Measurements and correlations in tri-partite systems

A system comprised of three oscillators A, B and C is studied. The oscillators B and C are interacting with each other, while the oscillator A does not interact with any of them. At t = 0 the system is in the state rho(AB)(0)circle times rho(C)(0). Two examples in which rho(AB)(0) is in separable and entangled states, are considered. It is shown that the oscillators A, C become entangled and that a measurement in C whose result is communicated classically to A, affects the state of the oscillator A. The work studies how the collapse due to the measurement at C, affects the state of the oscillator A.