%0 Journal Article %D 2023 %T Colloquium: Quantum and Classical Discrete Time Crystals %A Michael P. Zaletel %A Mikhail Lukin %A Christopher Monroe %A Chetan Nayak %A Frank Wilczek %A Norman Y. Yao %X

The spontaneous breaking of time translation symmetry has led to the discovery of a new phase of matter - the discrete time crystal. Discrete time crystals exhibit rigid subharmonic oscillations, which result from a combination of many-body interactions, collective synchronization, and ergodicity breaking. This Colloquium reviews recent theoretical and experimental advances in the study of quantum and classical discrete time crystals. We focus on the breaking of ergodicity as the key to discrete time crystals and the delaying of ergodicity as the source of numerous phenomena that share many of the properties of discrete time crystals, including the AC Josephson effect, coupled map lattices, and Faraday waves. Theoretically, there exists a diverse array of strategies to stabilize time crystalline order in both closed and open systems, ranging from localization and prethermalization to dissipation and error correction. Experimentally, many-body quantum simulators provide a natural platform for investigating signatures of time crystalline order; recent work utilizing trapped ions, solid-state spin systems, and superconducting qubits will be reviewed. Finally, this Colloquium concludes by describing outstanding challenges in the field and a vision for new directions on both the experimental and theoretical fronts.

%8 5/15/2023 %G eng %U https://arxiv.org/abs/2305.08904 %0 Journal Article %J Physical Review X %D 2022 %T Many-Body Quantum Teleportation via Operator Spreading in the Traversable Wormhole Protocol %A Thomas Schuster %A Bryce Kobrin %A Ping Gao %A Iris Cong %A Emil T. Khabiboulline %A Norbert M. Linke %A Mikhail D. Lukin %A Christopher Monroe %A Beni Yoshida %A Norman Y. Yao %X

By leveraging shared entanglement between a pair of qubits, one can teleport a quantum state from one particle to another. Recent advances have uncovered an intrinsically many-body generalization of quantum teleportation, with an elegant and surprising connection to gravity. In particular, the teleportation of quantum information relies on many-body dynamics, which originate from strongly-interacting systems that are holographically dual to gravity; from the gravitational perspective, such quantum teleportation can be understood as the transmission of information through a traversable wormhole. Here, we propose and analyze a new mechanism for many-body quantum teleportation -- dubbed peaked-size teleportation. Intriguingly, peaked-size teleportation utilizes precisely the same type of quantum circuit as traversable wormhole teleportation, yet has a completely distinct microscopic origin: it relies upon the spreading of local operators under generic thermalizing dynamics and not gravitational physics. We demonstrate the ubiquity of peaked-size teleportation, both analytically and numerically, across a diverse landscape of physical systems, including random unitary circuits, the Sachdev-Ye-Kitaev model (at high temperatures), one-dimensional spin chains and a bulk theory of gravity with stringy corrections. Our results pave the way towards using many-body quantum teleportation as a powerful experimental tool for: (i) characterizing the size distributions of operators in strongly-correlated systems and (ii) distinguishing between generic and intrinsically gravitational scrambling dynamics. To this end, we provide a detailed experimental blueprint for realizing many-body quantum teleportation in both trapped ions and Rydberg atom arrays; effects of decoherence and experimental imperfections are analyzed.

%B Physical Review X %V 12 %8 8/5/2022 %G eng %U https://arxiv.org/abs/2102.00010 %R 10.1103/physrevx.12.031013 %0 Journal Article %D 2021 %T Interactive Protocols for Classically-Verifiable Quantum Advantage %A Daiwei Zhu %A Gregory D. Kahanamoku-Meyer %A Laura Lewis %A Crystal Noel %A Or Katz %A Bahaa Harraz %A Qingfeng Wang %A Andrew Risinger %A Lei Feng %A Debopriyo Biswas %A Laird Egan %A Alexandru Gheorghiu %A Yunseong Nam %A Thomas Vidick %A Umesh Vazirani %A Norman Y. Yao %A Marko Cetina %A Christopher Monroe %X

