The transfer of the quantum correlation from two-mode nonclassical state field to the supercurrents in two distant SQUID rings

摘要

We have considered two distant mesoscopic superconducting quantum interference device (SQUID) rings A and B in the presence of two-mode nonclassical state fields and investigated the correlation of the supercurrents in the two rings using the normalized correlation function C_(AB). We show that when the parameter α is very small for the separable state with the density matrix ρ = (∣α, —α> <α, —α∣ + ∣—α,α> <—α,α∣)/2 and entangled coherent state (ECS) ∣u> = N_1(∣α, —α> + ∣—α, α>) fields, the dynamic behaviours of the normalized correlation function C_(AB) are similar, but it is quite different for the entangled coherent state |u'> = N_2(∣α, —α> — ∣—α, α>) field. When the parameter α is very large, the dynamic behaviours of C_(ab) are almost the same for the separable state, entangled coherent state ∣u> and ∣u'> fields. For the two-mode squeezed vacuum state field the maximum of C_(ab) increases monotonically with the squeezing parameter r, and as r → ∞, C_(AB) → 1. This means that the supercurrents in the two rings A and B are quantum mechanically correlated perfectly. It is concluded that not all the quantum correlations in the two-mode nonclassical state field can be transferred to the supercurrents; and the transfer depends on the state of the two-mode nonclassical state field prepared.