SiC-YiG X band quantum sensor for sensitive surface paramagnetic resonance applied to chemistry, biology, physics.

Here I present the SiC-YiG Quantum Sensor, allowing electron paramagnetic resonance (EPR) studies of monolayer or few nanometers thick chemical, biological or physical samples located on the sensor surface. It contains two parts, a 4H-SiC substrate with many paramagnetic silicon vacancies (V2) located below its surface, and YIG ferrimagnetic nanostripes. Spins sensing properties are based on optically detected double electron-electron spin resonance under the strong magnetic field gradient of nanostripes. Here I describe fabrication, magnetic, optical and spins sensing properties of this sensor. I show that the target spins sensitivity is at least five orders of magnitude larger than the one of standard X band EPR spectrometer, for which it constitutes, combined with a fiber bundle, a powerful upgrade for sensitive surface EPR. This sensor can determine the target spins planes EPR spectrum, their positions with a nanoscale precision of +/- 1 nm, and their 2D concentration down to 1/(20nm)2

Intrinsic decoherence and Rabi oscillation damping of Mn 2+and Co 2+ electron spin qubits in bulk ZnO

We demonstrate by pulse EPR that two electron spin qubits in bulk ZnO, the Mn2+ and the Co2+ spin qubits, which have, respectively, long $(T_{2}(6\ \text{K})= 178\ \mu\text{s})$ and short $(T_{2}(1.7\ \text{K})= 9\ \mu\text{s})$ transverse spin coherence time T2 at low temperature, have however very short and similar Rabi oscillation damping times, on the order of $T_{R}\approx250\ \text{ns}$ at low temperature. A detailed study of Mn2+ spin qubits has shown that the main contribution to the Rabi oscilation damping rate is temperature independent and proportional to the Rabi frequency. This main contribution to the damping rate during coherent microwave manipulation of spins is interpreted as due to the changes of the dipolar couplings induced by the long microwave pulse used in this kind of EPR nutation experiment. Strategies are suggested for overcoming this problem of Rabi oscillation overdamping in future spin-based quantum computers