Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session Y66: Non-Equilibrium Physics in AMO Systems IIFocus
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Sponsoring Units: DAMOP Chair: Kevin Singh, University of Chicago Room: Room 413 |
Friday, March 10, 2023 8:00AM - 8:36AM |
Y66.00001: Analog Quantum Simulations in Trapped-Ion Spin Chains Invited Speaker: Guido Pagano Laser cooled trapped ions offer unprecedented control over both internal and external degrees of freedom at the single-particle level. They are considered among the foremost candidates for realizing quantum simulation and computation platforms that can outperform classical computers in specific tasks. In this talk I will show how linear arrays of trapped 171Yb+ ions can be used as a versatile platform for studying out-of-equilibrium many-body quantum systems. I will show how linear ion chains [1] enabled the recent observation of universal non-equilibrium spin dynamics after multiple quenches [2]. In this case the spin system exhibits different system size scalings of the spin fluctuations dynamics depending on the different initial states and on the number of quenches [3]. Finally, I will conclude outlining the prospects of my new experimental system at Rice aimed at the simulation of dissipative Floquet dynamics [4] and at the realization of higher order spin interactions for the simulation of lattice gauge theories [5]. |
Friday, March 10, 2023 8:36AM - 8:48AM Author not Attending |
Y66.00002: Ideal band insulation and transitionless quantum driving Rafael S Hipolito, Paul M Goldbart Subjecting band insulators to electric fields generally induces transitions between the (filled) valence bands and the (empty) conduction bands. By applying ideas related to Berry's notion of transitionless quantum driving, we search for auxiliary fields capable of mitigating these transitions, so as to foster ideal insulating characteristics, even in the presence of time-dependent uniform electric fields. So far, transitionless quantum driving has primarily been invoked to suppress transitions state by state. However, the many-fermion character of the present setting of band insulators renders less stringent the challenge of engineering suitable auxiliary fields. Specifically, because the valence band is filled, and by identical particles, one need only mitigate transitions band by band. As a result, there is a broader family of auxiliary fields to choose from. This feature creates the opportunity for optimizing within a class of experimentally feasible (if not perfect) auxiliary fields, and thus of bringing systems close to ideal band insulation. |
Friday, March 10, 2023 8:48AM - 9:00AM |
Y66.00003: The complexity of estimating order parameters in quench dynamics of 1D Ising models Anupam Mitra, Philip D Blocher, Tameem Albash, Akimasa Miyake, Ivan H Deutsch In nonequilibrium dynamics, a common objective is estimating a dynamical order parameter, specified by the expectation value of local (few-body) observables. It is commonly accepted that if the full many-body state cannot be efficiently simulated, classical simulation of such order parameters is intractable. Here we demonstrate that the common lore is not always correct. We study this in the case of quench dynamics of 1D Ising spin chains in both integrable and chaotic models and explore the complexity of simulation based on a truncated matrix product state representation. We study dynamical quantum phase transitions and the growth of correlations using the Time Evolving Block Decimation (TEBD) algorithm. We show that even for models where exact simulations of the full many-body state are intractable due to volume-law growth of entanglement, the order parameters can be efficiently simulated. We quantify this based on the Hilbert-Schmidt distance between the exact and approximate reduced density matrices for different levels of truncation, which upper-bounds the error in estimating the expectation values of local observables. |
Friday, March 10, 2023 9:00AM - 9:12AM |
Y66.00004: Studying and measuring scrambling without out-of-time-ordered correlators Pablo M Poggi, Philip D Blocher, Sivaprasad T Omanakuttan, Karthik Chinni Scrambling in many-body systems refers to the spreading of initially localized information to the entire system and has become a key concept in the study of chaos in quantum systems. Most studies so far have focused on characterizing scrambling using out-of-time-ordered correlation functions (OTOCs), particularly through its early-time decay. However, scrambling is a complex process which involves operator spreading and growth, and a full characterization requires accessing more refined information on the operator dynamics at several timescales. Moreover, OTOCs are intrinsically hard to access experimentally, typically requiring time reversal of the dynamics or the use of auxiliary systems. In this work we study operator scrambling by expanding the target operator in a complete basis and studying the structure of the expansion coefficients treated as a probability distribution in the space of operators. We propose a new approach that allows us to obtain information about scrambling without time reversal nor ancillas, while also avoiding the arduous task of reconstructing the expansion coefficients directly. This is done by using the dynamics of random mixed states and only local measurements together with randomized sampling. We demonstrate our findings by studying diverse cases such as the tilted field Ising model undergoing both regular and chaotic dynamics, circuit models with varying non-Cliffordness, and the kicked collective spin models. |
