what is Quantum correlation

yashar

hi
i want to know that what is quantum and classical correlation.
is there any book or paper?
thanks

Mr_Physicist

That is a very general question, can you be more specific? In optics, classical correlations can be discussed in the context of coherence theory, such as in a laser beam. In quantum, particles are often said to have non-classical correlations when they are entangled. But meaning of correlation always depends upon the context.

yashar

i want to know what is physical idea behind "correlation function"

as you know in quantum we define <B(t)B(s)> , B(t) and B(s) are operators in different time. and angular bracket shows averaging.

is this definition say that if correlation function does not vanish then the observables corresponding to operators B(t) depend on each other in different time? in other words if correlation function does not vanish does the value of observable in time s affect the value of observable in time t?