Understanding non-classical correlation using optical hybrid states in noisy quantum channels
In this article we investigate the non-classical correlation in a macroscopic
physical system. As a tool, we consider an optical hybrid state that is a micro–
macro entangled state. Our strategy is to study the behavior of non-classical
correlation in an optical hybrid state that may go through noisy channels. We
study the violation of two inequalities, which are the CHSH-inequality and the
(generalized) CHSH-like-inequality, as measures of non-classical correlation.
First, we find that when on/off or parity measurements are used for the side
of the coherent state in an optical hybrid state, the violation of the CHSHinequality
is the same as that of the (generalized) CHSH-like-inequality.
Second, we see that each measurement provides a different value of violation
of (generalized) CHSH-inequality when it is an optical hybrid state that goes
through noisy channels. A suprising result is that the on/off measurement
can provide a violation of CHSH-inequality (or (generalized) CHSH-likeinequality)
for an optical hybrid state with any amount of colored noise. This
implies that colored noise cannot break the non-classical correlation in an
optical hybrid state.