Friday, March 10, 2023 9:12AM - 9:24AM |
Y66.00005: Relaxation of OTOC: effect of symmetries in integrable and non-integrable local Hamiltonians dario poletti, Vinitha Balachandran, Lea F Santos, Marcos Rigol Out-of-time ordered correlators (OTOCs) help characterize the scrambling of quantum information. We show that emergence of slow, algebraic, relaxation is expected in local Hamiltonians when the operators in the OTOC have non-zero diagonal elements in the energy basis, something that occurs when these operators have overlap with conserved quantities. Furthermore, the long-time slow relaxation of the OTOC can be predicted from studying simpler two-time correlator, and it is more strongly determined by the symmetry rather than integrability. Our numerical results corroborate our analytical expectations both for diagonal and off-diagonal elements of the OTOCs' local operators in the energy eigenbasis. |
Friday, March 10, 2023 9:24AM - 9:36AM |
Y66.00006: Exact solution of the fully-connected dissipative transverse Ising model David Roberts, Aashish A Clerk The dissipative transverse-field Ising model is central in the study of open quantum systems, not just due to its close connection with its well-studied closed-system analogue, but also thanks to its ability to be natively realized in a variety of atomic physics platforms, namely ion traps (long-range limit) and arrays of Rydberg atoms (short-range limit). Here, we present a simple closed-form solution for the steady state of the transverse-field Ising model subject to local spontaneous emission, in the limit that the Ising interaction is infinitely-long ranged. The exact solution exploits a "hidden" symmetry in the dissipative dynamics, which is phrased in terms of the square root of the steady-state density matrix [1]. This symmetry persists even when the external fields are inhomogeneous, and also yields closed-form solutions for all stationary moments, such as local magnetization and spin-spin correlations. |
Friday, March 10, 2023 9:36AM - 9:48AM |
Y66.00007: High-temperature criticality in power-law interacting spin systems Shijun Sun, Sergey Syzranov We study the phase transition of a d-dimensional XY model with power-law interactions ($1/r^{alpha}$), which can describe interactions in trapped-ion spin systems, Rydberg atoms, polar molecules, and magnetic atoms, as a function of the magnetic field $h$ along the $z$ direction and the temperature. Elementary magnetic excitations in the system (magnons) correspond to spin flips that propagate with dispersion $xi_{mathbf{k}}propto |mathbf{k}|^{alpha-d}$. Using the renormalization group approach, we demonstrate that the system exhibits a phase transition between weakly and strongly interacting phases. In the former, the system behaves as a gas of weakly interacting magnons. In the latter, low-energy magnetic excitations are strongly interacting. The phase transition can be triggered by increasing temperature or decreasing the magnetic field $h$. One can probe such transition by measuring the relaxation time of the magnetization. This transition is similar to the disorder-driven phase transitions in systems with power-law quasiparticle dispersion $xi_{mathbf{k}}propto |mathbf{k}|^{alpha-d}$ (e.g. three-dimensional Weyl and Dirac materials, cold-atom systems with long-range interactions). |
Friday, March 10, 2023 9:48AM - 10:00AM |
Y66.00008: Experimental verification of the area law of mutual information in quantum field theory Mohammadamin Tajik, Ivan Kukuljan, Spyros Sotiriadis, Bernhard Rauer, Thomas Schweigler, Federica Cataldini, João Sabino, Frederik S Møller, Philipp Schüttelkopf, Si-Cong Ji, Dries Sels, Eugene Demler, Joerg Schmiedmayer Theoretical understanding of the scaling of entropies and the mutual information in quantum many-body systems has led to significant advances in the research of correlated states of matter, quantum field theory, and gravity. |
Friday, March 10, 2023 10:00AM - 10:12AM |
Y66.00009: Non-Hermitian physics of levitated nanoparticle array Kazuki Yokomizo, Yuto Ashida The nonreciprocal interaction between two levitated nanoparticles is induced by the phase difference between the trapping lasers [1]. Such a system is naturally interpreted as a non-Hermitian system which effectively describes a nonequilibrium system. In this work, we propose that a levitated nanoparticle array is an ideal platform to investigate non-Hermitian physics. Then, the non-Bloch band theory [2] can analyze the behavior of the system. We find appearance of the dynamical-instability phase induced by the nonreciprocal hopping amplitude. Furthermore, we reveal that the continuum band has a branch point associated with the singularity point of the generalized Brillouin zone. [1] J. Rieser et al., Science 377, 987 (2022). [2] K. Yokomizo et al., Phys. Rev. Lett. 123, 066404 (2019). |
