Quantum mechanics challenges our intuition on the cause-effect relations in nature. Some fundamental concepts, including Reichenbach’s common cause principle or the notion of local realism, have to be reconsidered. Traditionally, this is witnessed by the violation of a Bell inequality. But are Bell ...

[Phys. Rev. Lett. 125, 230401] Published Wed Dec 02, 2020

]]>Measurements serve as the intermediate communication layer between the quantum world and our classical perception. So, the question of which measurements efficiently extract information from quantum systems is of central interest. Using quantum steering as a nonclassical phenomenon, we show that the...

[Phys. Rev. Lett. 125, 230402] Published Wed Dec 02, 2020

]]>Quantum teleportation provides a way to transmit unknown quantum states from one location to another. In the quantum world, multilevel systems which enable high-dimensional systems are more prevalent. Therefore, to completely rebuild the quantum states of a single particle remotely, one needs to tel...

[Phys. Rev. Lett. 125, 230501] Published Wed Dec 02, 2020

]]>Starting from the quantum-phase-estimate (QPE) algorithm, a method is proposed to construct entangled states that describe correlated many-body systems on quantum computers. Using operators for which the discrete set of eigenvalues is known, the QPE approach is followed by measurements that serve as...

[Phys. Rev. Lett. 125, 230502] Published Wed Dec 02, 2020

]]>We study the far from equilibrium prethermal dynamics of magnons in Heisenberg ferromagnets. We show that such systems exhibit universal self-similar scaling in momentum and time of the quasiparticle distribution function, with the scaling exponents independent of microscopic details or initial cond...

[Phys. Rev. Lett. 125, 230601] Published Wed Dec 02, 2020

]]>I identify a fundamental difference between classical and quantum dynamics in the linear response regime by showing that the latter is, in general, contextual. This allows me to provide an example of a quantum engine whose favorable power output scaling *unavoidably* requires nonclassical effects in t...

[Phys. Rev. Lett. 125, 230603] Published Wed Dec 02, 2020

]]>The gap of the Liouvillian spectrum gives the asymptotic decay rate of a quantum dissipative system, and therefore its inverse has been identified as the slowest relaxation time. Contrary to this common belief, we show that the relaxation time due to diffusive transports in a boundary dissipated man...

[Phys. Rev. Lett. 125, 230604] Published Wed Dec 02, 2020

]]>We present a class of Hamiltonians $H$ for which a sector of the Hilbert space invariant under a Lie group $G$, which is not a symmetry of $H$, possesses the essential properties of many-body scar states. These include the absence of thermalization and the “revivals” of special initial states in time evol...

[Phys. Rev. Lett. 125, 230602] Published Tue Dec 01, 2020

]]>We introduce a model of trapped bosons with contact interactions as well as Coulomb repulsion or gravitational attraction in one spatial dimension. We find the exact ground-state energy and many-body wave function. The density profile and the pair-correlation function are sampled using Monte Carlo m...

[Phys. Rev. Lett. 125, 220602] Published Wed Nov 25, 2020

]]>We study a class of two-dimensional models of classical hard-core particles with Vicsek type “exchange interaction” that aligns the directions of motion of nearby particles. By extending the Hohenberg-Mermin-Wagner theorem for the absence of spontaneous magnetization and the McBryan-Spencer bound fo...

[Phys. Rev. Lett. 125, 220601] Published Mon Nov 23, 2020

]]>Matrix product states and projected entangled pair states (PEPS) are powerful analytical and numerical tools to assess quantum many-body systems in one and higher dimensions, respectively. While matrix product states are comprehensively understood, in PEPS fundamental questions, relevant analyticall...

[Phys. Rev. Lett. 125, 210504] Published Fri Nov 20, 2020

]]>We report long coherence times (up to 300 ms) for near-surface bismuth donor electron spins in silicon coupled to a superconducting microresonator, biased at a clock transition. This enables us to demonstrate the partial absorption of a train of weak microwave fields in the spin ensemble, their stor...

[Phys. Rev. Lett. 125, 210505] Published Fri Nov 20, 2020

]]>Measurement-driven transitions between extensive and subextensive scaling of the entanglement entropy receive interest as they illuminate the intricate physics of thermalization and control in open interacting quantum systems. While this transition is well established for stroboscopic measurements i...

