Nearly Quantum-Limited Squids for a Gravitational Wave Antenna

Abstract

Nearly quantum-limited Superconducting QUantum Interference Devices (SQUIDs) have to be used in resonant mass gravitational wave antennas to reach a displacement sensitivity of the order of 10,21 mJ-iHz in a bandwidth of 100 Hz around the resonance frequency of about 900 Hz. The design of these SQUIDs will be described. We show that a good coupling between the inductive readout circuit and the SQUID can be obtained by choosing a relatively large hole size of the washer-type SQUID configuration.