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arXiv:2602.20410

A quantum-operator analysis of N-fold phase accumulation in coherence de Broglie wavelength interferometry

B. S. Ham

quant-phSubmitted Feb 23, 2026• Announced Feb 25, 2026• 0 citations• Revised Sep 28, 2026 (v3)
v1 · Feb 23, 2026v2 · Aug 20, 2026v3 · Sep 28, 2026
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Abstract

Quantum sensing exploits nonclassical states of light, including multiphoton entangled states and squeezed states, to achieve superresolution and/or super-sensitivity. However, its practical implementation is constrained by state-generation complexity, photon loss, and detection efficiency. Here, we present a quantum-operator analysis of coherence de Broglie wavelength (CBW) in an anti-symmetrically coupled Mach-Zehnder interferometer (MZI) architecture and clarify the origin of its superresolution and enhanced phase sensitivity. The two-mode SU(2) structure of the MZI, represented by Pauli operators, shows that successive basis-realigned transformations produce an Nth-order unitary U^N(phi), yielding N-fold phase accumulation (1+cosNphi). The quantum-operator description is particularly significant at the single-photon level, where even a single photon undergoes the Nth-order unitary evolution through its coherent evolution in the two-mode state space. This differs from entanglement-based quantum sensing based on photonic de Broglie wavelength interferometry, where N-fold phase accumulation is associated with an N-photon entangled state. The same SU(2) transformation also applies to coherent classical fields, establishing a classical-quantum correspondence of the CBW phase evolution. Fisher-information analysis further shows that the architecture-induced phase transformation yields an order-dependent enhancement of phase sensitivity without increasing the photon number or statistical sampling. CBW therefore provides an architecture-controlled route to high-order interferometric superresolution, accompanied by enhanced phase sensitivity, with potential applications to fringe-counting wavemetry and Fourier-transform-based sensing.

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Phase-shifting interferometry (PSI) promises excellent performance for quantitative phase measurement. However, the PSI is commonly realized by utilizing the Mach-Zehnder interferometer (MZI) fed with classical resources, and hence its phase sensitivity is hindered by the photon shot noise. In this paper, we propose to introduce specific phase-shifting algorithms into the well-established quantum-enhanced MZI, seeded by coherent and squeezed vacuum states and followed by single-mode intensity detection and difference intensity detection, to achieve quantitative phase measurement with sensitivity beyond that achieved by the corresponding Mach-Zehnder-type PSI with classical input. We show that when the average photon number of the coherent state is dominant, the optimal phase sensitivity of the Mach-Zehnder-type PSI with coherent plus squeezed vacuum input is better than the phase sensitivity of the Mach-Zehnder-type PSI with single coherent input under the same phase-sensing intensity condition in both of detection setups. We also show that for the typical MZI seeded with a high-power coherent state and a finitely squeezed vacuum state, the combination of intensity detection and phase-shifting algorithm can still improve the sensitivity of quantitative phase measurement. Furthermore, we derive the phase sensitivity of the fixed MZI as well as the quantum Cramér-Rao bound for two detection schemes. Finally, we explore the impacts of photon losses on the phase sensitivity enhancements of the Mach-Zehnder-type PSI and the fixed MZI in the high-intensity regime for each detection setup. The robustness to losses is compared between the Mach-Zehnder-type PSI and the fixed MZI. Our results may be helpful to promote the exploration of quantum-enhanced quantitative phase sensing.