[Phys. Rev. Lett. 125, 210602] Published Fri Nov 20, 2020

]]>We propose a hybrid quantum-classical atomic clock where the interrogation of atoms prepared in a spin-coherent (or weakly squeezed) state is used to feed back one or more highly spin-squeezed atomic states toward their optimal phase-sensitivity point. The hybrid clock overcomes the stability of a s...

[Phys. Rev. Lett. 125, 210503] Published Thu Nov 19, 2020

]]>The finite-time dynamics, apart from its fundamental importance in nonequilibrium thermodynamics, is of great significance in designing heat engine cycles. We build an experimental apparatus to test the predicted long-time $1/\tau $ scaling of the irreversible entropy generation in the finite-time ($\tau $) the...

[Phys. Rev. Lett. 125, 210601] Published Thu Nov 19, 2020

]]>Quantum resources shared by spacelike separated parties are subsumed into a unified framework.

[Phys. Rev. Lett. 125, 210402] Published Tue Nov 17, 2020

]]>Quantum no-cloning, the impossibility of perfectly cloning an arbitrary unknown quantum state, is one of the most fundamental limitations due to the laws of quantum mechanics, which underpin the physical security of quantum key distribution. Quantum physics does allow, however, approximate cloning w...

[Phys. Rev. Lett. 125, 210502] Published Tue Nov 17, 2020

]]>When an observable is measured on an evolving coherent quantum system twice, the first measurement generally alters the statistics of the second one, which is known as measurement backaction. We introduce, and push to its theoretical and experimental limits, a novel method of backaction evasion, whe...

[Phys. Rev. Lett. 125, 210401] Published Mon Nov 16, 2020

]]>Using a gate-learning protocol, it is shown how the number of qubits required to store an optimal quantum program scales with the desired accuracy of the implementation.

[Phys. Rev. Lett. 125, 210501] Published Mon Nov 16, 2020

]]>Bell inequalities are central tools for studying nonlocal correlations and their applications in quantum information processing. Identifying inequalities for many particles or measurements is, however, difficult due to the computational complexity of characterizing the set of local correlations. We ...

[Phys. Rev. Lett. 125, 200401] Published Fri Nov 13, 2020

]]>The ${\mathbb{Z}}_{2}\times {\mathbb{Z}}_{2}$ symmetry-protected topological (SPT) phase hosts a robust boundary qubit at zero temperature. At finite energy density, the SPT phase is destroyed and bulk observables equilibrate in finite time. Nevertheless, we predict parametric regimes in which the boundary qubit survives to arbitraril...

[Phys. Rev. Lett. 125, 200506] Published Fri Nov 13, 2020

]]>Quasicrystals are long-range ordered but not periodic, representing an interesting middle ground between order and disorder. We experimentally and numerically study the localization transition in the ground state of noninteracting and weakly interacting bosons in an eightfold symmetric quasicrystall...

[Phys. Rev. Lett. 125, 200604] Published Fri Nov 13, 2020

]]>We show that continuous quantum nondemolition (QND) measurement of an atomic ensemble is able to improve the precision of frequency estimation even in the presence of independent dephasing acting on each atom. We numerically simulate the dynamics of an ensemble with up to $N=150$ atoms initially prepa...

[Phys. Rev. Lett. 125, 200505] Published Thu Nov 12, 2020

]]>Potts spin systems play a fundamental role in statistical mechanics and quantum field theory and can be studied within the spin, the Fortuin–Kasteleyn (FK) bond or the $q$-flow (loop) representation. We introduce a Loop-Cluster (LC) joint model of bond-occupation variables interacting with $q$-flow vari...

[Phys. Rev. Lett. 125, 200603] Published Thu Nov 12, 2020

]]>We propose a method for detecting bipartite entanglement in a many-body mixed state based on estimating moments of the partially transposed density matrix. The estimates are obtained by performing local random measurements on the state, followed by postprocessing using the classical shadows framewor...

