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  • Single-Atom Quantum Probes for Ultracold Gases Boosted by Nonequilibrium Spin Dynamics
    Phys. Rev. X (IF 12.211) Pub Date : 2020-01-27
    Quentin Bouton, Jens Nettersheim, Daniel Adam, Felix Schmidt, Daniel Mayer, Tobias Lausch, Eberhard Tiemann, and Artur Widera
    更新日期:2020-01-27
  • Parity detection of propagating microwave fields
    Phys. Rev. X (IF 12.211) Pub Date : 
    Jean-Claude Besse, Simone Gasparinetti, Michele C. Collodo, Theo Walter, Ants Remm, Jonas Krause, Christopher Eichler, and Andreas Wallraff

    The parity of the number of elementary excitations present in a quantum system provides important insights into its physical properties. Parity measurements are used, for example, to tomographically reconstruct quantum states or to determine if a decay of an excitation has occurred, information which can be used for quantum error correction in computation or communication protocols. Here we demonstrate a versatile parity detector for propagating microwaves, which distinguishes between radiation fields containing an even or odd number n of photons, both in a single-shot measurement and without perturbing the parity of the detected field. We showcase applications of the detector for direct Wigner tomography of propagating microwaves and heralded generation of Schr{"o}dinger cat states. This parity detection scheme is applicable over a broad frequency range and may prove useful, for example, for heralded or fault-tolerant quantum communication protocols.

    更新日期:2020-01-26
  • Tractions and Stress Fibers Control Cell Shape and Rearrangements in Collective Cell Migration
    Phys. Rev. X (IF 12.211) Pub Date : 2020-01-23
    Aashrith Saraswathibhatla and Jacob Notbohm
    更新日期:2020-01-24
  • Nonergodic Delocalized States for Efficient Population Transfer within a Narrow Band of the Energy Landscape
    Phys. Rev. X (IF 12.211) Pub Date : 2020-01-24
    Vadim N. Smelyanskiy, Kostyantyn Kechedzhi, Sergio Boixo, Sergei V. Isakov, Hartmut Neven, and Boris Altshuler
    更新日期:2020-01-24
  • Nonlinear Dynamics of Human Aortas for Material Characterization
    Phys. Rev. X (IF 12.211) Pub Date : 2020-01-23
    Marco Amabili, Prabakaran Balasubramanian, Isabella Bozzo, Ivan D. Breslavsky, Giovanni Ferrari, Giulio Franchini, Francesco Giovanniello, and Chloé Pogue
    更新日期:2020-01-23
  • Current operators in Bethe Ansatz and Generalized Hydrodynamics: An exact quantum/classical correspondence
    Phys. Rev. X (IF 12.211) Pub Date : 
    Márton Borsi, Balázs Pozsgay, and Levente Pristyák

    Generalized Hydrodynamics is a recent theory that describes large scale transport properties of one dimensional integrable models. It is built on the (typically infinitely many) local conservation laws present in these systems, and leads to a generalized Euler type hydrodynamic equation. Despite the successes of the theory, one of its cornerstones, namely a conjectured expression for the currents of the conserved charges in local equilibrium has not yet been proven for interacting lattice models. Here we fill this gap, and compute an exact result for the mean values of current operators in Bethe Ansatz solvable systems, valid in arbitrary finite volume. Our exact formula has a simple semi-classical interpretation: the currents can be computed by summing over the charge eigenvalues carried by the individual bare particles, multiplied with an effective velocity describing their propagation in the presence of the other particles. Remarkably, the semi-classical formula remains exact in the interacting quantum theory, for any finite number of particles and also in the thermodynamic limit. Our proof is built on a form factor expansion and it is applicable to a large class of quantum integrable models.

    更新日期:2020-01-23
  • Ergodicity-breaking arising from Hilbert space fragmentation in dipole-conserving Hamiltonians
    Phys. Rev. X (IF 12.211) Pub Date : 
    Pablo Sala, Tibor Rakovszky, Ruben Verresen, Michael Knap, and Frank Pollmann

    We show that the combination of charge and dipole conservation—characteristic of fracton systems—leads to an extensive fragmentation of the Hilbert space, which in turn can lead to a breakdown of thermalization. As a concrete example, we investigate the out-of-equilibrium dynamics of one-dimensional spin-1 models that conserve charge (total Sz) and its associated dipole moment. First, we consider a minimal model including only three-site terms and find that the infinite temperature auto-correlation saturates to a finite value—showcasing non-thermal behavior. The absence of thermalization is identified as a consequence of the of the Hilbert space into exponentially many invariant subspaces in the local Sz basis, arising from the interplay of dipole conservation and local interactions. Second, we extend the model by including four-site terms and find that this perturbation leads to a : the system still has exponentially many invariant subspaces, but they are no longer sufficient to avoid thermalization for typical initial states. More generally, for any finite range of interactions, the system still exhibits non-thermal eigenstates appearing throughout the entire spectrum. We compare our results to charge and dipole moment conserving random unitary circuit models for which we reach identical conclusions.

    更新日期:2020-01-23
  • Quantum-Assisted Measurement of Atomic Diamagnetism
    Phys. Rev. X (IF 12.211) Pub Date : 2020-01-22
    Yaakov Y. Fein, Armin Shayeghi, Lukas Mairhofer, Filip Kiałka, Philipp Rieser, Philipp Geyer, Stefan Gerlich, and Markus Arndt
    更新日期:2020-01-23
  • Keeping It Together: Interleaved Kirigami Extension Assembly
    Phys. Rev. X (IF 12.211) Pub Date : 2020-01-21
    Xinyu Wang, Simon D. Guest, and Randall D. Kamien
    更新日期:2020-01-22
  • Critical switching in globally attractive chimeras
    Phys. Rev. X (IF 12.211) Pub Date : 
    Yuanzhao Zhang, Zachary G. Nicolaou, Joseph D. Hart, Rajarshi Roy, and Adilson E. Motter

    We report on a new type of chimera state that attracts almost all initial conditions and exhibits {power-law} switching behavior in networks of {coupled} oscillators. Such {} consist of two symmetric {configurations, which we refer to as} subchimeras, in which one cluster is synchronized and the other is incoherent. Despite each subchimera being linearly stable, switching chimeras are extremely sensitive to noise: arbitrarily small noise triggers and sustains persistent switching between the two symmetric subchimeras. The average switching frequency increases as a power law with the noise intensity, which is in contrast with the exponential scaling observed in typical stochastic transitions. Rigorous numerical analysis reveals that the {power-law} switching behavior originates from intermingled basins of attraction associated with the two subchimeras, which in turn are induced by chaos and symmetry in the system. The theoretical results are supported by experiments on coupled optoelectronic oscillators, which demonstrate the generality and robustness of switching chimeras.