Friday, March 10, 2023 10:12AM - 10:24AM |
Y66.00010: Effect of many-body interaction on synthetic Anderson Metal-Insulator transition in kicked quantum gases Mengxin Du Quasiperiodic kicked rotor is equivalent to a 3D disordered system that shows Anderson metal-insulator transition, which has been observed in experiments using atomic matter wave. Recent experimental observations of many-body dynamical delocalization in kicked quantum gases have offered a new platform for studying many-body effects in disordered systems formed by synthetic momentum space lattices. We study the effect of mean-field interaction on the dynamics of quasiperiodic kicked rotors and the resulting 3D Metal-Insulator transition. We compare the theoretical simulation with ongoing experimental results. |
Friday, March 10, 2023 10:24AM - 10:36AM Author not Attending |
Y66.00011: Time-periodic Lindblad master equations for quantum systems with engineered interactions and dissipation Sebastian Eggert, Simon B Jäger, Imke Schneider, Christoph Dauer, Jan M Giesen Floquet engineering describes the creation of exotic and correlated many-body quantum states by using time-periodic driving. However, driving usually generates heat in the quantum system which can eventually lead to thermalization and loss of coherence on long timescales. A pathway to circumvent these detrimental effects can be engineered dissipation that drains away part of the introduced energy and stabilizes the quantum system far away from equilibrium. One possibility to engineer dissipation and also interactions within the quantum system is by coupling it to bosonic modes. We will show how one can quite generally eliminate the bosonic modes in such a scenario and achieve a Lindblad master equation which includes the mediated interactions and dissipation. We apply this procedure to the time-periodic dissipative Dicke model, a workhorse for the recently observed dissipative time crystals, and confirm its validity. Our results pave the ways towards the theoretical description of many-body quantum systems with mediated interaction and dissipation in presence of periodic driving. |
Friday, March 10, 2023 10:36AM - 10:48AM Author not Attending |
Y66.00012: Organic polaritons beyond the quasiparticle picture Cesar L Ordonez Romero, Giuseppe Pirruccio, Arturo Camacho-Guardian, Hugo A Lara Garcia, Yesenia A Garcia Jomaso, David Ley Dominguez, Brenda Vargas Organic polaritons resulting from the strong hybridisation between photons and matter excitations have arisen as a suitable platform to device light-matter technological interfaces at room temperature. Despite their inherent complexity, organic polaritons are commonly regarded as coherent light-matter excitations that can be described in terms of Landau's quasiparticle approach. Here, we experimentally unveil the role of incoherent matter excitations on the polaritons by exploring the relevant energy-momentum parameter space. We demonstrate the emergence of a well-defined lower polariton branch and an intriguing fading of the upper polariton at its entrance to a continuum of matter excitations. This marks the breakdown of the simplistic quasiparticle picture for this branch and the formation of a more complex quantum state. Our experimental results are sustained by a general theoretical framework that allows understanding the light-matter hybridisation beyond the quasiparticle approach. Our work expands the understanding of organic polaritons in all their complexity and increases their technological significance. |
Friday, March 10, 2023 10:48AM - 11:00AM |
Y66.00013: Phase space geometry and optimal state preparation in quantum metrology with collective spins Manuel H Munoz Arias, Ivan H Deutsch, Pablo M Poggi We revisit well-known protocols in quantum metrology using collective spins and propose a unifying picture for optimal state preparation based on their semiclassical motion in phase space. We show how this framework allows for quantitative predictions of the timescales required to prepare various metrologically useful states, and that these predictions remain accurate even for moderate system sizes, surprisingly far from the classical limit. Furthermore, this framework allows us to build a geometric picture that relates optimal (exponentially fast) entangled probe preparation to the existence of separatrices connecting saddle points in phase space. We illustrate our results with the paradigmatic examples of the two-axis counter-twisting and twisting-and-turning Hamiltonians, where we provide analytical expressions for all the relevant optimal time scales. Finally, we propose a generalization of these models to include $p$-body collective interaction (or $p$-order twisting), beyond the usual case of $p=2$. Using our geometric framework, we prove a no-go theorem for the local optimality of these models for $p>2$. |
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