Zhi-Fei Li

Single-Step Phase-Engineered Pulse for Active Readout Cavity Reset in Superconducting Circuits

  1. Ren-Ze Zhao,
  2. Ze-An Zhao,
  3. Tian-Le Wang,
  4. Peng Wang,
  5. Sheng Zhang,
  6. Xiao-Yan Yang,
  7. Hai-Feng Zhang,
  8. Zhi-Fei Li,
  9. Yuan Wu,
  10. Zi-Hao Fu,
  11. Sheng-Ri Liu,
  12. Peng Duan,
  13. and Guo-Ping Guo
In a circuit QED architecture, we experimentally demonstrate a simple and hardware-efficient Single-Step Phase-Engineered (SSPE) pulse scheme for actively depopulating the readout cavity.
The method appends a reset segment with tailored amplitude and phase to a normal square readout pulse. Within the linear-response regime, the optimal reset amplitude scales proportionally with the readout amplitude, while the optimal reset phase remains nearly invariant, significantly simplifying the calibration process. By characterizing the cavity photons dynamics, we show that the SSPE pulse accelerates photon depletion by up to a factor of six compared to passive free decay. We further quantify the qubit backaction induced by the readout pulse and find that the SSPE pulse yields the lowest excitation and relaxation rates compared to a Square and CLEAR pulses. Our results establish the SSPE scheme as a practical and scalable approach for achieving fast, smooth, low-backaction cavity reset in superconducting quantum circuits.
arxiv pdf

Inverse designed Hamiltonians for perfect state transfer and remote entanglement generation, and applications in superconducting qubits

  1. Tian-Le Wang,
  2. Ze-An Zhao,
  3. Peng Wang,
  4. Sheng Zhang,
  5. Ren-Ze Zhao,
  6. Xiao-Yan Yang,
  7. Hai-Feng Zhang,
  8. Zhi-Fei Li,
  9. Yuan Wu,
  10. Peng Duan,
  11. Ming Gong,
  12. and Guo-Ping Guo
Hamiltonian inverse engineering enables the design of protocols for specific quantum evolutions or target state preparation. Perfect state transfer (PST) and remote entanglement generation
are notable examples, as they serve as key primitives in quantum information processing. However, Hamiltonians obtained through conventional methods often lack robustness against noise. Assisted by inverse engineering, we begin with a noise-resilient energy spectrum and construct a class of Hamiltonians, referred to as the dome model, that significantly improves the system’s robustness against noise, as confirmed by numerical simulations. This model introduces a tunable parameter m that modifies the energy-level spacing and gives rise to a well-structured Hamiltonian. It reduces to the conventional PST model at m=0 and simplifies to a SWAP model involving only two end qubits in the large-m regime. To address the challenge of scalability, we propose a cascaded strategy that divides long-distance PST into multiple consecutive PST steps. Our work is particularly suited for demonstration on superconducting qubits with tunable couplers, which enable rapid and flexible Hamiltonian engineering, thereby advancing the experimental potential of robust and scalable quantum information processing.
arxiv pdf