Xufeng Zhang

Electron on solid neon — a new solid-state single-electron qubit platform

  1. Xianjing Zhou,
  2. Gerwin Koolstra,
  3. Xufeng Zhang,
  4. Ge Yang,
  5. Xu Han,
  6. Brennan Dizdar,
  7. Divan Ralu,
  8. Wei Guo,
  9. Kater W. Murch,
  10. David I. Schuster,
  11. and Dafei Jin
The promise of quantum computing has driven a persistent quest for new qubit platforms with long coherence, fast operation, and large scalability. Electrons, ubiquitous elementary particles
of nonzero charge, spin, and mass, have commonly been perceived as paradigmatic local quantum information carriers. Despite superior controllability and configurability, their practical performance as qubits via either motional or spin states depends critically on their material environment. Here we report our experimental realization of a new qubit platform based upon isolated single electrons trapped on an ultraclean solid neon surface in vacuum. By integrating an electron trap in a circuit quantum electrodynamics architecture, we achieve strong coupling between the motional states of a single electron and microwave photons in an on-chip superconducting resonator. Qubit gate operations and dispersive readout are used to measure the energy relaxation time T1 of 15 μs and phase coherence time T2 over 200 ns, indicating that the electron-on-solid-neon qubit already performs near the state of the art as a charge qubit.
arxiv pdf

Magnon dark modes and gradient memory

  1. Xufeng Zhang,
  2. Chang-Ling Zou,
  3. Na Zhu,
  4. Florian Marquardt,
  5. Liang Jiang,
  6. and Hong X. Tang
Extensive efforts have been expended in developing hybrid quantum systems to overcome the short coherence time of superconducting circuits by introducing the naturally long-lived spin
degree of freedom. Among all the possible materials, single-crystal yttrium iron garnet has shown up very recently as a promising candidate for hybrid systems, and various highly coherent interactions, including strong and even ultra-strong coupling, have been demonstrated. One distinct advantage of these systems is that the spins are in the form of well-defined magnon modes, which allows flexible and precise tuning. Here we demonstrate that by dissipation engineering, a non-Markovian interaction dynamics between the magnon and the microwave cavity photon can be achieved. Such a process enables us to build a magnon gradient memory to store information in the magnon dark modes, which decouple from the microwave cavity and thus preserve a long life-time. Our findings provide a promising approach for developing long-lifetime, multimode quantum memories.
arxiv pdf