Flux tunable graphene-based superconducting quantum circuits coupled to 3D cavity

  1. Kuei-Lin Chiu,
  2. Youyi Chang,
  3. Avishma J. Lasrado,
  4. Cheng-Han Lo,
  5. Yung-Hsiang Chen,
  6. Tao-Yi Hsu,
  7. Yen-Chih Chen,
  8. Yi-Chen Tsai,
  9. Samina,
  10. Yen-Hsiang Lin,
  11. and Chung-Ting Ke
Correlation between transmon and its composite Josephson junctions (JJ) plays an important role in designing new types of superconducting qubits based on quantum materials. It is desirable
to have a type of device that not only allows exploration for use in quantum information processing but also probing intrinsic properties in the composite JJs. Here, we construct a flux-tunable 3D transmon-type superconducting quantum circuit made of graphene as a proof-of-concept prototype device. This 3D transmon-type device not only enables coupling to 3D cavities for microwave probes but also permits DC transport measurements on the same device, providing useful connections between transmon properties and critical currents associated with JJ’s properties. We have demonstrated how flux-modulation in cavity frequency and DC critical current can be correlated under the influence of Fraunhofer pattern of JJs in an asymmetric SQUID. The correlation analysis was further extended to link the flux-modulated transmon properties, such as flux-tunability in qubit and cavity frequencies, with SQUID symmetry analysis based on DC measurements. Our study paves the way towards integrating novel materials for exploration of new types of quantum devices for future technology while probing underlying physics in the composite materials.

Microwave amplification via interfering multi-photon processes in a half-waveguide quantum electrodynamics system

  1. Fahad Aziz,
  2. Kuan-Ting Lin,
  3. Ping-Yi Wen,
  4. Samina,
  5. Yu Chen Lin,
  6. Emely Wiegand,
  7. Ching-Ping Lee,
  8. Yu-Ting Cheng,
  9. Ching-Yeh Chen,
  10. Chin-Hsun Chien,
  11. Kai-Min Hsieh,
  12. Yu-Huan Huang,
  13. Ian Hou,
  14. Jeng-Chung Chen,
  15. Yen-Hsiang Lin,
  16. Anton Frisk Kockum,
  17. Guin-Dar Lin,
  18. and Io-Chun Hoi
We investigate the amplification of a microwave probe signal by a superconducting artificial atom, a transmon, strongly coupled to the end of a one-dimensional semi-infinite transmission
line. The end of the transmission line acts as a mirror for microwave fields. Due to the weak anharmonicity of the artificial atom, a strong pump field creates multi-photon excitations among the dressed states. Transitions between these dressed states, Rabi sidebands, give rise to either amplification or attenuation of the weak probe. We obtain a maximum amplitude amplification of about 18 %, higher than in any previous experiment with a single artificial atom, due to constructive interference between Rabi sidebands. We also characterize the noise properties of the system by measuring the spectrum of spontaneous emission.