Loopless multiterminal quantum circuits at odd parity

TL;DR

This paper explores the theoretical properties of loopless multiterminal hybrid superconducting devices with odd fermion parity, revealing unique energy-phase relationships, spin effects, and control mechanisms relevant for quantum circuits.

Contribution

It introduces a theoretical analysis of loopless multiterminal superconducting devices at odd parity, highlighting their energy-phase relationships, spin effects, and electric control capabilities.

Findings

Energy-phase relationship has a double minimum with opposite phase windings.

Spin-orbit coupling causes multi-axial spin splittings unlike two-terminal devices.

Weak spin-orbit strength leads to a controllable four-dimensional spin-chirality subspace.

Abstract

We theoretically investigate loopless multiterminal hybrid superconducting devices at odd fermion parity with time-reversal symmetry. We find that the energy-phase relationship has a double minimum corresponding to opposite windings of the superconducting phases. Spin-orbit coupling adds multi-axial spin splittings, which contrasts with two-terminal devices where spin dependence is uniaxial. Capacitive shunting localizes quantum circuit states in the wells and exponentially suppresses their splitting. For weak spin-orbit strength, the system has a four-dimensional spin-chirality low-energy subspace which can be universally controlled with electric fields only.