Achieving quantum computational advantage requires solving a classically intractable problem on a quantum device. Natural proposals rely upon the intrinsic hardness of classically simulating quantum mechanics; however, verifying the output is itself classically intractable. On the other hand, certain quantum algorithms (e.g. prime factorization via Shor's algorithm) are efficiently verifiable, but require more resources than what is available on near-term devices. One way to bridge the gap between verifiability and implementation is to use "interactions" between a prover and a verifier. By leveraging cryptographic functions, such protocols enable the classical verifier to enforce consistency in a quantum prover's responses across multiple rounds of interaction. In this work, we demonstrate the first implementation of an interactive quantum advantage protocol, using an ion trap quantum computer. We execute two complementary protocols -- one based upon the learning with errors problem and another where the cryptographic construction implements a computational Bell test. To perform multiple rounds of interaction, we implement mid-circuit measurements on a subset of trapped ion qubits, with subsequent coherent evolution. For both protocols, the performance exceeds the asymptotic bound for classical behavior; maintaining this fidelity at scale would conclusively demonstrate verifiable quantum advantage.

%8 12/9/2021 %G eng %U https://arxiv.org/abs/2112.05156 %0 Journal Article %D 2021 %T Observation of a prethermal discrete time crystal %A Antonis Kyprianidis %A Francisco Machado %A William Morong %A Patrick Becker %A Kate S. Collins %A Dominic V. Else %A Lei Feng %A Paul W. Hess %A Chetan Nayak %A Guido Pagano %A Norman Y. Yao %A Christopher Monroe %X

The conventional framework for defining and understanding phases of matter requires thermodynamic equilibrium. Extensions to non-equilibrium systems have led to surprising insights into the nature of many-body thermalization and the discovery of novel phases of matter, often catalyzed by driving the system periodically. The inherent heating from such Floquet drives can be tempered by including strong disorder in the system, but this can also mask the generality of non-equilibrium phases. In this work, we utilize a trapped-ion quantum simulator to observe signatures of a non-equilibrium driven phase without disorder: the prethermal discrete time crystal (PDTC). Here, many-body heating is suppressed not by disorder-induced many-body localization, but instead via high-frequency driving, leading to an expansive time window where non-equilibrium phases can emerge. We observe a number of key features that distinguish the PDTC from its many-body-localized disordered counterpart, such as the drive-frequency control of its lifetime and the dependence of time-crystalline order on the energy density of the initial state. Floquet prethermalization is thus presented as a general strategy for creating, stabilizing and studying intrinsically out-of-equilibrium phases of matter.

%8 2/2/2021 %G eng %U https://arxiv.org/abs/2102.01695 %0 Journal Article %J Annual Review of Condensed Matter Physics %D 2020 %T Discrete Time Crystals %A Dominic V. Else %A Christopher Monroe %A Chetan Nayak %A Norman Y. Yao %X

Experimental advances have allowed for the exploration of nearly isolated quantum many-body systems whose coupling to an external bath is very weak. A particularly interesting class of such systems is those which do not thermalize under their own isolated quantum dynamics. In this review, we highlight the possibility for such systems to exhibit new non-equilibrium phases of matter. In particular, we focus on "discrete time crystals", which are many-body phases of matter characterized by a spontaneously broken discrete time translation symmetry. We give a definition of discrete time crystals from several points of view, emphasizing that they are a non-equilibrium phenomenon, which is stabilized by many-body interactions, with no analog in non-interacting systems. We explain the theory behind several proposed models of discrete time crystals, and compare a number of recent realizations, in different experimental contexts. 

%B Annual Review of Condensed Matter Physics %V 11 %P 467-499 %8 3/10/2020 %G eng %U https://arxiv.org/abs/1905.13232 %R https://doi.org/10.1146/annurev-conmatphys-031119-050658 %0 Journal Article %D 2018 %T Verified Quantum Information Scrambling %A Kevin A. Landsman %A Caroline Figgatt %A Thomas Schuster %A Norbert M. Linke %A Beni Yoshida %A Norman Y. Yao %A Christopher Monroe %X

Quantum scrambling is the dispersal of local information into many-body quantum entanglements and correlations distributed throughout the entire system. This concept underlies the dynamics of thermalization in closed quantum systems, and more recently has emerged as a powerful tool for characterizing chaos in black holes. However, the direct experimental measurement of quantum scrambling is difficult, owing to the exponential complexity of ergodic many-body entangled states. One way to characterize quantum scrambling is to measure an out-of-time-ordered correlation function (OTOC); however, since scrambling leads to their decay, OTOCs do not generally discriminate between quantum scrambling and ordinary decoherence. Here, we implement a quantum circuit that provides a positive test for the scrambling features of a given unitary process. This approach conditionally teleports a quantum state through the circuit, providing an unambiguous litmus test for scrambling while projecting potential circuit errors into an ancillary observable. We engineer quantum scrambling processes through a tunable 3-qubit unitary operation as part of a 7-qubit circuit on an ion trap quantum computer. Measured teleportation fidelities are typically ∼80%, and enable us to experimentally bound the scrambling-induced decay of the corresponding OTOC measurement.

