16 May 2023 Tue 4 pm

The Coulomb blockade for tunneling of Cooper pairs between a bulk superconductor and a small superconducting dot can be removed electrostatically, which brings superconducting condensates on both conductors into entanglement. These quantum states, called Cooper pair box (CPB) states, form and implement a quantum information bit-qubit. Time-dependent mechanical displacement of the dot allows spatial transportation of the Cooper pair box, providing transfering of quantum information in space (so-called "flying qubit states"). Observation of such states formed on movable CPB can be achieved by injection of electrons into it from external non-superconducting electrodes. We show that nonzero electric current occurring due to Andreev reflection phenomenon occurs at zero driving voltage and is determined by the mechanical motion of CPB, and movable qubit states. The latter can be identified through the oscillatory dependence of the current on the electrostatic gate potential applied to the device.

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