Anomalous dynamics in which local perturbations spread faster than diffusion are ubiquitously observed in the long-time behavior of a wide variety of systems. Here, the manner by which such systems evolve towards their asymptotic superdiffusive behavior is explored using the 1D Lévy walk of order $1\&...$

[Phys. Rev. Lett. 124, 140601] Published Mon Apr 06, 2020

]]>The non-Abelian topological phase with Fibonacci anyons minimally supports universal quantum computation. In order to investigate the possible phase transitions out of the Fibonacci topological phase, we propose a generic quantum-net wave function with two tuning parameters dual with each other, and...

[Phys. Rev. Lett. 124, 130603] Published Fri Apr 03, 2020

]]>Disorder in quantum systems can lead to the disruption of long-range order in the ground state and to the localization of the elementary excitations. Here we exhibit an alternative paradigm, by which disorder preserves long-range order in the ground state, while it localizes the elementary excitatio...

[Phys. Rev. Lett. 124, 130604] Published Thu Apr 02, 2020

]]>A quantum machine-learning network can fix spin-flip errors in a manner analogous to classical data being denoised by an autoencoder.

[Phys. Rev. Lett. 124, 130502] Published Tue Mar 31, 2020

]]>Dynamical universality is the observation that the dynamical properties of different systems might exhibit universal behavior that are independent of the system details. In this Letter, we study the longtime dynamics of a one-dimensional noisy quantum magnetic model, and find that even though the sy...

[Phys. Rev. Lett. 124, 130602] Published Tue Mar 31, 2020

]]>Noise in quantum computing is countered with quantum error correction. Achieving optimal performance will require tailoring codes and decoding algorithms to account for features of realistic noise, such as the common situation where the noise is biased towards dephasing. Here we introduce an efficie...

[Phys. Rev. Lett. 124, 130501] Published Mon Mar 30, 2020

]]>We analyze work extraction from a qubit into a waveguide (WG) acting as a battery, where work is the coherent component of the energy radiated by the qubit. The process is stimulated by a wave packet whose mean photon number (the battery’s charge) can be adjusted. We show that the extracted work is ...

[Phys. Rev. Lett. 124, 130601] Published Mon Mar 30, 2020

]]>We describe a Sagnac interferometer suitable for rotation sensing, implemented using an atomic Bose-Einstein condensate confined in a harmonic magnetic trap. The atom wave packets are split and recombined by standing-wave Bragg lasers, and the trapping potential steers the packets along circular tra...

[Phys. Rev. Lett. 124, 120403] Published Fri Mar 27, 2020

]]>Physical systems close to a quantum phase transition exhibit a divergent susceptibility, suggesting that an arbitrarily high precision may be achieved by exploiting quantum critical systems as probes to estimate a physical parameter. However, such an improvement in sensitivity is counterbalanced by ...

[Phys. Rev. Lett. 124, 120504] Published Fri Mar 27, 2020

]]>We show—both theoretically and experimentally—that Einstein-Podolsky-Rosen steering can be distilled. We present a distillation protocol that outputs a perfectly correlated system—the singlet assemblage—in the asymptotic infinite-copy limit, even for inputs that are arbitrarily close to being unstee...

[Phys. Rev. Lett. 124, 120402] Published Thu Mar 26, 2020

]]>We investigate a quantum many-body lattice system of one-dimensional spinless fermions interacting with a dynamical ${Z}_{2}$ gauge field. The gauge field mediates long-range attraction between fermions resulting in their confinement into bosonic dimers. At strong coupling we develop an exactly solvable ef...

[Phys. Rev. Lett. 124, 120503] Published Thu Mar 26, 2020

]]>We introduce a resource theory of channels relevant to communication via quantum channels, in which the set of constant channels—useless channels for communication tasks—are considered as free resources. We find that our theory with such a simple structure is useful to address central problems in qu...

[Phys. Rev. Lett. 124, 120502] Published Wed Mar 25, 2020

]]>Measurement incompatibility describes two or more quantum measurements whose expected joint outcome on a given system cannot be defined. This purely nonclassical phenomenon provides a necessary ingredient in many quantum information tasks such as violating a Bell inequality or nonlocally steering pa...

