1. nanomechanical cat-states generated by dc-voltage driven cooper pair box qubit

Danko Radic

University of Zagreb, Croatia

15 December 2020 Tue 4 pm

                                      IBS Center for Theoretical Physics of Complex Systems (PCS), Administrative Office (B349), Theory Wing, 3rd floor

                                      Expo-ro 55, Yuseong-gu, Daejeon, South Korea, 34126 Tel: +82-42-878-8633                     

Encoding the quantum information into coherent mechanical states is an important goal for quantum communication due to robustness of such macroscopic multi-phonon states with respect to external perturbation.  Motivated by this challenge we study the nanoelectromechanical system consisting of Cooper pair box qubit performing nanomechanical vibrations between two bulk superconductors. We demonstrate that a bias voltage applied to superconductors may generate states which are represented by the entanglement of the qubit states with a cat-states (superposition of coherent states) of the nanomechanical oscillator. Tracking the formation and development of such states by calculating the corresponding (negative) Wigner function and entropy of entanglement we propose the experimentally feasible detection of the effect by measuring the average current which attains specific features due to the entanglement.