Miniature dc SQUID devices for the detection of single atomic spin-flips

We report progress towards a superconducting quantum interference device (SQUID) based system capable of detecting single atomic spin-flips. The scaling of the flux sensitivity with SQUID loop dimension of miniature Nb dc SQUIDs is examined and shown experimentally to vary as predicted. Our smallest device, with loop size 3 x 3 mum(2), is capable of detecting a few spins in a 1 Hz bandwidth. We address the task of depositing a sample, of nanoscale dimension, within the SQUID loop. (C) 2001 Published by Elsevier Science B.V.