[Phys. Rev. Lett. 125, 200501] Published Wed Nov 11, 2020

]]>Entanglement plays a central role in quantum information processing and quantum physics. However, few effective ways are known to detect the amount of entanglement of an unknown quantum state. Here, we propose a scheme to estimate the entanglement negativity for any bipartition of a composite system...

[Phys. Rev. Lett. 125, 200502] Published Wed Nov 11, 2020

]]>For building a scalable quantum processor with superconducting qubits, $ZZ$ interaction is of great concern because its residual has a crucial impact to two-qubit gate fidelity. Two-qubit gates with fidelity meeting the criterion of fault-tolerant quantum computation have been demonstrated using $ZZ$ in...

[Phys. Rev. Lett. 125, 200503] Published Wed Nov 11, 2020

]]>Mitigating crosstalk errors, whether classical or quantum mechanical, is critically important for achieving high-fidelity entangling gates in multiqubit circuits. For weakly anharmonic superconducting qubits, unwanted $ZZ$ interactions can be suppressed by combining qubits with opposite anharmonicity....

[Phys. Rev. Lett. 125, 200504] Published Wed Nov 11, 2020

]]>Recent research has considered the stochastic thermodynamics of multiple interacting systems, representing the overall system as a Bayes net. I derive fluctuation theorems governing the entropy production (EP) of arbitrary sets of the systems in such a Bayes net. I also derive “conditional” fluctuat...

[Phys. Rev. Lett. 125, 200602] Published Tue Nov 10, 2020

]]>We study the decay rate $\theta (a)$ that characterizes the late time exponential decay of the first-passage probability density ${F}_{a}(t|0)\sim {e}^{-\theta (a)t}$ of a diffusing particle in a one dimensional confining potential $U(x)$, starting from the origin, to a position located at $a>0$. For general confining potential $U...$

[Phys. Rev. Lett. 125, 200601] Published Mon Nov 09, 2020

]]>Entangled resources enable quantum sensing that achieves Heisenberg scaling, a quadratic improvement on the standard quantum limit, but preparing large $N$ spin entangled states is challenging in the presence of decoherence. We present a quantum control strategy using highly nonlinear geometric phase ...

[Phys. Rev. Lett. 125, 190403] Published Fri Nov 06, 2020

]]>We extend to quenched-disordered systems the variational scheme for real-space renormalization group calculations that we recently introduced for homogeneous spin Hamiltonians. When disorder is present our approach gives access to the flow of the renormalized Hamiltonian distribution, from which one...

[Phys. Rev. Lett. 125, 190601] Published Tue Nov 03, 2020

]]>At low temperature, collective excitations of one-dimensional (1D) interacting fermions exhibit spin-charge separation, a unique feature predicted by the Tomonaga-Luttinger liquid (TLL) theory, but a rigorous understanding remains challenging. Using the thermodynamic Bethe ansatz (TBA) formalism, we...

[Phys. Rev. Lett. 125, 190401] Published Mon Nov 02, 2020

]]>Quantum cellular automata are unitary maps that preserve locality and respect causality. We identify them, in any dimension, with simple tensor networks (projected entangled pair unitary) whose bond dimension does not grow with the system size. As a result, they satisfy an area law for the entanglem...

[Phys. Rev. Lett. 125, 190402] Published Mon Nov 02, 2020

]]>Unlike the entanglement of quantum states, very little is known about the entanglement of bipartite channels, called dynamical entanglement. Here we work with the partial transpose of a superchannel, and use it to define computable measures of dynamical entanglement, such as the negativity. We show ...

[Phys. Rev. Lett. 125, 180505] Published Fri Oct 30, 2020

]]>We introduce and study a novel class of sensors whose sensitivity grows exponentially with the size of the device. Remarkably, this drastic enhancement does not rely on any fine-tuning, but is found to be a stable phenomenon immune to local perturbations. Specifically, the physical mechanism behind ...

[Phys. Rev. Lett. 125, 180403] Published Thu Oct 29, 2020

]]>We explore the relationship between symmetrization and entanglement through measurements on few-particle systems in a multiwell potential. In particular, considering two or three trapped atoms, we measure and distinguish correlations arising from two different physical origins: antisymmetrization of...

