Measurement scheme of the Berry phase in superconducting circuits

TL;DR

This paper proposes a novel measurement scheme for observing the Berry phase in superconducting circuits using a flux-assisted Cooper pair pump, potentially enabling high-precision current standards.

Contribution

It introduces a new method to measure the Berry phase in superconducting circuits by linking pumped current to Berry phase and employing a Josephson junction for detection.

Findings

Derived equations for maximum pumped current based on adiabaticity

Optimized the sluice for high-accuracy pumping

Proposed a detection method via Josephson junction switching

Abstract

We present a measurement scheme for observing the Berry phase in a flux assisted Cooper pair pump - the Cooper pair sluice. In contrast to the recent experiments, in which the sluice was employed to generate accurate current through a resistance, we consider a device in a superconducting loop. This arrangement introduces a connection between the pumped current and the Berry phase accumulated during the adiabatic pumping cycles. From the adiabaticity criterion, we derive equations for the maximum pumped current and optimize the sluice accordingly. These results apply also to the high accuracy pumping which results in a potential candidate for a metrological current standard. For measuring the pumped current, an additional Josephson junction is installed into the superconducting loop. We show in detail that the switching of this system from superconducting state into normal state as a consequence of an external current pulse through it may be employed to probe the pumped current. The experimental realization of our scheme would be the first observation of the Berry phase in superconducting circuits.