Detection of a quantum particle on a lattice under repeated projective measurements

Dhar, Shrabanti and Dasgupta, Subinay and Dhar, Abhishek and Sen, Diptiman (2015) Detection of a quantum particle on a lattice under repeated projective measurements. In: PHYSICAL REVIEW A, 91 (6).

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Abstract

We consider a quantum particle, moving on a lattice with a tight-binding Hamiltonian, which is subjected to measurements to detect its arrival at a particular chosen set of sites. The projective measurements are made at regular time intervals tau, and we consider the evolution of the wave function until the time a detection occurs. We study the probabilities of its first detection at some time and, conversely, the probability of it not being detected (i.e., surviving) up to that time. We propose a general perturbative approach for understanding the dynamics which maps the evolution operator, which consists of unitary transformations followed by projections, to one described by a non-Hermitian Hamiltonian. For some examples of a particle moving on one-and two-dimensional lattices with one or more detection sites, we use this approach to find exact expressions for the survival probability and find excellent agreement with direct numerical results. A mean-field model with hopping between all pairs of sites and detection at one site is solved exactly. For the one-and two-dimensional systems, the survival probability is shown to have a power-law decay with time, where the power depends on the initial position of the particle. Finally, we show an interesting and nontrivial connection between the dynamics of the particle in our model and the evolution of a particle under a non-Hermitian Hamiltonian with a large absorbing potential at some sites.

Item Type:	Journal Article
Publication:	PHYSICAL REVIEW A
Publisher:	AMER PHYSICAL SOC
Additional Information:	Copy right for this article belongs to the AMER PHYSICAL SOC, ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
Department/Centre:	Division of Physical & Mathematical Sciences > Centre for High Energy Physics
Date Deposited:	19 Jul 2015 09:34
Last Modified:	19 Jul 2015 09:34
URI:	http://eprints.iisc.ac.in/id/eprint/51868

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