    更新日期:2020-01-22
  • Observation of Three-Photon Spontaneous Parametric Down-Conversion in a Superconducting Parametric Cavity
    Phys. Rev. X (IF 12.211) Pub Date : 2020-01-16
    C. W. Sandbo Chang, Carlos Sabín, P. Forn-Díaz, Fernando Quijandría, A. M. Vadiraj, I. Nsanzineza, G. Johansson, and C. M. Wilson
    更新日期:2020-01-17
  • Coexistence of Surface and Bulk Ferromagnetism Mimics Skyrmion Hall Effect in a Topological Insulator
    Phys. Rev. X (IF 12.211) Pub Date : 2020-01-17
    K. M. Fijalkowski, M. Hartl, M. Winnerlein, P. Mandal, S. Schreyeck, K. Brunner, C. Gould, and L. W. Molenkamp
    更新日期:2020-01-17
  • Real-Time Observation of Stacking Faults in Gold Shock Compressed to 150 GPa
    Phys. Rev. X (IF 12.211) Pub Date : 2020-01-15
    Surinder M. Sharma, Stefan J. Turneaure, J. M. Winey, P. A. Rigg, N. Sinclair, Xiaoming Wang, Y. Toyoda, and Y. M. Gupta
    更新日期:2020-01-15
  • Conformal Quasicrystals and Holography
    Phys. Rev. X (IF 12.211) Pub Date : 2020-01-14
    Latham Boyle, Madeline Dickens, and Felix Flicker
    更新日期:2020-01-15
  • Accelerating polaritons with external electric and magnetic fields
    Phys. Rev. X (IF 12.211) Pub Date : 
    T. Chervy, P. Knüppel, H. Abbaspour, M. Lupatini, S. Fält, W. Wegscheider, M. Kroner, and A. Imamoǧlu

    It is widely assumed that photons cannot be manipulated using electric or magnetic fields. Even though hybridization of photons with electronic polarization to form exciton-polaritons has paved the way to a number of ground-breaking experiments in semiconductor microcavities, the neutral bosonic nature of these quasiparticles has severely limited their response to external gauge fields. Here, we demonstrate polariton acceleration by external electric and magnetic fields in the presence of nonperturbative coupling between polaritons and itinerant electrons, leading to formation of new quasiparticles termed polaron-polaritons. We identify the generation of electron density gradients by the applied fields to be primarily responsible for inducing a gradient in polariton energy, which in turn leads to acceleration along a direction determined by the applied fields. Remarkably, we also observe that different polarization components of the polaritons can be accelerated in opposite directions when the electrons are in ν=1 integer quantum Hall state.

    更新日期:2020-01-15
  • Ab InitioFew-Mode Theory for Quantum Potential Scattering Problems
    Phys. Rev. X (IF 12.211) Pub Date : 2020-01-13
    Dominik Lentrodt and Jörg Evers
    更新日期:2020-01-13
  • Partial Up-Up-Down Order with the Continuously Distributed Order Parameter in the Triangular AntiferromagnetTmMgGaO4
    Phys. Rev. X (IF 12.211) Pub Date : 2020-01-10
    Yuesheng Li, Sebastian Bachus, Hao Deng, Wolfgang Schmidt, Henrik Thoma, Vladimir Hutanu, Yoshifumi Tokiwa, Alexander A. Tsirlin, and Philipp Gegenwart
    更新日期:2020-01-10
  • Mapping and modeling the nanomechanics of bare and protein-coated lipid nanotubes
    Phys. Rev. X (IF 12.211) Pub Date : 
    Guillaume Lamour, Antoine Allard, Juan Pelta, Sid Labdi, Martin Lenz, and Clément Campillo

    Membrane nanotubes are continuously assembled and disassembled by the cell to generate and dispatch transport vesicles, for instance in endocytosis. While these processes crucially involve the ill-understood local mechanics of the nanotube, existing micromanipulation assays only give access to its global mechanical properties Here we develop a new platform to study this local mechanics using atomic force microscopy (AFM). On a single coverslip we quickly generate millions of substrate-bound nanotubes, out of which dozens can be imaged by AFM in a single experiment. A full theoretical description of the AFM tip-membrane interaction allows us to accurately relate AFM measurements of the nanotubes’ heights, widths, and rigidities to the membrane bending rigidity and tension thus demonstrating our assay as an accurate probe of nanotube mechanics. We reveal a universal relationship between nanotube height and rigidity, which is unaffected by the specific conditions of attachment to the substrate. Moreover, we show that the parabolic shape of force-displacement curves results from thermal fluctuations of the membrane that collides intermittently with the AFM tip. We also show that membrane nanotubes can exhibit high resilience against extreme lateral compression. Finally, we mimic in vivo actin polymerization on nanotubes, and use AFM to assess the induced changes in nanotube physical properties. Our assay may help unravel the local mechanics of membrane-protein interactions, including membrane remodeling in nanotube scission and vesicle formation.

