Charge noise and overdrive effects in dispersive readout of charge and spin qubits

Solid-state qubits incorporating quantum dots can be read out by gate reflectometry. In this theory talk, I will describe physical mechanisms that render such reflectometry-based readout schemes imperfect, focusing on semiconductor charge qubits and singlet-triplet spin qubits. In our model, we account for readout errors due to slow charge noise, and due to overdriving, when a too strong probe is causing errors. A key result is that the readout fidelity saturates at large probe strengths. We also point out the existence of severe readout errors appearing in a resonance-like fashion as the pulse strength is increased, and show that these errors are related to probe-induced multi-photon transitions. Besides providing practical guidelines toward optimized readout, the results I present might also inspire ways to use gate reflectometry for device characterization.

Reference: https://arxiv.org/abs/2006.12391, accepted to Phys Rev Applied.