Non-classical correlation of two-mode squeezed light in asymmetric optical-loss conditions

Abstract

Quantum illumination is an attractive scheme for target detection utilizing quantum entanglement to improve error probability of discrimination for target presence or absence even in a lossy and noisy environment. In the quantum illumination with two-mode squeezed vacuum states, one of the entangled beams, a signal beam is transmitted towards a lossy optical medium. And the other beam, a reference beam is directly sent to receiver with a lossless channel. So, the entangled light beams are affected by the asymmetric optical loss. In this work we calculate the correlation variance of quadrature phase amplitudes of two-mode squeezed light under the asymmetric optical-loss conditions and discuss its non-classical correlation based on Duan’s and Simon’s inseparability criterion. The asymmetric optical loss sensitively increases the correlation variance and violates the inseparability criterion. In this work we consider asymmetric two-mode squeezed light as an initial state where the signal beam has larger quadrature phase amplitudes than the reference beam. After exposition to the asymmetric optical loss only the quadrature phase amplitudes of the signal beam is attenuated and become comparable to those of the reference beam. As a result it is expected that the asymmetric two-mode squeezed light has an ability to compensate the effect of the asymmetric optical loss and can maintain the inseparability criterion in the sense of Duan and Simon.