Broadband Purcell Filter for Fast Superconducting Qubit Reset and Readout

  1. Yu Zhao,
  2. Zhixu Chen,
  3. Hanxian Liu,
  4. Mingze Liu,
  5. Zixing Liu,
  6. Hao Pang,
  7. Meiyan Wan,
  8. Changkun Wu,
  9. Liuzhu Zhong,
  10. Sai Li,
  11. Yuefeng Yuan,
  12. Yuxuan Zhou,
  13. Ji Jiang,
  14. Ji Chu,
  15. and Song Liu
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.

M2CS: A Microwave Measurement and Control System for Large-scale Superconducting Quantum Processors

  1. Jiawei Zhang,
  2. Xuandong Sun,
  3. Zechen Guo,
  4. Yuefeng Yuan,
  5. Yubin Zhang,
  6. Ji Chu,
  7. Wenhui Huang,
  8. Yongqi Liang,
  9. Jiawei Qiu,
  10. Daxiong Sun,
  11. Ziyu Tao,
  12. Jiajian Zhang,
  13. Weijie Guo,
  14. Ji Jiang,
  15. Xiayu Linpeng,
  16. Yang Liu,
  17. Wenhui Ren,
  18. Jingjing Niu,
  19. Youpeng Zhong,
  20. and Dapeng Yu
As superconducting quantum computing continues to advance at an unprecedented pace, there is a compelling demand for the innovation of specialized electronic instruments that act as
crucial conduits between quantum processors and host computers. Here, we introduce a Microwave Measurement and Control System (M2CS) dedicated for large-scale superconducting quantum processors. M2CS features a compact modular design that balances overall performance, scalability, and flexibility. Electronic tests of M2CS show key metrics comparable to commercial instruments. Benchmark tests on transmon superconducting qubits further show qubit coherence and gate fidelities comparable to state-of-the-art results, confirming M2CS’s capability to meet the stringent requirements of quantum experiments run on intermediate-scale quantum processors. The system’s compact and scalable design offers significant room for further enhancements that could accommodate the measurement and control requirements of over 1000 qubits, and can also be adopted to other quantum computing platforms such as trapped ions and silicon quantum dots. The M2CS architecture may also be applied to wider range of scenarios, such as microwave kinetic inductance detectors, as well as phased array radar systems.