scholarly journals QUANTUM DYNAMICS WITH AN ENSEMBLE OF HAMILTONIANS

2013 ◽  
Vol 27 (26) ◽  
pp. 1330019 ◽  
Author(s):  
ARMIN RAHMANI
Keyword(s):  
Disordered Systems ◽  
Quantum Dynamics ◽  
Nonequilibrium Dynamics ◽  
Quantum Evolution ◽  
Many Body ◽  
Driven Systems ◽  
Shortcuts To Adiabaticity ◽  
New Directions ◽  
Time Quantum ◽  
Many Body Systems

We review recent progress in the nonequilibrium dynamics of thermally isolated many-body quantum systems, evolving with an ensemble of Hamiltonians as opposed to deterministic evolution with a single time-dependent Hamiltonian. Such questions arise in (i) quantum dynamics of disordered systems, where different realizations of disorder give rise to an ensemble of real-time quantum evolutions, (ii) quantum evolution with noisy Hamiltonians (temporal disorder), which leads to stochastic Schrödinger equations, and, (iii) in the broader context of quantum optimal control, where one needs to analyze an ensemble of permissible protocols in order to find one that optimizes a given figure of merit. The theme of ensemble quantum evolution appears in several emerging new directions in noneqilibrium quantum dynamics of thermally isolated many-body systems, which include many-body localization, noise-driven systems, and shortcuts to adiabaticity.

scholarly journals Controlling quantum many-body dynamics in driven Rydberg atom arrays

Science ◽  
2021 ◽  
Vol 371 (6536) ◽  
pp. 1355-1359
Author(s):  
D. Bluvstein ◽  
A. Omran ◽  
H. Levine ◽  
A. Keesling ◽  
G. Semeghini ◽  
...  
Keyword(s):  
Hilbert Space ◽  
Quantum Dynamics ◽  
Information Science ◽  
Complex Dynamics ◽  
Rydberg Atom ◽  
System Size ◽  
Nonequilibrium Dynamics ◽  
Many Body ◽  
Many Body Systems ◽  
Space Dynamics

The control of nonequilibrium quantum dynamics in many-body systems is challenging because interactions typically lead to thermalization and a chaotic spreading throughout Hilbert space. We investigate nonequilibrium dynamics after rapid quenches in a many-body system composed of 3 to 200 strongly interacting qubits in one and two spatial dimensions. Using a programmable quantum simulator based on Rydberg atom arrays, we show that coherent revivals associated with so-called quantum many-body scars can be stabilized by periodic driving, which generates a robust subharmonic response akin to discrete time-crystalline order. We map Hilbert space dynamics, geometry dependence, phase diagrams, and system-size dependence of this emergent phenomenon, demonstrating new ways to steer complex dynamics in many-body systems and enabling potential applications in quantum information science.

scholarly journals Probing Many-Body Systems Near Spectral Degeneracies

Symmetry ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1796
Author(s):  
Klaus Ziegler
Keyword(s):  
Decay Rate ◽  
Correlation Matrix ◽  
Time Correlation ◽  
General Concept ◽  
Quantum Systems ◽  
Quantum Evolution ◽  
Many Body ◽  
Space Localization ◽  
Many Body Systems ◽  
Random Times

The diagonal elements of the time correlation matrix are used to probe closed quantum systems that are measured at random times. This enables us to extract two distinct parts of the quantum evolution, a recurrent part and an exponentially decaying part. This separation is strongly affected when spectral degeneracies occur, for instance, in the presence of spontaneous symmetry breaking. Moreover, the slowest decay rate is determined by the smallest energy level spacing, and this decay rate diverges at the spectral degeneracies. Probing the quantum evolution with the diagonal elements of the time correlation matrix is discussed as a general concept and tested in the case of a bosonic Josephson junction. It reveals for the latter characteristic properties at the transition to Hilbert-space localization.

Discrete Time Crystals

2020 ◽  
Vol 11 (1) ◽  
pp. 467-499 ◽  
Author(s):  
Dominic V. Else ◽  
Christopher Monroe ◽  
Chetan Nayak ◽  
Norman Y. Yao
Keyword(s):  
Discrete Time ◽  
Quantum Dynamics ◽  
Many Body ◽  
Time Translation ◽  
Translation Symmetry ◽  
Interesting Class ◽  
Many Body Systems ◽  
Definition Of ◽  
Many Body Interactions ◽  
Time Crystals

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 that do not thermalize under their own isolated quantum dynamics. In this review, we highlight the possibility for such systems to exhibit new nonequilibrium 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 nonequilibrium phenomenon that is stabilized by many-body interactions, with no analog in noninteracting systems. We explain the theory behind several proposed models of discrete time crystals, and compare several recent realizations, in different experimental contexts.

Thermal Gaussian molecular dynamics for quantum dynamics simulations of many-body systems: Application to liquid para-hydrogen

2011 ◽  
Vol 134 (17) ◽  
pp. 174109 ◽  
Author(s):  
Ionuţ Georgescu ◽  
Jason Deckman ◽  
Laura J. Fredrickson ◽  
Vladimir A. Mandelshtam
Keyword(s):  
Molecular Dynamics ◽  
Quantum Dynamics ◽  
Para Hydrogen ◽  
Many Body ◽  
Many Body Systems ◽  
Dynamics Simulations

scholarly journals Many-body quantum dynamics slows down at low density

2020 ◽  
Vol 9 (5) ◽  
Author(s):  
Xiao Chen ◽  
Yingfei Gu ◽  
Andrew Lucas
Keyword(s):  
Lyapunov Exponent ◽  
Density Dependence ◽  
Quantum Dynamics ◽  
Chemical Potential ◽  
Quantum Circuits ◽  
Many Body ◽  
Many Body Quantum Dynamics ◽  
Energy Conserving ◽  
Kitaev Model ◽  
Many Body Systems

We study quantum many-body systems with a global U(1) conservation law, focusing on a theory of N interacting fermions with charge conservation, or N interacting spins with one conserved component of total spin. We define an effective operator size at finite chemical potential through suitably regularized out-of-time-ordered correlation functions. The growth rate of this density-dependent operator size vanishes algebraically with charge density; hence we obtain new bounds on Lyapunov exponents and butterfly velocities in charged systems at a given density, which are parametrically stronger than any Lieb-Robinson bound. We argue that the density dependence of our bound on the Lyapunov exponent is saturated in the charged Sachdev-Ye-Kitaev model. We also study random automaton quantum circuits and Brownian Sachdev-Ye-Kitaev models, each of which exhibit a different density dependence for the Lyapunov exponent, and explain the discrepancy. We propose that our results are a cartoon for understanding Planckian-limited energy-conserving dynamics at finite temperature.

Quantum dynamics research in India: a perspective

2021 ◽  
Vol 34 (10) ◽  
pp. 100401
Author(s):  
Amit Dutta ◽  
Krishnendu Sengupta
Keyword(s):  
Quantum Dynamics ◽  
Ultracold Atoms ◽  
Significant Contribution ◽  
Experimental Studies ◽  
Original Research ◽  
Special Issue ◽  
Many Body ◽  
Research Papers ◽  
Tremendous Progress ◽  
Many Body Systems

Abstract Comprehending out-of-equilibrium properties of quantum many-body systems is still an emergent area of recent research. The upsurge in this area is motivated by tremendous progress in experimental studies, the key platforms being ultracold atoms and trapped ion systems. There has been a significant contribution from India to this vibrant field. This special issue which includes both review articles and original research papers highlights some of these contributions.

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