  In quantum mechanics the time dimension is treated as a parameter, while the
three space dimensions are treated as observables. This assumption is both
untested and inconsistent with relativity. From dimensional analysis, we expect
quantum effects along the time axis to be of order an attosecond. Such effects
are not ruled out by current experiments. But they are large enough to be
detected with current technology, if sufficiently specific predictions can be
made. To supply such we use path integrals. The only change required is to
generalize the usual three dimensional paths to four. We predict a large
variety of testable effects. The principal effects are additional dispersion in
time and full equivalence of the time/energy uncertainty principle to the
space/momentum one. Additional effects include interference, diffraction, and
entanglement in time. The usual ultraviolet divergences do not appear: they are
suppressed by a combination of dispersion in time and entanglement in time. The
approach here has no free parameters; it is therefore falsifiable. As it treats
time and space with complete symmetry and does not suffer from the ultraviolet
divergences, it may provide a useful starting point for attacks on quantum
gravity.
