact, tested numerically on an explicit one-dimensional model, suggests the possibility of designing quantum sensors to determine in a very simple way whether the external field strength has an assigned value or not.
- [23] arXiv:2403.18586 [pdf, other]
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Title: Quantum backflow current in a ring: Optimal bounds and fractalityComments: 10 pages, 3 figuresSubjects: Quantum Physics (quant-ph)
The probability density of a quantum particle moving freely within a circular ring can exhibit local flow patterns inconsistent with its angular momentum, a phenomenon known as quantum backflow. In this study, we examine a quantum particle confined to a ring and prepared in a state composed of a fixed (yet arbitrary) number of lowest energy eigenstates with non-negative angular momentum. We investigate the time-dependent behavior of the probability current at a specified point along the ring's circumference. We establish precise lower and upper bounds for this probability current, thereby delineating the exact scope of the quantum backflow effect. We also present an analytical expression for a quantum state that yields a record-high backflow probability transfer, reaching over 95% of the theoretical bound. Furthermore, our investigation yields compelling numerical and analytical evidence supporting the conjecture that the current-versus-time function associated with states maximizing backflow probability transfer forms a fractal curve with a dimension of 7/4. The observed fractality may provide a characteristic, experimentally-relevant signature of quantum backflow near the probability-transfer bound.
- [24] arXiv:2403.18662 [pdf, other]
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Title: Benchmarking Quantum Generative Learning: A Study on Scalability and Noise Resilience using QUARKAuthors: Florian J. Kiwit, Maximilian A. Wolf, Marwa Marso, Philipp Ross, Jeanette M. Lorenz, Carlos A. Riofrío, Andre LuckowSubjects: Quantum Physics (quant-ph)
Quantum computing promises a disruptive impact on machine learning algorithms, taking advantage of the exponentially large Hilbert space available. However, it is not clear how to scale quantum machine learning (QML) to industrial-level applications. This paper investigates the scalability and noise resilience of quantum generative learning applications. We consider the training performance in the presence of statistical noise due to finite-shot noise statistics and quantum noise due to decoherence to analyze the scalability of QML methods. We employ rigorous benchmarking techniques to track progress and identify challenges in scaling QML algorithms, and show how characterization of QML systems can be accelerated, simplified, and made reproducible when the QUARK framework is used. We show that QGANs are not as affected by the curse of dimensionality as QCBMs and to which extent QCBMs are resilient to noise.
- [25] arXiv:2403.18676 [pdf, other]
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Title: Mollow-like triplets in ultra-fast resonant absorptionAuthors: Axel Stenquist, Felipe Zapata, Edvin Olofsson, Yijie Liao, Elna Sveborg, Jakob Nicolai Bruhnke, Claudio Verdozzi, Jan Marcus DahlströmComments: Article: 5 pages, 3 figures. Supplemental material: 6 pages, 5 figuresSubjects: Quantum Physics (quant-ph); Atomic Physics (physics.atom-ph)
We show that resonant absorption of smooth laser fields can yield Mollow-like triplet patterns. General conditions for such triplets are derived and illustrated with a super-Gaussian pulse sequence. Gaussian pulses can not exhibit triplets, super-Gaussian pulses can form triplets depending on the pulse area and flat-top pulses can produce absorption triplets after one Rabi cycle. Our results are compared side-by-side with resonance fluorescence to emphasize similarities and differences between these unlike observables. In the high-intensity limit, we show that the central absorption peak is asymmetric, which we attribute to non-linear photoionization, beyond two-level atomic physics.
- [26] arXiv:2403.18733 [pdf, other]
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Title: Light-cone feature selection for quantum machine learningSubjects: Quantum Physics (quant-ph)
Feature selection plays an essential role in improving the predictive performance and interpretability of trained models in classical machine learning. On the other hand, the usability of conventional feature selection could be limited for quantum machine learning tasks; the technique might not provide a clear interpretation on embedding quantum circuits for classical data tasks and, more importantly, is not applicable to quantum data tasks. In this work, we propose a feature selection method with a specific focus on quantum machine learning. Our scheme treats the light-cones (i.e., subspace) of quantum models as features and then select relevant ones through training of the corresponding local quantum kernels. We numerically demonstrate its versatility for four different applications using toy tasks: (1) feature selection of classical inputs, (2) circuit architecture search for data embedding, (3) compression of quantum machine learning models and (4) subspace selection for quantum data. The proposed framework paves the way towards applications of quantum machine learning to practical tasks. Also, this technique could be used to practically test if the quantum machine learning tasks really need quantumness, while it is beyond the scope of this work.
- [27] arXiv:2403.18753 [pdf, other]
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Title: General quantum resources provide advantages in work extraction tasksComments: 5+3 pages; 1 figureSubjects: Quantum Physics (quant-ph)
We provide a thermodynamic task to certify the general quantum resources of both states and channels via work extraction, showing that general quantum resources provide advantages in work extraction. Such work extraction tasks can be further applied to certify quantum entanglement in a one-sided device-independent way. As an application, we report a novel type of anomalous energy flow -- a type of locally extractable energy that is attributed to the globally distributed entanglement. Finally, we show that the existence of this novel anomalous energy flow is equivalent to measurement incompatibility.
