  It is argued that our universe happens to be in a state of statistical
equilibrium at the hidden-variable level, such that nonlocality is masked by
quantum noise. To account for this 'quantum equilibrium', we outline a
subquantum statistical mechanics in configuration space, and an H-theorem
analogous to the classical coarse-graining H-theorem. Foundational issues in
statistical mechanics are addressed, and an alternative explanation based on
'typicality' is criticised. An estimate is given for the relaxation timescale,
and an illustrative numerical simulation is provided. Assuming the universe
began in quantum non-equilibrium, we sketch a scenario in which relaxation is
suppressed at very early times by the rapid expansion of space, raising the
possibility that deviations from quantum theory could survive to the present
day for relic cosmological particles that decoupled sufficiently early. It is
concluded that quantum noise is a remnant of the big bang and, like the
microwave background, should be probed experimentally. Possible tests with
relic particles are briefly discussed.