%G eng %U https://arxiv.org/abs/1806.02807 %0 Journal Article %J Physical Review A %D 2015 %T Bilayer fractional quantum Hall states with ultracold dysprosium %A Norman Y. Yao %A Steven D. Bennett %A Chris R. Laumann %A Benjamin L. Lev %A Alexey V. Gorshkov %X We show how dipolar interactions between dysprosium atoms in an optical lattice can be used to obtain fractional quantum Hall states. In our approach, dysprosium atoms are trapped one atom per site in a deep optical lattice with negligible tunneling. Microwave and spatially dependent optical dressing fields are used to define an effective spin-1/2 or spin-1 degree of freedom in each atom. Thinking of spin-1/2 particles as hardcore bosons, dipole-dipole interactions give rise to boson hopping, topological flat bands with Chern number 1, and the \nu = 1/2 Laughlin state. Thinking of spin-1 particles as two-component hardcore bosons, dipole-dipole interactions again give rise to boson hopping, topological flat bands with Chern number 2, and the bilayer Halperin (2,2,1) state. By adjusting the optical fields, we find a phase diagram, in which the (2,2,1) state competes with superfluidity. Generalizations to solid-state magnetic dipoles are discussed. %B Physical Review A %V 92 %P 033609 %8 2015/09/10 %G eng %U http://arxiv.org/abs/1505.03099v1 %N 3 %! Phys. Rev. A %R 10.1103/PhysRevA.92.033609 %0 Journal Article %J Physical Review A %D 2015 %T Fractional Quantum Hall States of Rydberg Polaritons %A Mohammad F. Maghrebi %A Norman Y. Yao %A Mohammad Hafezi %A Thomas Pohl %A Ofer Firstenberg %A Alexey V. Gorshkov %X We propose a scheme for realizing fractional quantum Hall states of light. In our scheme, photons of two polarizations are coupled to different atomic Rydberg states to form two flavors of Rydberg polaritons that behave as an effective spin. An array of optical cavity modes overlapping with the atomic cloud enables the realization of an effective spin-1/2 lattice. We show that the dipolar interaction between such polaritons, inherited from the Rydberg states, can be exploited to create a flat, topological band for a single spin-flip excitation. At half filling, this gives rise to a photonic (or polaritonic) fractional Chern insulator -- a lattice-based, fractional quantum Hall state of light. %B Physical Review A %V 91 %P 033838 %8 2015/03/31 %G eng %U http://arxiv.org/abs/1411.6624v1 %N 3 %! Phys. Rev. A %R 10.1103/PhysRevA.91.033838 %0 Journal Article %J Physical Review Letters %D 2014 %T Many-body dynamics of dipolar molecules in an optical lattice %A Kaden R. A. Hazzard %A Bryce Gadway %A Michael Foss-Feig %A Bo Yan %A Steven A. Moses %A Jacob P. Covey %A Norman Y. Yao %A Mikhail D. Lukin %A Jun Ye %A Deborah S. Jin %A Ana Maria Rey %X Understanding the many-body dynamics of isolated quantum systems is one of the central challenges in modern physics. To this end, the direct experimental realization of strongly correlated quantum systems allows one to gain insights into the emergence of complex phenomena. Such insights enable the development of theoretical tools that broaden our understanding. Here, we theoretically model and experimentally probe with Ramsey spectroscopy the quantum dynamics of disordered, dipolar-interacting, ultracold molecules in a partially filled optical lattice. We report the capability to control the dipolar interaction strength, and we demonstrate that the many-body dynamics extends well beyond a nearest-neighbor or mean-field picture, and cannot be quantitatively described using previously available theoretical tools. We develop a novel cluster expansion technique and demonstrate that our theoretical method accurately captures the measured dependence of the spin dynamics on molecule number and on the dipolar interaction strength. In the spirit of quantum simulation, this agreement simultaneously benchmarks the new theoretical method and verifies our microscopic understanding of the experiment. Our findings pave the way for numerous applications in quantum information science, metrology, and condensed matter physics. %B Physical Review Letters %V 113 %8 2014/11/7 %G eng %U http://arxiv.org/abs/1402.2354v1 %N 19 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.113.195302 %0 Journal Article %J Physical Review B %D 2013 %T Controllable quantum spin glasses with magnetic impurities embedded in quantum solids %A Mikhail Lemeshko %A Norman Y. Yao %A Alexey V. Gorshkov %A Hendrik Weimer %A Steven D. Bennett %A Takamasa Momose %A Sarang Gopalakrishnan %X Magnetic impurities