mass-energy-equivalence

Composite quantum particles, such as atoms and molecules, are promising tools for probing quantum systems under gravitational effects. However, greater understanding of mass–energy equivalence in composite particles and their interactions with external environments is required.

Can we use composite particles to tease out quantum features of temperature, in analogy to how idealised clocks have been used to probe the quantum nature of time?

When composite particles with internal mass-energy states move through spacetime they must be described by quantum states with minimum uncertainty in position and velocity, not momentum.