[Phys. Rev. Lett. 124, 120401] Published Tue Mar 24, 2020

]]>To realize fault-tolerant quantum computing, it is necessary to store quantum information in logical qubits with error correction functions, realized by distributing a logical state among multiple physical qubits or by encoding it in the Hilbert space of a high-dimensional system. Quantum gate opera...

[Phys. Rev. Lett. 124, 120501] Published Tue Mar 24, 2020

]]>We provide a generalization of the matrix product operator formalism for string-net projected entangled pair states (PEPS) to include nonunitary solutions of the pentagon equation. These states provide the explicit lattice realization of the Galois conjugated counterparts of ($2+1$)-dimensional topolo...

[Phys. Rev. Lett. 124, 120601] Published Mon Mar 23, 2020

]]>An analytical prediction is established of how an isolated many-body quantum system relaxes towards its thermal longtime limit under the action of a time-independent perturbation, but still remaining sufficiently close to a reference case whose temporal relaxation is known. This is achieved within t...

[Phys. Rev. Lett. 124, 120602] Published Mon Mar 23, 2020

]]>We provide a strategy for the exact inference of the average as well as the fluctuations of the entropy production in nonequilibrium systems in the steady state, from the measurements of arbitrary current fluctuations. Our results are built upon the finite-time generalization of the thermodynamic un...

[Phys. Rev. Lett. 124, 120603] Published Mon Mar 23, 2020

]]>We consider the paradigm of an overdamped Brownian particle in a potential well, which is modulated through an external protocol, in the presence of stochastic resetting. Thus, in addition to the short range diffusive motion, the particle also experiences intermittent long jumps that reset the parti...

[Phys. Rev. Lett. 124, 110608] Published Fri Mar 20, 2020

]]>We examine how the magnetic susceptibility obtained by the quench experiment on isolated quantum systems is related to the isothermal and adiabatic susceptibilities defined in thermodynamics. Under the conditions similar to the eigenstate thermalization hypothesis, together with some additional natu...

[Phys. Rev. Lett. 124, 110609] Published Fri Mar 20, 2020

]]>We demonstrate that the negative volume of any $s$-parametrized quasiprobability, including the Glauber-Sudashan $P$ function, can be consistently defined and forms a continuous hierarchy of nonclassicality measures that are linear optical monotones. These measures belong to an operational resource theo...

[Phys. Rev. Lett. 124, 110404] Published Thu Mar 19, 2020

]]>We give rigorous analytical results on the temporal behavior of two-point correlation functions—also known as dynamical response functions or Green’s functions—in closed many-body quantum systems. We show that in a large class of translation-invariant models the correlation functions factorize at la...

[Phys. Rev. Lett. 124, 110605] Published Thu Mar 19, 2020

]]>We consider the optimization of a finite-time Carnot engine characterized by small dissipations. We bound the power with a simple inequality and show that the optimal strategy is to perform small cycles around a given working point, which can be, thus, chosen optimally. Remarkably, this optimal poin...

[Phys. Rev. Lett. 124, 110606] Published Thu Mar 19, 2020

]]>The occurrence of an inverse current, where the sign of the induced current is opposite to the applied force, is a highly counterintuitive phenomenon. We show that inverse currents in coupled transport (ICC) of energy and particle can occur in a one-dimensional interacting Hamiltonian system when it...

[Phys. Rev. Lett. 124, 110607] Published Thu Mar 19, 2020

]]>Counterpropagating photon beams generate quasiparticle–hole pairs in graphene in a process analogous to pair production in QED.

[Phys. Rev. Lett. 124, 110403] Published Wed Mar 18, 2020

]]>We study a method to simulate quantum many-body dynamics of spin ensembles using measurement-based feedback. By performing a weak collective measurement on a large ensemble of two-level quantum systems and applying global rotations conditioned on the measurement outcome, one can simulate the dynamic...

