9 research outputs found
Quantum Non-Demolition Detection of Strongly Correlated Systems
Preparation, manipulation, and detection of strongly correlated states of
quantum many body systems are among the most important goals and challenges of
modern physics. Ultracold atoms offer an unprecedented playground for
realization of these goals. Here we show how strongly correlated states of
ultracold atoms can be detected in a quantum non-demolition scheme, that is, in
the fundamentally least destructive way permitted by quantum mechanics. In our
method, spatially resolved components of atomic spins couple to quantum
polarization degrees of freedom of light. In this way quantum correlations of
matter are faithfully mapped on those of light; the latter can then be
efficiently measured using homodyne detection. We illustrate the power of such
spatially resolved quantum noise limited polarization measurement by applying
it to detect various standard and "exotic" types of antiferromagnetic order in
lattice systems and by indicating the feasibility of detection of superfluid
order in Fermi liquids.Comment: Published versio
Experimental long-lived entanglement of two macroscopic objects
Entanglement is considered to be one of the most profound features of quantum
mechanics. An entangled state of a system consisting of two subsystems cannot
be described as a product of the quantum states of the two subsystems. In this
sense the entangled system is considered inseparable and nonlocal. It is
generally believed that entanglement manifests itself mostly in systems
consisting of a small number of microscopic particles. Here we demonstrate
experimentally the entanglement of two objects, each consisting of about 10^12
atoms. Entanglement is generated via interaction of the two objects - more
precisely, two gas samples of cesium atoms - with a pulse of light, which
performs a non-local Bell measurement on collective spins of the samples. The
entangled spin state can be maintained for 0.5 millisecond. Besides being of
fundamental interest, the robust, long-lived entanglement of material objects
demonstrated here is expected to be useful in quantum information processing,
including teleportation of quantum states of matter and quantum memory.Comment: Submitted to Nature, June 9, 2001, 11 pages, 3 figures. Contents
changed following referees' suggestion
Multimode entaglement of light and atomic ensembles via off-resonant coherent forward scattering
Raman shines back
Texte complet ici: http://rdcu.be/pGLTInternational audienceCoherent backscattering experiments indicate that spontaneous Raman scattering is a coherent process that can lead to macroscopically observable interference phenomena in disordered solid-state samples