Simultaneous amplitude and phase spectroscopy using two-photon interference

Quantum Physics [Submitted on 16 Mar 2026] Simultaneous amplitude and phase spectroscopy using two-photon interference Kyle M. Jordan (1,2,3), Yingwen Zhang (1,2,3), Frédéric Bouchard (1), Duncan England (1), Philip J. Bustard (1), Benjamin J. Sussman (1,2,3), Jeff S. Lundeen (2,3), Andrew H. Proppe (1,2,3) ((1) National Research Council Canada, (2) Department of Physics and Nexus for Quantum Technology, University of Ottawa, (3) University of Ottawa-NRC Joint Center for Extreme Photonics) Quantum spectroscopy seeks to probe chemical systems using nonclassical light, which has properties that are qualitatively and quantitatively different than conventional light sources. One promising technique uses intensity-correlated twin beams of light to reduce the noise sources inherent to absorption spectroscopy. However, measurements of the phase shift imparted by the chemical sample, which provides complementary information to the absorption, continue to be a challenge. Here, we propose and demonstrate a scheme using entangled photon pairs that can simultaneously measure both the absorption and phase shift of a sample with extremely low optical intensities and with relatively fast few-minute acquisition times. This method combines the previous use of intensity correlations with a broadband quantum interferometer utilizing two-photon interference to measure the complete linear optical response of the sample. Our work shows that precise measurements of absorption can also be made phase-sensitive using suitable choices of probe beam and detection scheme. This enables a new class of quantum spectroscopy schemes which measure absorption and phase with a single probe. Our technique is relevant to the characterization of a wide array of chemical and biological samples, such as quantum dots and organic fluorophores, and may be useful for spectroscopic measurements that are otherwise constrained in intensity. Comments: 30 pages, 5 figures Subjects: Quantum Physics (quant-ph); Optics (physics.optics) Cite as: arXiv:2603.15944 [quant-ph]   (or arXiv:2603.15944v1 [quant-ph] for this version)   https://doi.org/10.48550/arXiv.2603.15944 Focus to learn more Submission history From: Kyle Jordan [view email] [v1] Mon, 16 Mar 2026 21:50:35 UTC (790 KB) Access Paper: view license Current browse context: quant-ph < prev   |   next > new | recent | 2026-03 Change to browse by: physics physics.optics References & Citations INSPIRE HEP NASA ADS Google Scholar Semantic Scholar Export BibTeX Citation Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer (What is the Explorer?) Connected Papers Toggle Connected Papers (What is Connected Papers?) Litmaps Toggle Litmaps (What is Litmaps?) scite.ai Toggle scite Smart Citations (What are Smart Citations?) Code, Data, Media Demos Related Papers About arXivLabs Which authors of this paper are endorsers? | Disable MathJax (What is MathJax?)