Photoemission and absorption under coherent and entangled-photon-pair illumination

Quantum Physics [Submitted on 15 Apr 2026] Photoemission and absorption under coherent and entangled-photon-pair illumination Malvin Carl Teich, Mark C. Booth, Francesco Lissandrin, Bahaa E. A. Saleh The phenomena of subthreshold photoemission and absorption under coherent and entangled-photon-pair illumination are reviewed, and the generation and properties of entangled-photon pairs are surveyed. Three prominent forms of subthreshold photoemission are examined: one-photon Fermi-tail photoemission (FTP), two-photon photoemission (TPP), and entangled-two-photon photoemission (ETPP). Experimental methods for measuring subthreshold photocurrents and photoelectron count rates are discussed, along with strategies for enhancing selected contributions. Experimental observations of FTP from a CsK_2Sb photocathode in a photomultiplier tube (PMT), under both coherent and entangled-photon-pair illumination, are reviewed, and the role of FTP as a noise source in two-photon measurements is elucidated. TPP from Na and CsK_2Sb photocathodes in a PMT under classical-light illumination is considered, as are TPP and ETPP from a CsK_2Sb photocathode in a channel photomultiplier (CPM) under coherent and entangled-photon-pair illumination. The observation of ETPP is facilitated by the use of a CPM, which suppresses FTP, and by low-intensity illumination, which minimizes TPP. Quantum models of TPP and ETPP accord well with experiment. Entangled-two-photon absorption (ETPA) is analyzed, as are its applications in entangled-two-photon fluorescence microscopy (ETPFM) and entangled-two-photon spectroscopy (ETPS). The three principal forms of subthreshold absorption parallel those of subthreshold photoemission: singleton-induced Boltzmann-tail absorption; cousin-induced/singleton-pair-induced two-photon absorption; and twin-induced ETPA. Heuristic particle and fully quantum models of these processes are compared, and experimental studies of ETPA and ETPFM, together with methods for enhancing their observability, are summarized. Comments: 113 pages, 25 figures, 404 references, review paper Subjects: Quantum Physics (quant-ph); Optics (physics.optics) Cite as: arXiv:2604.13375 [quant-ph]   (or arXiv:2604.13375v1 [quant-ph] for this version)   https://doi.org/10.48550/arXiv.2604.13375 Focus to learn more Submission history From: Malvin Teich [view email] [v1] Wed, 15 Apr 2026 00:47:21 UTC (14,686 KB) Access Paper: HTML (experimental) view license Current browse context: quant-ph < prev   |   next > new | recent | 2026-04 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?)