embedded in inert solids can exhibit long coherence times and interact with one another via their intrinsic anisotropic dipolar interaction. We argue that, as a consequence of these properties, disordered ensembles of magnetic impurities provide an effective platform for realizing a controllable, tunable version of the dipolar quantum spin glass seen in LiHo$_x$Y$_{1-x}$F$_4$. Specifically, we propose and analyze a system composed of dysprosium atoms embedded in solid helium. We describe the phase diagram of the system and discuss the realizability and detectability of the quantum spin glass and antiglass phases. %B Physical Review B %V 88 %8 2013/7/24 %G eng %U http://arxiv.org/abs/1307.1130v1 %N 1 %! Phys. Rev. B %R 10.1103/PhysRevB.88.014426 %0 Journal Article %J Physical Review A %D 2013 %T Quantum Logic between Remote Quantum Registers %A Norman Y. Yao %A Zhe-Xuan Gong %A Chris R. Laumann %A Steven D. Bennett %A L. -M. Duan %A Mikhail D. Lukin %A Liang Jiang %A Alexey V. Gorshkov %X We analyze two approaches to quantum state transfer in solid-state spin systems. First, we consider unpolarized spin-chains and extend previous analysis to various experimentally relevant imperfections, including quenched disorder, dynamical decoherence, and uncompensated long range coupling. In finite-length chains, the interplay between disorder-induced localization and decoherence yields a natural optimal channel fidelity, which we calculate. Long-range dipolar couplings induce a finite intrinsic lifetime for the mediating eigenmode; extensive numerical simulations of dipolar chains of lengths up to L=12 show remarkably high fidelity despite these decay processes. We further consider the extension of the protocol to bosonic systems of coupled oscillators. Second, we introduce a quantum mirror based architecture for universal quantum computing which exploits all of the spins in the system as potential qubits. While this dramatically increases the number of qubits available, the composite operations required to manipulate "dark" spin qubits significantly raise the error threshold for robust operation. Finally, as an example, we demonstrate that eigenmode-mediated state transfer can enable robust long-range logic between spatially separated Nitrogen-Vacancy registers in diamond; numerical simulations confirm that high fidelity gates are achievable even in the presence of moderate disorder. %B Physical Review A %V 87 %8 2013/2/6 %G eng %U http://arxiv.org/abs/1206.0014v1 %N 2 %! Phys. Rev. A %R 10.1103/PhysRevA.87.022306 %0 Journal Article %J Physical Review Letters %D 2013 %T Realizing Fractional Chern Insulators with Dipolar Spins %A Norman Y. Yao %A Alexey V. Gorshkov %A Chris R. Laumann %A Andreas M. Läuchli %A Jun Ye %A Mikhail D. Lukin %X Strongly correlated quantum systems can exhibit exotic behavior controlled by topology. We predict that the \nu=1/2 fractional Chern insulator arises naturally in a two-dimensional array of driven, dipolar-interacting spins. As a specific implementation, we analyze how to prepare and detect synthetic gauge potentials for the rotational excitations of ultra-cold polar molecules trapped in a deep optical lattice. While the orbital motion of the molecules is pinned, at finite densities, the rotational excitations form a fractional Chern insulator. We present a detailed experimental blueprint for KRb, and demonstrate that the energetics are consistent with near-term capabilities. Prospects for the realization of such phases in solid-state dipolar systems are discussed as are their possible applications. %B Physical Review Letters %V 110 %8 2013/4/29 %G eng %U http://arxiv.org/abs/1212.4839v1 %N 18 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.110.185302 %0 Journal Article %J Nature Communications %D 2013 %T Topologically Protected Quantum State Transfer in a Chiral Spin Liquid %A Norman Y. Yao %A Chris R. Laumann %A Alexey V. Gorshkov %A Hendrik Weimer %A Liang Jiang %A J. Ignacio Cirac %A Peter Zoller %A Mikhail D. Lukin %X Topology plays a central role in ensuring the robustness of a wide variety of physical phenomena. Notable examples range from the robust current carrying edge states associated with the quantum Hall and the quantum spin Hall effects to proposals involving topologically protected quantum memory and quantum logic operations. Here, we propose and analyze a topologically protected channel for the transfer of quantum states between remote quantum nodes. In our approach, state transfer is mediated by the edge