- [28] arXiv:2403.18768 [pdf, other]
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Title: Efficient Generation of Multi-partite Entanglement between Non-local Superconducting Qubits using Classical FeedbackAuthors: Akel Hashim, Ming Yuan, Pranav Gokhale, Larry Chen, Christian Juenger, Neelay Fruitwala, Yilun Xu, Gang Huang, Liang Jiang, Irfan SiddiqiSubjects: Quantum Physics (quant-ph)
Quantum entanglement is one of the primary features which distinguishes quantum computers from classical computers. In gate-based quantum computing, the creation of entangled states or the distribution of entanglement across a quantum processor often requires circuit depths which grow with the number of entangled qubits. However, in teleportation-based quantum computing, one can deterministically generate entangled states with a circuit depth that is constant in the number of qubits, provided that one has access to an entangled resource state, the ability to perform mid-circuit measurements, and can rapidly transmit classical information. In this work, aided by fast classical FPGA-based control hardware with a feedback latency of only 150 ns, we explore the utility of teleportation-based protocols for generating non-local, multi-partite entanglement between superconducting qubits. First, we demonstrate well-known protocols for generating Greenberger-Horne-Zeilinger (GHZ) states and non-local CNOT gates in constant depth. Next, we utilize both protocols for implementing an unbounded fan-out (i.e., controlled-NOT-NOT) gate in constant depth between three non-local qubits. Finally, we demonstrate deterministic state teleportation and entanglement swapping between qubits on opposite side of our quantum processor.
- [29] arXiv:2403.18790 [pdf, other]
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Title: Squeezing below the ground state of motion of a continuously monitored levitating nanoparticleAuthors: Qiongyuan Wu, Diana Chisholm, Rafael Muffato, Tiberius Georgescu, Jack Homans, Hendrik Ulbricht, Matteo Carlesso, Mauro PaternostroComments: 12 pages, 4 figures, comments are welcome!Subjects: Quantum Physics (quant-ph)
Squeezing is a crucial resource for quantum information processing and quantum sensing. In levitated nanomechanics, squeezed states of motion can be generated via temporal control of the trapping frequency of a massive particle. However, the amount of achievable squeezing typically suffers from detrimental environmental effects. We analyze the performance of a scheme that, by embedding careful time-control of trapping potentials and fully accounting for the most relevant sources of noise -- including measurement backaction -- achieves significant levels of mechanical squeezing. The feasibility of our proposal, which is close to experimental state-of-the-art, makes it a valuable tool for quantum state engineering.
- [30] arXiv:2403.18793 [pdf, other]
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Title: Theory of quantum error mitigation for non-Clifford gatesSubjects: Quantum Physics (quant-ph)
Quantum error mitigation techniques mimic noiseless quantum circuits by running several related noisy circuits and combining their outputs in particular ways. How well such techniques work is thought to depend strongly on how noisy the underlying gates are. Weakly-entangling gates, like $R_{ZZ}(\theta)$ for small angles $\theta$, can be much less noisy than entangling Clifford gates, like CNOT and CZ, and they arise naturally in circuits used to simulate quantum dynamics. However, such weakly-entangling gates are non-Clifford, and are therefore incompatible with two of the most prominent error mitigation techniques to date: probabilistic error cancellation (PEC) and the related form of zero-noise extrapolation (ZNE). This paper generalizes these techniques to non-Clifford gates, and comprises two complementary parts. The first part shows how to effectively transform any given quantum channel into (almost) any desired channel, at the cost of a sampling overhead, by adding random Pauli gates and processing the measurement outcomes. This enables us to cancel or properly amplify noise in non-Clifford gates, provided we can first characterize such gates in detail. The second part therefore introduces techniques to do so for noisy $R_{ZZ}(\theta)$ gates. These techniques are robust to state preparation and measurement (SPAM) errors, and exhibit concentration and sensitivity--crucial features in many experiments. They are related to randomized benchmarking, and may also be of interest beyond the context of error mitigation. We find that while non-Clifford gates can be less noisy than related Cliffords, their noise is fundamentally more complex, which can lead to surprising and sometimes unwanted effects in error mitigation. Whether this trade-off can be broadly advantageous remains to be seen.
- [31] arXiv:2403.18813 [pdf, ps, other]
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Title: Equivalence Checking of Quantum Circuits by Model CountingSubjects: Quantum Physics (quant-ph)
Verifying equivalence between two quantum circuits is a hard problem, that is nonetheless crucial in compiling and optimizing quantum algorithms for real-world devices. This paper gives a Turing reduction of the (universal) quantum circuits equivalence problem to weighted model counting (WMC). Our starting point is a folklore theorem showing that equivalence checking of quantum circuits can be done in the so-called Pauli-basis. We combine this insight with a WMC encoding of quantum circuit simulation, which we extend with support for the Toffoli gate. Finally, we prove that the weights computed by the model counter indeed realize the reduction. With an open-source implementation, we demonstrate that this novel approach can outperform a state-of-the-art equivalence-checking tool based on ZX calculus and decision diagrams.
Cross-lists for Thu, 28 Mar 24
- [32] arXiv:2403.18102 (cross-list from math.CT) [pdf, ps, other]
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Title: The operadic theory of convexityComments: 42 pagesSubjects: Category Theory (math.CT); Information Theory (cs.IT); Quantum Physics (quant-ph)
In this article, we characterize convexity in terms of algebras over a PROP, and establish a tensor-product-like symmetric monoidal structure on the category of convex sets. Using these two structures, and the theory of $\scr{O}$-monoidal categories, we state and prove a Grothendieck construction for lax $\scr{O}$-monoidal functors into convex sets. We apply this construction to the categorical characterization of entropy of Baez, Fritz, and Leinster, and to the study of quantum contextuality in the framework of simplicial distributions.