[Phys. Rev. Lett. 125, 180402] Published Wed Oct 28, 2020

]]>Spectroscopy is an important tool for probing the properties of materials, chemicals, and biological samples. We design a practical transmitter-receiver system that exploits entanglement to achieve a provable quantum advantage over all spectroscopic schemes based on classical sources. To probe the a...

[Phys. Rev. Lett. 125, 180502] Published Wed Oct 28, 2020

]]>Quantum correlations in observables of multiple systems not only are of fundamental interest, but also play a key role in quantum information processing. As a signature of these correlations, the violation of Bell inequalities has not been demonstrated with multipartite hybrid entanglement involving...

[Phys. Rev. Lett. 125, 180503] Published Wed Oct 28, 2020

]]>The current understanding of aging phenomena is mainly confined to the study of systems with short-ranged interactions. Little is known about the aging of long-ranged systems. Here, the aging in the phase-ordering kinetics of the two-dimensional Ising model with power-law long-range interactions is ...

[Phys. Rev. Lett. 125, 180601] Published Wed Oct 28, 2020

]]>We introduce an equation for density matrices that ensures a monotonic decrease of the free energy and reaches a fixed point at the Gibbs thermal. We build a variational approach for many-body systems that can be applied to a broad class of states, including all bosonic and fermionic Gaussian, as we...

[Phys. Rev. Lett. 125, 180602] Published Wed Oct 28, 2020

]]>We study how perturbations affect dynamics of integrable many-body quantum systems, causing transition from integrability to chaos. Looking at spin transport in the Heisenberg chain with impurities we find that in the thermodynamic limit transport gets diffusive already at an infinitesimal perturbat...

[Phys. Rev. Lett. 125, 180605] Published Wed Oct 28, 2020

]]>We have implemented a Walsh-Hadamard gate, which performs a quantum Fourier transform, in a superconducting qutrit. The qutrit is encoded in the lowest three energy levels of a capacitively shunted flux device, operated at the optimal flux-symmetry point. We use an efficient decomposition of the Wal...

[Phys. Rev. Lett. 125, 180504] Published Tue Oct 27, 2020

]]>Constraints on work extraction are fundamental to our operational understanding of the thermodynamics of both classical and quantum systems. In the quantum setting, finite-time control operations typically generate coherence in the instantaneous energy eigenbasis of the dynamical system. Thermodynam...

[Phys. Rev. Lett. 125, 180603] Published Tue Oct 27, 2020

]]>The eigenstate entanglement entropy is a powerful tool to distinguish integrable from generic quantum-chaotic models. In integrable models, the average eigenstate entanglement entropy (over all Hamiltonian eigenstates) has a volume-law coefficient that generally depends on the subsystem fraction. In...

[Phys. Rev. Lett. 125, 180604] Published Tue Oct 27, 2020

]]>Shock waves are examples of the far-from-equilibrium behavior of matter; they are ubiquitous in nature, yet the underlying microscopic mechanisms behind their formation are not well understood. Here, we study the dynamics of dispersive quantum shock waves in a one-dimensional Bose gas, and show that...

[Phys. Rev. Lett. 125, 180401] Published Mon Oct 26, 2020

]]>Adiabatic quantum computing enables the preparation of many-body ground states. Realization poses major experimental challenges: Direct analog implementation requires complex Hamiltonian engineering, while the digitized version needs deep quantum gate circuits. To bypass these obstacles, we suggest ...

[Phys. Rev. Lett. 125, 180501] Published Mon Oct 26, 2020

]]>Resonance fluorescence has played a major role in quantum optics with predictions and later experimental confirmation of nonclassical features of its emitted light such as antibunching or squeezing. In the Rayleigh regime where most of the light originates from the scattering of photons with subnatu...

[Phys. Rev. Lett. 125, 170402] Published Fri Oct 23, 2020

]]>All known examples suggesting an exponential separation between classical simulation algorithms and stoquastic adiabatic quantum computing (StoqAQC) exploit symmetries that constrain adiabatic dynamics to effective, symmetric subspaces. The symmetries produce large effective eigenvalue gaps, which i...

