Improved Quantum Sensing with a Single Solid-State Spin via Spin-to-Charge Conversion

Abstract

Efficient optical read-out of single, solid-state electronic spins at room temperature is a key challenge for nanoscale quantum sensing. Nitrogen-vacancy color centers in diamond have a fast optical spin-state read-out mechanism, but it provides little information in a single shot, because the spin state is destroyed before many photons can be collected. Recently, a technique based on spin-to-charge conversion (SCC) was demonstrated that circumvents this problem by converting the spin state to a long-lived charge state. Here, we study how the choice of spin read-out technique impacts the performance of a single nitrogen-vacancy center in bulk diamond for quantum-sensing applications. Specifically, we show that the SCC technique results in an order-of-magnitude reduction in spin read-out noise per shot and a factor of 5 increase in ac-magnetometry sensitivity compared with the conventional optical read-out method. Crucially, these improvements are obtained for a low collection efficiency and bulk diamond geometry, which opens up the SCC technique to a wide array of sensing applications. We identify applications where single-shot spin read-out noise, rather than sensitivity, is the limiting factor (e.g., low duty cycle pulsed sequences in biomagnetometry involving long dead times).