Физика Низких Температур: Том 47, Выпуск 4 (Апрель 2021), c. 315-321 ( к оглавлению , назад )
Entanglement between charge qubit states and coherent states of nanomechanical resonator generated by ac Josephson effect
O. M. Bahrova1, L. Y. Gorelik2, and S. I. Kulinich1
1B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine Kharkiv 61103, Ukraine
2Department of Physics, Chalmers University of Technology, Göteborg SE-412 96, Sweden
Received December 9, 2020, published online February 26, 2021
We considered a nanoelectromechanical system consisting of a movable Cooper-pair box qubit which is subject to an electrostatic field, and coupled to the two bulk superconductors via tunneling processes. We suggest that qubit dynamics is related to the one of a quantum oscillator and demonstrate that a bias voltage applied between superconductors generates states represented by the entanglement of qubit states and coherent states of the oscillator if certain resonant conditions are fulfilled. It is shown that a structure of this entanglement may be controlled by the bias voltage in a way that gives rise to the entanglement incorporating so-called cat-states — the superposition of coherent states. We characterize the formation and development of such states analyzing the entropy of entanglement and corresponding Wigner function. The experimentally feasible detection of the effect by measuring the average current is also considered.
Key words: superconducting nanowire, Josephson current, Cooper-pair box, entanglement states.