{
  "id": 1552911,
  "title": "Three photons at once beat the standard photon test",
  "url": "https://urgent.news/2026/08/17/three-photons-at-once-beat-the-standard-photon-test",
  "topic": "culture",
  "section": "Culture",
  "published": "2026-08-17T20:00:05.000Z",
  "source": {
    "name": "Phys.org",
    "slug": "phys-org",
    "url": "https://phys.org/news/2026-08-photons-standard-photon.html"
  },
  "original_language": "en",
  "account": "Physicists at the University of Twente have enhanced the conventional test for the purity of individual photons. By allowing three photons to interfere simultaneously rather than just two, their experiment extracts more information from each measurement. This advancement surpasses even an ideal, error-free execution of the traditional method. The research findings were published in Physical Review Letters.\n\nQuantum technology hinges on photons being as indistinguishable as feasible. However, in reality, they seldom meet this criterion. Laboratories therefore gauge the degree of similarity between photons before the experiment. Since 1987, this has been achieved using the Hong-Ou-Mandel experiment, which involves two photons encountering at a beam splitter. The two photons always traverse the splitter together if they are truly identical. Dr. Stefan van den Hoven, a doctoral student and lead author of the study, explains that the Hong-Ou-Mandel test is not only a foundational experiment in quantum optics but also the initial benchmark for quantum researchers.\n\nThe standard test compares two photons at a time. Consequently, when dealing with ten photons, there are already 45 distinct pairs to scrutinize. Moreover, individual measurements yield no conclusive results. A quantum experiment generates one outcome at a time, and it is only after thousands of repetitions that the frequency of each outcome becomes apparent. This distribution uncovers how alike the photons are.\n\nThe Twente researchers introduced a second beam splitter behind the initial one, enabling a third photon to participate. This enhancement leverages the very attribute that renders photonic quantum technology potent: interference among photons. Consequently, each measurement now imparts more insight into the degree of similarity between the photons. Roughly twenty percent fewer repetitions are necessary to achieve identical precision. To confirm that this configuration is optimal, the researchers turn to the Fisher information matrix, a concept from information science that quantifies the extent to which a measurement informs about an unknown quantity. Their design is demonstrably optimal for three photons. While it could potentially be extended to four or five photons, its superiority in these scenarios remains uncertain.\n\nIn practice, most theoretical quantum benefits are lost due to noise, which can result in the loss of particles along the way. With three photons, the risk of loss is higher than with two. However, this setup cleverly circumvents this drawback. If a photon is lost, the remaining two photons automatically yield the customary two-photon measurement. Both tests occur concurrently. Dr. van den Hoven remarked, \"It's a bet you can't lose.\" Currently, the method is most pertinent to quantum optics laboratories. In the future, it could potentially serve as a calibration step or an integrated test module within a large-scale photonic quantum computer.",
  "summary": "Physicists at the University of Twente have improved the standard test for the quality of individual particles of light. By letting three photons interfere at the same time instead of two, they draw more information from every measurement. Their experiment outperforms even a perfect, noise-free run of the old method. The work appeared in Physical Review Letters.",
  "key_points": [
    "Three photons interfere simultaneously in enhanced photon purity test",
    "Outperforms ideal execution of traditional Hong-Ou-Mandel experiment",
    "Enables more information extraction from each photon measurement"
  ],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}