- [33] arXiv:2403.18131 (cross-list from math.OC) [pdf, other]
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Title: Convergence of Iterative Quadratic Programming for Robust Fixed-Endpoint Transfer of Bilinear SystemsSubjects: Optimization and Control (math.OC); Quantum Physics (quant-ph)
We present a computational method for open-loop minimum-norm control synthesis for fixed-endpoint transfer of bilinear ensemble systems that are indexed by two continuously varying parameters. We suppose that one ensemble parameter scales the homogeneous, linear part of the dynamics, and the second parameter scales the effect of the applied control inputs on the inhomogeneous, bilinear dynamics. This class of dynamical systems is motivated by robust quantum control pulse synthesis, where the ensemble parameters correspond to uncertainty in the free Hamiltonian and inhomogeneity in the control Hamiltonian, respectively. Our computational method is based on polynomial approximation of the ensemble state in parameter space and discretization of the evolution equations in the time domain using a product of matrix exponentials corresponding to zero-order hold controls over the time intervals. The dynamics are successively linearized about control and trajectory iterates to formulate a sequence of quadratic programs for computing perturbations to the control that successively improve the objective until the iteration converges. We use a two-stage computation to first ensure transfer to the desired terminal state, and then minimize the norm of the control function. The method is demonstrated for the canonical uniform transfer problem for the Bloch system that appears in nuclear magnetic resonance, as well as the matter-wave splitting problem for the Raman-Nath system that appears in ultra-cold atom interferometry.
- [34] arXiv:2403.18263 (cross-list from hep-ex) [pdf, other]
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Title: New Constraints on Exotic Spin-Spin-Velocity-Dependent Interactions with Solid-State Quantum SensorsAuthors: Yue Huang, Hang Liang, Man Jiao, Pei Yu, Xiangyu Ye, Yijin Xie, Yi-Fu Cai, Chang-Kui Duan, Ya Wang, Xing Rong, Jiangfeng DuSubjects: High Energy Physics - Experiment (hep-ex); Quantum Physics (quant-ph)
We report new experimental results on exotic spin-spin-velocity-dependent interactions between electron spins. We designed an elaborate setup that is equipped with two nitrogen-vacancy (NV) ensembles in diamonds. One of the NV ensembles serves as the spin source, while the other functions as the spin sensor. By coherently manipulating the quantum states of two NV ensembles and their relative velocity at the micrometer scale, we are able to scrutinize exotic spin-spin-velocity-dependent interactions at short force ranges. For a T-violating interaction, $V_6$, new limits on the corresponding coupling coefficient, $f_6$, have been established for the force range shorter than 1 cm. For a P,T-violating interaction, $V_{14}$, new constraints on the corresponding coupling coefficient, $f_{14}$, have been obtained for the force range shorter than 1 km.
- [35] arXiv:2403.18303 (cross-list from cond-mat.mes-hall) [pdf, other]
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Title: Classical dynamics and semiclassical analysis of excitons in cuprous oxideComments: 16 pages, 10 figures, accepted for publication in Phys. Rev. BSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Chaotic Dynamics (nlin.CD); Quantum Physics (quant-ph)
Excitons, as bound states of electrons and holes, embody the solid state analogue of the hydrogen atom, whose quantum spectrum is explained within a classical framework by the Bohr-Sommerfeld atomic model. In a first hydrogenlike approximation the spectra of excitons are also well described by a Rydberg series, however, due to the surrounding crystal environment deviations from this series can be observed. A theoretical treatment of excitons in cuprous oxide needs to include the band structure of the crystal, leading to a prominent fine-structure splitting in the quantum spectra. This is achieved by introducing additional spin degrees of freedom into the system, making the existence and meaningfulness of classical exciton orbits in the physical system a non-trivial question. Recently, we have uncovered the contributions of periodic exciton orbits directly in the quantum mechanical recurrence spectra of cuprous oxide [J. Ertl et al., Phys. Rev. Lett. 129, 067401 (2022)] by application of a scaling technique and fixing the energy of the classical dynamics to a value corresponding to a principle quantum number $n=5$ in the hydrogenlike case. Here, we present a comprehensive derivation of the classical and semiclassical theory of excitons in cuprous oxide. In particular, we investigate the energy dependence of the exciton dynamics. Both the semiclassical and quantum mechanical recurrence spectra exhibit stronger deviations from the hydrogenlike behavior with decreasing energy, which is related to a growing influence of the spin-orbit coupling and thus a higher velocity of the secular motion of the exciton orbits. The excellent agreement between semiclassical and quantum mechanical exciton recurrence spectra demonstrates the validity of the classical and semiclassical approach to excitons in cuprous oxide.
