A gate-tunable graphene Josephson parametric amplifier

  1. Guilliam Butseraen,
  2. Arpit Ranadive,
  3. Nicolas Aparicio,
  4. Kazi Rafsanjani Amin,
  5. Abhishek Juyal,
  6. Martina Esposito,
  7. Kenji Watanabe,
  8. Takashi Taniguchi,
  9. Nicolas Roch,
  10. François Lefloch,
  11. and Julien Renard
With a large portfolio of elemental quantum components, superconducting quantum circuits have contributed to dramatic advances in microwave quantum optics. Of these elements, quantum-limited
parametric amplifiers have proven to be essential for low noise readout of quantum systems whose energy range is intrinsically low (tens of μeV ). They are also used to generate non classical states of light that can be a resource for quantum enhanced detection. Superconducting parametric amplifiers, like quantum bits, typically utilize a Josephson junction as a source of magnetically tunable and dissipation-free nonlinearity. In recent years, efforts have been made to introduce semiconductor weak links as electrically tunable nonlinear elements, with demonstrations of microwave resonators and quantum bits using semiconductor nanowires, a two dimensional electron gas, carbon nanotubes and graphene. However, given the challenge of balancing nonlinearity, dissipation, participation, and energy scale, parametric amplifiers have not yet been implemented with a semiconductor weak link. Here we demonstrate a parametric amplifier leveraging a graphene Josephson junction and show that its working frequency is widely tunable with a gate voltage. We report gain exceeding 20 dB and noise performance close to the standard quantum limit. Our results complete the toolset for electrically tunable superconducting quantum circuits and offer new opportunities for the development of quantum technologies such as quantum computing, quantum sensing and fundamental science.

A CMOS compatible platform for high impedance superconducting quantum circuits

  1. Kazi Rafsanjani Amin,
  2. Carine Ladner,
  3. Guillaume Jourdan,
  4. Sebastien Hentz,
  5. Nicolas Roch,
  6. and Julien Renard
Aluminium based platforms have allowed to reach major milestones for superconducting quantum circuits. For the next generation of devices, materials that are able to maintain low microwave
losses while providing new functionalities, such as large kinetic inductance or compatibility with CMOS platform are sought for. Here we report on a combined direct current (DC) and microwave investigation of titanium nitride lms of dierent thicknesses grown using CMOS compatible methods. For microwave resonators made of TiN lm of thickness ∼3 nm, we measured large kinetic inductance LK ∼ 240 pH/sq, high mode impedance of ∼ 4.2 kΩ while maintaining microwave quality factor ∼ 10^5 in the single photon limit. We present an in-depth study of the microwave loss mechanisms in these devices that indicates the importance of quasiparticles and provide insights for further improvement.