Feedforward suppression of readout-induced faults in quantum error correction

Abstract: We propose a method to reduce readout-induced faults, applicable in settings like quantum error correction with repeated measurement cycles. The method consists of an adaptive readout sequence conditioned on each check qubit's readout result from the previous cycle. For readout errors, correlated preparation errors and measurement-induced leakage that are stronger in a particular qubit state, this feedforward protocol can suppress the physical qubit errors. Focusing on a simple realization of conditionally flipping (by an X gate) the state of check qubits before their measurement, we investigate the effect of such state-dependent errors using simulations in the setup of a low-density parity check code. We show that the suggested protocol can reduce both logical errors and decoding time, two important aspects of fault-tolerant quantum computations.