  Quantum measurements have been intensively researched over decades due to
quantum advantage of Heisenberg limit beating the standard quantum limit toward
potential applications of quantum metrology. The kernel of quantum measurements
is in the quantum correlation between bipartite photon pairs or squeezed light
quenched by one parameter over corresponding noncommuting variable satisfying
Heisenberg uncertainty principle. As a result, quantum measurements bring a
quantum gain of the square root law in measurement sensitivity. Photonic de
Broglie waves (PBW) have been the key feature of such a gain in quantum
metrology especially for phase resolution enhancement beyond the classical
limit of Rayleigh criterion or simply the diffraction limit. Due to extremely
low efficiency of higher-order entangled photon pair generations such as a NOON
state, however, the implementation of PBW for quantum metrology has been
severely limited. Here, a completely different mechanism of quantum
measurements is introduced for a new type of PBW and presented for its
potential application of a modified Sagnac interferometer, where the resolution
enhancement is several orders of magnitude higher than its classical
counterpart.