[Phys. Rev. Lett. 125, 170504] Published Fri Oct 23, 2020

]]>We present an algorithm for studying quantum systems at finite temperature using continuous matrix product operator representation. The approach handles both short-range and long-range interactions in the thermodynamic limit without incurring any time discretization error. Moreover, the approach pro...

[Phys. Rev. Lett. 125, 170604] Published Fri Oct 23, 2020

]]>Ultracold gases provide an unprecedented level of control for the investigation of soliton dynamics and collisions. We present a scheme for deterministically preparing pairs of three-component solitons in a Bose-Einstein condensate. Our method is based on local spin rotations which simultaneously im...

[Phys. Rev. Lett. 125, 170401] Published Thu Oct 22, 2020

]]>We report the analog simulation of an ergodic-localized junction by using an array of 12 coupled superconducting qubits. To perform the simulation, we fabricated a superconducting quantum processor that is divided into two domains: one is a driven domain representing an ergodic system, while the sec...

[Phys. Rev. Lett. 125, 170503] Published Thu Oct 22, 2020

]]>Computable information density (CID), the ratio of the length of a losslessly compressed data file to that of the uncompressed file, is a measure of order and correlation in both equilibrium and nonequilibrium systems. Here we show that correlation lengths can be obtained by decimation, thinning a c...

[Phys. Rev. Lett. 125, 170601] Published Thu Oct 22, 2020

]]>We propose and test a method to interpolate sparsely sampled signals by a stochastic process with a broad range of spatial and/or temporal scales. To this end, we extend the notion of a fractional Brownian bridge, defined as fractional Brownian motion with a given scaling (Hurst) exponent $H$ and with...

[Phys. Rev. Lett. 125, 170602] Published Wed Oct 21, 2020

]]>We demonstrate how to explore phase diagrams with automated and unsupervised machine learning to find regions of interest for possible new phases. In contrast to supervised learning, where data is classified using predetermined labels, we here perform anomaly detection, where the task is to differen...

[Phys. Rev. Lett. 125, 170603] Published Wed Oct 21, 2020

]]>Quantum compiling, a process that decomposes the quantum algorithm into a series of hardware-compatible commands or elementary gates, is of fundamental importance for quantum computing. We introduce an efficient algorithm based on deep reinforcement learning that compiles an arbitrary single-qubit g...

[Phys. Rev. Lett. 125, 170501] Published Mon Oct 19, 2020

]]>We present an efficient approach to achieving arbitrary, high-fidelity control of a multilevel quantum system using optimal control techniques. As an demonstration, we implement a continuous, software-defined microwave pulse to realize a $0\leftrightarrow 2$ SWAP gate that achieves an average gate fidelity of 99.4%....

[Phys. Rev. Lett. 125, 170502] Published Mon Oct 19, 2020

]]>Finding optical setups producing measurement results with a targeted probability distribution is hard, as *a priori* the number of possible experimental implementations grows exponentially with the number of modes and the number of devices. To tackle this complexity, we introduce a method combining re...

[Phys. Rev. Lett. 125, 160401] Published Fri Oct 16, 2020

]]>The characterization of quantum features in large Hilbert spaces is a crucial requirement for testing quantum protocols. In the continuous variable encoding, quantum homodyne tomography requires an amount of measurement that increases exponentially with the number of involved modes, which practicall...

[Phys. Rev. Lett. 125, 160504] Published Fri Oct 16, 2020

]]>Quasiperiodically driven quantum systems are predicted to exhibit quantized topological properties, in analogy with the quantized transport properties of topological insulators. We use a single nitrogen-vacancy center in diamond to experimentally study a synthetic quantum Hall effect with a two-tone...

[Phys. Rev. Lett. 125, 160505] Published Fri Oct 16, 2020

]]>Simulating the topological phases of matter in synthetic quantum simulators is a topic of considerable interest. Given the universality of digital quantum simulators, the prospect of digitally simulating exotic topological phases is greatly enhanced. However, it is still an open question how to real...

