Protocol for high fidelity readout in the photon blockade regime of circuit QED

TL;DR

This paper proposes a high-fidelity qubit readout method in circuit QED using bistability in the photon blockade regime, achieved through a tailored control sequence, promising >98% fidelity with realistic parameters.

Contribution

It introduces a novel readout scheme leveraging metastable states and a linear chirp control in circuit QED, enhancing fidelity without extra circuit elements.

Findings

Achieves >98% readout fidelity.

Demonstrates high contrast in qubit state discrimination.

Validates the approach with realistic circuit QED parameters.

Abstract

The driven-damped Jaynes-Cummings model in the regime of strong coupling is found to exhibit a coexistence between the quantum photon blockaded state and a quasi-coherent bright state. We characterize the slow time scales and the basin of attraction of these metastable states using full quantum simulations. This form of bistability can be useful for implementing a qubit readout scheme that does not require additional circuit elements. We propose a coherent control sequence that makes use of a simple linear chirp of drive amplitude and frequency as well as qubit frequency. By optimizing the parameters of the system and the control pulse we demonstrate theoretically very high readout fidelities (>98%) and high contrast, with experimentally realistic parameters for qubits implemented in the circuit QED architecture.