[Phys. Rev. Lett. 124, 110503] Published Wed Mar 18, 2020

]]>By using highly entangled states, quantum metrology guarantees a precision impossible with classical measurements. Unfortunately such states can be very susceptible to noise, and it is a great challenge of the field to maintain quantum advantage in realistic conditions. In this Letter we investigate...

[Phys. Rev. Lett. 124, 110502] Published Tue Mar 17, 2020

]]>We analyze the dynamics of an initially trapped cloud of interacting quantum particles on a lattice under a linear (Stark) potential. We reveal a dichotomy: initially trapped interacting systems possess features typical of both many-body-localized and thermalizing systems. We consider both fermions ...

[Phys. Rev. Lett. 124, 110603] Published Tue Mar 17, 2020

]]>We use a near quantum limited detector to experimentally track individual quantum state trajectories of a driven qubit formed by the hybridization of a waveguide cavity and a transmon circuit. For each measured quantum coherent trajectory, we separately identify energy changes of the qubit as heat a...

[Phys. Rev. Lett. 124, 110604] Published Tue Mar 17, 2020

]]>A generalization of quantum discord to multipartite systems is proposed. A key feature of our formulation is its consistency with the conventional definition of discord in bipartite systems. It is by construction zero only for systems with classically correlated subsystems and is a non-negative quan...

[Phys. Rev. Lett. 124, 110401] Published Mon Mar 16, 2020

]]>We propose a time-of-arrival operator in quantum mechanics by conditioning on a quantum clock. This allows us to bypass some of the problems of previous proposals, and to obtain a Hermitian time of arrival operator whose probability distribution arises from the Born rule and which has a clear physic...

[Phys. Rev. Lett. 124, 110402] Published Mon Mar 16, 2020

]]>Two trapped ions a few meters apart are entangled through a photonic interface with 94% fidelity.

[Phys. Rev. Lett. 124, 110501] Published Mon Mar 16, 2020

]]>A remarkable feature of quantum many-body systems is the orthogonality catastrophe that describes their extensively growing sensitivity to local perturbations and plays an important role in condensed matter physics. Here we show that the dynamics of the orthogonality catastrophe can be fully charact...

[Phys. Rev. Lett. 124, 110601] Published Mon Mar 16, 2020

]]>The Rényi entanglement entropy in quantum many-body systems can be viewed as the difference in free energy between partition functions with different trace topologies. We introduce an external field $\lambda $ that controls the partition function topology, allowing us to define a notion of nonequilibrium wor...

[Phys. Rev. Lett. 124, 110602] Published Mon Mar 16, 2020

]]>We prove that matrix-product unitaries with on-site unitary symmetries are *completely* classified by the (chiral) index and the cohomology class of the symmetry group $G$, provided that we can add trivial and symmetric ancillas with arbitrary on-site representations of $G$. If the representations in both...

[Phys. Rev. Lett. 124, 100402] Published Fri Mar 13, 2020

]]>As a promising candidate for exhibiting quantum computational supremacy, Gaussian boson sampling (GBS) is designed to exploit the ease of experimental preparation of Gaussian states. However, sufficiently large and inevitable experimental noise might render GBS classically simulable. In this work, w...

[Phys. Rev. Lett. 124, 100502] Published Fri Mar 13, 2020

]]>Introducing a notion of locality into the random Liouvillian of a many-body quantum system reveals clustered eigenvalues with sharp separation of relaxation timescales.

[Phys. Rev. Lett. 124, 100604] Published Fri Mar 13, 2020

]]>A powerful perspective in understanding nonequilibrium quantum dynamics is through the time evolution of its entanglement content. Yet apart from a few guiding principles for the entanglement entropy, to date, much less is known about the refined characteristics of entanglement propagation. Here, we...

[Phys. Rev. Lett. 124, 100605] Published Fri Mar 13, 2020

]]>It is now experimentally possible to entangle thousands of qubits, and efficiently measure each qubit in parallel in a distinct basis. To fully characterize an unknown entangled state of $n$ qubits, one requires an exponential number of measurements in $n$, which is experimentally unfeasible even for mo...

