This work aims at exploiting the quantum properties of light in order to develop new communication devices. The study is devoted to the quadrature components (quantum continuous variables) of a single mode of the electromagnetic field in the pulsed regime. A quantum key distribution protocol using coherent states has been demonstrated, and opens the way for practical high-rate quantum cryptography devices.
In order to study the use of quantum specificities such as squeezing and entanglement, we have developed a new source of pulsed squeezed states and entangled states. This source is based on the nonlinear conversions of ultrashort pulses. We also describe the first observation of a degaussification protocol, that maps individual pulses of squeezed vacuum onto non-Gaussian states. Finally, we study some optical set-ups allowing for a loophole-free Bell test using continuous variables and efficient homodyne detections.
Quantum information - quantum communication - quantum cryptography - continuous variables - pulsed homodyne detection - femtosecond pulses - parametric amplification - squeezed states - non-Gaussian states - entanglement - Bell's inequalities