A Four-Channel BiCMOS Transmitter for a Quantum Magnetometer Based on Nitrogen-Vacancy Centers in Diamond

Quantum sensors based on solid-state defects, such as the nitrogen-vacancy (NV) center in diamond, offer very good room-temperature sensitivity, long-term stability, and the potential for calibration-free measurements. However, most quantum sensors still suffer from a bulky size and weight, low energy efficiency, and high costs, prohibiting their widespread use. Here, we present custom-designed chip-integrated microwave (MW) electronics for a miniaturized, low-cost, and highly scalable quantum magnetometer based on NV centers in diamond. The presented electronics include a quadrature phase-locked loop (QPLL) chip to generate the required local oscillator signal at around 7 GHz with a wide tuning range of 22% and a low phase noise (PN) of - 122 dBc/Hz at 1-MHz offset from a 7-GHz carrier for broadband low-noise magnetometry. In addition, the magnetometer electronics comprise a 4-channel transmitter chip, which can provide currents up to 412 mA(pp) into a custom-designed inductor over a wide frequency range from 6.4 to 8 GHz. In combination with a custom-designed coil, manufactured on a glass substrate for optical transparency, which features a large active area of ( pi x 180 x 180 mu m(2) ), this current is sufficient to produce strong MW magnetic fields up to B-1=(1/2)& sdot;B-ac=170 mu T , enabling pulsed optically detected magnetic resonance (ODMR) experiments. In proof-of-concept ODMR experiments, the presented chip-based spin control system produces fast Rabi oscillations of 5.49 MHz. The measured dc and ac magnetic field limits of detection (LOD) of the presented magnetometer are 32 nT/Hz (1/2) and 300 pT/Hz (1/2) , respectively.