[Phys. Rev. Lett. 124, 100401] Published Tue Mar 10, 2020

]]>The chain rule for the classical relative entropy ensures that the relative entropy between probability distributions on multipartite systems can be decomposed into a sum of relative entropies of suitably chosen conditional distributions on the individual systems. Here, we prove a chain rule inequal...

[Phys. Rev. Lett. 124, 100501] Published Tue Mar 10, 2020

]]>We consider current-current deformations that generalize $T\overline{T}$ ones, and show that they may be also introduced for integrable spin chains. In analogy with the integrable QFT setup, we define the deformation as a modification of the $S$ matrix in the Bethe equations. Using results by Bargheer, Beisert an...

[Phys. Rev. Lett. 124, 100601] Published Tue Mar 10, 2020

]]>We combine matrix product operator techniques with Chebyshev polynomial expansions and present a method that is able to explore spectral properties of quantum many-body Hamiltonians. In particular, we show how this method can be used to probe thermalization of large spin chains without explicitly si...

[Phys. Rev. Lett. 124, 100602] Published Tue Mar 10, 2020

]]>We discuss a self-contained spin-boson model for a measurement-driven engine, in which a demon generates work from thermal excitations of a quantum spin via measurement and feedback control. Instead of granting it full direct access to the spin state and to Landauer’s erasure strokes for optimal per...

[Phys. Rev. Lett. 124, 100603] Published Tue Mar 10, 2020

]]>Magic-state distillation (or nonstabilizer state manipulation) is a crucial component in the leading approaches to realizing scalable, fault-tolerant, and universal quantum computation. Related to nonstabilizer state manipulation is the resource theory of nonstabilizer states, for which one of the g...

[Phys. Rev. Lett. 124, 090505] Published Fri Mar 06, 2020

]]>We introduce, for each state of a bosonic quantum field, its quadrature coherence scale (QCS), a measure of the range of its quadrature coherences. Under coupling to a thermal bath, the purity and QCS are shown to decrease on a timescale inversely proportional to the QCS squared. The states most fra...

[Phys. Rev. Lett. 124, 090402] Published Thu Mar 05, 2020

]]>We discuss quantum annealing of the two-dimensional transverse-field Ising model on a D-Wave device, encoded on $L\times L$ lattices with $L\le 32$. Analyzing the residual energy and deviation from maximal magnetization in the final classical state, we find an optimal $L$ dependent annealing rate $v$ for which the t...

[Phys. Rev. Lett. 124, 090502] Published Thu Mar 05, 2020

]]>Discrete structures in Hilbert space play a crucial role in finding optimal schemes for quantum measurements. We solve the problem of whether a complete set of five isoentangled mutually unbiased bases exists in dimension four, providing an explicit analytical construction. The reduced density matri...

[Phys. Rev. Lett. 124, 090503] Published Thu Mar 05, 2020

]]>The quantum approximate optimization algorithm (QAOA) has rapidly become a cornerstone of contemporary quantum algorithm development. Despite a growing range of applications, only a few results have been developed towards understanding the algorithm’s ultimate limitations. Here we report that QAOA e...

[Phys. Rev. Lett. 124, 090504] Published Thu Mar 05, 2020

]]>Multipartite entanglement serves as a vital resource for quantum information processing. Generally, its generation requires complex beam splitting processes which limit scalability. A promising trend is to integrate multiple nonlinear processes into a single device via frequency or time multiplexing...

[Phys. Rev. Lett. 124, 090501] Published Tue Mar 03, 2020

]]>We exploit a few- to many-body approach to study strongly interacting dipolar bosons in the quasi-one-dimensional system. The dipoles attract each other while the short range interactions are repulsive. Solving numerically the multiatom Schrödinger equation, we discover that such systems can exhibit...

[Phys. Rev. Lett. 124, 090401] Published Mon Mar 02, 2020

]]>How do we search for the entire family tree of possible intermediate states, without unwanted random guesses, starting from a stationary state on the energy landscape all the way down to energy minima? Here we introduce a general numerical method that constructs the pathway map, which guides our und...

