{"id":1181,"date":"2019-07-06T15:58:53","date_gmt":"2019-07-06T13:58:53","guid":{"rendered":"https:\/\/webs.uab.cat\/giq\/seminar\/reversing-unknown-quantum-transformations-a-universal-protocol-for-inverting-general-unitary-operations\/"},"modified":"2019-07-06T15:58:53","modified_gmt":"2019-07-06T13:58:53","slug":"reversing-unknown-quantum-transformations-a-universal-protocol-for-inverting-general-unitary-operations","status":"publish","type":"seminar","link":"https:\/\/webs.uab.cat\/giq\/seminar\/reversing-unknown-quantum-transformations-a-universal-protocol-for-inverting-general-unitary-operations\/","title":{"rendered":"Reversing unknown quantum transformations: A universal protocol for inverting general unitary operations"},"content":{"rendered":"<p>Given a general d-dimensional unitary operation&nbsp;for which, apart from the dimension, its description is unknown, is it possible to implement its inverse operation&nbsp;with a universal protocol that works for every unitary? How does the situation change when k uses of unitary operation&nbsp; are allowed? In this paper we show that any universal protocol implementing the inverse of a general unitary&nbsp;with a positive heralded probability requires at least d\u22121 uses of this unitary. For the cases where k\u2265d\u22121 uses are accessible, we construct a parallel and sequential protocol, whose respective probability of failure decreases linearly and exponentially. We then analyse protocols with indefinite causal order. These more general protocols still cannot yield the inverse of a general d-dimensional unitary operation with k&lt;d\u22121 uses. However we show via a general semidefinite programming that protocols with indefinite causal order attain a higher success probability when k&gt;d\u22121. We will also introduce the notion of delayed input-state protocols and provides a one-to-one correspondence between the unitary learning (unitary store and<br \/>\nretrieve) problem and universal parallel protocols for unitary transposition.<br \/>\n&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Given a general d-dimensional unitary operation&nbsp;for which, apart from the dimension, its description is unknown, is it possible to implement its inverse operation&nbsp;with a universal protocol that works for every unitary? How does the situation change when k uses of unitary operation&nbsp; are allowed? In this paper we show that any universal protocol implementing the [&hellip;]<\/p>\n","protected":false},"author":20,"featured_media":0,"template":"","class_list":["post-1181","seminar","type-seminar","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/webs.uab.cat\/giq\/wp-json\/wp\/v2\/seminar\/1181","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\/20"}],"wp:attachment":[{"href":"https:\/\/webs.uab.cat\/giq\/wp-json\/wp\/v2\/media?parent=1181"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}