    更新日期:2020-01-10
  • Using a Recurrent Neural Network to Reconstruct Quantum Dynamics of a Superconducting Qubit from Physical Observations
    Phys. Rev. X (IF 12.211) Pub Date : 2020-01-09
    E. Flurin, L. S. Martin, S. Hacohen-Gourgy, and I. Siddiqi
    更新日期:2020-01-09
  • Slow quantum thermalization and many-body revivals from mixed phase space
    Phys. Rev. X (IF 12.211) Pub Date : 
    A. A. Michailidis, C. J. Turner, Z. Papić, D. A. Abanin, and M. Serbyn

    Relaxation of few-body quantum systems can strongly depend on the initial state when the system’s semiclassical phase space is , i.e., regions of chaotic motion coexist with regular islands. In recent years, there has been much effort to understand the process of thermalization in strongly interacting quantum systems that often lack an obvious semiclassical limit. Time-dependent variational principle (TDVP) allows to systematically derive an effective classical (nonlinear) dynamical system by projecting unitary many-body dynamics onto a manifold of weakly-entangled variational states. We demonstrate that such dynamical systems generally possess mixed phase space. When TDVP errors are small, the mixed phase space leaves a footprint on the exact dynamics of the quantum model. For example, when the system is initialized in a state belonging to a stable periodic orbit or the surrounding regular region, it exhibits persistent many-body quantum revivals. As a proof of principle, we identify new types of ``quantum many-body scars", i.e., initial states that lead to long-time oscillations in a model of interacting Rydberg atoms in one and two dimensions. Intriguingly, the initial states that give rise to most robust revivals are typically entangled states. On the other hand, even when TDVP errors are large, as in the thermalizing tilted-field Ising model, initializing the system in a regular region of phase space leads to surprising slowdown of thermalization. Our work establishes TDVP as a method for identifying interacting quantum systems with anomalous dynamics in arbitrary dimensions. Moreover, the mixed-phase space classical variational equations allow to find slowly-thermalizing initial conditions in interacting models. Our results shed light on a link between classical and quantum chaos, pointing towards possible extensions of classical Kolmogorov-Arnold-Moser (KAM) theorem to quantum systems.

    更新日期:2020-01-09
  • Classical Dimers on Penrose Tilings
    Phys. Rev. X (IF 12.211) Pub Date : 2020-01-08
    Felix Flicker, Steven H. Simon, and S. A. Parameswaran
    更新日期:2020-01-08
  • Increasing the Representation Accuracy of Quantum Simulations of Chemistry without Extra Quantum Resources
    Phys. Rev. X (IF 12.211) Pub Date : 2020-01-07
    Tyler Takeshita, Nicholas C. Rubin, Zhang Jiang, Eunseok Lee, Ryan Babbush, and Jarrod R. McClean
    更新日期:2020-01-07
  • Full-field terahertz imaging at kilohertz frame-rates using atomic vapor
    Phys. Rev. X (IF 12.211) Pub Date : 
    Lucy A. Downes, Andrew R. MacKellar, Daniel J. Whiting, Cyril Bourgenot, Charles S. Adams, and Kevin J. Weatherill

    There is much interest in employing terahertz (THz) radiation across a range of imaging applications but so far technologies have struggled to achieve the necessary framerates. Here we demonstrate a THz imaging system based upon efficient THz-to-optical conversion in atomic vapour, where full-field images can be collected at ultra-high speeds using conventional optical camera technology. For a 0.55~THz field we show an effective 1,cm2 sensor with near diffraction-limited spatial resolution and a minimum detectable power of 190±30,fWs−1/2, per 40×40,m pixel capable of video capture at 3000 frames per second. This combination of speed and sensitivity represents a step change in the state of the art of THz imaging, and will likely lead to its uptake in wider industrial settings.

    更新日期:2020-01-07
  • Topological elasticity of flexible structures
    Phys. Rev. X (IF 12.211) Pub Date : 
    Adrien Saremi and Zeb Rocklin

    Flexible mechanical metamaterials possess repeating structural motifs that imbue them with novel, exciting properties including programmability, anomalous elastic moduli and nonlinear and robust response. We address such structures via micromorphic continuum elasticity, which allows highly nonuniform deformations (missed in conventional elasticity) within unit cells that nevertheless vary smoothly between cells. We show that the bulk microstructure gives rise to boundary elastic terms. Discrete lattice theories have shown that critically coordinated structures possess a topological invariant which determines the placement of low-energy modes on edges of such a system. We show that in continuum systems a new topological invariant emerges which relates the difference in the number of such modes between two opposing edges. Guided by the continuum limit of the lattice structures, we identify macroscopic experimental observables for these topological properties that may be observed independently on a new length scale above that of the microstructure.

    更新日期:2020-01-07
  • Spatiotemporal Mapping of a Photocurrent Vortex in MonolayerMoS2Using Diamond Quantum Sensors
    Phys. Rev. X (IF 12.211) Pub Date : 2020-01-06
    Brian B. Zhou, Paul C. Jerger, Kan-Heng Lee, Masaya Fukami, Fauzia Mujid, Jiwoong Park, and David D. Awschalom
    更新日期:2020-01-06
  • Marvels and pitfalls of the Langevin algorithm in noisy high-dimensional inference
    Phys. Rev. X (IF 12.211) Pub Date : 
    Stefano Sarao Mannelli, Giulio Biroli, Chiara Cammarota, Florent Krzakala, Pierfrancesco Urbani, and Lenka Zdeborová

    Gradient-descent-based algorithms and their stochastic versions have widespread applications in machine learning and statistical inference. In this work we perform an analytic study of the performances of the one most commonly considered in physics, the Langevin algorithm, in the context of noisy high-dimensional inference. We employ the Langevin algorithm to sample the posterior probability measure for the spiked matrix-tensor model. The typical behaviour of this algorithm is described by a system of integro-differential equations that we call the Langevin state evolution, whose solution is compared with the one of the state evolution of approximate message passing (AMP). Our results show that, remarkably, the algorithmic threshold of the Langevin algorithm is sub-optimal with respect to the one given by AMP. This phenomenon is due to the residual glassiness present in that region of parameters. We present also a simple heuristic expression of the transition line which appears to be in agreement with the numerical results.

