72 research outputs found
Conditions for spin squeezing in a cold 87Rb ensemble
We study the conditions for generating spin squeezing via a quantum
non-demolition measurement in an ensemble of cold 87Rb atoms. By considering
the interaction of atoms in the 5S_{1/2}(F=1) ground state with probe light
tuned near the D2 transition, we show that, for large detunings, this system is
equivalent to a spin-1/2 system when suitable Zeeman substates and quantum
operators are used to define a pseudo-spin. The degree of squeezing is derived
for the rubidium system in the presence of scattering causing decoherence and
loss. We describe how the system can decohere and lose atoms, and predict as
much as 75% spin squeezing for atomic densities typical of optical dipole
traps.Comment: 9 pages, 3 figures, submitted to J. Opt. B: Quantum Semiclass. Opt.
Proceedings of ICSSUR'0
Polarization-based Light-Atom Quantum Interface with an All-optical Trap
We describe the implementation of a system for studying light-matter
interactions using an ensemble of cold rubidium 87 atoms, trapped in a
single-beam optical dipole trap. In this configuration the elongated shape of
the atomic cloud increases the strength of the collective light-atom coupling.
Trapping all-optically allows for long storage times in a low decoherence
environment. We are able to perform several thousands of measurements on one
atomic ensemble with little destruction. We report results on paramagnetic
Faraday rotations from a macroscopically polarized atomic ensemble. Our results
confirm that strong light-atom coupling is achievable in this system which
makes it attractive for single-pass quantum information protocols.Comment: 8 pages, 4 figure
Diffraction effects on light-atomic ensemble quantum interface
We present a simple method to include the effects of diffraction into the
description of a light-atomic ensemble quantum interface in the context of
collective variables. Carrying out a scattering calculation we single out the
purely geometrical effect. We apply our method to the experimentally relevant
case of Gaussian shaped atomic samples stored in single beam optical dipole
traps and probed by a Gaussian beam. We derive analytical scaling relations for
the effect of the interaction geometry and compare our findings to results from
1-dimensional models of light propagation.Comment: 13 pages, 7 figures, comments welcom
Hamiltonian Design in Atom-Light Interactions with Rubidium Ensembles: A Quantum Information Toolbox
We study the coupling between collective variables of atomic spin and light
polarization in an ensemble of cold 87Rb probed with polarized light. The
effects of multiple hyperfine levels manifest themselves as a rank-2 tensor
polarizability, whose irreducible components can be selected by means of probe
detuning. The D1 and D2 lines of Rb are explored and we identify different
detunings which lead to Hamiltonians with different symmetries for rotations.
As possible applications of these Hamiltonians, we describe schemes for spin
squeezing, quantum cloning, quantum memory, and measuring atom number.Comment: 6 pages, 4 figures; added reference
Heterodyne non-demolition measurements on cold atomic samples: towards the preparation of non-classical states for atom interferometry
We report on a novel experiment to generate non-classical atomic states via
quantum non-demolition (QND) measurements on cold atomic samples prepared in a
high finesse ring cavity. The heterodyne technique developed for the QND
detection exhibits an optical shot-noise limited behavior for local oscillator
optical power of a few hundred \muW, and a detection bandwidth of several GHz.
This detection tool is used in single pass to follow non destructively the
internal state evolution of an atomic sample when subjected to Rabi
oscillations or a spin-echo interferometric sequence.Comment: 23 page
Prospects for photon blockade in four level systems in the N configuration with more than one atom
We show that for appropriate choices of parameters it is possible to achieve
photon blockade in idealised one, two and three atom systems. We also include
realistic parameter ranges for rubidium as the atomic species. Our results
circumvent the doubts cast by recent discussion in the literature (Grangier et
al Phys. Rev Lett. 81, 2833 (1998), Imamoglu et al Phys. Rev. Lett. 81, 2836
(1998)) on the possibility of photon blockade in multi-atom systems.Comment: 8 page, revtex, 7 figures, gif. Submitted to Journal of Optics B:
Quantum and Semiclassical Optic
Intensity-dependent dispersion under conditions of electromagnetically induced transparency in coherently prepared multistate atoms
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