Towards a heralded eigenstate preserving measurement of multi-qubit parity in circuit QED

Abstract

Eigenstate-preserving multi-qubit parity measurements lie at the heart of stabilizer quantum error correction, which is a promising approach to mitigate the problem of decoherence in quantum computers. In this work we explore a high-fidelity, eigenstate-preserving parity readout for superconducting qubits dispersively coupled to a microwave resonator, where the parity bit is encoded in the amplitude of a coherent state of the resonator. Detecting photons emitted by the resonator via a current biased Josephson junction yields information about the parity bit. We analyse theoretically the measurement back-action in the limit of a strongly coupled fast detector and show that in general such a parity measurement, while approximately Quantum Non-Demolition (QND) is not eigenstate-preserving. To remediate this shortcoming we propose a simple dynamical decoupling technique during photon detection, which greatly reduces decoherence within a given parity subspace. Furthermore, by applying a sequence of fast displacement operations interleaved with the dynamical decoupling pulses, the natural bias of this binary detector can be efficiently suppressed. Finally, we introduce the concept of a heralded parity measurement, where a detector click guarantees successful multi-qubit parity detection even for finite detection efficiency.

References in corpus (8)

• Fault-Tolerant Quantum Dynamical Decoupling
• Detecting arbitrary quantum errors via stabilizer measurements on a sublattice of the surface code
• Detecting bit-flip errors in a logical qubit using stabilizer measurements
• Demonstration of weight-four parity measurements in the surface code architecture
• Microwave Photon Detector in Circuit QED
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• Implementing and characterizing precise multi-qubit measurements
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Cited by in corpus (3)

• A Fault-Tolerant Honeycomb Memory
• Qubit Parity Measurement by Parametric Driving in Circuit QED
• Always-On Quantum Error Tracking with Continuous Parity Measurements