Flip-chip-based fast inductive parity readout of a planar superconducting island

TL;DR

This paper demonstrates a fast, non-destructive, and high-fidelity real-time parity measurement technique for superconducting islands using flip-chip inductive coupling, advancing quantum information processing in solid-state qubits.

Contribution

It introduces a novel flip-chip inductive readout method enabling rapid, accurate, and non-destructive parity detection in superconducting devices, with potential applications in quantum computing.

Findings

Achieved parity state resolution with SNR ≈ 3 in 20 μs

Fidelity of parity detection exceeds 98%

Parity state lifetime extends into milliseconds

Abstract

Properties of superconducting devices depend sensitively on the parity (even or odd) of the quasiparticles they contain. Encoding quantum information in the parity degree of freedom is central in several emerging solid-state qubit architectures. Yet, accurate, non-destructive, and time-resolved parity measurement is a challenging and long-standing issue. Here we report on control and real-time parity measurement in a superconducting island embedded in a superconducting loop and realized in a hybrid two-dimensional heterostructure using a microwave resonator. Device and readout resonator are located on separate chips, connected via flip-chip bonding, and couple inductively through vacuum. The superconducting resonator detects the parity-dependent circuit inductance, allowing for fast and non-destructive parity readout. We resolved even and odd parity states with signal-to-noise ratio SNR $\approx3$ with an integration time of $20~\mu$s and detection fidelity exceeding 98%. Real-time parity measurement showed state lifetime extending into millisecond range. Our approach will lead to better understanding of coherence-limiting mechanisms in superconducting quantum hardware and provide novel readout schemes for hybrid qubits.