  The classically defined minimum uncertainty of the optical phase is known as
the standard quantum limit or shot-noise limit (SNL) originating in the
uncertainty principle of quantum mechanics. Based on SNL, the phase sensitivity
is inversely proportional to the square root K, where K is the number of
interfering photons or statistically measured events. Thus, using a high-power
laser is advantageous to enhance sensitivity due to the square root K gain in
the signal-to-noise ratio. In a typical interferometer, however, the resolution
remains in the diffraction limit of the K=1 case unless the interfering photons
are resolved as in quantum sensing. Here, a projection-measurement method in
quantum sensing is adapted for an interferometer to achieve an additional
square root K gain in resolution. For the projection measurement, the
interference fringe of an interferometer can be Kth-powered to replace the
Kth-order intensity product. To understand many-wave interference-caused
enhanced resolution, several types of interferometers are numerically compared
to draw corresponding resolution parameters. As a result, the achieved
resolution by the Kth power to an N-slit interferometer exceeds the diffraction
limit and the Heisenberg limit in quantum sensing.