[Phys. Rev. Lett. 124, 090601] Published Mon Mar 02, 2020

]]>We derive detailed and integral quantum fluctuation theorems for heat exchange in a quantum correlated bipartite thermal system using the framework of dynamic Bayesian networks. Contrary to the usual two-projective-measurement scheme that is known to destroy quantum features, these fluctuation relat...

[Phys. Rev. Lett. 124, 090602] Published Mon Mar 02, 2020

]]>We consider an active run-and-tumble particle (RTP) in $d$ dimensions and compute exactly the probability $S(t)$ that the $x$ component of the position of the RTP does not change sign up to time $t$. When the tumblings occur at a constant rate, we show that $S(t)$ is independent of $d$ for any finite time $t$ (an...

[Phys. Rev. Lett. 124, 090603] Published Mon Mar 02, 2020

]]>In the two-component Fermi gas with a contact interaction, a pseudogap regime can exist at temperatures between the superfluid critical temperature ${T}_{c}$ and a temperature ${T}^{*}>{T}_{c}$. This regime is characterized by pairing correlations without superfluidity. However, in the unitary limit of infinite sca...

[Phys. Rev. Lett. 124, 090604] Published Mon Mar 02, 2020

]]>We solve the general problem of determining, through imaging, the three-dimensional positions of $N$ weak incoherent pointlike emitters in an arbitrary spatial configuration. We show that a structured measurement strategy in which a passive linear interferometer feeds into an array of photodetectors i...

[Phys. Rev. Lett. 124, 080503] Published Thu Feb 27, 2020

]]>We study renormalization group flows in a space of observables computed by Monte Carlo simulations. As an example, we consider three-dimensional clock models, i.e., the $XY$ spin model perturbed by a ${Z}_{q}$ symmetric anisotropy field. For $q=4$, 5, 6, a scaling function with two relevant arguments describes...

[Phys. Rev. Lett. 124, 080602] Published Thu Feb 27, 2020

]]>The continuous spontaneous localization model solves the measurement problem of standard quantum mechanics by coupling the mass density of a quantum system to a white-noise field. Since the mass density is not uniquely defined in general relativity, this model is ambiguous when applied to cosmology....

[Phys. Rev. Lett. 124, 080402] Published Wed Feb 26, 2020

]]>The only known way to study quantum field theories in nonperturbative regimes is using numerical calculations regulated on discrete space-time lattices. Such computations, however, are often faced with exponential signal-to-noise challenges that render key physics studies untenable even with next ge...

[Phys. Rev. Lett. 124, 080501] Published Wed Feb 26, 2020

]]>Quantum teleportation transfers and processes quantum information through quantum entanglement channels. It is one of the most versatile protocols in quantum information science and leads to many remarkable applications, particularly the one-way quantum computing. Here, we show, for the first time, ...

[Phys. Rev. Lett. 124, 080502] Published Wed Feb 26, 2020

]]>The Lévy hypothesis states that inverse square Lévy walks are optimal search strategies because they maximize the encounter rate with sparse, randomly distributed, replenishable targets. It has served as a theoretical basis to interpret a wealth of experimental data at various scales, from molecular...

[Phys. Rev. Lett. 124, 080601] Published Wed Feb 26, 2020

]]>The existence of ideal quantum measurements is one of the fundamental predictions of quantum mechanics. In theory, an ideal measurement projects a quantum state onto the eigenbasis of the measurement observable, while preserving coherences between eigenstates that have the same eigenvalue. The quest...

[Phys. Rev. Lett. 124, 080401] Published Tue Feb 25, 2020

]]>We propose a physical realization of quantum cellular automata (QCA) using arrays of ultracold atoms excited to Rydberg states. The key ingredient is the use of programmable multifrequency couplings which generalize the Rydberg blockade and facilitation effects to a broader set of nonadditive, unita...

[Phys. Rev. Lett. 124, 070503] Published Fri Feb 21, 2020

]]>The state of a superconducting qubit can be preserved by increasing the drive strength, thus introducing further control over decoherence processes.

[Phys. Rev. Lett. 124, 070401] Published Thu Feb 20, 2020

]]>We report the experimental observation of tunable, nonreciprocal quantum transport of a Bose-Einstein condensate in a momentum lattice. By implementing a dissipative Aharonov-Bohm (AB) ring in momentum space and sending atoms through it, we demonstrate a directional atom flow by measuring the moment...

