![\"Measuring](\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2025\/09\/measuring-the-quantum.jpg\" "\\"Achieving")
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Achieving the entanglement measurement of the W state. Credit: KyotoU \/ Takeuchi lab<\/p>\n
The concept of quantum entanglement is emblematic of the gap between classical and quantum physics. Referring to a situation in which it is impossible to describe the physics of each photon separately, this key characteristic of quantum mechanics defies the classical expectation that each particle should have a reality of its own, which gravely concerned Einstein.<\/p>\n
Understanding the potential of this concept is essential for the realization of powerful new quantum technologies.<\/p>\n
Developing such technologies will require the ability to freely generate a multi-photon<\/a> quantum entangled state<\/a>, and then to efficiently identify what kind of entangled state is present. However, when performing conventional quantum tomography, a method commonly used for state estimation, the number of measurements required grows exponentially with the number of photons, posing a significant data collection problem.<\/p>\n If available, an entangled measurement can identify the entangled state with a one-shot approach. Such a measurement for the Greenberger-Horne-Zeilinger\u2014GHZ\u2014entangled quantum state<\/a> has been realized, but for the W state, the other representative entangled multi-photon state, it has been neither proposed nor discovered experimentally.<\/p>\n This motivated a team of researchers at Kyoto University and Hiroshima University to take on this challenge, ultimately succeeding in developing a new method of entangled measurement to identify the W state. The paper is published<\/a> in the journal Science Advances.<\/p>\n “More than 25 years after the initial proposal concerning the entangled measurement for GHZ states, we have finally obtained the entangled measurement for the W state as well, with genuine experimental demonstration for 3-photon W states,” says corresponding author Shigeki Takeuchi.<\/p>\n The team focused on the characteristics of the W state’s cyclic shift symmetry, and theoretically proposed a method to create an entangled measurement using a photonic quantum circuit that performs quantum Fourier transformation for the W state of any number of photons.<\/p>\n They created a device to demonstrate the proposed method for three photons using high-stability optical quantum circuits, which allowed the device to operate stably without active control for an extended period of time.<\/p>\n By inserting three single photons into the device in appropriate polarization states, the team was able to demonstrate that the device can distinguish different types of three-photon W states, each corresponding to a specific non-classical correlation between the three input photons.<\/p>\n The researchers were able to evaluate the fidelity of the entangled measurement, which is equal to the probability of obtaining the correct result for a pure W-state input.<\/p>\n This achievement opens the door for quantum teleportation, or the transfer of quantum information. It could also lead to new quantum communication protocols, the transfer of multi-photon quantum entangled states, and new methods for measurement-based quantum computing.<\/p>\n “In order to accelerate the research and development of quantum technologies, it is crucial to deepen our understanding of basic concepts to come up with innovative ideas,” says Takeuchi.<\/p>\n In the future, the team aims to apply their method to a larger-scale, more general multi-photon quantum entangled state, and plans to develop on-chip photonic quantum circuits for entangled measurements.<\/p>\n More information:<\/strong> \n\t\t\t\t\t\t\t\t\t\t\t\t\tProvided by \t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/p>\n \n\t\t\t\t\t\t\t\t\t\t\t\tCitation<\/strong>: \n\t\t\t\t\t\t\t\t\t\t\t This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
\n\t\t\t\t\t\t\t\t\t\t\t\tGeobae Park et al, Entangled Measurement for W states, Science Advances (2025). DOI: 10.1126\/sciadv.adx4180<\/a>. www.science.org\/doi\/10.1126\/sciadv.adx4180<\/a><\/p>\n
\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tKyoto University<\/a>
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\n\t\t\t\t\t\t\t\t\t\t\t\tMeasuring the quantum W state: Seeing a trio of entangled photons in one go (2025, September 12)
\n\t\t\t\t\t\t\t\t\t\t\t\tretrieved 12 September 2025
\n\t\t\t\t\t\t\t\t\t\t\t\tfrom https:\/\/phys.org\/news\/2025-09-quantum-state-trio-entangled-photons.html\n\t\t\t\t\t\t\t\t\t\t\t <\/p>\n
\n\t\t\t\t\t\t\t\t\t\t\t part may be reproduced without the written permission. The content is provided for information purposes only.\n\t\t\t\t\t\t\t\t\t\t\t <\/p>\n","protected":false},"excerpt":{"rendered":"Achieving the entanglement measurement of the W state. Credit: KyotoU \/ Takeuchi lab The concept of quantum entanglement…\n","protected":false},"author":3,"featured_media":222148,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[25],"tags":[493,494,492,489,159,490,158,491,67,132,68],"class_list":{"0":"post-222147","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-physics","8":"tag-materials","9":"tag-nanotech","10":"tag-physics","11":"tag-physics-news","12":"tag-science","13":"tag-science-news","14":"tag-technology","15":"tag-technology-news","16":"tag-united-states","17":"tag-unitedstates","18":"tag-us"},"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@us\/115194039315512437","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts\/222147","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/comments?post=222147"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts\/222147\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/media\/222148"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/media?parent=222147"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/categories?post=222147"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/tags?post=222147"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}