Enhancing qubit readout through dissipative sub-Poissonian dynamics

TL;DR

This paper introduces a method to significantly reduce qubit readout errors by leveraging sub-Poissonian relaxation dynamics through intermediate states, improving measurement fidelity without increasing signal-to-noise ratio.

Contribution

It demonstrates that sub-Poissonian relaxation via intermediate states can lower readout errors even at moderate SNR levels, offering a new approach for quantum measurement schemes.

Findings

Reduces single-shot readout error rate by orders of magnitude.

Effective for moderate SNR ($\\lesssim 100$) and few intermediate states ($\\lesssim 10$).

Applicable to spin-to-charge and parity-to-charge conversion schemes.

Abstract

Single-shot qubit readout typically combines high readout contrast with long-lived readout signals, leading to large signal-to-noise ratios and high readout fidelities. In recent years, it has been demonstrated that both readout contrast and readout signal lifetime, and thus the signal-to-noise ratio, can be enhanced by forcing the qubit state to transition through intermediate states. In this work, we demonstrate that the sub-Poissonian relaxation statistics introduced by intermediate states can reduce the single-shot readout error rate by orders of magnitude even when there is no increase in signal-to-noise ratio. These results hold for moderate values of the signal-to-noise ratio ($\mathcal{S} \lesssim 100$) and a small number of intermediate states ($N \lesssim 10$). The ideas presented here could have important implications for readout schemes relying on the detection of transient charge states, such as spin-to-charge conversion schemes for semiconductor spin qubits and parity-to-charge conversion schemes for topologically protected Majorana qubits.