- [36] arXiv:2403.18319 (cross-list from physics.atom-ph) [pdf, other]
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Title: Doppler-assisted quantum resonances through swappable excitation pathways in Potassium vaporComments: 16 pages, 11 figuresSubjects: Atomic Physics (physics.atom-ph); Optics (physics.optics); Quantum Physics (quant-ph)
We report the observation of two additional sub-natural line width quantum interference in the $D_2$ manifold of $^{39}K$ vapor, in addition to the usual single Electromagnetically induced transparency peak. The other two features appear exclusively because $^{39}K$ ground hyperfine splitting is smaller than the Doppler broadened absorption profile. This allows probe and control beams to swap their transition pathways. The control beam detuning captures the nature of the coherence, therefore an unusual phenomenon of conversion from perfect transparency to enhanced absorption is observed and explained by utilizing adiabatic elimination of the excited state in the Master equation. Controlling such dark and bright resonances leads to new applications in quantum technologies viz. frequency offset laser stabilization and long-lived quantum memory.
- [37] arXiv:2403.18394 (cross-list from cond-mat.str-el) [pdf, ps, other]
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Title: Vertex corrections to conductivity in the Holstein model: A numerical-analytical studyComments: main text: 28 pages, 12 figures; supplementary material: 13 pages, 5 figuresSubjects: Strongly Correlated Electrons (cond-mat.str-el); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Chemical Physics (physics.chem-ph); Quantum Physics (quant-ph)
The optical-conductivity profile carries information on electronic dynamics in interacting quantum many-body systems. Its computation is a formidable task that is usually approached by invoking the single-particle (bubble) approximation and neglecting the vertex corrections. Their importance remains elusive even in model Hamiltonian calculations. Here, we combine analytical arguments with our recent breakthroughs in numerically exact and approximate calculations of finite-temperature real-time correlation functions to thoroughly assess the importance of vertex corrections in the one-dimensional Holstein polaron model. We find, both analytically and numerically, vanishing vertex corrections to optical conductivity in the limits of zero electron--phonon interaction, zero electronic bandwidth, and infinite temperature. Furthermore, our numerical results show that vertex corrections to the electron mobility also vanish in many parameter regimes between these limits. In some of these cases, the vertex corrections still introduce important qualitative changes to the optical-conductivity profile in comparison to the bubble approximation even though the self-energy remains approximately local. We trace these changes back to the bubble approximation not fully capturing a time-limited slow-down of the electron on intermediate time scales between ballistic and diffusive transport. We find that the vertex corrections are overall most pronounced for intermediate electron--phonon interaction and may increase or decrease the bubble-approximation mobility depending on the values of model parameters.
- [38] arXiv:2403.18460 (cross-list from hep-th) [pdf, other]
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Title: Probing the quantum nature of gravity using a Bose-Einstein condensate; "Erste Abhandlung"Comments: 24 pages LATEX,comments are welcomeSubjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); Quantum Physics (quant-ph)
The effect of noise induced by gravitons has been investigated using a Bose-Einstein condensate. The gravitational wave perturbation is then considerd as a sum of discrete Fourier modes in the momentum space. Coming to an operatorial representation and quantizing the phase space variables via appropriately introduced canonincal commutation relations between the canonically conjugate variables corresponding to the graviton and bosonic part of the total system, one obtains a proper quantum gravity setup. Then we obtain the Bogoliubov coefficients from the solution of the time-dependent part of the pseudo-Goldstone boson and construct the covariance metric for the bosons initially being in a squeezed state. Using the stochastic average of the Fisher information, we obtain a lower bound on the amplitude parameter of the gravitational wave. As the entire calculation is done at zero temperature, the bosonic system, by construction, will behave as a Bose-Einstein condensate. For a Bose-Einstein condensate with a single mode, we observe that the lower bound of the expectation value of the square of the uncertainty in the amplitude measurement does not become infinite when the total observational term approaches zero. In order to sum over all possible momentum modes, we next consider a noise term with a suitable Gaussian weight factor which decays over time. We then obtain the lower bound on the final expectation value of the square of the variance in the amplitude parameter. Because of the noise induced by the graviton, there is a minimum value of the measurement time below which it is impossible to detect any gravitational wave using a Bose-Einstein condensate. Finally, we consider interaction between the phonon modes of the Bose-Einstein condensate which results in a decoherence. We observe that the decoherence effect becomes significant for gravitons with minimal squeezing.
- [39] arXiv:2403.18470 (cross-list from cond-mat.mes-hall) [pdf, other]
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Title: Generalized bulk-boundary correspondence in periodically driven non-Hermitian systemsComments: 29 pages,16 figures, Topical ReviewJournal-ref: J. Phys.: Condens. Matter 36,243001(2024)Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Quantum Physics (quant-ph)
We present a pedagogical review of the periodically driven non-Hermitian systems, particularly on the rich interplay between the non-Hermitian skin effect and the topology. We start by reviewing the non-Bloch band theory of the static non-Hermitian systems and discuss the establishment of its generalized bulk-boundary correspondence. Ultimately, we focus on the non-Bloch band theory of two typical periodically driven non-Hermitian systems: harmonically driven non-Hermitian system and periodically quenched non-Hermitian system. The non-Bloch topological invariants were defined on the generalized Brillouin zone and the real space wave functions to characterize the Floquet non-Hermtian topological phases. Then, the generalized bulk-boundary correspondence was established for the two typical periodically driven non-Hermitian systems. Additionally, we review novel phenomena in the higher-dimensional periodically driven non-Hermitian systems, including Floquet non-Hermitian higher-order topological phases and Floquet hybrid skin-topological modes. The experimental realizations and recent advances have also been surveyed. Finally, we end with a summarization and hope this pedagogical review can motivate further research on Floquet non-Hermtian topological physics.
