Detection of Squeezed Light by Coherently Superposed Detector States

Menwuyelet Melaku, Deribe Hirpo

With the aid of the solutions of the Quantum Langevin equations, we have calculated the Q-functions for the two-mode coherent and subharmonic cavity light beams. We have then determined the Q-function for the superposed two-mode coherent and subharmonic cavity light beams. With the help of the pertinent Q-functions for cavity light beams, we determined the photon statistics, quadrature statistics, and entanglement. we have obtained that the superposed two-mode coherent and subharmonic cavity light beams are in a squeezed state and the squeezing occurs in the plus quadrature. Besides, our analysis shows that at steady state and at threshold, the superposed two-mode coherent and subharmonic light beams have a maximum squeezing of $25\%$ below the two-mode vacuum-state level. We have also clearly shown that the superposed two-mode light beam is entangled at steady-state and threshold and the entanglement turned out to be observed in the highly correlated squeezed photons with $75\%$ degree of entanglement.

Valerio Annovazzi-Lodi, Silvano Donati, Sabina Merlo

Gerd Breitenbach, Stephan Schiller, J. Mlynek

Fesseha Kassahun

We first calculate the mean photon number and quadrature variance of superposed coherent and squeezed light, following a procedure of analysis based on combining the Hamiltonians and using the usual definition for the quadrature variance of superposed light beams. This procedure of analysis leads to physically unjustifiable mean photon number of the coherent light and quadrature variance of the superposed light. We then determine both of these properties employing a procedure of analysis based on superposing the Q functions and applying a slightly modified definition for the quadrature variance of a pair of superposed light beams. We find the expected mean photon number of the coherent light and the quadrature variance of the superposed light. Moreover, the quadrature squeezing of the superposed output light turns out to be equal to that of the superposed cavity light.

Menwuyelet Melaku, Deribe Hirpo

We examined a two-mode coherent and subharmonic light beam within a cavity that is coupled to a two-mode vacuum reservoir through a single port mirror. Utilizing the solutions of the quantum Langevin equations, we developed Q-functions for the two-mode coherent and subharmonic cavity light beams. Subsequently, we calculated the Q-function for the superposed two-mode light beams in question. By leveraging the relevant Q-functions for the superposed cavity light beams, we investigated the quadrature statistics and entanglement. To conduct our analysis, we focused on a quantum system characterized by Gaussian operators with a zero mean. We have identified that the superposed two-mode coherent and subharmonic cavity light beams are in a squeezed state, with the squeezing occurring in the plus quadrature. Moreover, our analysis revealed that at steady state and at threshold, the superposed two-mode coherent and subharmonic light beams exhibit a maximum squeezing of 25% below the two-mode vacuum-state level. We have also clearly illustrated, using continuous variable entanglement criteria, that the superposed two-mode cavity light beams are entangled at both steady-state and threshold, with the entanglement being manifested in the highly correlated squeezed photons, which show a 75% degree of entanglement. Our analysis, applying Cauchy-Schewarz, Hillary-Zubiary, and Logarithmic Negativity entanglement criteria, further confirmed that the superposed cavity light beams in question are entangled. The Logarithmic Negativity criteria validated the entanglement of the superposed light, indicating a 50% degree of entanglement.

Guang‐Can Guo, Peizhou Huang, Dun Yao