Diamond defect centers are promising solid state magnetometers. Single centers allow for high spatial resolution field imaging but are limited in their magnetic field sensitivity to around 10 nT/Hz^(1/2) at room-temperature. Using defect center ensem
bles sensitivity can be scaled as N^(1/2) when N is the number of defects. In the present work we use an ensemble of 1e11 defect centers for sensing. By carefully eliminating all noise sources like laser intensity fluctuations, microwave amplitude and phase noise we achieve a photon shot noise limited field sensitivity of 0.9 pT/Hz^(1/2) at room-temperature with an effective sensor volume of 8.5e-4 mm^3. The smallest field we measured with our device is 100 fT. While this denotes the best diamond magnetometer sensitivity so far, further improvements using decoupling sequences and material optimization could lead to fT/Hz^(1/2) sensitivity.
We have investigated the electrodynamic properties of High-Tc strip-lines made by ion irradiation, in order to evaluate the potentialities of such a technology for RSFQ superconductor digital electronic. SQUID loops of different length and width have
been fabricated by ion bombardment of 70 nm thick films through e-beam lithographied shadow masks, and measured at different temperatures. The voltage modulations have been recorded by direct injection of a control current in the SQUIDs arms. The corresponding line inductances have been measured and compared with 3D simulations. A quantitative agreement has been obtained leading to typical values of 0.4 pH/microns without ground plane.
