Inductive Superconducting Quantum Interference Proximity Transistor: The L-SQUIPT

Abstract

The design for an inductive superconducting quantum interference proximity transistor with enhanced performance, the L-SQUIPT, is presented and analyzed. The interferometer is based on a double-loop structure, where each ring comprises a superconductor-normal metal-superconductor mesoscopic Josephson weak-link and the read-out electrode is implemented in the form of a superconducting tunnel probe. Our design allows both to improve the coupling of the transistor to the external magnetic field and to increase the characteristic magnetic flux transfer functions, thereby leading to an improved ultrasensitive quantum limited magnetometer. The L-SQUIPT behavior is analyzed in both the dissipative and the dissipationless Josephson-like operation modes, in the dissipative or in the dissipationless Josephson-like operation mode in the latter case by exploiting both an inductive and a dispersive readout scheme. The improved performance makes the L-SQUIPT promising for magnetic field detection as well as for specific applications in quantum technology, where a responsive dispersive magnetometry at milliKelvin temperatures is required.