Batch fabrication of nano-SQUIDs for the single spin detection

The superconducting quantum interference device (SQUID) is well known as a super sensitive spin detector. The minimal detectable spin number of a SQUID is proportional to the size of its superconducting loop. Hence, nano-SQUIDs consisted of two constricted junctions are possible to be scaled down towards the single spin detection. Here, we are going to present our current research progress on a top-down batch fabrication process of NbN nano-SQUIDs. Ultra-thin NbN film of high quality can be grown on MgO substrate epitaxially. The spin sensitivity of such thin film nano-SQUID can be further enhanced by coupling spins directly to the constricted junctions.