    更新日期:2020-01-06
  • High-Fidelity Measurement of Qubits Encoded in Multilevel Superconducting Circuits
    Phys. Rev. X (IF 12.211) Pub Date : 2020-01-02
    Salvatore S. Elder, Christopher S. Wang, Philip Reinhold, Connor T. Hann, Kevin S. Chou, Brian J. Lester, Serge Rosenblum, Luigi Frunzio, Liang Jiang, and Robert J. Schoelkopf
    更新日期:2020-01-04
  • Spectroscopic Visualization of a Robust Electronic Response of Semiconducting Nanowires to Deposition of Superconducting Islands
    Phys. Rev. X (IF 12.211) Pub Date : 2020-01-03
    Jonathan Reiner, Abhay Kumar Nayak, Amit Tulchinsky, Aviram Steinbok, Tom Koren, Noam Morali, Rajib Batabyal, Jung-Hyun Kang, Nurit Avraham, Yuval Oreg, Hadas Shtrikman, and Haim Beidenkopf
    更新日期:2020-01-04
  • Direct comparison of many-body methods for realistic electronic Hamiltonians
    Phys. Rev. X (IF 12.211) Pub Date : 
    Kiel T. Williams, Yuan Yao, Jia Li, Li Chen, Hao Shi, Mario Motta, Chunyao Niu, Ushnish Ray, Sheng Guo, Robert J. Anderson, Junhao Li, Lan Nguyen Tran, Chia-Nan Yeh, Bastien Mussard, Sandeep Sharma, Fabien Bruneval, Mark van Schilfgaarde, George H. Booth, Garnet Kin-Lic Chan, Shiwei Zhang, Emanuel Gull, Dominika Zgid, Andrew Millis, Cyrus J. Umrigar, and Lucas K. Wagner

    A large collaboration carefully benchmarks 20 first principles many-body electronic structure methods on a test set of 7 transition metal atoms, and their ions and monoxides. Good agreement is attained between 3 systematically converged methods, resulting in experiment-free reference values. These reference values are used to assess the accuracy of modern emerging and scalable approaches to the many-electron problem. The most accurate methods obtain energies indistinguishable from experimental results, with the agreement mainly limited by the experimental uncertainties. Comparison between methods enables a unique perspective on calculations of many-body systems of electrons.

    更新日期:2020-01-04
  • 更新日期:2019-12-31
  • Asymptotic Security Analysis of Discrete-Modulated Continuous-Variable Quantum Key Distribution
    Phys. Rev. X (IF 12.211) Pub Date : 2019-12-30
    Jie Lin, Twesh Upadhyaya, and Norbert Lütkenhaus
    更新日期:2019-12-30
  • Quantum Skyrmions in Frustrated Ferromagnets
    Phys. Rev. X (IF 12.211) Pub Date : 2019-12-27
    Vivek Lohani, Ciarán Hickey, Jan Masell, and Achim Rosch
    更新日期:2019-12-27
  • Crossover of Charge Fluctuations across the Strange Metal Phase Diagram
    Phys. Rev. X (IF 12.211) Pub Date : 2019-12-26
    Ali A. Husain, Matteo Mitrano, Melinda S. Rak, Samantha Rubeck, Bruno Uchoa, Katia March, Christian Dwyer, John Schneeloch, Ruidan Zhong, G. D. Gu, and Peter Abbamonte
    更新日期:2019-12-27
  • Spin-orbital-intertwined nematic state in FeSe
    Phys. Rev. X (IF 12.211) Pub Date : 
    J. Li, B. Lei, D. Zhao, L. P. Nie, D. W. Song, L. X. Zheng, S. J. Li, B. L. Kang, X. G. Luo, T. Wu, and X. H. Chen

    {The importance of the spin-orbit coupling (SOC) effect in Fe-based superconductors (FeSCs) has recently been under hot debate. Considering the Hund’s coupling-induced electronic correlation, the understanding of the role of SOC in FeSCs is not trivial and still elusive. Here, through a comprehensive study of 77Se and 57Fe nuclear magnetic resonance, a nontrivial SOC effect is revealed in the nematic state of FeSe. Firstly, the orbital-dependent spin susceptibility, determined by the anisotropy of the 57Fe Knight shift, indicates a predominant role from the 3 orbital, which suggests the coexistence of local and itinerant spin degrees of freedom (d.o.f.) in the FeSe. Then, we reconfirm that the orbital reconstruction below the nematic transition temperature ( ∼ 90 K) happens not only on the 3 and 3 orbitals but also on the 3 orbital, which is beyond a trivial ferro-orbital order picture. Moreover, our results also indicate the development of a coherent coupling between the local and itinerant spin d.o.f. below , which is ascribed to a Hund’s coupling-induced electronic crossover on the orbital. . The present work not only reveals a nontrivial SOC effect in the nematic state but also sheds light on the mechanism of nematic transition in FeSe.

    更新日期:2019-12-26
  • Nematic state in CeAuSb2
    Phys. Rev. X (IF 12.211) Pub Date : 
    S. Seo, Xiaoyu Wang, S. M. Thomas, M. C. Rahn, D. Carmo, F. Ronning, E. D. Bauer, R. D. dos Reis, M. Janoschek, J. D. Thompson, R. M. Fernandes, and P. F. S. Rosa

    At ambient pressure and zero field, tetragonal CeAuSb2 hosts stripe antiferromagnetic order at TN=6.3~K. Here we first show via bulk thermodynamic probes and x-ray diffraction measurements that this magnetic order is connected with a structural phase transition to a superstructure which likely breaks C4 symmetry, thus signaling nematic order. The temperature-field-pressure phase diagram of CeAuSb2 subsequently reveals the emergence of additional ordered states under applied pressure at a multicritical point. Our phenomenological model supports the presence of a vestigial nematic phase in CeAuSb2 akin to iron-based high-temperature superconductors; however, superconductivity, if present, remains to be discovered.

    更新日期:2019-12-26
  • Intrinsic Anomalous Nernst Effect Amplified by Disorder in a Half-Metallic Semimetal
    Phys. Rev. X (IF 12.211) Pub Date : 2019-12-24
    Linchao Ding, Jahyun Koo, Liangcai Xu, Xiaokang Li, Xiufang Lu, Lingxiao Zhao, Qi Wang, Qiangwei Yin, Hechang Lei, Binghai Yan, Zengwei Zhu, and Kamran Behnia
    更新日期:2019-12-25
  • Topological insulator state and collapse of the quantum Hall effect in a three-dimensional Dirac semimetal heterojunction
    Phys. Rev. X (IF 12.211) Pub Date : 
    David Kealhofer, Luca Galletti, Timo Schumann, Alexey Suslov, and Susanne Stemmer

