Ultra low noise YBCO nanoSQUIDs implementing nanowires
  We present results on ultra low noise YBa$_2$Cu$_3$O$_{7-\delta}$ nano Superconducting QUantum Interference Devices (nanoSQUIDs). To realize such devices, we implemented high quality YBCO nanowires, working as weak links between two electrodes. We observe critical current modulation as a function of an externally applied magnetic field in the full temperature range below the transition temperature $T_C$. The white flux noise below 1 $\mu \Phi_0/\sqrt{\mathrm{Hz}}$ at T = 8 K makes our nanoSQUIDs very attractive for the detection of small spin systems. 
Riccardo Arpaia, Marco Arzeo, Shahid Nawaz, Sophie Charpentier,   Floriana Lombardi, and Thilo Bauch
cond-mat.supr-con