Quantum Zeno effect and the many-body entanglement transition
TLDR
In this paper, a hybrid quantum circuit model consisting of both unitary gates and projective measurements is introduced, where the measurements are made at random positions and times throughout the system.Abstract:
We introduce and explore a one-dimensional ``hybrid'' quantum circuit model consisting of both unitary gates and projective measurements. While the unitary gates are drawn from a random distribution and act uniformly in the circuit, the measurements are made at random positions and times throughout the system. By varying the measurement rate we can tune between the volume law entangled phase for the random unitary circuit model (no measurements) and a ``quantum Zeno phase'' where strong measurements suppress the entanglement growth to saturate in an area law. Extensive numerical simulations of the quantum trajectories of the many-particle wave functions (exploiting Clifford circuitry to access systems up to 512 qubits) provide evidence for a stable ``weak measurement phase'' that exhibits volume-law entanglement entropy, with a coefficient decreasing with increasing measurement rate. We also present evidence for a continuous quantum dynamical phase transition between the ``weak measurement phase'' and the ``quantum Zeno phase,'' driven by a competition between the entangling tendencies of unitary evolution and the disentangling tendencies of projective measurements. Detailed steady-state and dynamic critical properties of this quantum entanglement transition are accessed.read more
Citations
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Non-Hermitian Physics
TL;DR: In this article, a review of non-Hermitian classical and quantum physics can be found, with an overview of how diverse classical systems, ranging from photonics, mechanics, electrical circuits, acoustics to active matter, can be used to simulate non-hermitian wave physics.
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Measurement-Induced Phase Transitions in the Dynamics of Entanglement
TL;DR: The growth of entanglement in a quantum system changes qualitatively when it is observed more frequently than a certain critical rate as discussed by the authors, an important insight for describing quantum systems computationally.
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Unitary-projective entanglement dynamics
TL;DR: In this article, a toy model of Bell pair dynamics was constructed and it was shown that measurements can keep a system in a state of low, i.e., area-law, entanglement, in contrast with the volume-law entenglement produced by generic pure unitary time evolution.
References
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Quantum computation and quantum information
TL;DR: This special issue of Mathematical Structures in Computer Science contains several contributions related to the modern field of Quantum Information and Quantum Computing, with a focus on entanglement.
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Holographic Derivation of Entanglement Entropy from the anti de Sitter Space/Conformal Field Theory Correspondence
Shinsei Ryu,Tadashi Takayanagi +1 more
TL;DR: It is argued that the entanglement entropy in d + 1 dimensional conformal field theories can be obtained from the area of d dimensional minimal surfaces in AdS(d+2), analogous to the Bekenstein-Hawking formula for black hole entropy.
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Entanglement entropy and quantum field theory
Pasquale Calabrese,John Cardy +1 more
TL;DR: In this article, a systematic study of entanglement entropy in relativistic quantum field theory is carried out, where the von Neumann entropy is defined as the reduced density matrix ρA of a subsystem A of a 1+1-dimensional critical system, whose continuum limit is a conformal field theory with central charge c, and the results are verified for a free massive field theory.
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Chaos and quantum thermalization
TL;DR: It is shown that a bounded, isolated quantum system of many particles in a specific initial state will approach thermal equilibrium if the energy eigenfunctions which are superposed to form that state obey Berry's conjecture, and argued that these results constitute a sound foundation for quantum statistical mechanics.
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Quantum statistical mechanics in a closed system
TL;DR: A closed quantum-mechanical system with a large number of degrees of freedom does not necessarily give time averages in agreement with the microcanonical distribution, so by adding a finite but very small perturbation in the form of a random matrix, the results of quantum statistical mechanics are recovered.