mode of a chiral spin liquid. We demonstrate that the proposed method is intrinsically robust to realistic imperfections associated with disorder and decoherence. Possible experimental implementations and applications to the detection and characterization of spin liquid phases are discussed. %B Nature Communications %V 4 %P 1585 %8 2013/3/12 %G eng %U http://arxiv.org/abs/1110.3788v1 %! Nat Comms %R 10.1038/ncomms2531 %0 Journal Article %J Nature Communications %D 2012 %T Scalable Architecture for a Room Temperature Solid-State Quantum Information Processor %A Norman Y. Yao %A Liang Jiang %A Alexey V. Gorshkov %A Peter C. Maurer %A Geza Giedke %A J. Ignacio Cirac %A Mikhail D. Lukin %X The realization of a scalable quantum information processor has emerged over the past decade as one of the central challenges at the interface of fundamental science and engineering. Much progress has been made towards this goal. Indeed, quantum operations have been demonstrated on several trapped ion qubits, and other solid-state systems are approaching similar levels of control. Extending these techniques to achieve fault-tolerant operations in larger systems with more qubits remains an extremely challenging goal, in part, due to the substantial technical complexity of current implementations. Here, we propose and analyze an architecture for a scalable, solid-state quantum information processor capable of operating at or near room temperature. The architecture is applicable to realistic conditions, which include disorder and relevant decoherence mechanisms, and includes a hierarchy of control at successive length scales. Our approach is based upon recent experimental advances involving Nitrogen-Vacancy color centers in diamond and will provide fundamental insights into the physics of non-equilibrium many-body quantum systems. Additionally, the proposed architecture may greatly alleviate the stringent constraints, currently limiting the realization of scalable quantum processors. %B Nature Communications %V 3 %P 800 %8 2012/4/24 %G eng %U http://arxiv.org/abs/1012.2864v1 %! Nat Comms %R 10.1038/ncomms1788 %0 Journal Article %J Physical Review Letters %D 2012 %T Topological Flat Bands from Dipolar Spin Systems %A Norman Y. Yao %A Chris R. Laumann %A Alexey V. Gorshkov %A Steven D. Bennett %A Eugene Demler %A Peter Zoller %A Mikhail D. Lukin %X We propose and analyze a physical system that naturally admits two-dimensional topological nearly flat bands. Our approach utilizes an array of three-level dipoles (effective S = 1 spins) driven by inhomogeneous electromagnetic fields. The dipolar interactions produce arbitrary uniform background gauge fields for an effective collection of conserved hardcore bosons, namely, the dressed spin-flips. These gauge fields result in topological band structures, whose bandgap can be larger than the corresponding bandwidth. Exact diagonalization of the full interacting Hamiltonian at half-filling reveals the existence of superfluid, crystalline, and supersolid phases. An experimental realization using either ultra-cold polar molecules or spins in the solid state is considered. %B Physical Review Letters %V 109 %8 2012/12/26 %G eng %U http://arxiv.org/abs/1207.4479v3 %N 26 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.109.266804 %0 Journal Article %J Physical Review Letters %D 2011 %T Robust Quantum State Transfer in Random Unpolarized Spin Chains %A Norman Y. Yao %A Liang Jiang %A Alexey V. Gorshkov %A Zhe-Xuan Gong %A Alex Zhai %A L. -M. Duan %A Mikhail D. Lukin %X We propose and analyze a new approach for quantum state transfer between remote spin qubits. Specifically, we demonstrate that coherent quantum coupling between remote qubits can be achieved via certain classes of random, unpolarized (infinite temperature) spin chains. Our method is robust to coupling strength disorder and does not require manipulation or control over individual spins. In principle, it can be used to attain perfect state transfer over arbitrarily long range via purely Hamiltonian evolution and may be particularly applicable in a solid-state quantum information processor. As an example, we demonstrate that it can be used to attain strong coherent coupling between Nitrogen-Vacancy centers separated by micrometer distances at room temperature. Realistic imperfections and decoherence effects are analyzed. %B Physical Review Letters %V 106 %8 2011/1/27 %G eng %U http://arxiv.org/abs/1011.2762v2 %N 4 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.106.040505