- [40] arXiv:2403.18510 (cross-list from cond-mat.quant-gas) [pdf, other]
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Title: Observation of vortices in a dipolar supersolidAuthors: Eva Casotti, Elena Poli, Lauritz Klaus, Andrea Litvinov, Clemens Ulm, Claudia Politi, Manfred J. Mark, Thomas Bland, Francesca FerlainoComments: 14 pages, 9 figuresSubjects: Quantum Gases (cond-mat.quant-gas); Quantum Physics (quant-ph)
Supersolids are states of matter that spontaneously break two continuous symmetries: translational invariance due to the appearance of a crystal structure and phase invariance due to phase locking of single-particle wave functions, responsible for superfluid phenomena. While originally predicted to be present in solid helium, ultracold quantum gases provided a first platform to observe supersolids, with particular success coming from dipolar atoms. Phase locking in dipolar supersolids has been probed through e.g. measurements of the phase coherence and gapless Goldstone modes, but quantized vortices, a hydrodynamic fingerprint of superfluidity, have not yet been observed. Here, with the prerequisite pieces at our disposal, namely a method to generate vortices in dipolar gases and supersolids with two-dimensional crystalline order, we report on the theoretical investigation and experimental observation of vortices in the supersolid phase. Our work reveals a fundamental difference in vortex seeding dynamics between unmodulated and modulated quantum fluids. This opens the door to study the hydrodynamic properties of exotic quantum systems with multiple spontaneously broken symmetries, in disparate domains such as quantum crystals and neutron stars.
- [41] arXiv:2403.18523 (cross-list from cond-mat.quant-gas) [pdf, other]
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Title: Exact Solution of Bipartite Fluctuations in One-Dimensional FermionsComments: 17 pages, 6 figuresSubjects: Quantum Gases (cond-mat.quant-gas); Statistical Mechanics (cond-mat.stat-mech); Quantum Physics (quant-ph)
Emergence of hydrodynamics in quantum many-body systems has recently garnered growing interest. The recent experiment of ultracold atoms [J. F. Wienand et al., arXiv:2306.11457] studied emergent hydrodynamics in hard-core bosons using a bipartite fluctuation, which quantifies how the particle number fluctuates in a subsystem. In this Letter, we theoretically study the variance of a bipartite fluctuation in one-dimensional noninteracting fermionic dynamics starting from an alternating state, deriving the exact solution of the variance and its asymptotic linear growth law for the long-time dynamics. To compare the theoretical prediction with the experiment, we generalize our exact solution by incorporating the incompleteness of the initial alternating state, deriving the general linear growth law analytically. We find that it quantitatively describes the experimentally observed variance growth without any fitting parameters.
- [42] arXiv:2403.18617 (cross-list from math-ph) [pdf, ps, other]
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Title: Quantum concentration inequalities and equivalence of the thermodynamical ensembles: an optimal mass transport approachComments: 26 pagesSubjects: Mathematical Physics (math-ph); Quantum Physics (quant-ph)
We prove new concentration inequalities for quantum spin systems which apply to any local observable measured on any product state or on any state with exponentially decaying correlations. Our results do not require the spins to be arranged in a regular lattice, and cover the case of observables that contain terms acting on spins at arbitrary distance. Moreover, we introduce a local W1 distance, which quantifies the distinguishability of two states with respect to local observables. We prove a transportation-cost inequality stating that the local W1 distance between a generic state and a state with exponentially decaying correlations is upper bounded by a function of their relative entropy. Finally, we apply such inequality to prove the equivalence between the canonical and microcanonical ensembles of quantum statistical mechanics and the weak eigenstate thermalization hypothesis for the Hamiltonians whose Gibbs states have exponentially decaying correlations.
- [43] arXiv:2403.18677 (cross-list from cond-mat.quant-gas) [pdf, other]
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Title: A blue repulsive potential for dysprosium Bose-Einstein condensatesAuthors: Niccolò Preti, Nicolò Antolini, Giulio Biagioni, Andrea Fioretti, Giovanni Modugno, Luca Tanzi, Carlo GabbaniniComments: 7 pages, 8 figuresSubjects: Quantum Gases (cond-mat.quant-gas); Atomic Physics (physics.atom-ph); Quantum Physics (quant-ph)
Short-wavelength repulsive potentials for quantum gases allow to realize new systems and to study new phenomena. Here we report the realization of repulsive optical potentials for dysprosium atoms in the blue region of the spectrum, at wavelengths close to 400 nm. We employ a spectrallyfiltered diode laser system to measure both scalar and tensorial components of the polarizability of dysprosium, which we find in good agreement with the theoretical predictions. We demonstrate the implementation of potential strengths appropriate to manipulate Bose-Einstein condensates, with scattering-limited lifetimes exceeding one second. This type of optical potentials opens interesting directions for the study of dipolar superfluids and supersolids.