    Thin films promise new opportunities for the manipulation of surface states of topological semimetals with the potential to realize new states that cannot be obtained in bulk materials. Here, we report transport studies of gated Hall bar structures fabricated from approximately 50-nm-thick, (001)-oriented epitaxial films of cadmium arsenide, a prototype three-dimensional Dirac semimetal, at magnetic fields up to 45 T. The films exhibit a quantized Hall effect with pronounced odd-integer plateaus that is strikingly different from that of the more widely studied (112)-oriented films. We show that the unusual quantum Hall effect is a consequence of the inverted, bulk band structure of cadmium arsenide that creates topological insulator-like states at bottom and top interfaces, each exhibiting a half-integer quantum Hall effect. A small potential offset between the two surfaces results in crossing of the Landau levels and gives rise to the filling factor sequences observed in the experiments. Moreover, at large negative gate biases, the filling factor {$$} = 1 is abruptly preempted by an insulating state that is accompanied by the collapse of the well-developed quantum Hall effect We suggest that this new phase cannot be explained within a single particle picture and discuss the role of Coulomb interactions between spatially separated surface states.

    更新日期:2019-12-25
  • Quantum computing with rotation-symmetric bosonic codes
    Phys. Rev. X (IF 12.211) Pub Date : 
    Arne L. Grimsmo, Joshua Combes, and Ben Q. Baragiola

    Bosonic rotation codes, introduced here, are a broad class of bosonic error-correcting codes based on phase-space rotation symmetry. We present a universal quantum computing scheme applicable to a subset of this class—number-phase codes—which includes the well-known cat and binomial codes, among many others. The entangling gate in our scheme is code-agnostic and can be used to interface different rotation-symmetric encodings. In addition to a universal set of operations, we propose a teleportation-based error correction scheme that allows recoveries to be tracked entirely in software. Focusing on cat and binomial codes as examples, we compute average gate fidelities for error correction under simultaneous loss and dephasing noise and show numerically that the error-correction scheme is close to optimal for error-free ancillae and ideal measurements. Finally, we present a scheme for fault-tolerant, universal quantum computing based on concatenation of number-phase codes and Bacon-Shor subsystem codes.

    更新日期:2019-12-25
  • Topological and subsystem codes on low-degree graphs with flag qubits
    Phys. Rev. X (IF 12.211) Pub Date : 
    Christopher Chamberland, Guanyu Zhu, Theodore J. Yoder, Jared B. Hertzberg, and Andrew W. Cross

    In this work we introduce two code families, which we call the heavy hexagon code and heavy square code. Both code families are implemented by assigning physical data and ancilla qubits to both vertices and edges of low degree graphs. Such a layout is particularly suitable for superconducting qubit architectures to minimize frequency collisions and crosstalk. In some cases, frequency collisions can be reduced by several orders of magnitude. The heavy hexagon code is a hybrid surface/Bacon-Shor code mapped onto a (heavy) hexagonal lattice whereas the heavy square code is the surface code mapped onto a (heavy) square lattice. In both cases, the lattice includes all the ancilla qubits required for fault-tolerant error-correction. Naively, the limited qubit connectivity might be thought to limit the error-correcting capability of the code to less than its full distance. Therefore, essential to our construction is the use of flag qubits. We modify minimum weight perfect matching decoding to efficiently and scalably incorporate information from measurements of the flag qubits and correct up to the full code distance while respecting the limited connectivity. Simulations show that high threshold values for both codes can be obtained using our decoding protocol. Further, our decoding scheme can be adapted to other topological code families.

    更新日期:2019-12-25
  • Fast high-fidelity quantum non-demolition qubit readout via a non-perturbative cross-Kerr coupling
    Phys. Rev. X (IF 12.211) Pub Date : 
    R. Dassonneville, T. Ramos, V. Milchakov, L. Planat, É. Dumur, F. Foroughi, J. Puertas, S. Leger, K. Bharadwaj, J. Delaforce, C. Naud, W. Hasch-Guichard, J. J. García-Ripoll, N. Roch, and O. Buisson

    Qubit readout is an indispensable element of any quantum information processor. In this work, we experimentally demonstrate a non-perturbative cross-Kerr coupling between a transmon and harmonic oscillator which enables an improved quantum non-demolition (QND) readout for superconducting qubits. The new mechanism uses the same experimental techniques as the standard QND qubit readout in the dispersive approximation, but due to its non-perturbative nature, it maximizes the speed, the single-shot fidelity and the QND properties of the readout. In addition, it minimizes the effect of unwanted decay channels such as the Purcell effect. We observed a single-shot readout fidelity of for short pulses, and we quantified a QND-ness of for long measurement pulses with repeated single-shot readouts.

    更新日期:2019-12-25
  • Black Hole Ringdown: The Importance of Overtones
    Phys. Rev. X (IF 12.211) Pub Date : 2019-12-23
    Matthew Giesler, Maximiliano Isi, Mark A. Scheel, and Saul A. Teukolsky
    更新日期:2019-12-23
  • Similarities and differences between LaNiO2and CaCuO2and implications for superconductivity
    Phys. Rev. X (IF 12.211) Pub Date : 
    A. S. Botana and M. R. Norman

    The recent observation of superconductivity in hole-doped NdNiO2 has generated considerable attention. The similarities and differences between this infinite-layer nickelate and cuprates are still an open question. To address this issue we derive, via first principles calculations, essential facts related to the electronic structure and magnetism of RNiO2 (R= La, Nd) in comparison to their cuprate analog CaCuO2. From this detailed comparison, we find that RNiO2 are promising as cuprate analogs. Besides the much larger d-p energy splitting, and the presence of R-5d states near the Fermi energy in the parent compound, all other electronic structure parameters seem to be favorable in the context of superconductivity as inferred from the cuprates. In particular, the large value of the longer range hopping t′ and the eg energy splitting are similar to those obtained in cuprates. Doping further acts to increase the cuprate-like character of these nickelates by suppressing the self-doping effect of the R-5d bands.

