Observation of flux qubit states with the help of a superconducting differential double contour interferometer

TL;DR

This paper proposes a novel superconducting interferometer device, the DDCI, to observe flux qubit states by phase coupling, enabling continuous and fundamental investigation of macroscopic quantum superpositions.

Contribution

Introduction of the superconducting differential double contour interferometer (DDCI) for phase-based flux qubit state detection, offering continuous observation capabilities.

Findings

Large critical current jumps correlate with flux qubit state changes

Continuous voltage monitoring reveals real-time qubit dynamics

Potential for fundamental studies of macroscopic quantum superpositions

Abstract

The quantum states of flux qubit is suggested to observe with the help of a new device, the superconducting differential double contour interferometer (DDCI). The flux qubit and the superconducting quantum interference device (DC-SQUID) are connected in the DDCI through the phase of the wave function rather than through magnetic flux. The critical current of DC-SQUID should change to the maximum value at the change of the flux qubit state thanks to this phase coupling. A large jump in the critical current and voltage enables to observe continuously the change in time the state of the flux qubit. This observation can have fundamental importance for the investigation of the superposition of macroscopic quantum states.