Mehdi Hatefipour

Characterizing losses in InAs two-dimensional electron gas-based gatemon qubits

  1. William M. Strickland,
  2. Jaewoo Lee,
  3. Lukas Baker,
  4. Krishna Dindial,
  5. Bassel Heiba Elfeky,
  6. Mehdi Hatefipour,
  7. Peng Yu,
  8. Ido Levy,
  9. Vladimir E. Manucharyan,
  10. and Javad Shabani
The tunnelling of cooper pairs across a Josephson junction (JJ) allow for the nonlinear inductance necessary to construct superconducting qubits, amplifiers, and various other quantum
circuits. An alternative approach using hybrid superconductor-semiconductor JJs can enable a superconducting qubit architecture with full electric field control. Here we present continuous-wave and time-domain characterization of gatemon qubits based on an InAs 2DEG. We show that the qubit undergoes a vacuum Rabi splitting with a readout cavity and we drive coherent Rabi oscillations between the qubit ground and first excited states. We measure qubit coherence times to be T1= 100 ns over a 1.5 GHz tunable band. While various loss mechanisms are present in III-V gatemon circuits we detail future directions in enhancing the coherence times of qubit devices on this platform.
arxiv pdf

Epitaxial Superconductor-Semiconductor Two-Dimensional Systems for Superconducting Quantum Circuits

  1. Joseph O'Connell Yuan,
  2. Kaushini S. Wickramasinghe,
  3. William M. Strickland,
  4. Matthieu C. Dartiailh,
  5. Kasra Sardashti,
  6. Mehdi Hatefipour,
  7. and Javad Shabani
Qubits on solid state devices could potentially provide the rapid control necessary for developing scalable quantum information processors. Materials innovation and design breakthroughs
have increased functionality and coherence of qubits substantially over the past two decades. Here we show by improving interface between InAs as a semiconductor and Al as a superconductor, one can reliably fabricate voltage-controlled Josephson junction field effect transistor (JJ-FET) that can be used as tunable qubits, resonators, and coupler switches. We find that band gap engineering is crucial in realizing a two-dimensional electron gas near the surface. In addition, we show how the coupling between the semiconductor layer and the superconducting contacts can affect qubit properties. We present the anharmonicity and coupling strengths from one and two-photon absorption in a quantum two level system fabricated with a JJ-FET.
arxiv pdf