Yuntao Xu

10-GHz superconducting cavity piezo-optomechanics for microwave-optical photon conversion

  1. Xu Han,
  2. Wei Fu,
  3. Changchun Zhong,
  4. Chang-Ling Zou,
  5. Yuntao Xu,
  6. Ayed Al Sayem,
  7. Mingrui Xu,
  8. Sihao Wang,
  9. Risheng Cheng,
  10. Liang Jiang,
  11. and Hong X. Tang
Coherent photon conversion between microwave and optics holds promise for the realization of distributed quantum networks, in particular, the architecture that incorporates superconducting
quantum processors with optical telecommunication channels. High-frequency gigahertz piezo-mechanics featuring low thermal excitations offers an ideal platform to mediate microwave-optical coupling. However, integrating nanophotonic and superconducting circuits at cryogenic temperatures to simultaneously achieve strong photon-phonon interactions remains a tremendous challenge. Here, we report the first demonstration of an integrated superconducting cavity piezo-optomechanical converter where 10-GHz phonons are resonantly coupled with photons in a superconducting microwave and a nanophotonic cavities at the same time. Benefited from the cavity-enhanced interactions, efficient bidirectional microwave-optical photon conversion is realized with an on-chip efficiency of 0.07% and an internal efficiency of 5.8%. The demonstrated superconducting piezo-optomechanical interface makes a substantial step towards quantum communication at large scale, as well as novel explorations in hybrid quantum systems such as microwave-optical photon entanglement and quantum sensing.
arxiv pdf

Radiative cooling of a superconducting resonator

  1. Mingrui Xu,
  2. Xu Han,
  3. Chang-Ling Zou,
  4. Wei Fu,
  5. Yuntao Xu,
  6. Changchun Zhong,
  7. Liang Jiang,
  8. and Hong X. Tang
Cooling microwave resonators to near the quantum ground state, crucial for their operation in the quantum regime, is typically achieved by direct device refrigeration to a few tens
of millikelvin. However, in quantum experiments that require high operation power such as microwave-to-optics quantum transduction, it is desirable to operate at higher temperatures with non-negligible environmental thermal excitations, where larger cooling power is available. In this Letter, we present a radiative cooling protocol to prepare a superconducting microwave mode near its quantum ground state in spite of warm environment temperatures for the resonator. In this proof-of-concept experiment, the mode occupancy of a 10-GHz superconducting resonator thermally anchored at 1.02~K is reduced to 0.44±0.05 by radiatively coupling to a 70-mK cold load. This radiative cooling scheme allows high-operation-power microwave experiments to work in the quantum regime, and opens possibilities for routing microwave quantum states to elevated temperatures.
arxiv pdf