Broadband Purcell Filter for Fast Superconducting Qubit Reset and Readout

• URL: http://arxiv.org/abs/2609.14081v1
• Date: Sat, 12 Sep 2026 17:53:02 GMT
• Title: Broadband Purcell Filter for Fast Superconducting Qubit Reset and Readout
• Abstract summary: We present a broadband Purcell filter that decouples the reset and readout paths.<n>The filter employs two engineered notches - an intrinsic notch and a bandstop notch.<n>We experimentally demonstrate Purcell-limited relaxation times exceeding 1 ms across a 1.2 GHz bandwidth.
• Score: 8.949869616042532
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Rapid reset and readout of qubit states are essential for quantum error correction, yet accelerating these operations through stronger coupling to a dissipative environment inevitably increases qubit decay via the Purcell effect. Here we present a broadband Purcell filter that decouples the reset and readout paths, enabling both operations to be independently optimized without compromising qubit coherence. The filter employs two engineered notches - an intrinsic notch and a bandstop notch - to provide broadband Purcell protection, together with an additional reset stub that creates a reset mode below the protected band. To enable fast reset while suppressing filter-mediated interactions between qubits, we couple each qubit to a dedicated reset resonator. We experimentally demonstrate Purcell-limited relaxation times exceeding 1 ms across a 1.2 GHz bandwidth, simultaneously with 500 ns readout without a Josephson parametric amplifier and 100 ns reset with 99.6% efficiency. The reset resonator is designed with a deliberate kappa-chi mismatch, which suppresses photon-shot-noise-induced dephasing by a factor of 70 compared to the readout resonator. Our work provides a scalable hardware solution that resolves the traditional trade-off between fast qubit operations and qubit protection, advancing the prospects for fault-tolerant quantum computing.

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