Fig. 4: Combination of electrical and optical structures and observation of spin properties under negative bias.

a Schematic drawing of a sample showing a colour centre integrated into a SIL within the depletion zone of the Schottky contact. Inset: ground state level structure with spin hyperfine splitting. b Electron and nuclear spin memory coherence measured with various dynamical decoupling sequences. The dashed line shows the T₁ limit. All data sets are fitted by stretched exponential decays. c Charge resonant check histogram for 0 V and -30 V accumulated over several hours, showing higher count rates for the depleted case. d Single-shot readout (quantum circuit diagram in inset) histogram for both voltages. Using the more distinct Poissonian distribution for negative bias allows higher measurement rates by more favourable pre-selecting thresholds. e Top: blue histogram shows best CRC measurement which can be attributed to the best frequency overlap of resonant laser and optical transition. Simulation of CRC measurement with a laser detuned by the defect’s natural halfwidth half-maximum (HWHM). Bottom: success rate is defined as the fraction of the total SSR events which will be used for data processing, as a function of the chosen collection threshold for normal and depleted case. Dashed lines show first and second moment of photon counts distribution of defect detuned by half width half maximum. Depleted colour centres yield a measurement fidelity of more than 99% (μ + 3σ) without losing more than half of SSR events.