Vincent Boyer

Entangled Images from Four-Wave Mixing

Two beams of light can be quantum mechanically entangled through correlations of their phase and intensity fluctuations. For a pair of spatially extended image-carrying light fields, the concept of entanglement can be applied not only to the entire images but also to their smaller details. We used a spatially multimode amplifier based on four-wave mixing in a hot vapor to produce twin images that exhibit localized entanglement. The images can be bright fields that display position-dependent quantum noise reduction in their intensity difference or vacuum twin beams that are strongly entangled when projected onto a large range of different spatial modes. The high degree of spatial entanglement demonstrates that the system is an ideal source for parallel continuous-variable quantum information protocols.

Strong relative intensity squeezing by four-wave mixing in rubidium vapor

We have measured ¿6.3 dB of relative intensity squeezing at 795 nm, generated by stimulated, nondegenerate four-wave mixing in a hot rubidium vapor. This scheme is of interest for experiments involving cold atoms or atomic ensembles.

Tunable delay of Einstein–Podolsky–Rosen entanglement

Entangled systems display correlations that are stronger than can be obtained classically. This makes entanglement an essential resource for a number of applications, such as quantum information processing, quantum computing and quantum communications. The ability to control the transfer of entanglement between different locations will play a key role in these quantum protocols and enable quantum networks. Such a transfer requires a system that can delay quantum correlations without significant degradation, effectively acting as a short-term quantum memory. An important benchmark for such systems is the ability to delay Einstein–Podolsky–Rosen (EPR) levels of entanglement and to be able to tune the delay. EPR entanglement is the basis for a number of quantum protocols, allowing the remote inference of the properties of one system (to better than its standard quantum limit) through measurements on the other correlated system. Here we show that a four-wave mixing process based on a double-lambda scheme in hot 85Rb vapour allows us to obtain an optically tunable delay for EPR entangled beams of light. A significant maximum delay, of the order of the width of the cross-correlation function, is achieved. The four-wave mixing also preserves the quantum spatial correlations of the entangled beams. We take advantage of this property to delay entangled images, making this the first step towards a quantum memory for images.

Strong Low-Frequency Quantum Correlations From a Four-Wave Mixing Amplifier

Using a simple scheme based on nondegenerate four-wave mixing in a hot vapor, we generate bright twin beams which display a quantum noise reduction in the intensity difference of more than

Ultraslow propagation of matched pulses by four-wave mixing in an atomic vapor

8\phantom{\rule{0.3em}{0ex}}\mathrm{dB}

Generation of Spatially Broadband Twin Beams for Quantum Imaging

. The absence of a cavity makes the system immune to external perturbations, and strong quantum noise reduction is observed at frequencies as low as

Dynamic manipulation of Bose-Einstein condensates with a spatial light modulator

4.5\phantom{\rule{0.3em}{0ex}}\mathrm{kHz}

Multi GPU Implementation of the Simplex Algorithm

and over a large frequency range.

Role of the phase-matching condition in nondegenerate four-wave mixing in hot vapors for the generation of squeezed states of light

We have observed the ultraslow propagation of matched pulses in nondegenerate four-wave mixing in a hot atomic vapor. Probe pulses as short as 70 ns can be delayed by a tunable time of up to 40 ns with little broadening or distortion. During the propagation, a probe pulse is amplified and generates a conjugate pulse which is faster and separates from the probe pulse before getting locked to it at a fixed delay. The precise timing of this process allows us to determine the key coefficients of the susceptibility tensor. The fact that the same configuration has been shown to generate quantum correlations makes this system very promising in the context of quantum information processing.

Understanding the production of dual Bose-Einstein condensation with sympathetic cooling

We generate spatially multimode twin beams using 4-wave mixing in a hot atomic vapor in a phase-insensitive traveling-wave amplifier configuration. The far-field coherence area measured at 3.5 MHz is shown to be much smaller than the angular bandwidth of the process and bright twin images with independently quantum-correlated subareas can be generated with little distortion. The available transverse degrees of freedom form a high-dimensional Hilbert space that we use to produce quantum-correlated twin beams with finite orbital angular momentum.