Flexible Readout and Unconditional Reset for Superconducting Multiqubit Processors with Tunable Purcell Filters.

Area of Science:

• Quantum Computing
• Superconducting Circuits
• Quantum Error Correction

Background:

• High-fidelity qubit readout and reset are essential for quantum error correction and advanced quantum algorithms.
• Maintaining qubit coherence during these operations is a significant challenge.

Purpose of the Study:

• To design and demonstrate a scalable architecture for flexible qubit readout and rapid unconditional reset.
• To improve qubit coherence and mitigate noise sources in superconducting quantum systems.

Main Methods:

• Utilized frequency-tunable nonlinear Purcell filters for dynamic control of readout resonator linewidth.
• Implemented a multilevel readout protocol for enhanced signal-to-noise ratio and photon noise suppression.
• Leveraged an adjacent coupling channel for rapid, unconditional qubit reset, including leakage states.

Main Results:

• Achieved a record readout fidelity of 99.3% without quantum-limited amplifiers.
• Demonstrated unconditional qubit reset of |2⟩ and |1⟩ states within 200 ns (error rates ≤1%).
• Showcased reset of the |1⟩ state within 75 ns with error rates ≤1%.
• The filter mitigated photon-induced dephasing and Purcell effect, preserving qubit coherence.

Conclusions:

• The developed scalable Purcell filter architecture offers exceptional performance in qubit readout, reset, and protection.
• This technology represents a promising hardware component for advancing fault-tolerant quantum computing.
• The architecture enables flexible control and improved efficiency for superconducting qubits.