[Phys. Rev. Lett. 125, 160503] Published Thu Oct 15, 2020

]]>Information is physical but information is also processed in finite time. Where computing protocols are concerned, finite-time processing in the quantum regime can dynamically generate coherence. Here we show that this can have significant thermodynamic implications. We demonstrate that quantum cohe...

[Phys. Rev. Lett. 125, 160602] Published Thu Oct 15, 2020

]]>In the age of the post-Moore era, the next-generation computing model would be a hybrid architecture consisting of different physical components, such as photonic chips. In 2008, it was proposed that the solving of the NAND-tree problem can be sped up by quantum walk. This scheme is groundbreaking d...

[Phys. Rev. Lett. 125, 160502] Published Wed Oct 14, 2020

]]>Symmetry-breaking dynamical phase transitions (DPTs) abound in the fluctuations of nonequilibrium systems. Here, we show that the spectral features of a particular class of DPTs exhibit the fingerprints of the recently discovered time-crystal phase of matter. Using Doob’s transform as a tool, we pro...

[Phys. Rev. Lett. 125, 160601] Published Wed Oct 14, 2020

]]>We provide an explicit construction of a universal gate set for continuous-variable quantum computation with microwave circuits. Such a universal set has been first proposed in quantum-optical setups, but its experimental implementation has remained elusive in that domain due to the difficulties in ...

[Phys. Rev. Lett. 125, 160501] Published Mon Oct 12, 2020

]]>As a modern approach for the foundation of quantum theory, existing studies of general probabilistic theories gave various models of states and measurements that are quite different from quantum theory. In this Letter, to seek a more realistic situation, we investigate models approximately close to ...

[Phys. Rev. Lett. 125, 150402] Published Fri Oct 09, 2020

]]>We solve two long-standing problems for stochastic descriptions of open quantum system dynamics. First, we find the classical stochastic processes corresponding to non-Markovian quantum state diffusion and non-Markovian quantum jumps in projective Hilbert space. Second, we show that the diffusive li...

[Phys. Rev. Lett. 125, 150403] Published Fri Oct 09, 2020

]]>Using a multiple-image reconstruction method applied to a harmonically trapped Bose gas, we determine the equation of state of uniform matter across the critical transition point, within the local density approximation. Our experimental results provide the canonical description of pressure as a func...

[Phys. Rev. Lett. 125, 150404] Published Fri Oct 09, 2020

]]>In quantum mechanics, geometry has been demonstrated as a useful tool for inferring nonclassical behaviors and exotic properties of quantum systems. One standard approach to illustrate the geometry of quantum systems is to project the quantum state space onto the Euclidean space via measurements of ...

[Phys. Rev. Lett. 125, 150401] Published Thu Oct 08, 2020

]]>Controlled manipulation, storage, and retrieval of quantum information is essential for quantum communication and computing. Quantum memories for light, realized with cold atomic samples as the storage medium, are prominent for their high storage efficiencies and lifetime. We demonstrate the control...

[Phys. Rev. Lett. 125, 150501] Published Thu Oct 08, 2020

]]>In a network, a channel introduces correlations to the parties that aim to establish a communication protocol. We present a framework of nonlocal network coding by exploiting a Bell scenario and show the usefulness of nonlocal and quantum resources in network coding. Two-sender and two-receiver inte...

[Phys. Rev. Lett. 125, 150502] Published Thu Oct 08, 2020

]]>Certifying that quantum devices behave as intended is crucial for quantum information science. Here, methods are developed for certification of both state preparation devices and measurement devices based on prepare-and-measure experiments with independent devices. The experimenter assumes the indep...

[Phys. Rev. Lett. 125, 150503] Published Tue Oct 06, 2020

]]>Limited quantum memory is one of the most important constraints for near-term quantum devices. Understanding whether a small quantum computer can simulate a larger quantum system, or execute an algorithm requiring more qubits than available, is both of theoretical and practical importance. In this L...

[Phys. Rev. Lett. 125, 150504] Published Tue Oct 06, 2020

]]>In a large scale trapped atomic ion quantum computer, high-fidelity two-qubit gates need to be extended over all qubits with individual control. We realize and characterize high-fidelity two-qubit gates in a system with up to four ions using radial modes. The ions are individually addressed by two t...

