How useful is parametric phase squeezing

Murray Wolinsky, H. J. Carmichael

Hidenori Koyano, Tomohiko Uyematsu, Norihiro Yoshida +1 more

Abstract In this paper, characteristics of degenerate parametric amplifiers are analyzed and are expected to be useful as a generator of a squeezed state or a noiseless amplifier for an optical wave. Especially, when a degenerate parametric amplifier is used as a noiseless amplifier or a squeezed‐state generator (squeezer), the depletion of the pumping light which has been neglected affects the quantum noise characteristic of the squeezed light. This effect is analyzed in this paper. Further, when the incident light does not satisfy the phase matching condition, the effect of this phase shift on the gain and quantum noise characteristics of the degenerate parametric amplifier is studied. On the other hand, when a degenerate parametric amplifier is used as a preamplifier for the receiving side of the communication system, the phase noise of the pumping light can be a cause of degradation of the communication system performance. The phase noise of the pumping light is classified as the phase shift and the phase fluctuation caused by the quantum noise and then the effects of these phase noises on the quantum noise characteristics of the squeezed light are analyzed. Further, in the BPSK optical coherent communication system, the effect of the phase noise on the bit error rate is analyzed. A quantitative evaluation is made to determine how small the phase noise of the pumping light should be in order not to degrade the error rate.

Vlasta Peřinová

It is well known that during the ℓth-subharmonic generation general ℓ-photon states evolve from an arbitrary state of the pump mode. For the second-subharmonic generation with an initial coherent state the assumption of pump nondepletion, the so called parametric approximation, is very useful for obtaining closed formulas. The resulting state then is an ordinary squeezed vacuum. The parametric approximation is ineffective for ℓ > 2 not only because closed formulas are not obtained, but also because it is proven that no quantum state is defined for nonzero higher-order squeezing [1]. This finding motivated a definition of the ℓ-photon coherent state [2],

E. Giacobino

V. V. Dodonov, Olga V. Man’ko, Vladimir I. Man’ko

Richard J. Birrittella, Jason Ziskind, Edwin E. Hach +2 more

We investigate the presence of spin- and planar-squeezing in generalized superpositions of atomic (or spin) coherent states. Spin-squeezing has been shown to be a useful tool in determining the presence of entanglement in multipartite systems, such as collections of two-level atoms, as well as being an indication of reduced projection noise and sub-shot-noise-limited phase uncertainty in Ramsey spectroscopy, suitable for measuring phases ϕ ∼ 0 . On the other hand, planar-squeezed states display reduced projection noise in two directions simultaneously and have been shown to lead to enhanced metrological precision in measuring phases without the need for explicit prior knowledge of the phase value. In this paper, we show that the generalized superposition state can be parametrized to display both spin-squeezing along all orthogonal axes and planar-squeezing along all orthogonal planes for all values of J > 1 / 2 . We close with an application of the maximally spin- and planar-squeezed states to quantum metrology.