The role of squeezing in quantum key distribution with continuous variables based on homodyne detection and post-selection is investigated. It is shown that amplitude squeezing creates strong correlations between the signals of the legitimate receiver and a potential eavesdropper. Postselection of the received pulses can therefore be used to reduce the eavesdropper’s knowledge of the raw key, w...

We demonstrate spin squeezing in a room temperature ensemble of approximately 10(12) cesium atoms using their internal structure, where the necessary entanglement is created between nuclear and electronic spins of each individual atom. This state provides improvement in measurement sensitivity beyond the standard quantum limit for quantum memory experiments and applications in quantum metrology...

Atomic resonance fluorescence, emitted near the surface of a four-wave mixing phase conjugator, exhibits squeezing for certain values of the optical parameters of the incident laser field and for a certain range of the phase-conjugate reflectivity. A condition for the occurrence of squeezing is derived, and it is shown that the presence of the phaseconjugating medium tends to increase the quant...

A theoretical method is developed to treat wideband pulsed squeezing in a traveling-wave parametric amplifier with group-velocity dispersion. Classical stochastic wave equations that are fully equivalent to operator equations of motion are developed and solved numerically. It is found that squeezing occurs over the entire phase-matching bandwidth, although the degree of squeezing decreases when...