- [44] arXiv:2403.18683 (cross-list from cond-mat.quant-gas) [pdf, other]
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Title: Exploring the Berezinskii-Kosterlitz-Thouless Transition in a Two-dimensional Dipolar Bose GasComments: 8 pages, 4 figues, supplementary informationSubjects: Quantum Gases (cond-mat.quant-gas); Other Condensed Matter (cond-mat.other); Quantum Physics (quant-ph)
Long-range and anisotropic dipolar interactions induce complex order in quantum systems. It becomes particularly interesting in two-dimension (2D), where the superfluidity with quasi-long-range order emerges via Berezinskii-Kosterlitz-Thouless (BKT) mechanism, which still remains elusive with dipolar interactions. Here, we observe the BKT transition from a normal gas to the superfluid phase in a quasi-2D dipolar Bose gas of erbium atoms. Controlling the orientation of dipoles, we characterize the transition point by monitoring extended coherence and measuring the equation of state. This allows us to gain a systematic understanding of the BKT transition based on an effective short-range description of dipolar interaction in 2D. Additionally, we observe anisotropic density fluctuations and non-local effects in the superfluid regime, which establishes the dipolar nature of the 2D superfluid. Our results lay the ground for understanding the behavior of dipolar bosons in 2D and open up opportunities for examining complex orders in a dipolar superfluid.
- [45] arXiv:2403.18691 (cross-list from cond-mat.stat-mech) [pdf, other]
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Title: Building defect conformal field theory from the Sachdev-Ye-Kitaev interactionsComments: 15 pages, 6 figuresSubjects: Statistical Mechanics (cond-mat.stat-mech); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics - Theory (hep-th); Quantum Physics (quant-ph)
The coupling between defects and extended critical degrees of freedom gives rise to the intriguing theory known as defect conformal field theory (CFT). In this work, we introduce a novel family of boundary and interface CFTs by coupling $N$ Majorana chains with SYK$_q$ interactions at the defect. Our analysis reveals that the interaction with $q=2$ constitutes a new marginal defect. Employing a versatile saddle point method, we compute unique entanglement characterizations, including the $g$-function and effective central charge, of the defect CFT. Furthermore, we analytically evaluate the transmission coefficient using CFT techniques. Surprisingly, the transmission coefficient deviates from the universal relation with the effective central charge across the defect at the large $N$ limit, suggesting that our defect CFT extends beyond all known examples of Gaussian defect CFT.
- [46] arXiv:2403.18716 (cross-list from cs.CR) [pdf, other]
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Title: Statistical testing of random number generators and their improvement using randomness extractionComments: 20+10 pages, 8 figures and 28 tables. Comments are welcome!Subjects: Cryptography and Security (cs.CR); Quantum Physics (quant-ph)
Random number generators (RNGs) are notoriously hard to build and test, especially in a cryptographic setting. Although one cannot conclusively determine the quality of an RNG by testing the statistical properties of its output alone, running numerical tests is both a powerful verification tool and the only universally applicable method. In this work, we present and make available a comprehensive statistical testing environment (STE) that is based on existing statistical test suites. The STE can be parameterised to run lightweight (i.e. fast) all the way to intensive testing, which goes far beyond what is required by certification bodies. With it, we benchmark the statistical properties of several RNGs, comparing them against each other. We then present and implement a variety of post-processing methods, in the form of randomness extractors, which improve the RNG's output quality under different sets of assumptions and analyse their impact through numerical testing with the STE.
- [47] arXiv:2403.18801 (cross-list from math-ph) [pdf, other]
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Title: Nonstandard Lagrangians and branched Hamiltonians: A brief reviewComments: Preliminary version, comments are welcomeSubjects: Mathematical Physics (math-ph); Exactly Solvable and Integrable Systems (nlin.SI); Classical Physics (physics.class-ph); Quantum Physics (quant-ph)
Time and again, non-conventional forms of Lagrangians have found attention in the literature. For one thing, such Lagrangians have deep connections with several aspects of nonlinear dynamics including specifically the types of the Li\'{e}nard class; for another, very often the problem of their quantization opens up multiple branches of the corresponding Hamiltonians, ending up with the presence of singularities in the associated eigenfunctions. In this article, we furnish a brief review of the classical theory of such Lagrangians and the associated branched Hamiltonians, starting with the example of Li\'{e}nard-type systems. We then take up other cases where the Lagrangians depend upon the velocity with powers greater than two while still having a tractable mathematical structure, while also describing the associated branched Hamiltonians for such systems. For various examples, we emphasize upon the emergence of the notion of momentum-dependent mass in the theory of branched Hamiltonians.
- [48] arXiv:2403.18812 (cross-list from cs.DS) [pdf, other]
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Title: On the Communication Complexity of Approximate Pattern MatchingComments: 62 pages; abstract shortenedSubjects: Data Structures and Algorithms (cs.DS); Quantum Physics (quant-ph)
The decades-old Pattern Matching with Edits problem, given a length-$n$ string $T$ (the text), a length-$m$ string $P$ (the pattern), and a positive integer $k$ (the threshold), asks to list all fragments of $T$ that are at edit distance at most $k$ from $P$. The one-way communication complexity of this problem is the minimum amount of space needed to encode the answer so that it can be retrieved without accessing the input strings $P$ and $T$.
The closely related Pattern Matching with Mismatches problem (defined in terms of the Hamming distance instead of the edit distance) is already well understood from the communication complexity perspective: Clifford, Kociumaka, and Porat [SODA 2019] proved that $\Omega(n/m \cdot k \log(m/k))$ bits are necessary and $O(n/m \cdot k\log (m|\Sigma|/k))$ bits are sufficient; the upper bound allows encoding not only the occurrences of $P$ in $T$ with at most $k$ mismatches but also the substitutions needed to make each $k$-mismatch occurrence exact.
