Qubit Metrology of Ultralow Phase Noise Using Randomized Benchmarking

Further advances in the fidelity of quantum information systems will rely on precise measurements of ever smaller amounts of noise. The authors present a technique based on randomized benchmarking that is ideal for measuring noise at the small timescales and low error rates relevant to fault-tolerant error-correction schemes. Their SQUID-based test qubit is found to be limited not by $1/f$ flux noise, but rather by telegraph noise too small to be studied with standard methods.