Gated Conditional Displacement Readout of Superconducting Qubits

Area of Science:

• Quantum Computing
• Superconducting Circuits
• Quantum Information Science

Background:

• Superconducting qubits are a leading platform for quantum computation.
• Efficient and high-fidelity readout of qubit states is crucial for scalable quantum processors.
• Current readout methods can suffer from crosstalk and dephasing, limiting performance.

Purpose of the Study:

• To introduce a novel interaction between superconducting qubits and a readout cavity.
• To demonstrate state-conditional coherent state displacement for qubit readout.
• To enable high-fidelity, low-dephasing measurement of individual qubits in a multi-qubit system.

Main Methods:

• Engineered a specific interaction coupling superconducting qubits to a readout resonator.
• Utilized a phase-sensitive amplifier to measure the in-phase quadrature of the cavity state.
• Implemented a multi-qubit architecture sharing a single readout resonator.

Main Results:

• Achieved state-conditional displacement of a coherent state in the readout cavity.
• Demonstrated measurement of a target qubit's state with minimal dephasing of other coupled qubits.
• The measured observable directly corresponds to the qubit's state via the in-phase quadrature.

Conclusions:

• The novel qubit-cavity interaction facilitates efficient and selective qubit readout.
• This technique offers a promising pathway towards faster superconducting qubit measurements.
• Potential applications include improved bosonic quantum error-correcting codes and scalable quantum computing architectures.