Despite recent improvements in the running time [Charalampopoulos, Kociumaka, and Wellnitz; FOCS 2020 and 2022], the communication complexity of Pattern Matching with Edits remained unexplored, with a lower bound of $\Omega(n/m \cdot k\log(m/k))$ bits and an upper bound of $O(n/m \cdot k^3\log m)$ bits stemming from previous research. In this work, we prove an upper bound of $O(n/m \cdot k \log^2 m)$ bits, thus establishing the optimal communication complexity up to logarithmic factors. We also show that $O(n/m \cdot k \log m \log (m|\Sigma|))$ bits allow encoding, for each $k$-error occurrence of $P$ in $T$, the shortest sequence of edits needed to make the occurrence exact.
We leverage the techniques behind our new result on the communication complexity to obtain quantum algorithms for Pattern Matching with Edits.
Replacements for Thu, 28 Mar 24
- [49] arXiv:2112.15469 (replaced) [pdf, other]
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Title: Polariton Creation in Coupled Cavity Arrays with Spectrally Disordered EmittersAuthors: Jesse Patton, Victoria A. Norman, Eliana C. Mann, Brinda Puri, Richard T. Scalettar, Marina RadulaskiSubjects: Quantum Physics (quant-ph); Strongly Correlated Electrons (cond-mat.str-el); Optics (physics.optics)
- [50] arXiv:2202.11386 (replaced) [pdf, other]
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Title: Addition and Differentiation of ZX-diagramsSubjects: Quantum Physics (quant-ph)
- [51] arXiv:2306.06004 (replaced) [pdf, other]
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Title: Unraveling a cavity induced molecular polarization mechanism from collective vibrational strong couplingAuthors: Dominik Sidler, Thomas Schnappinger, Anatoly Obzhirov, Michael Ruggenthaler, Markus Kowalewski, Angel RubioSubjects: Quantum Physics (quant-ph); Materials Science (cond-mat.mtrl-sci); Chemical Physics (physics.chem-ph)
- [52] arXiv:2306.12862 (replaced) [pdf, other]
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Title: Optimization tools for distance-preserving flag fault-tolerant error correctionComments: 33 pages, 18 figures. v2: minor correction. v3: added analysis on memory footprint saving and numerical simulation on the effect of idling noise. v4: minor correctionSubjects: Quantum Physics (quant-ph)
- [53] arXiv:2307.05656 (replaced) [pdf, other]
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Title: Universal stability of coherently diffusive 1D systems with respect to decoherenceAuthors: F. S. Lozano-Negro, E. Alvarez Navarro, N. C. Chávez, F. Mattiotti, F. Borgonovi, H. M. Pastawski, G. L. CelardoComments: Main: 7 pages, 3 figures. Appendix: 15 pages, 10 figuresSubjects: Quantum Physics (quant-ph)
- [54] arXiv:2307.10147 (replaced) [pdf, other]
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Title: Tangling schedules eases hardware connectivity requirements for quantum error correctionComments: 36 pages, 26 figures. Main changes: Added 2 more figures, added more explanation in some sectionsSubjects: Quantum Physics (quant-ph)
- [55] arXiv:2307.12599 (replaced) [pdf, other]
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Title: Characteristics, Implementation and Applications of Special Perfect Entangler CircuitsComments: 11 pages, comments are welcomeSubjects: Quantum Physics (quant-ph)
- [56] arXiv:2309.14411 (replaced) [pdf, other]
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Title: Signatures of Parafermion Zero Modes in Fractional Quantum Hall-Superconductor HeterostructuresComments: v1: 6 pages, 4 figures; v2: 8 pages, 5 figures, appendix addedSubjects: Strongly Correlated Electrons (cond-mat.str-el); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Superconductivity (cond-mat.supr-con); Quantum Physics (quant-ph)
- [57] arXiv:2310.07058 (replaced) [pdf, other]
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Title: Ion Trap with In-Vacuum High Numerical Aperture Imaging for a Dual-Species Modular Quantum ComputerAuthors: Allison L. Carter, Jameson O'Reilly, George Toh, Sagnik Saha, Mikhail Shalaev, Isabella Goetting, Christopher MonroeComments: 9 pages, 6 figures, published versionJournal-ref: Rev. Sci. Instrum. 95, 033201 (2024)Subjects: Quantum Physics (quant-ph); Atomic Physics (physics.atom-ph)
- [58] arXiv:2310.15103 (replaced) [pdf, other]
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Title: Emulating moiré materials with quasiperiodic circuit quantum electrodynamicsComments: 11 pages, 5 figuresSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Superconductivity (cond-mat.supr-con); Quantum Physics (quant-ph)
- [59] arXiv:2310.16709 (replaced) [pdf, other]
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Title: Sampling reduced density matrix to extract fine levels of entanglement spectrumSubjects: Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics - Theory (hep-th)
- [60] arXiv:2310.20432 (replaced) [pdf, other]
