Room 117

Universal decoherence due to gravitational time dilation

Himanshu Badhani

IMSc

The physics of low-energy quantum systems is usually studied
without explicit consideration of the background spacetime. Phenomena
inherent to quantum theory in curved spacetime, such as Hawking
radiation, are typically assumed to be relevant only for extreme
physical conditions: at high energies and in strong gravitational
fields. Here we consider low-energy quantum mechanics in the presence
of gravitational time dilation and show that the latter leads to the
decoherence of quantum superpositions. Time dilation induces a
universal coupling between the internal degrees of freedom and the
centre of mass of a composite particle. The resulting correlations
lead to decoherence in the particle position, even without any
external environment. We also show that the weak time dilation on
Earth is already sufficient to affect micrometre-scale objects.
Gravity can therefore account for the emergence of classicality and
this effect could in principle be tested in future matter-wave
experiments.

Ref: Nature Phys 11, 668–672 (2015) doi:10.1038/nphys3366

Link: www.nature.com/articles/nphys3366