The escape physics of single shot measurement of flux qubit with dcSQUID

TL;DR

This paper analyzes the physics behind single-shot measurements of flux qubits using dc SQUIDs, focusing on the equilibrium switching current distribution and comparing theoretical predictions with experimental data.

Contribution

It provides an analytic calculation of the dc-SQUID switching current distribution for flux qubits, bridging the gap between theory and experimental observations.

Findings

Analytic expressions for switching current distribution

Good agreement with experimental data from Delft and NTT

Insights into measurement physics of flux qubits

Abstract

In most experiments on flux qubits,the "measurement" is performed by coupling the system to a dc SQUID and recording the distribution of switching currents for the latter;this measurement protocol is very far from the classic von Neumann ("projective") scheme,in that very little information is obtained from a single run,rather one has to repeat the experiment tens of thosands of times to extract anything useful.Here, concentrating on the equlibrium behavior of the flux qubit,we carry out an analytic calculation of the dc-SQUID switching current distribution as a function of external bias flux on the qubit,and compare our predictions with the data from experiments conducted at Delft and NTT.