Quantum control by von Neumann measurements

Alexander Pechen, Nikolai Il'in, Feng Shuang, Herschel Rabitz

Research output: Contribution to journalArticle

71 Scopus citations

Abstract

A general scheme is presented for controlling quantum systems using evolution driven by nonselective von Neumann measurements, with or without an additional tailored electromagnetic field. As an example, a two-level quantum system controlled by nonselective quantum measurements is considered. The control goal is to find optimal system observables such that consecutive nonselective measurement of these observables transforms the system from a given initial state into a state which maximizes the expected value of a target operator (the objective). A complete analytical solution is found including explicit expressions for the optimal measured observables and for the maximal objective value given any target operator, any initial system density matrix, and any number of measurements. As an illustration, upper bounds on measurement-induced population transfer between the ground and the excited states for any number of measurements are found. The anti-Zeno effect is recovered in the limit of an infinite number of measurements. In this limit the system becomes completely controllable. The results establish the degree of control attainable by a finite number of measurements.

Original languageEnglish (US)
Article number052102
JournalPhysical Review A - Atomic, Molecular, and Optical Physics
Volume74
Issue number5
DOIs
StatePublished - Nov 9 2006

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics

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