Controllable quantum-information transfer in superconducting networks

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Superconducting quantum circuits are a strong candidate for the main building blocks of quantum processors which are nowadays sufficiently advanced for scaling-up them into complex quantum machines. To transfer quantum information between the processing or storage nodes we need flying qubits propagating in spatial modes. Although single photons are currently considered to be a natural choice for this role, the implementation of a quantum interface between stationary superconducting and flying photonic qubits requires a lot of very complicated engineering efforts. The planned bilateral activity has been initiated by recent progress in electron quantum optics, a novel platform aiming to study the behavior of electrons in ballistic quantum conductors using paradigms and methods of quantum optics, and intends to develop and/or to improve superconducting network components for fully controlled processing and transfer of quantum information encoded in the quantum state of quasiparticle excitations and kinematic vortices.The proposed joint activities target to prepare a theoretical basis for a future European project with participation of French and Italian experimentalists. Namely, it is planned (i) to model ballistic transport of spatially localized wave packets across superconducting mesoscopic networks, (ii) to simulate the environmentally assisted single-electron transfer across the superconducting grid in order to understand the quantum-to-classical transition in superconducting networks, (iii) to perform theoretical analysis of possible interfaces between stationary superconducting qubits and charge flying qubits, (iv) to elaborate the technique able to control the distribution of currents within the network by impact of a non-equilibrium state created in one or several superconducting transmission lines, (v) to study experimentally spin-imbalance effect on internal structure of superconducting Mo-Re and Pb strips with a scanning tunneling microscope, (vi) to investigate theoretically the spin-imbalance relaxation time in superconductors and effect of interactions between the spinful excitations and the condensate, and (vii) to elucidate the possibility of controlled generation of kinematic vortices in superconducting quasi-two-dimensional films. Dissemination of the obtained results will be carried out through the usual scientific channels (scientific publications in specialized journals, presentations at international conferences and workshops, institute reports, and student works).