General Relativistic Decoherence with Applications to Dark Matter Detection

Quantum mechanics allows for states in macroscopic superpositions, but they ordinarily undergo rapid decoherence due to interactions with their environment. A system that only interacts gravitationally, such as an arrangement of dark matter (DM), may exhibit slow decoherence. In this Letter, we compute the decoherence rate of a quantum object within general relativity, focusing on superposed metric oscillations; a rare quantum general relativistic result. For axion DM in a superposition of the field’s phase, we find that DM in the Milky Way is robust against decoherence, while a spatial superposition is not. This novel phase behavior may impact direct detection experiments.

Figure 1

A schematic representation of a probe particle scattered by dark matter in a superposition of macroscopic states, evolving into an entangled state $|\mathrm{\Psi }⟩$ [see Eq. (1)], where the probe particle’s state is altered by gravitational interaction.