[Phys. Rev. Lett. 125, 150505] Published Tue Oct 06, 2020

]]>This Letter presents a neural estimator for entropy production (NEEP), that estimates entropy production (EP) from trajectories of relevant variables without detailed information on the system dynamics. For steady state, we rigorously prove that the estimator, which can be built up from different ch...

[Phys. Rev. Lett. 125, 140604] Published Fri Oct 02, 2020

]]>Zel’dovich proposed that electromagnetic (EM) waves with angular momentum reflected from a rotating metallic, lossy cylinder will be amplified. However, we are still lacking a direct experimental EM-wave verification of this fifty-year-old prediction due to the challenging conditions in which the ph...

[Phys. Rev. Lett. 125, 140801] Published Fri Oct 02, 2020

]]>Multipartite entanglement (ME) is the fundamental ingredient for building quantum networks. The scale of ME determines its quantum information carrying and processing capability. Most of the current efforts for boosting the scale of ME focus on increasing the number of entangled nodes. However, the ...

[Phys. Rev. Lett. 125, 140501] Published Thu Oct 01, 2020

]]>Quantum entanglement is fragile to thermal fluctuations, which raises the question whether finite temperature phase transitions support long-range entanglement similar to their zero temperature counterparts. Here we use quantum Monte Carlo simulations to study the third Renyi negativity, a generaliz...

[Phys. Rev. Lett. 125, 140603] Published Wed Sep 30, 2020

]]>We demonstrate the power of 2D tensor networks for obtaining large deviation functions of dynamical observables in a classical nonequilibrium setting. Using these methods, we analyze the previously unstudied dynamical phase behavior of the fully 2D asymmetric simple exclusion process with biases in ...

[Phys. Rev. Lett. 125, 140601] Published Tue Sep 29, 2020

]]>The thermodynamic uncertainty relation (TUR) describes a trade-off relation between nonequilibrium currents and entropy production and serves as a fundamental principle of nonequilibrium thermodynamics. However, currently known TURs presuppose either specific initial states or an infinite-time avera...

[Phys. Rev. Lett. 125, 140602] Published Tue Sep 29, 2020

]]>Coherent superposition and entanglement are two fundamental aspects of nonclassicality. Here we provide a quantitative connection between the two on the level of operations by showing that the dynamical coherence of an operation upper bounds the dynamical entanglement that can be generated from it w...

[Phys. Rev. Lett. 125, 130401] Published Fri Sep 25, 2020

]]>The Jaynes-Cummings model is a cornerstone of light-matter interactions. While finite, the model provides an illustrative example of renormalization in perturbation theory. We show, however, that exact renormalization reveals a rich nonperturbative structure, and that the model provides a physical e...

[Phys. Rev. Lett. 125, 130402] Published Fri Sep 25, 2020

]]>Analyzing particle density fluctuations in space and time provides an alternative method for computing thermal conductivity of liquids.

[Phys. Rev. Lett. 125, 130602] Published Tue Sep 22, 2020

]]>We study quantum information scrambling in spin models with both long-range all-to-all and short-range interactions. We argue that a simple global, spatially homogeneous interaction together with local chaotic dynamics is sufficient to give rise to fast scrambling, which describes the spread of quan...

[Phys. Rev. Lett. 125, 130601] Published Mon Sep 21, 2020

]]>Estimation of the properties of a physical system with minimal uncertainty is a central task in quantum metrology. Optical phase estimation is at the center of many metrological tasks where the value of a physical parameter is mapped to the phase of an electromagnetic field and single-shot measureme...

[Phys. Rev. Lett. 125, 120505] Published Fri Sep 18, 2020

]]>How a closed interacting quantum many-body system relaxes and dephases as a function of time is a fundamental question in thermodynamic and statistical physics. In this Letter, we analyze and observe the persistent temporal fluctuations after a quantum quench of a tunable long-range interacting tran...

[Phys. Rev. Lett. 125, 120605] Published Fri Sep 18, 2020

]]>We show that the entropy production rate bounds the rate at which physical processes can be performed in stochastic systems far from equilibrium. In particular, we prove the fundamental tradeoff $\u27e8{\dot{S}}_{e}\u27e9\mathcal{T}\ge {k}_{B}$ between the entropy flow $\u27e8{\dot{S}}_{e}\u27e9$ into the reservoirs and the mean time $\mathcal{T}$ to complete any process ...

