Seminar: Charge Flying Qubits in Quantum-Coherent Electronic Circuits

Electron quantum optics explores coherent single-electron charge pulse propagation in electronic nanoscale circuits akin to table-top photon setups. While past experiments focused on normal-state conductors, incorporating superconductors holds promise for exploiting the electron-hole degree of freedom in quantum sensing applications and quantum information processing. Here, we propose and analyze a tunable mechanism for converting single-electron pulses into holes through Andreev processes on a superconductor [1]. We develop a Floquet-Nambu scattering formalism to demonstrate the dynamic conversion of charge pulses and the controllable generation of coherent electron-hole superpositions through interferometric magnetic flux control [2]. As a result, we propose an on-demand source of flying qubits where the tunable electron-hole superposition can function as a carrier of quantum information. A Wigner function representation also allows us to visualize the response function of this charge flying qubit both in the time and in the frequency domain [3]. Our discussion covers optimal conditions in realistic scenarios, affirming the feasibility of our proposal with current technology. 

[1] P. Burset, B. Roussel, M. Moskalets, C. Flindt, Phys. Rev. Lett. 135, 246303 (2025)

[2] P. Burset, B. Roussel, M. Moskalets, C. Flindt, Phys. Rev. B 112, 245412 (2025)

[3] B. Roussel, P. Burset, C. Flindt, Phys. Rev. B 112, 014506 (2025)