Controllable quantum-information transfer in superconducting networks

超导量子电路是量子处理器主要组成部分的有力候选者，这些处理器现在已经足够先进，可以将其放大到复杂的量子机中。为了在处理或存储节点之间传输量子信息，我们需要在空间模式中传播飞行量子比特。尽管单光子目前被认为是这一角色的自然选择，但实现静止超导和飞行光子量子比特之间的量子界面需要大量非常复杂的工程努力。计划中的双边活动是由电子量子光学的最新进展启动的，这是一个新的平台，旨在使用量子光学的范式和方法研究电子在弹道量子导体中的行为，并打算开发和/或改进超导网络组件，用于完全控制处理和传输以准粒子激发和运动涡旋的量子态编码的量子信息。拟议的联合活动旨在为未来由法国和意大利实验者参与的欧洲项目准备理论基础。也就是说，计划(I)模拟空间局域波包在超导介观网络上的弹道传输，(Ii)模拟环境辅助的单电子在超导网格上的转移，以便了解超导网络中的量子到经典的转变，(Iii)对静止的超导量子比特和电荷飞行量子比特之间的可能界面进行理论分析，(Iv)阐述能够通过在一个或几个超导传输线中产生的非平衡态的影响来控制网络内的电流分布的技术，(V)用扫描隧道显微镜从实验上研究自旋不平衡对超导Mo-Re和Pb带材内部结构的影响；(Vi)从理论上研究超导体的自旋不平衡弛豫时间以及自旋激发与凝聚体相互作用的影响；(Vii)阐明在超导准二维薄膜中控制运动涡旋产生的可能性。将通过通常的科学渠道(在专业期刊上发表科学出版物、在国际会议和讲习班上发表演讲、研究所报告和学生作品)传播所取得的成果。

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).