arXiv subjects

Anne Louchet

Publications and source records attributed to Anne Louchet.

4 recordsLinked to original sources

arXiv2009

Squeezing of Atomic Quantum Projection Noise

We provide a framework for understanding recent experiments on squeezing of a collective atomic pseudo-spin, induced by a homodyne measurement on off-resonant probe light interrogating the atoms. The detection of light decimates the atomic state distribution and we discuss the conditions under which the resulting reduced quantum fluctuations are metrologically relevant. In particular, we consider a dual probe scheme which benefits from a cancelation of classical common mode noise sources such that quantum fluctuations from light and atoms are the main contributions to the detected signal.

quant-ph↗

arXiv2007

Optical Excitation of Nuclear Spin Coherence in Tm3+:YAG

A thulium-doped crystal is experimentally shown to be an excellent candidate for broadband quantum storage in a solid-state medium. For the first time, nuclear spin coherence is optically excited, detected and characterized in such a crystal. The lifetime of the spin coherence -- the potential storage entity -- is measured by means of Raman echo to be about 300 $μ$s over a wide range of ground state splittings. This flexibility, attractive for broadband operation, and well fitted to existing quantum sources, results from the simple hyperfine structure, contrasting with Pr- and Eu- doped crystals.

quant-ph↗

arXiv2006

Branching ratio measurement of a "Lambda" system in Tm3+:YAG under magnetic field

A three-level Lambda system in Tm3+ doped YAG crystal is experimentally investigated in the prospect of quantum information processing. Zeeman effect is used to lift the nuclear spin degeneracy of this ion. In a previous paper [de Seze et al. Phys. Rev. B, 73, 85112 (2006) we measured the gyromagnetic tensor components and concluded that adequate magnetic field orientation could optimize the optical connection of both ground state sublevels to each one of the excited state sublevels, thus generating Lambda systems. Here we report on the direct measurement of the transition probability ratio along the two legs of the Lambda. Measurement techniques combine frequency selective optical pumping with optical nutation or photon echo processes.

quant-ph↗

arXiv2005

Experimental Tailoring of a Three-Level Lambda System in Tm3+:YAG

Quantum information transfer from light to atom ensembles and vice versa has both basic and practical importance. Among the relevant topics let us mention entanglement and decoherence of macroscopic systems, together with applications to quantum memory for long distance quantum cryptography. Although the first experimental demonstrations have been performed in atomic vapors and clouds, rare earth ion doped crystals are also interesting media for such processes. In this paper we address Tm3+ ions capability to behave as three-level lambda systems, a key ingredient to convert optical excitation into a spontaneous- emission-free spin wave. Indeed Tm3+ falls within reach of light sources that can be stabilized easily to the required degree. In the absence of zero-field hyperfine structure we apply an external magnetic field to lift the nuclear spin degeneracy in Tm3+:YAG. We experimentally determine the gyromagnetic tensor components with the help of spectral hole-burning techniques. Then appropriate orientation of the applied field enables us to optimize the transition probability ratio along the two legs of the lambda. The resulting three-level lambda system should suit quantum information processing requirements.

quant-ph↗