[Phys. Rev. Lett. 124, 070402] Published Thu Feb 20, 2020

]]>Secure twin-field quantum key distribution over 509 km in optical fiber has been achieved, using independent lasers with a remote frequency-locking technique.

[Phys. Rev. Lett. 124, 070501] Published Thu Feb 20, 2020

]]>Quantum measurement is essential to both the foundations and practical applications of quantum information science. Among many possible models of quantum measurement, feedback measurements that dynamically update their physical structure are highly interesting due to their flexibility, which enables...

[Phys. Rev. Lett. 124, 070502] Published Wed Feb 19, 2020

]]>We report a stable and efficient complex Langevin sampling scheme for performing approximation-free numerical simulations directly on the path-integral coherent-states field theory for an assembly of interacting bosons. We apply the method to generate the $\lambda $ line of critical phase transitions associa...

[Phys. Rev. Lett. 124, 070601] Published Wed Feb 19, 2020

]]>Pixels in 2D video data provide information regarding the physics of pattern formation via an extension of the inversion problem applied to still images.

[Phys. Rev. Lett. 124, 060201] Published Fri Feb 14, 2020

]]>We use machine optimization to develop a quantum sensing scheme that achieves significantly better sensitivity than traditional schemes with the same quantum resources. Utilizing one-axis twisting dynamics to generate quantum entanglement, we find that, rather than dividing the temporal resources in...

[Phys. Rev. Lett. 124, 060402] Published Fri Feb 14, 2020

]]>We study the estimation of the overlap between two unknown pure quantum states of a finite-dimensional system, given $M$ and $N$ copies of each type. This is a fundamental primitive in quantum information processing that is commonly accomplished from the outcomes of $N$ swap tests, a joint measurement on ...

[Phys. Rev. Lett. 124, 060503] Published Fri Feb 14, 2020

]]>Brownian motion is a Gaussian process described by the central limit theorem. However, exponential decays of the positional probability density function $P(X,t)$ of packets of spreading random walkers, were observed in numerous situations that include glasses, live cells, and bacteria suspensions. We ...

[Phys. Rev. Lett. 124, 060603] Published Fri Feb 14, 2020

]]>Antiparallel spins are superior in orienteering to parallel spins. This intriguing phenomenon is tied to entanglement associated with quantum measurements rather than quantum states. Using photonic systems, we experimentally realize the optimal orienteering protocols based on parallel spins and anti...

[Phys. Rev. Lett. 124, 060502] Published Thu Feb 13, 2020

]]>What is the fastest way to heat a system which is coupled to a temperature controlled oven? The intuitive answer is to use only the hottest temperature available. However, we show that often it is possible to achieve an exponentially faster heating protocol. Surprisingly, this protocol can have a pr...

[Phys. Rev. Lett. 124, 060602] Published Thu Feb 13, 2020

]]>Quantum teleportation is a fundamental building block of quantum communications and quantum computations, transferring quantum states between distant physical entities. In the context of quantum secret sharing, the teleportation of quantum information shared by multiple parties without concentrating...

[Phys. Rev. Lett. 124, 060501] Published Tue Feb 11, 2020

]]>We study the quantum fluctuations in a one-dimensional Bose-Einstein condensate realizing an analogous acoustic black hole. The taking into account of evanescent channels and of zero modes makes it possible to accurately reproduce recent experimental measurements of the density correlation function....

[Phys. Rev. Lett. 124, 060401] Published Mon Feb 10, 2020

]]>We study fluctuations of interfaces in the Kardar-Parisi-Zhang (KPZ) universality class with curved initial conditions. By simulations of a cluster growth model and experiments with liquid-crystal turbulence, we determine the universal scaling functions that describe the height distribution and the ...

[Phys. Rev. Lett. 124, 060601] Published Mon Feb 10, 2020

]]>Motivated by the prediction of fractonic topological defects in a quantum crystal, we utilize a reformulated elasticity duality to derive a description of a fracton phase in terms of coupled *vector* U(1) gauge theories. The fracton order and restricted mobility emerge as a result of an unusual Gauss ...

