  Understanding quantum mechanics within curved spacetime is a key stepping
stone towards understanding the nature of spacetime itself. Whilst various
theoretical models have been developed,
  it is significantly more challenging to carry out actual experiments that
probe quantum mechanics in curved spacetime.
  By adding Sagnac interferometers into the arms of a Hong-Ou-Mandel (HOM)
interferometer that is placed on a mechanically rotating platform, we show that
non-inertial motion modifies the symmetry of an entangled biphoton state.
  As the platform rotation speed is increased, we observe that HOM interference
dips transform into HOM interference peaks. This indicates that the photons
pass from perfectly indistinguishable (bosonic behaviour), to perfectly
distinguishable (fermionic behavior), therefore demonstrating a mechanism for
how spacetime can affect quantum systems. The work is increasingly relevant in
the real world as we move towards global satellite quantum communications, and
paves the way for further fundamental research that could test the influence of
non-inertial motion (and equivalently curved spacetime) on quantum
entanglement.