    更新日期:2019-12-23
  • Erratum: Engineering Matter Interactions Using Squeezed Vacuum [Phys. Rev. X7, 021041 (2017)]
    Phys. Rev. X (IF 12.211) Pub Date : 2019-12-20
    Sina Zeytinoğlu, Ataç İmamoğlu, and Sebastian Huber
    更新日期:2019-12-21
  • Quantum-Assisted Measurement of Atomic Diamagnetism
    Phys. Rev. X (IF 12.211) Pub Date : 
    Yaakov Y. Fein, Armin Shayeghi, Lukas Mairhofer, Filip Kiałka, Philipp Rieser, Philipp Geyer, Stefan Gerlich, and Markus Arndt

    We report the first measurement of ground state diamagnetism of isolated neutral atoms in an atomic beam. We realize this using magnetic deflection of fringes in a long baseline matter-wave interferometer. The observed diamagnetic susceptibilities of −5.8±0.2±0.3×10−9m3/kg for barium and −6.9±0.3±0.6×10−9m3/kg for strontium are in good agreement with the theory values, and correspond to a measured force on the order of 10−26 N. The high force sensitivity also allowed us to observe the isotope dependence of the interference visibility due to the nuclear permanent magnetic moment, thereby demonstrating a new method for neutral isotope selection. The universality of the technique allows the magnetism of a wide range of atoms and molecules to be studied in the gas phase.

    更新日期:2019-12-21
  • Mode-locked topological insulator laser utilizing synthetic dimensions
    Phys. Rev. X (IF 12.211) Pub Date : 
    Zhaoju Yang, Eran Lustig, Gal Harari, Yonatan Plotnik, Miguel A. Bandres, Yaakov Lumer, and Mordechai Segev

    We propose a system that exploits the fundamental features of topological photonics and synthetic dimensions to force many semiconductor laser resonators to synchronize, mutually lock, and under suitable modulation emit a train of transform-limited mode-locked pulses. These lasers exploit the Floquet topological edge states in a 1D array of ring resonators, which corresponds to a 2D topological system with one spatial dimension and one synthetic frequency dimension. We show that the lasing state of the multi-element laser system possesses the distinct characteristics of spatial topological edge states while exhibiting topologically protected transport. The topological synthetic-space edge mode imposes a constant-phase difference between the multi-frequency modes on the edges, and together with modulation of the individual elements forces the ensemble of resonators to mode-lock and emit short pulses, robust to disorder in the multi-resonator system. Our results offer a proof-of-concept mechanism to actively mode-lock a laser diode array of many lasing elements, which is otherwise extremely difficult due to the presence of many spatial modes of the array. The topological synthetic-space concepts proposed here offer an avenue to overcome this major technological challenge, and open new opportunities in laser physics.

    更新日期:2019-12-21
  • Weak Crystallization of Fluctuating Skyrmion Textures in MnSi
    Phys. Rev. X (IF 12.211) Pub Date : 2019-12-20
    J. Kindervater, I. Stasinopoulos, A. Bauer, F. X. Haslbeck, F. Rucker, A. Chacon, S. Mühlbauer, C. Franz, M. Garst, D. Grundler, and C. Pfleiderer
    更新日期:2019-12-20
  • Optimal renormalization group transformation from information theory
    Phys. Rev. X (IF 12.211) Pub Date : 
    Patrick M. Lenggenhager, Doruk Efe Gökmen, Zohar Ringel, Sebastian D. Huber, and Maciej Koch-Janusz

    Recently, a novel real-space renormalisation group (RG) algorithm was introduced. By maximising an information-theoretic quantity, the real-space mutual information, the algorithm identifies the relevant low-energy degrees of freedom. Motivated by this, we investigate the information theoretic properties of coarse-graining procedures, for both translationally invariant and disordered systems. We prove that a perfect RSMI coarse-graining does not increase the range of interactions in the renormalized Hamiltonian, and, for disordered systems, suppresses generation of correlations in the renormalized disorder distribution, being in this sense . We empirically verify decay of those measures of complexity, as a function of information retained by the RG, on the examples of arbitrary coarse-grainings of the clean and random Ising chain. The results establish a direct and quantifiable connection between properties of RG viewed as a compression scheme, and those of physical objects i.e.~Hamiltonians and disorder distributions. We also study the effect of constraints on the number and type of coarse-grained degrees of freedom on a generic RG procedure.

    更新日期:2019-12-20
  • Rheo-acoustic gels: Tuning mechanical and flow properties of colloidal gels with ultrasonic vibrations
    Phys. Rev. X (IF 12.211) Pub Date : 
    Thomas Gibaud, Noémie Dag‘es, Pierre Lidon, Guillaume Jung, L. Christian Ahouré, Michael Sztucki, Arnaud Poulesquen, Nicolas Hengl, Frédéric Pignon, and Sébastien Manneville

    Colloidal gels, where nanoscale particles aggregate into an elastic yet fragile network, are at the heart of materials that combine specific optical, electrical and mechanical properties. Tailoring the viscoelastic features of colloidal gels in real-time thanks to an external stimulus currently appears as a major challenge in the design of "smart" soft materials. Here we present rheo-acoustic gels a new class of materials that are ultrasound sensitive. By using a combination of rheological and structural characterization, we evidence and quantify a strong softening in three widely different colloidal gels submitted to ultrasonic vibrations (with submicron amplitude and frequency 20–500~kHz). This softening is attributed to the fragmentation of the gel network into large clusters that may or may not fully re-aggregate once ultrasound is turned off depending on the acoustic intensity. Ultrasound is further shown to dramatically decrease the gel yield stress and accelerate shear-induced fluidization, thus opening the way to a full control of elastic and flow properties by ultrasonic vibrations.

    更新日期:2019-12-20
  • Subdiffusion and heat transport in a tilted two-dimensional Fermi-Hubbard system
    Phys. Rev. X (IF 12.211) Pub Date : 
    Elmer Guardado-Sanchez, Alan Morningstar, Benjamin M. Spar, Peter T. Brown, David A. Huse, and Waseem S. Bakr

    Using quantum gas microscopy we study the late-time effective hydrodynamics of an isolated cold-atom Fermi-Hubbard system subject to an external linear potential (a ``tilt"). The tilt is along one of the principal directions of the two-dimensional (2D) square lattice and couples mass transport to local heating through energy conservation. Due to this coupling the system quickly heats up to near infinite temperature in the lowest band of the lattice. We study the high-temperature transport and thermalization in our system by observing the decay of prepared initial density waves as a function of wavelength λ and tilt strength and find that the associated decay time τ crosses over as the tilt strength is increased from characteristically diffusive to subdiffusive with τ∝λ4. In order to explain the underlying physics and emphasize its universal nature we develop a hydrodynamic model that exhibits this crossover. For strong tilts, the subdiffusive transport rate is set by a thermal diffusivity, which we are thus able to measure as a function of tilt in this regime. We further support our understanding by probing the local inverse temperature of the system at strong tilts, finding good agreement with our theoretical predictions. Finally, we discuss the relation of the strongly tilted limit of our system to recently studied 1D models which may exhibit nonergodic dynamics.

