Quantum-noise-limited amplification of feeble microwaves using a graphene Josephson junction-based microwave circuit

The core of quantum information processing involves preparing, manipulating, and efficiently detecting quantum states. In cQED architecture probing quantum systems in a single-photon regime is challenging as the output signals that carry information about the quantum state of these systems are very feeble. Hence, amplification with the least added noise is crucial before signal processing at room temperature. The Josephson parametric amplifiers (JPA) are the routinely used devices for low-noise amplification of quantum signals, which improves the signal-to-noise ratio significantly. The existing JPAs are based on Al-AlOx-Al tunnel junctions where magnetic flux is the control knob for biasing the devices. Our recent work demonstrates the implementation of a gate-tunable JPA using a graphene Josephson junction, where we change the device bias using electrostatic gating [1]. Electrostatic control is advantageous over magnetic flux control in cQED devices as it uses a very localized electric field which causes less interference. In addition and in contrast with the Al-based tunnel junctions, the attractive material properties of graphene: low heat capacity, and low electron-phonon coupling, imply a single-photon detector integrated with the quantum noise limited amplifier is realizable using our device.

[1] J. Sarkar et al., Quantum noise limited microwave amplification using a graphene Josephson junction, arXiv:2204.02103.