{"id":2142,"date":"2023-10-16T16:56:25","date_gmt":"2023-10-16T14:56:25","guid":{"rendered":"https:\/\/webs.uab.cat\/giq\/?post_type=seminar&#038;p=2142"},"modified":"2023-10-16T16:56:25","modified_gmt":"2023-10-16T14:56:25","slug":"maximum-tolerable-excess-noise-in-cv-qkd-and-improved-lower-bound-on-two-way-capacities","status":"publish","type":"seminar","link":"https:\/\/webs.uab.cat\/giq\/seminar\/maximum-tolerable-excess-noise-in-cv-qkd-and-improved-lower-bound-on-two-way-capacities\/","title":{"rendered":"Maximum tolerable excess noise in CV-QKD and improved lower bound on two-way\u00a0capacities\u00a0"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">The two-way capacities of quantum channels determine the ultimate entanglement and secret-key distribution rates achievable by two distant parties that are connected by a noisy transmission line, in absence of quantum repeaters. Since repeaters will likely be expensive to build and maintain, a central open problem of quantum communication is to understand what performances are achievable without them. In our work we find a new lower bound on the energy-constrained and unconstrained two-way quantum and secret-key capacities of all phase-insensitive bosonic Gaussian channels, which are realistic models for the noise affecting optical fibres or free-space links. Ours is the first lower bound on the two-way quantum capacity that shows explicitly that entanglement distribution is always possible when the channel is not entanglement breaking. This completely solves a crucial open problem of the field, namely, establishing the maximum excess noise which is tolerable in continuous-variable quantum key distribution. In addition, our construction is fully explicit, i.e. we devise and optimise a concrete entanglement distribution and distillation protocol that works by combining recurrence and hashing protocols. The talk is based on our recent results, which are detailed in our paper (<a rel=\"noreferrer noopener\" href=\"https:\/\/arxiv.org\/abs\/2303.1286\" target=\"_blank\">https:\/\/arxiv.org\/abs\/2303.1286<\/a>)\u00a0co-authored with Prof. Ludovico Lami and Prof. Vittorio Giovannetti<\/p>\n","protected":false},"excerpt":{"rendered":"<p>The two-way capacities of quantum channels determine the ultimate entanglement and secret-key distribution rates achievable by two distant parties that are connected by a noisy transmission line, in absence of quantum repeaters. Since repeaters will likely be expensive to build and maintain, a central open problem of quantum communication is to understand what performances are [&hellip;]<\/p>\n","protected":false},"author":2608,"featured_media":0,"template":"","class_list":["post-2142","seminar","type-seminar","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/webs.uab.cat\/giq\/wp-json\/wp\/v2\/seminar\/2142","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/webs.uab.cat\/giq\/wp-json\/wp\/v2\/seminar"}],"about":[{"href":"https:\/\/webs.uab.cat\/giq\/wp-json\/wp\/v2\/types\/seminar"}],"author":[{"embeddable":true,"href":"https:\/\/webs.uab.cat\/giq\/wp-json\/wp\/v2\/users\/2608"}],"wp:attachment":[{"href":"https:\/\/webs.uab.cat\/giq\/wp-json\/wp\/v2\/media?parent=2142"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}