Regensburg 2022 – scientific programme
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QI: Fachverband Quanteninformation
QI 13: Implementations: Superconducting Qubits
QI 13.3: Talk
Friday, September 9, 2022, 10:15–10:30, H8
How to correctly account for time-varying fluxes in superconducting circuits — •Ahmed Kenawy1, Fabian Hassler2, David DiVincenzo1, and Roman Riwar1 — 1Peter Grünberg Institute, Theoretical Nanoelectronics, Forschungszentrum Jülich — 2JARA-Institute for Quantum Information, RWTH Aachen University
Time-varying fluxes are a ubiquitous tool to control superconducting hardware. Surprisingly, however, the existing literature has never fully accounted for the electro-motive force induced by the magnetic field. Here, we propose a general recipe to construct a low-energy Hamiltonian, taking as input only the circuit geometry and the solution of the external magnetic fields. We apply this recipe to the example of a dc SQUID and show that the assignment of individual capacitances to each Josephson junction is possible only if we permit those capacitances to be negative, time-dependent, or even momentarily singular. Such anomalous capacitances lead, among others, to a strong enhancement of qubit relaxation rates. Then, we tackle the problem of driven topological quantum circuits, focusing on two weakly coupled Kitaev chains and study how the electro-motive force modifies the time-dependent fractional Josephson effect.