[Phys. Rev. Lett. 125, 120604] Published Wed Sep 16, 2020

]]>A family of two-qubit gate combinations that can decrease the circuit depth for NISQ processors is demonstrated using gmon superconducting qubits.

[Phys. Rev. Lett. 125, 120504] Published Tue Sep 15, 2020

]]>In this work, we address the question of how a closed quantum system thermalizes in the presence of a random external potential. By investigating the quench dynamics of the isolated quantum spherical $p$-spin model, a paradigmatic model of a mean-field glass, we aim to shed new light on this complex p...

[Phys. Rev. Lett. 125, 120602] Published Tue Sep 15, 2020

]]>A nanomechanical resonator detects and isolates acoustic waves from a remote thermal source.

[Phys. Rev. Lett. 125, 120603] Published Tue Sep 15, 2020

]]>The interaction between the electric dipole moment of a trapped molecular ion and the phonon modes of the confined Coulomb crystal couples the orientation of the molecule to its motion. We consider the practical feasibility of harnessing this interaction to initialize, process, and read out quantum ...

[Phys. Rev. Lett. 125, 120501] Published Mon Sep 14, 2020

]]>Identifying topological properties is a major challenge because, by definition, topological states do not have a local order parameter. While a generic solution to this challenge is not available yet, a broad class of topological states, namely, symmetry-protected topological (SPT) states, can be id...

[Phys. Rev. Lett. 125, 120502] Published Mon Sep 14, 2020

]]>Accurate control of two-level systems is a longstanding problem in quantum mechanics. One such quantum system is the frequency-bin qubit: a single photon existing in superposition of two discrete frequency modes. In this Letter, we demonstrate fully arbitrary control of frequency-bin qubits in a qua...

[Phys. Rev. Lett. 125, 120503] Published Mon Sep 14, 2020

]]>Data structure has a dramatic impact on the properties of neural networks, yet its significance in the established theoretical frameworks is poorly understood. Here we compute the Vapnik-Chervonenkis entropy of a kernel machine operating on data grouped into equally labeled subsets. At variance with...

[Phys. Rev. Lett. 125, 120601] Published Mon Sep 14, 2020

]]>Contrary to conventional wisdom, a sufficiently small, cold object warms to the temperature of its surroundings faster than a warm object cools, according to a new theory.

[Phys. Rev. Lett. 125, 110602] Published Fri Sep 11, 2020

]]>A new method to study the evolution of a nondegenerate quantum system out of equilibrium explains the results of a recent experiment reporting universal quench dynamics of a Bose gas.

[Phys. Rev. Lett. 125, 110404] Published Thu Sep 10, 2020

]]>Quantum networks play a major role in long-distance communication, quantum cryptography, clock synchronization, and distributed quantum computing. Generally, these protocols involve many independent sources sharing entanglement among distant parties that, upon measuring their systems, generate corre...

[Phys. Rev. Lett. 125, 110505] Published Thu Sep 10, 2020

]]>We report the experimental realization of heralded distribution of single-photon path entanglement at telecommunication wavelengths in a repeater-like architecture. The entanglement is established upon detection of a single photon, originating from one of two spontaneous parametric down-conversion p...

[Phys. Rev. Lett. 125, 110506] Published Thu Sep 10, 2020

]]>The entropy production rate associated with broken time-reversal symmetry provides an essential characterization of nanosystems out of equilibrium, from driven colloidal particles to molecular motors. Limited access to the dynamical states is generally expected to hinder the correct estimation of th...

[Phys. Rev. Lett. 125, 110601] Published Thu Sep 10, 2020

]]>We experimentally demonstrate that electrically neutral particles, neutrons, can be used to directly visualize the electrostatic field inside a target volume that can be physically isolated or occupied. Electric field images are obtained using a spin-polarized neutron beam with a recently developed ...

[Phys. Rev. Lett. 125, 110801] Published Thu Sep 10, 2020

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