A gate-tunable graphene Josephson parametric amplifier.

With a large portfolio of elemental quantum components, superconducting quantum circuits have contributed to advances in microwave quantum optics 1 . Of these elements, quantum-limited parametric amplifiers 2-4 are essential for low noise readout of quantum systems whose energy range is intrinsically low (tens of μeV) 5,6 . They are also used to generate non-classical states of light that can be a resource for quantum enhanced detection 7 . Superconducting parametric amplifiers, such as quantum bits, typically use a Josephson junction as a source of magnetically tunable and dissipation-free non-linearity. In recent years, efforts have been made to introduce semiconductor weak links as electrically tunable non-linear elements, with demonstrations of microwave resonators and quantum bits using semiconductor nanowires 8,9 , a two-dimensional electron gas 10 , carbon nanotubes 11 and graphene 12,13 . However, given the challenge of balancing non-linearity, 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 expand the toolset for electrically tunable superconducting quantum circuits. They also offer opportunities for the development of quantum technologies such as quantum computing, quantum sensing and for fundamental science 14 .