Gated conditional displacement readout of superconducting qubits

TL;DR

This paper introduces a new qubit readout method using a conditional displacement interaction in superconducting circuits, enabling faster measurements and potential applications in quantum error correction.

Contribution

The authors demonstrate a novel interaction mechanism for superconducting qubits that improves readout fidelity and reduces dephasing in multi-qubit systems.

Findings

Achieved conditional displacement of cavity states based on qubit states

Demonstrated minimal dephasing of non-target qubits during measurement

Showed potential for faster readout and bosonic quantum error correction

Abstract

We have realized a new interaction between superconducting qubits and a readout cavity that results in the displacement of a coherent state in the cavity, conditioned on the state of the qubit. This conditional state, when it reaches the cavity-following, phase-sensitive amplifier, matches its measured observable, namely the in-phase quadrature. In a setup where several qubits are coupled to the same readout resonator, we show it is possible to measure the state of a target qubit with minimal dephasing of the other qubits. Our results suggest novel directions for faster readout of superconducting qubits and implementations of bosonic quantum error-correcting codes.