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学术报告


12月24日学术报告

发布时间:2015-12-22

报告题目:Quantum information processing with atoms trapped near an optical nanofiber: dispersive 

response theory with applications to QND measurement and spin squeezing

单     位:University of New Mexico 
报 告 人:戚晓东
时     间:12月24日(周四)下午2:30

Abstract:While optical fibers have been used for primary quantum communications, atom-fiber and atom-

waveguide based quantum interfaces have been proposed as effective elements to implement necessary 

quantum repeaters, quantum data buses and quantum chips to enable long-haul quantum communications 

and broader quantum information processing applications. We study the strong coupling between photons 

and atoms that can be achieved in an optical nanofiber geometry when the interaction is dispersive. While

the Purcell enhancement factor for spontaneous emission into the guided mode does not reach the strong-

coupling regime for individual atoms, one can obtain high cooperativity for ensembles of a few thousand 

atoms due to the tight confinement of the guided modes and constructive interference over the entire chain

 of trapped atoms. We studied the theory of the phase shift and polarization rotation induced on the guided

 light by the trapped atoms using the dyadic Green's function method. The Green's function is related to a full

 Heisenberg-Langevin treatment of the dispersive response of the quantized field to tensor polarizable atoms. 

In this talk, I will illustrate how do we apply our formalism to quantum nondemolition (QND) measurement of

 the atoms via polarimetry. We study shot-noise-limited detection of atom number for atoms in a completely

 mixed spin state and the squeezing of projection noise for atoms in clock states. Compared with squeezing of

 atomic ensembles in free space, we capitalize on unique features that arise in the nanofiber geometry including

 anisotropy of both the intensity and polarization of the guided modes. We use a first principles stochastic master

 equation to model the squeezing as function of time in the presence of decoherence due to optical pumping. 

We find a peak metrological squeezing of ~5 dB is achievable with current technology for ~2500 atoms prepared 

in clock states trapped 180 nm from the surface of a nanofiber with radius a=225 nm. The theory established can 

be used to guide the design of nanofiber- or waveguide-based quantum interfaces.



References:
[1] X. Qi, B. Q. Baragiola, P. S. Jessen, I. H. Deutsch, ArXiv:1509.02625 [quant-ph].
[2] S. T. Dawkins, R. Mitsch, D. Reitz, E. Vetsch, and A. Rauschenbeutel, Phys. Rev. Lett. 107, 243601 (2011).
[3] I. H. Deutsch and P. S. Jessen, Optics Communications 283, 681 (2010).