Quantum Zeno effect appears in stages

Snizhko, Kyrylo; Kumar, Parveen; Romito, Alessandro

doi:10.1103/physrevresearch.2.033512

Cited by 50 publications

(49 citation statements)

References 46 publications

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“…Similar behavior can be found in the long-time behavior of general open quantum dynamics [77]. An interesting question would be which of the features described here will carry over when one employs weak measurements or open quantum dynamics [23,24,27,[78][79][80].…”

Section: Additional Examplessupporting

confidence: 71%

Dark states of quantum search cause imperfect detection

Thiel

Mualem

Meidan

et al. 2020

Phys. Rev. Research

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We consider a quantum walk where a detector repeatedly probes the system with fixed rate 1/τ until the walker is detected. This is a quantum version of the first-passage problem. We focus on the total probability P det that the particle is eventually detected in some target state, for example, on a node r d on a graph, after an arbitrary number of detection attempts. Analyzing the dark and bright states for finite graphs and more generally for systems with a discrete spectrum, we provide an explicit formula for P det in terms of the energy eigenstates which is generically τ independent. We find that disorder in the underlying Hamiltonian renders perfect detection, P det = 1, and then expose the role of symmetry with respect to suboptimal detection. Specifically, we give a simple upper bound for P det that is controlled by the number of equivalent (with respect to the detection) states in the system. We also extend our results to infinite systems, for example, the detection probability of a quantum walk on a line, which is τ dependent and less than half, well below Polya's optimal detection for a classical random walk.

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Section: Additional Examplessupporting

confidence: 71%

Dark states of quantum search cause imperfect detection

Thiel

Mualem

Meidan

et al. 2020

Phys. Rev. Research

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“…Therefore, the steady-state density matrix retains no information about the statistical features of the observables studied in this work. However, the analysis of the spectrum of the GKLS equation could reveal useful information associated to the typical time scale associated to the onset of the Zeno regime [8].…”

Section: Analytical Approachmentioning

confidence: 99%

“…To this purpose we compare the full no-click evolution with the one generated by theĤ eff [Eq. (8)] for different values of g.…”

Section: Validity Of the Non-hermitian Effective Hamiltonianmentioning

confidence: 99%

“…Measurements lie at the heart of quantum mechanics and of its intrinsic statistical interpreta-tion [1]. They are known to fundamentally perturb the state of a quantum system, leading to the famous wave-function collapse, or to hamper its evolution in the Hilbert space, as in the celebrated Quantum Zeno Effect (QZE), where frequent projective measurements on a system can lead to its full localization [2,3,4,5,6,7,8]. In the field of quantum information the role of measurements as a resource has been extensively discussed and also experimentally demonstrated [9,10,11,12,13].…”

Section: Introductionmentioning

confidence: 99%

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Many-Body Quantum Zeno Effect and Measurement-Induced Subradiance Transition

Biella

Schiró

2021

Quantum

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It is well known that by repeatedly measuring a quantum system it is possible to completely freeze its dynamics into a well defined state, a signature of the quantum Zeno effect. Here we show that for a many-body system evolving under competing unitary evolution and variable-strength measurements the onset of the Zeno effect takes the form of a sharp phase transition. Using the Quantum Ising chain with continuous monitoring of the transverse magnetization as paradigmatic example we show that for weak measurements the entanglement produced by the unitary dynamics remains protected, and actually enhanced by the monitoring, while only above a certain threshold the system is sharply brought into an uncorrelated Zeno state. We show that this transition is invisible to the average dynamics, but encoded in the rare fluctuations of the stochastic measurement process, which we show to be perfectly captured by a non-Hermitian Hamiltonian which takes the form of a Quantum Ising model in an imaginary valued transverse field. We provide analytical results based on the fermionization of the non-Hermitian Hamiltonian in supports of our exact numerical calculations.

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“…In this case, the evolution is unitary; therefore, the rank of the state is preserved. For instance, recent impressive improvements in experimental settings have allowed the observation that the decays induced by a Rabi oscillator in a 2-level system are coherent and continuous processes [5] (see also [6] for theoretical analysis).…”

Section: Motivation and Previous Workmentioning

confidence: 99%

From Geometry to Coherent Dissipative Dynamics in Quantum Mechanics

2021

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Starting from the geometric description of quantum systems, we propose a novel approach to time-independent dissipative quantum processes according to which energy is dissipated but the coherence of the states is preserved. Our proposal consists of extending the standard symplectic picture of quantum mechanics to a contact manifold and then obtaining dissipation by using appropriate contact Hamiltonian dynamics. We work out the case of finite-level systems for which it is shown, by means of the corresponding contact master equation, that the resulting dynamics constitute a viable alternative candidate for the description of this subclass of dissipative quantum systems. As a concrete application, motivated by recent experimental observations, we describe quantum decays in a 2-level system as coherent and continuous processes.

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Quantum Zeno effect appears in stages

Cited by 50 publications

References 46 publications

Dark states of quantum search cause imperfect detection

Dark states of quantum search cause imperfect detection

Many-Body Quantum Zeno Effect and Measurement-Induced Subradiance Transition

From Geometry to Coherent Dissipative Dynamics in Quantum Mechanics

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