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The approach removes side channels from the source modulation side while retaining detector-side advantages typical of measurement-device-independent designs. Single-photon interference supports good key-rate behavior, particularly over high-loss channels, and phase mis-matching improves sifting efficiency for the multi-user scenario.",{"@graph":69,"@context":114},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":40,"@type":76,"position":81},"https://docshare.wps.com/document/research-report/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/fully-passive-quantum-conference-key-agreement/203848/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/fully-passive-quantum-conference-key-agreement/203848.png","ImageObject",300,407,{"name":92,"@type":93},"Cart","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-10-10","2026-09-04",true,{"@type":102,"interactionType":103,"userInteractionCount":19},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108],{"name":109,"@type":110,"acceptedAnswer":111},"Why is phase mis-matching important in the multi-user scenario?","Question",{"text":112,"@type":113},"Fully passive protocols often suffer heavy sifting in multi-user settings; phase mis-matching significantly improves sifting efficiency and yields reasonable overall performance.","Answer","https://schema.org",{"og:url":83,"og:type":116,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":118,"canonical":83},"index,follow",{"doc_id":120,"site_id":62},203848,1788564351,{"code":4,"msg":5,"data":123},{"doc_id":120,"user_id":124,"nickname":92,"user_avatar":125,"doc_module":4,"category_id":39,"category_name":40,"doc_title":65,"doc_description":67,"doc_content":126,"file_id":127,"file_url":128,"file_type":129,"file_size":130,"view_count":19,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":52,"language":131,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":132,"faqs":133,"seo_title":134,"seo_description":67,"update_tm":121,"read_time":135},18829141979164,"https://eur-avatar.wpscdn.com/davatar_6f874abed73319feea01a86fa6f0fab8","arXiv :2407 . 15761v3 [ quant-ph] 27 Apr 2026  \nFully Passive Quantum Conference Key Agreement  \nJinjie Li, 1 Wenyuan Wang, 1, 2, ∗ and H. F. Chau 1, 2,†  \n1 Department of Physics, University of Hong Kong, Pokfulam Road, Hong Kong.  \n2 HK Institute of Quantum Science & Technology, University of Hong Kong, Pokfulam Road, Hong Kong.  \n(Dated: April 28, 2026)  \nQuantum Conference Key Agreement (CKA) provides a secure method for multi-party communication. A recently developed interference-based prepare-and-measure quantum CKA possesses the advantages of measurement-device-independence, namely, being immune to side-channels from the detector side. Besides, it achieves good key rate performance, especially for high-loss channels, due to the use of single photon interference. Meanwhile, several fully passive QKD schemes have been proposed, which eliminate all side channels from the source modulation side. We extend the fully passive idea to an interference-based CKA, which has a high level of implementation security for many-user communication.  \nI. INTRODUCTION  \nQuantum Key Distribution (QKD) enables secure communication between two parties by leveraging the principles of quantum mechanics, resulting in information-theoretic security. [1, 2] . QKD has been extensively developed both theoretically and experimentally over the past few decades. One major challenge in implementing QKD arises from the side channels that are inherently embedded in imperfect experimental equipment [3–7] . A novel protocol, called MDI-QKD [8], ensures immunity from all loopholes on the detector side. Later, TF-QKD [9, 10] was proposed, which possesses the same detector side immunity and overcomes the fundamental rate-distance limit of QKD by using singlephoton interference. While QKD is typically applied between two parties, efforts have been made to explore information-theoretically secure communication among many users through quantum network or quantum Conference Key Agreement (CKA) [11–22] . In this paper, all CKA use quantum particles and channels. Notably, among the CKA protocols, several recently proposed ones are inspired by TF-QKD and are based on single-photon interference. They can achieve good key rate performance, especially under high-loss scenarios [23–25] .  \nThe side channels from source modulators can be eliminated by applying a recently proposed idea called fully passive QKD [26–30] . Such side channels may leak information to an eavesdropper or be attacked using a Trojan-horse attack [3, 6] . Passive decoy [31, 32] and passive encoding [32] respectively remove the active modulators that generate the desired intensity or polarization of signals, replacing them with local detection and post-selection. On the other hand, fully passive QKD simultaneously post-selects both intensity and polarization, removing all modulators from the sources. This idea  \n∗ Corresponding author: [wenyuan.wang@naist.ac.jp. Present](wenyuan.wang@naist.ac.jp. Present) address: Nara Institute of Science and Technology, Japan  \n† Corresponding author: hfchau@hku.hk  \nwas first applied to BB84 [26–28] and later to MDI-QKD [33, 34] . Using a different source design, two fully passive schemes for TF-QKD [35] and CV-QKD [36] have also been proposed. Recently, there have also been reports of successful experimental demonstrations of fully passive QKD [29, 30] . Those works demonstrated that while enjoying the benefit of better security at the sources, not much key rate performance needs to be sacrificed.  \nIn this work, we combine the idea of fully passive QKD with CKA, named fully passive CKA, that could possess advantages from both ideas. Our main contributions and the challenges we met of this work are as follows:  \n• We for the first time apply the fully passive scheme to a multi-user scenario, along with the application of a phase mis-matching strategy, results in a good sifting efficiency and reasonable performance. Fully passive protocols often suffer from heavy ","cbCaiui9oZqvPaac","https://ap.wps.com/l/cbCaiui9oZqvPaac","pdf",626032,"English","# Introduction\n## Previous works\n### Passive TF QKD\n## Fully passive CKA protocol overview\n## Implementation security and security proof\n## Key rate simulation for four-party case\n## Discussions and future development","[{\"question\":\"Why is phase mis-matching important in the multi-user scenario?\",\"answer\":\"Fully passive protocols often suffer heavy sifting in multi-user settings; phase mis-matching significantly improves sifting efficiency and yields reasonable overall performance.\"}]","Fully Passive Quantum Conference Key Agreement | PDF",25]