Progress Towards a Low Temperature Superfluid ⁴He Josephson Junction using 2D Nanoporous Materials

We describe ongoing efforts to realize a superfluid ⁴He weak-link deep within the superfluid regime, providing a robust platform for novel macroscopic quantum devices, such as ultra-sensitive inertial quantum sensors, quantum-limited acoustic amplifiers, and qubits. Our approach aims to leverage recent advancements in the synthesis of 2D nanoporous materials with sub-nanometer pore sizes, enabling weak coupling via geometric constrictions with characteristic dimensions comparable to the coherence length at low-temperatures. We present measurements of driven superfluid motion through solid-state apertures, including phase-slip observations, made using our hydromechanical-resonator-based experimental cell. We also report progress measuring superflow through 2D materials, with graphene serving as an opaque control.