[Phys. Rev. Lett. 124, 050402] Published Fri Feb 07, 2020

]]>Suppose that Alice and Bob are located in distant laboratories, which are connected by an ideal quantum channel. Suppose further that they share many copies of a quantum state ${\rho}_{ABE}$, such that Alice possesses the $A$ systems and Bob the $BE$ systems. In our model, there is an identifiable part of Bob’s l...

[Phys. Rev. Lett. 124, 050503] Published Fri Feb 07, 2020

]]>The local stability of a weakly dissipative heat engine is analyzed and linked to an energetic multi-objective optimization perspective. This constitutes a novel issue in the unified study of cyclic energy converters, opening the perspective to the possibility that stability favors self-optimization...

[Phys. Rev. Lett. 124, 050603] Published Fri Feb 07, 2020

]]>This Letter exposes a tight connection between the thermodynamic efficiency of information processing and predictive inference. A generalized lower bound on dissipation is derived for *partially observable* information engines which are allowed to use temperature differences. It is shown that the rete...

[Phys. Rev. Lett. 124, 050601] Published Thu Feb 06, 2020

]]>Constraints play an important role in the entanglement dynamics of many quantum systems. We develop a diagrammatic formalism to exactly evaluate the entanglement spectrum of random pure states in large constrained Hilbert spaces. The resulting spectra may be classified into universal “phases” depend...

[Phys. Rev. Lett. 124, 050602] Published Thu Feb 06, 2020

]]>We report the experimental implementation of discrete-time topological quantum walks of a Bose-Einstein condensate in momentum space. Introducing stroboscopic driving sequences to the generation of a momentum lattice, we show that the dynamics of atoms along the lattice is effectively governed by a ...

[Phys. Rev. Lett. 124, 050502] Published Wed Feb 05, 2020

]]>We discuss the relation between entanglement and nonlocality in the hidden nonlocality scenario. Hidden nonlocality signifies nonlocality that can be activated by applying local filters to a particular state that admits a local hidden-variable model in the Bell scenario. We present a fully biseparab...

[Phys. Rev. Lett. 124, 050401] Published Mon Feb 03, 2020

]]>The fundamental problem of sampling from the limiting distribution of quantum walks on networks, known as *mixing*, finds widespread applications in several areas of quantum information and computation. Of particular interest in most of these applications is the minimum time beyond which the instantan...

[Phys. Rev. Lett. 124, 050501] Published Mon Feb 03, 2020

]]>Superradiant phases, previously known in the context of critical phenomena, are shown to be an intrinsic property of the ultrastrong coupling limit.

[Phys. Rev. Lett. 124, 040404] Published Fri Jan 31, 2020

]]>We study the quantum Fisher information (QFI) and, thus, the multipartite entanglement structure of thermal pure states in the context of the eigenstate thermalization hypothesis (ETH). In both the canonical ensemble and the ETH, the quantum Fisher information may be explicitly calculated from the r...

[Phys. Rev. Lett. 124, 040605] Published Fri Jan 31, 2020

]]>Motivated by an unexpected experimental observation from the Cambridge group, [Eigen *et al.*, Nature **563**, 221 (2018)], we study the evolution of the momentum distribution of a degenerate Bose gas quenched from the weakly interacting regime to the unitary regime. For the two-body problem, we establish...

[Phys. Rev. Lett. 124, 040403] Published Thu Jan 30, 2020

]]>We develop a general framework to describe the thermodynamics of microscopic heat engines driven by arbitrary periodic temperature variations and modulations of a mechanical control parameter. Within the slow-driving regime, our approach leads to a universal trade-off relation between efficiency and...

[Phys. Rev. Lett. 124, 040602] Published Wed Jan 29, 2020

]]>Even though the eigenstate thermalization hypothesis (ETH) may be introduced as an extension of the random matrix theory, physical Hamiltonians and observables differ from random operators. One of the challenges is to embed local integrals of motion (LIOMs) within the ETH. Here we make steps towards...