    更新日期:2019-12-20
  • Topological Elasticity of Nonorientable Ribbons
    Phys. Rev. X (IF 12.211) Pub Date : 2019-12-19
    Denis Bartolo and David Carpentier
    更新日期:2019-12-19
  • Experimental Evidence of Hydrodynamic Instantons: The Universal Route to Rogue Waves
    Phys. Rev. X (IF 12.211) Pub Date : 2019-12-18
    Giovanni Dematteis, Tobias Grafke, Miguel Onorato, and Eric Vanden-Eijnden
    更新日期:2019-12-19
  • Photo-induced nonequilibrium response in heavily underdoped YBa2Cu3O6.45probed by time-resolved terahertz spectroscopy
    Phys. Rev. X (IF 12.211) Pub Date : 
    S. J. Zhang, Z. X. Wang, H. Xiang, X. Yao, Q. M. Liu, L. Y. Shi, T. Lin, T. Dong, D. Wu, and N. L. Wang

    Intense laser pulses have recently emerged as a tool to tune between different orders in complex quantum materials. Among different light-induced phenomena, transient superconductivity far above the equilibrium transition temperature in cuprates is particularly attractive. Key to those experiments was the resonant pumping of specific phonon modes, which was believed to suppress the competing orders and induce superconducting phase coherence. Here, we present a comprehensive study of photo-induced nonequilibrium response in underdoped YBa2Cu3O6+x. We find that upon photo-excitations, Josephson plasma edge in superconducting state is initially removed accompanied by quasiparticle excitations, and subsequently reappears at frequency lower than the static plasma edge within short time. In normal state, an enhancement or weaker edge-like shape is indeed induced by pump pulses in the reflectance spectrum accompanied by simultaneous rises in both real and imaginary parts of conductivity. We compare the pump-induced effects between near- and mid-infrared excitations and exclude phonon pumping as a scenario for the photo-induced effects above. We further elaborate the transient responses in normal state are unlikely to be explained by photo-induced superconductivity.

    更新日期:2019-12-19
  • Extracting the field theory description of a quantum many-body system from experimental data
    Phys. Rev. X (IF 12.211) Pub Date : 
    Torsten V. Zache, Thomas Schweigler, Sebastian Erne, Jörg Schmiedmayer, and Jürgen Berges

    Quantum field theory is a powerful tool to describe the relevant physics governing complex quantum many-body systems. Here we develop a general pathway to extract the irreducible building blocks of quantum field theoretical descriptions and its parameters purely from experimental data. This is accomplished by extracting the one-particle irreducible (1PI) correlation functions from which one can construct all physical observables. To match the capabilities of experimental techniques, our approach employs a formulation of quantum field theory based on equal-time correlation functions only. We illustrate the theoretical foundations of our procedure by applying it to the sine-Gordon model in thermal equilibrium, and then demonstrate explicitly how to extract these quantities from an experiment where we quantum simulate the sine-Gordon model by two tunnel-coupled superfluids. We extract all 1PI correlation functions up to the 1PI four-point function (interaction vertex) and their variation with momentum, encoding the `running’ of the couplings. The measured 1PI correlation functions are compared to the theoretical estimates, verifying our procedure. Our work opens new ways of addressing complex many-body questions emerging in a large variety of settings from fundamental science to practical quantum technology.

    更新日期:2019-12-19
  • Non-Abelian symmetries and disorder: A broad non-ergodic regime and anomalous thermalization
    Phys. Rev. X (IF 12.211) Pub Date : 
    Ivan V. Protopopov, Rajat K. Panda, Tommaso Parolini, Antonello Scardicchio, Eugene Demler, and Dmitry A. Abanin

    Previous studies revealed a crucial effect of symmetries on the properties of a single particle moving in a disorder potential. More recently, a phenomenon of many-body localization (MBL) has been attracting much theoretical and experimental interest. MBL systems are characterized by the emergence of quasi-local integrals of motion, and by the area-law entanglement entropy scaling of its eigenstates. In this paper, we investigate the effect of a non-Abelian SU(2) symmetry on the dynamical properties of a disordered Heisenberg chain. While SU(2) symmetry is inconsistent with conventional MBL, a new non-ergodic regime is possible. In this regime, the eigenstates exhibit faster than area-law, but still strongly sub-thermal scaling of the entanglement entropy. Using extensive exact diagonalization simulations, we establish that this non-ergodic regime is indeed realized in the strongly disordered Heisenberg chains. We use real-space renormalization group (RSRG) to construct approximate excited eigenstates by tree tensor networks, and demonstrate the accuracy of this procedure for systems of size up to L=26. As the effective disorder strength is decreased, a crossover to the thermalizing phase occurs. To establish the ultimate fate of the non-ergodic regime in the thermodynamic limit, we develop a novel approach for describing many-body processes that are usually neglected by RSRG. This approach is capable of describing systems of size L≈2000. We characterize the resonances that arise due to such processes, finding that they involve an ever growing number of spins as the system size is increased. Crucially, the probability of finding resonances grows with the system’s size. Even at strong disorder, we can identify a large length scale beyond which resonances proliferate. Presumably, this would eventually drive the system to a thermalizing phase. However, the extremely long thermalization time scales indicate that a broad non-ergodic regime will be observable experimentally. Our study demonstrates that, similar to the case of single-particle localization, symmetries control dynamical properties of disordered, many-body systems. The approach introduced here provides a versatile tool for describing a broad range of disordered many-body systems, well beyond sizes accessible in previous studies.

