QUANTUM MEASUREMENT, GRAVITATION, AND LOCALITY

This essay argues that when measurement processes involve energies of the order of the Planck scale, the fundamental assumption of locality may no longer be a good approximation. Idealized position measurements of two distinguishable spin-0 particles are considered. The measurements alter the space-time metric in a fundamental manner governed by the commutation relations [x(i), p(j)] = ihBAR delta(ij) and the classical field equations of gravitation. This in-principle unavoidable change in the space-time metric destroys the commutativity (and hence locality) of position measurement operators.