Detecting Planck-Scale Dark Matter with Quantum Interference

In spite of the large astronomical evidence for its effects, the nature of dark matter remains enigmatic. Particles that interact only, or almost only, gravitationally, in particular with masses around the Planck mass-the fundamental scale of quantum gravity-are intriguing candidates. Here, we show that there is a theoretical possibility to directly detect such particles using highly sensitive gravity-mediated quantum phase shifts. In particular, we illustrate a protocol utilizing Josephson junctions.