Direct Measurement of a sin(2φ) Current Phase Relation in a Graphene Superconducting Quantum Interference Device.

In a Josephson junction, the current phase relation relates the phase variation of the superconducting order parameter φ, between the two superconducting leads connected through a weak link, to the dissipationless current. This relation is the fingerprint of the junction. It is usually dominated by a sin(φ) harmonic, however, its precise knowledge is necessary to design superconducting quantum circuits with tailored properties.

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. Of these elements, quantum-limited parametric amplifiers are 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.