Manipulation of first- and second-order quantum coherence with undetected photons through path identity
Phys. Rev. Applied 25, 014031 – Published 13 January, 2026
DOI: https://doi.org/10.1103/8b89-22tm
Abstract
Path identity offers a powerful way for generating and detecting quantum states, particularly in quantum imaging and metrology with undetected photons. However, previous manipulations of first-order coherence in path identity systems have been restricted to dynamic phases. Here we extend the phase control into the geometric phase, arising from cyclic evolution in a photon’s state space, and further introduce rotational Doppler shifts as its dynamic counterpart. For second-order coherence, photon indistinguishability between two undetected photons plays a critical role, traditionally adjusted via the relative time delay. Here, we demonstrate the adjustment of photon indistinguishability via orbital angular momentum (OAM) mode conversion in an undetected photon. As the OAM mode changes, we observe distinct peaks and dips in the second-order coherence curve. Our experimental results are in good agreement with theoretical predictions. These results expand the toolbox for quantum coherence manipulation in path identity systems and may enable broader applications, such as enhanced quantum sensing, imaging, and high-dimensional entanglement, with undetected photons.