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Title: Demonstration of a parity-time symmetry breaking phase transition using superconducting and trapped-ion qutritsAuthors: Alena S. Kazmina, Ilia V. Zalivako, Alexander S. Borisenko, Nikita A. Nemkov, Anastasiia S. Nikolaeva, Ilya A. Simakov, Arina V. Kuznetsova, Elena Yu. Egorova, Kristina P. Galstyan, Nikita V. Semenin, Andrey E. Korolkov, Ilya N. Moskalenko, Nikolay N. Abramov, Ilya S. Besedin, Daria A. Kalacheva, Viktor B. Lubsanov, Aleksey N. Bolgar, Evgeniy O. Kiktenko, Ksenia Yu. Khabarova, Alexey Galda, Ilya A. Semerikov, Nikolay N. Kolachevsky, Nataliya Maleeva, Aleksey K. FedorovComments: 20 pages, 10 figuresJournal-ref: Phys. Rev. A 109, 032619 (2024)Subjects: Quantum Physics (quant-ph)
- [61] arXiv:2311.03353 (replaced) [pdf, other]
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Title: Topological Orders Beyond Topological Quantum Field TheoriesComments: 14 pages, 4 figuresSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Strongly Correlated Electrons (cond-mat.str-el); Quantum Physics (quant-ph)
- [62] arXiv:2311.15801 (replaced) [pdf, other]
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Title: Quantum magnetometry using discrete-time quantum walkComments: 11 pages, 8 figuresJournal-ref: Phys. Rev. A **109**, 032608 (2024)Subjects: Quantum Physics (quant-ph)
- [63] arXiv:2311.18325 (replaced) [pdf, other]
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Title: Non-Hermitian second-order topological superconductorsComments: 8 pages, 5 figuresJournal-ref: Phys.Rev.B 109,125420(2024)Subjects: Superconductivity (cond-mat.supr-con); Quantum Physics (quant-ph)
- [64] arXiv:2312.00649 (replaced) [pdf, other]
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Title: Robustness of Quantum Chaos and Anomalous Relaxation in Open Quantum CircuitsComments: 13 pages, 8 figures. v2: expanded discussion and numerical resultsSubjects: Statistical Mechanics (cond-mat.stat-mech); Disordered Systems and Neural Networks (cond-mat.dis-nn); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics - Theory (hep-th); Quantum Physics (quant-ph)
- [65] arXiv:2312.01590 (replaced) [pdf, other]
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Title: Quantum search algorithm on weighted databasesComments: 5 pages, 4 figuresSubjects: Quantum Physics (quant-ph)
- [66] arXiv:2312.06764 (replaced) [pdf, other]
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Title: Dimensional Reduction in Quantum OpticsComments: V2: updated to match published version, 35 pages (14 pages of appendix), 8 figures, RevTex 4.2Journal-ref: Phys. Rev. Res. 6, 013285 (2024)Subjects: Quantum Physics (quant-ph); Atomic Physics (physics.atom-ph)
- [67] arXiv:2401.14101 (replaced) [pdf, other]
- [68] arXiv:2401.15067 (replaced) [pdf, other]
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Title: Universality conditions of unified classical and quantum reservoir computingComments: 13 pages, 1 figureSubjects: Quantum Physics (quant-ph); Computational Physics (physics.comp-ph)
- [69] arXiv:2402.04628 (replaced) [pdf, other]
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Title: Distinguishing pure and thermal states by Landauer's principle in open systemsAuthors: Hao XuComments: 15 pages, 1 figure; v2: minor corrections, accepted by EPJCSubjects: Quantum Physics (quant-ph); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
- [70] arXiv:2403.02022 (replaced) [pdf, other]
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Title: Heat and Work in Quantum Thermodynamics: a Cybernetic ApproachComments: 9 pages, 3 figuresSubjects: Quantum Physics (quant-ph)
- [71] arXiv:2403.03283 (replaced) [pdf, other]
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Title: Deterministic Bethe state preparationComments: 12 pages + supplementary material; v2: minor improvementsSubjects: Quantum Physics (quant-ph)
- [72] arXiv:2403.08742 (replaced) [pdf, other]
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Title: Multichannel quantum defect theory of strontium bound Rydberg statesSubjects: Atomic Physics (physics.atom-ph); Quantum Physics (quant-ph)
- [73] arXiv:2403.09514 (replaced) [pdf, other]
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Title: Quantum Fourier Transform using Dynamic CircuitsComments: 4 pages, 2 figures (main text) + 4 pages, 2 figures (appendix)Subjects: Quantum Physics (quant-ph)
- [74] arXiv:2403.09944 (replaced) [pdf, other]
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Title: Markovian and non-Markovian master equations versus an exactly solvable model of a qubit in a cavityComments: 28 pages, 9 figures. v2: added new referencesSubjects: Quantum Physics (quant-ph); Other Condensed Matter (cond-mat.other)
- [75] arXiv:2403.13634 (replaced) [pdf, ps, other]
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Title: A Secure Quantum Key Distribution Protocol Using Two-Particle TransmissionComments: 14 pages, revised version to improve claritySubjects: Quantum Physics (quant-ph)
- [76] arXiv:2403.17029 (replaced) [pdf, ps, other]
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Title: Relativistic exponential-type spinor orbitals and their use in many-electron Dirac equation solutionAuthors: Ali BagciComments: 11Subjects: Quantum Physics (quant-ph)
- [77] arXiv:2403.17794 (replaced) [pdf, other]
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Title: Fermihedral: On the Optimal Compilation for Fermion-to-Qubit EncodingJournal-ref: ASPLOS 2024Subjects: Quantum Physics (quant-ph); Emerging Technologies (cs.ET)
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