Sequential Dispersive Measurement of a Superconducting Qubit

Area of Science:

• Quantum computing
• Superconducting circuits
• Quantum information science

Background:

• Dispersive readout of superconducting qubits faces limitations like the Purcell effect and cavity mode transients.
• Efficient and high-fidelity qubit measurement is crucial for advancing quantum computation.

Purpose of the Study:

• To present a novel superconducting device for sequential measurement of transmon qubits.
• To overcome common limitations in dispersive readout methods.
• To achieve fast and high-fidelity qubit state determination.

Main Methods:

• A superconducting device enabling on-demand coupling to a measurement channel.
• Loading a readout resonator coupled to the transmon qubit.
• Utilizing a microwave pump for rapid upconversion and release of resonator content.
• Measuring released field quadratures and performing Wigner tomography.

Main Results:

• Achieved a readout fidelity of 97.5% within a total measurement time of 220 ns.
• Demonstrated a characteristic release time of 10 ns, significantly shorter than the resonator lifetime.
• Characterized the non-Gaussian nature and dynamics of the readout mode.

Conclusions:

• The developed device effectively disables common dispersive readout limitations.
• The rapid, on-demand measurement technique enables high-fidelity qubit readout.
• This approach advances the capabilities for quantum information processing with superconducting qubits.