[Phys. Rev. Lett. 124, 040603] Published Wed Jan 29, 2020

]]>The accurate and reliable description of measurement devices is a central problem in both observing uniquely nonclassical behaviors and realizing quantum technologies from powerful computing to precision metrology. To date quantum tomography is the prevalent tool to characterize quantum detectors. H...

[Phys. Rev. Lett. 124, 040402] Published Tue Jan 28, 2020

]]>At a quantum critical point, the low-energy physics of a quantum spin chain is described by conformal field theory (CFT). Given the Hamiltonian of a critical spin chain, we propose a variational method to build an approximate lattice representation ${\varphi}_{\alpha}$ of the corresponding primary CFT operators ${\varphi}_{\alpha}^{\mathrm{CFT}}$...

[Phys. Rev. Lett. 124, 040604] Published Tue Jan 28, 2020

]]>We uncover a topological classification applicable to open fermionic systems governed by a general class of Lindblad master equations. These “quadratic Lindbladians” can be captured by a non-Hermitian single-particle matrix which describes internal dynamics as well as system-environment coupling. We...

[Phys. Rev. Lett. 124, 040401] Published Mon Jan 27, 2020

]]>Events in mesoscopic systems often take place at first-passage times, as is for instance the case for a colloidal particle that escapes a metastable state. An interesting question is how much work an external agent has done on a particle when it escapes a metastable state. We develop a thermodynamic...

[Phys. Rev. Lett. 124, 040601] Published Mon Jan 27, 2020

]]>Communication in a network generally takes place through a sequence of intermediate nodes connected by communication channels. In the standard theory of communication, it is assumed that the communication network is embedded in a classical spacetime, where the relative order of different nodes is we...

[Phys. Rev. Lett. 124, 030502] Published Fri Jan 24, 2020

]]>A simple model of a row of frictional disks predicts an oscillatory instability that leads to dynamic friction.

[Phys. Rev. Lett. 124, 030602] Published Fri Jan 24, 2020

]]>We consider the precision $\mathrm{\Delta}\phi $ with which the parameter $\phi $, appearing in the unitary map ${U}_{\phi}={e}^{i\phi \mathrm{\Lambda}}$, acting on some type of probe system, can be estimated when there is a finite amount of prior information about $\phi $. We show that, if ${U}_{\phi}$ acts $n$ times in total, then, asymptotically in $n$, there is a tight lowe...

[Phys. Rev. Lett. 124, 030501] Published Thu Jan 23, 2020

]]>Recent advances in non-Hermitian physical systems have led to numerous novel optical phenomena and applications. Such systems typically involve gain and loss associated with dissipative coupling to the environment, hence interesting quantum phenomena are often washed out, rendering most realizations...

[Phys. Rev. Lett. 124, 030401] Published Wed Jan 22, 2020

]]>When a qubit or spin interacts with others under a many-body Hamiltonian, the information it contains progressively scrambles. Here, nuclear spins of an adamantane crystal are used as a quantum simulator to monitor such dynamics through out-of-time-order correlators, while a Loschmidt echo (LE) asse...

[Phys. Rev. Lett. 124, 030601] Published Tue Jan 21, 2020

]]>Researchers detected the effect of rotating a crystal on the spin of an embedded particle, a result that could lead to ultrasensitive rotation sensors.

[Phys. Rev. Lett. 124, 020401] Published Fri Jan 17, 2020

]]>Bell inequalities constitute a key tool in quantum information theory: they not only allow one to reveal nonlocality in composite quantum systems, but, more importantly, they can be used to certify relevant properties thereof. We provide a general construction of Bell inequalities that are maximally...

[Phys. Rev. Lett. 124, 020402] Published Fri Jan 17, 2020

]]>Quantum error correction is expected to be essential in large-scale quantum technologies. However, the substantial overhead of qubits it requires is thought to greatly limit its utility in smaller, near-term devices. Here we introduce a new family of special-purpose quantum error-correcting codes th...

[Phys. Rev. Lett. 124, 020504] Published Fri Jan 17, 2020

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