Martin Wood Complex, Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU
Professor Nicolas Treps, Laboratoire Kastler Brossel
Abstract
Quantum optical metrology aims at identifying the ultimate sensitivity bounds for the estimation of
parameters encoded into an optical field. In many practical applications, such as imaging, microscopy,
and remote sensing, the parameter of interest is encoded not only in the quantum state of the field but
also in its spatio-temporal distribution, i.e., in its modal structure. In this context, we propose both a
theoretical framework and an experimental approach to derive bounds and perform measurements that
are quantum-optimal, either in the single-parameter or in the multi-parameter settings.
We illustrate this with two incoherent sources in a three-parameter scenario: separation, centroid, and relative intensity. We perform multi-parameter estimation using a spatial mode
demultiplexing technique. We determine separations well below the diffraction limit and achieve sensitive
joint estimation of separation, centroid, and relative brightness over a broad range of scene configurations,
in a single experimental setting. We further compare different estimators, in particular using an approach
based on relative belief ratios.
[1] Boeschoten, A., Sorelli, G., Gessner, M., Fabre, C., Treps, N. (2026). Estimation of multiple parameters encoded in the modal structure of light. Optica Quantum, 4(1), 48-54.
[2] Grateau, A., Boeschoten, A., Favin-L´evˆeque, T., Herrera, I., Treps, N. (2026). Multiparameter
estimation for the superresolution of two incoherent sources (arXiv:2601.14876), to appear in Phys.
Rev. Lett.
[3] S. U. Shringarpure, Y. S. Teo, H. Jeong, M. Evans, L. L. S´anchez-Soto, A. Grateau, A. Boeschoten,
and N. Treps, Experimental evidence-based sub-Rayleigh source discrimination, Phys. Rev. A 114,
043713 (2026)