Twin photons and squeezed light

Pierre Meystre, Murray Sargent

Katsuyuki Kasai, Noriaki Onodera, Jiangrui Gao +1 more

We have generated bright squeezed light and quantum-correlated twin photon beams by using a cw semimonolithic KTP Optical Parametric Oscillator (OPO), which exhibits a low oscillation threshold and is capable of oscillating even in the free-running (no external-feedback) condition. The pump beam reflected by the OPO, after a cascading nonlinearity process in the crystal, appears as bright squeezed light. The squeezing observed on the reflected pump beam from the semimonolithic OPO was 30% (inferred squeezing: 48%). The signal and idler beams generated by the optical parametric oscillator are highly quantum-correlated twin photon beams. Since the squeezing property of the intensity difference between the twin photonbeams is robust in the condition where the two fields are balanced, the squeezing can be observed even in the freerunning condition of the OPO. This intensity-difference squeezing observed between the twin photon beams from the free-running semimonolithic OPO was 70% (inferred squeezing: 87%).

Daniel F. Walls

Hai-jun Yu, Hong-Yi Fan

We explore the time evolution law of a two-mode squeezed light field (pure state) passing through twin diffusion channels, and we find that the final state is a squeezed chaotic light field (mixed state) with entanglement, which shows that even though the two channels are independent of each other, since the two modes of the initial state are entangled with each other, the final state remains entangled. Nevertheless, although the squeezing (entanglement) between the two modes is weakened after the diffusion, it is not completely removed. We also highlight the law of photon number evolution. In the calculation process used in this paper, we make full use of the summation method within the ordered product of operators and the generating function formula for two-variable Hermite polynomials.

Claude Fabre

Solomon Getahun

We have analyzed the statistical and squeezing properties of the signal mode applying the solution of c-number Langivin equations for the combination of the twin signal light beams. We have found that the mean photon number to be twofold of that of a twin signal light beam. And a large part of the mean photon number is confined in a relatively small frequency interval. In addition, we have shown that the local quadrature squeezing of the signal mode is in general greater than the global quadrature squeezing and approaches to the global quadrature squeezing as increases. Moreover, the one-mode subharmonic light beams have a maximum amplified squeezing of 75% below the vacuum state level and occurs in frequency interval.