Controlled decoherence in an atom interferometer

Autor: David E. Pritchard, Tony D. Roberts, Alexander D. Cronin, David A. Kokorowski
Rok vydání: 2003
Předmět:
Zdroj: Fortschritte der Physik. 51:313-317
ISSN: 1521-3978
0015-8208
Popis: Interactionwithanenvironmentusuallydestroysquantumcoherence.Hereweshowtheopposite:addinganenvironmentcanprotectcoherence.Wehavedemonstratedsuchamethodforcontrollingspatialdecoherenceby adding an environment that interacts with spin.In general, decoherence of a quantum system results from entanglement with an unmeasured reservoir,referred to as the environment. The rate of decoherence depends on the system-environment interaction,and therefore on the state of both the system and the environment. We have engineered two differentenvironments: one which destroys coherence for atoms with a particular spin, and a second which causesonly a little decoherence but changes the spin of atoms by optical pumping. The time-ordering of the twoenvironments is important, because one environment prepares atoms in a decoherence-free state.Using an atom’s spin to control the rate of photon scattering – and thus the rate of spatial decoherence– is basically as simple as optical pumping. However, the dynamics of decoherence change when thesame environment that causes decoherence also modifies the rate of decoherence. We use two separatedenvironments to illustrate this point.The system we are dealing with is a beam of atoms in an interferometer. Each atom can travel in asuperpositionofpaths,andthespatialcoherencebetweenthepathsismeasuredasatomfringecontrast[1,2].Thetwoengineeredenvironmentsareresonantlaserbeamswhichspontaneouslyscatterphotonsfromatomsin the interferometer as discussed in [3–6]. The setup is shown in Fig. 1.First we review how entanglement with a single environment causes spatial decoherence for the atoms.Then we present the controlled decoherence experiment using two separated environments.
Databáze: OpenAIRE
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