QUANTUM STATE OF JOSEPHSON JUNCTION AS COOPER PAIR NUMBER-PHASE ENTANGLED STATE IN THE BOSONIC OPERATOR JOSEPHSON MODEL
Hong-Yi Fan, Ji‐Suo Wang, Xiang‐Guo Meng · International Journal of Modern Physics B · 2007
Based on Feynman's explanation about Cooper pair that "a bound pair acts as a Bose particle" and the bosonic operator Hamiltonian of the Josephson junction, we realize that the quantum state of the Josephson junction is a Cooper pair number-phase entangled state constructed by the phase operator across the junction. Its Schmidt decomposition is derived. The Cooper pair number-phase squeezed state's projection onto this entangled state leads to a geometric distribution.