A quantum mechanical analysis of the coherence de Broglie wavelength for superresolution and enhanced sensitivity in a coupled interferometer scheme
Quantum sensing has drawn considerable attention as a means to overcome the fundamental limitations in classical sensing. In practice, however, quantum sensing has been strongly constrained by photon loss, the achievable photon number N in N00N states, and a finite squeezing level in squeezed states. These limitations are particularly critical to photon-loss-sensitive applications such as LiDAR as well as to general sensing platforms that require large effective N, such as ring-laser gyroscopes. Recently, fundamentally different sensing platforms have been reported to overcome both classical and quantum constraints in a practical regime. One such approach exploits the coherence de Broglie wavelength (CBW) realized in an anti-symmetrically coupled Mach-Zehnder interferometer architecture. Here, a pure quantum mechanical analysis of the CBW is presented for a loss-free sensing mechanism of superresolution. Furthermore, CBW-enhanced sensitivity is derived from Fisher information, whose enhancement over the standard quantum limit is sqrt(N). Finally, a proof-of-principle demonstration of CBW is presented for lambda_CBW=lambda_0/2, which is analogous to the N00N-state-based quantum sensing for N=2.