Escape from the zero-voltage state in hysteretic dc-SQUIDs with different dimensionless inductance

We studied the escape process from the zero-voltage state to the running state in hysteretic dc-SQUIDs made with trilayer Nb-AlOx-Nb junctions. We analyze the experimental results, according to the thermal activation model, for devices having similar parameters except for the dimensionless inductance ?L, which however is always very small. The interest in hysteretic dc-SQUIDs is in the possibility of using them to perform non-invasive measurements of the flux states in rf-SQUIDs: this achievement would be very important both in tests of macroscopic quantum properties of SQUIDs and in measurements on a class of quantum bits that has been recently proposed, based on magnetic flux states in SQUIDs.