    更新日期:2019-12-19
  • Phase Transition in the Recoverability of Network History
    Phys. Rev. X (IF 12.211) Pub Date : 2019-12-17
    Jean-Gabriel Young, Guillaume St-Onge, Edward Laurence, Charles Murphy, Laurent Hébert-Dufresne, and Patrick Desrosiers
    更新日期:2019-12-18
  • Real-time observation of stacking faults in gold shock-compressed to 150 GPa
    Phys. Rev. X (IF 12.211) Pub Date : 
    Surinder M. Sharma, Stefan J. Turneaure, J. M. Winey, P. A. Rigg, N. Sinclair, Xiaoming Wang, Y. Toyoda, and Y. M. Gupta

    A microscopic-level understanding of the high-pressure states achieved under shock compression, including comparisons with static compression, is a long-standing and important scientific challenge. Unlike hydrostatic compression, uniaxial strains inherent to shock compression result in plastic deformation and abundant lattice defects. At high pressures (> 50 GPa), the role of shock-induced deformation and defects remains an open question. Due to the nanosecond time scales in shock experiments, real-time in situ observations of shock-induced lattice defects have been challenging. Here, we present synchrotron x-ray diffraction measurements on laser-shock-compressed gold that provide the first unambiguous in situ measurements of stacking faults (SFs), likely formed by partial dislocations, during shock compression. SF abundance increases monotonically with shock compression up to 150 GPa, where SFs comprise almost every 6th atomic layer. Our results show that SFs play an important role in the plastic deformation of face-centered-cubic metals shocked to high stresses, providing a quantitative benchmark for future theoretical developments.

    更新日期:2019-12-18
  • Topological Insulator-to-Weyl Semimetal Transition in Strongly Correlated Actinide System UNiSn
    Phys. Rev. X (IF 12.211) Pub Date : 2019-12-16
    Vsevolod Ivanov, Xiangang Wan, and Sergey Y. Savrasov
    更新日期:2019-12-17
  • Synchronization to big-data: Nudging the Navier-Stokes equations for data assimilation of turbulent flows
    Phys. Rev. X (IF 12.211) Pub Date : 
    Patricio Clark Di Leoni, Andrea Mazzino, and Luca Biferale

    Nudging is an important data assimilation technique where partial field measurements are used to control the evolution of a dynamical system and/or to reconstruct the entire phase-space configuration of the supplied flow. Here, we apply it to the canonical problem of fluid dynamics: three dimensional homogeneous and isotropic turbulence. By doing numerical experiments we perform a systematic assessment of how well the technique reconstructs large- and small-scales features of the flow with respect to the quantity and the quality/type of data supplied to it. The types of data used are: (i) field values on a fixed number of spatial locations (Eulerian nudging), (ii) Fourier coefficients of the fields on a fixed range of wavenumbers (Fourier nudging), or (iii) field values along a set of moving probes inside the flow (Lagrangian nudging). We present state-of-the-art quantitative measurements of the scale-by-scale {} and a detailed discussion of the probability distribution function of the reconstruction error, by comparing the nudged field and the {} point-by-point. Furthermore, we show that for more complex flow configurations, like the case of anisotropic rotating turbulence, the presence of cyclonic and anticyclonic structures leads to unexpectedly better performances of the algorithm. We discuss potential further applications of nudging to a series of applied flow configurations, including the problem of field-reconstruction in thermal Rayleigh-B'enard convection and in magnetohydrodynamics (MHD), and to the determination of optimal parametrisation for small-scale turbulent modeling. Our study fixes the standard requirements for future applications of nudging to complex turbulent flows.

    更新日期:2019-12-17
  • Coexistence of surface and bulk ferromagnetism mimics skyrmion Hall effect in a topological insulator
    Phys. Rev. X (IF 12.211) Pub Date : 
    K. M. Fijalkowski, M. Hartl, M. Winnerlein, P. Mandal, S. Schreyeck, K. Brunner, C. Gould, and L. W. Molenkamp

    Here we report the investigation of the anomalous Hall effect in the magnetically doped topological insulator (V,Bi,Sb)2Te3. We find it contains two contributions of opposite sign. Both components are found to depend differently on carrier density, leading to a sign inversion of the total anomalous Hall effect as a function of applied gate voltage. The two contributions are found to have different magnetization reversal fields, which in combination with a temperature dependent study points towards the coexistence of two ferromagnetic orders in the system. Moreover, we find that the sign of total anomalous Hall response of the system depends on the thickness and magnetic doping density of the magnetic layer. The thickness dependence suggests that the two ferromagnetic components originate from the surface and bulk of the magnetic topological insulator film. We believe that our observations provide insight on the magnetic behavior, and thus will contribute to an eventual understanding of the origin of magnetism in this material class. In addition, our data bears a striking resemblance to anomalous Hall signals often associated with skyrmion contributions. Our analysis provides a straightforward explanation for both the magnetic field dependence of the Hall signal and the observed change in sign without needing to invoke skyrmions, and thus suggest that caution is needed when making claims of effects from skyrmion phases.

    更新日期:2019-12-17
  • Direct measurement of the impact of teaching experimentation in physics labs
    Phys. Rev. X (IF 12.211) Pub Date : 
    Emily M. Smith, Martin M. Stein, Cole Walsh, and N. G. Holmes

    While there have been many calls to improve the quality of instructional physics labs, there exists little research on the effectiveness of lab instruction. This study provides a direct comparison between labs that have goals to reinforce physics content to those that emphasize experimentation skills. In this controlled study, all students attended the same lecture and discussion sections, had the same homework and exams, but attended labs that had one of two aims: teaching experimentation or reinforcing content. We compared students’ engagement with experimentation during the lab as well as the impacts on students’ exam performance and attitudes and beliefs about experimental physics. We found no measurable differences between lab conditions on students’ exam performance. Nonetheless, we found measurable and significant improvements in students’ engagement in expertlike experimentation practices and attitudes and beliefs about experimental physics for students in the experimentation labs. The benefits of the experimentation labs were stable across two subsequent semesters of implementation, as measured via standardized assessments. The results provide direct evidence of the extensive benefits of using labs to teach experimentation, while directly demonstrating that shifting instructional goals and structure in labs can occur without cost to performance on course exams.

    更新日期:2019-12-17
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