00532nas a2200157 4500008003900000022001400039245007500053210006900128260001600197300001100213490000700224100001500231700001400246700001300260856010100273 2019 d a0022-248800aEvery entangled state provides an advantage in classical communication0 aEvery entangled state provides an advantage in classical communi cJan-07-2019 a0722010 v601 aBäuml, S.1 aWinter, A1 aYang, D. uhttp://aip.scitation.org/doi/10.1063/1.5091856http://aip.scitation.org/doi/pdf/10.1063/1.509185601506nas a2200181 4500008003900000022002500039245007300064210006900137260000800206300001400214490000700228520096300235100001901198700001601217700001401233700001301247856006401260 2016 d a0032-9460, 1608-325300aClassical capacities of quantum channels with environment assistance0 aClassical capacities of quantum channels with environment assist cjul a214–2380 v523 aA quantum channel physically is a unitary interaction between an information carrying system and an environment, which is initialized in a pure state before the interaction. Conventionally, this state, as also the parameters of the interaction, is assumed to be fixed and known to the sender and receiver. Here, following the model introduced by us earlier [1], we consider a benevolent third party, i.e., a helper, controlling the environment state, and show how the helper’s presence changes the communication game. In particular, we define and study the classical capacity of a unitary interaction with helper, in two variants: one where the helper can only prepare separable states across many channel uses, and one without this restriction. Furthermore, two even more powerful scenarios of pre-shared entanglement between helper and receiver, and of classical communication between sender and helper (making them conferencing encoders) are considered.1 aKarumanchi, S.1 aMancini, S.1 aWinter, A1 aYang, D. uhttps://link.springer.com/article/10.1134/S003294601603002900724nas a2200181 4500008003900000022001400039245005600053210005600109260001600165490000800181100001800189700001800207700001300225700001300238700001400251700001800265856025900283 2016 d a0031-900700aEntanglement and Coherence in Quantum State Merging0 aEntanglement and Coherence in Quantum State Merging cJan-06-20160 v1161 aStreltsov, A.1 aChitambar, E.1 aRana, S.1 aBera, N.1 aWinter, A1 aLewenstein, M uhttp://link.aps.org/doi/10.1103/PhysRevLett.116.240405http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevLett.116.240405/fulltexthttp://link.aps.org/accepted/10.1103/PhysRevLett.116.240405http://link.aps.org/article/10.1103/PhysRevLett.116.24040503324nas a2200445 4500008003900000022001400039245010700053210006900160260000800229300001600237490000700253520193200260653003302192653002002225653002202245653002502267653001902292653003202311653002002343653001302363653003502376653001302411653003102424653004202455653002302497653003102520653002102551653002602572653002502598653002402623653001402647653003902661653003102700653003102731653002402762100001302786700001702799700001402816856004802830 2016 d a0018-944800aOn {Zero}-{Error} {Communication} via {Quantum} {Channels} in the {Presence} of {Noiseless} {Feedback}0 aZero Error Communication via Quantum Channels in the Presence of csep a5260–52770 v623 aWe initiate the study of zero-error communication via quantum channels when the receiver and the sender have at their disposal a noiseless feedback channel of unlimited quantum capacity, generalizing Shannon's zero-error communication theory with instantaneous feedback. We first show that this capacity is only a function of the linear span of Choi-Kraus operators of the channel, which generalizes the bipartite equivocation graph of a classical channel, and which we dub non-commutative bipartite graph. Then, we go on to show that the feedback-assisted capacity is non-zero (allowing for a constant amount of activating noiseless communication) if and only if the non-commutative bipartite graph is non-trivial, and give a number of equivalent characterizations. This result involves a far-reaching extension of the conclusive exclusion of quantum states. We then present an upper bound on the feedback-assisted zero-error capacity, motivated by a conjecture originally made by Shannon and proved later by Ahlswede. We demonstrate that this bound to have many good properties, including being additive and given by a minimax formula. We also prove a coding theorem showing that this quantity is the entanglement-assisted capacity against an adversarially chosen channel from the set of all channels with the same Choi-Kraus span, which can also be interpreted as the feedback-assisted unambiguous capacity. The proof relies on a generalization of the Postselection Lemma (de Finetti reduction) that allows to reflect additional constraints, and which we believe to be of independent interest. This capacity is a relaxation of the feedback-assisted zero-error capacity; however, we have to leave open the question of whether they coincide in general. We illustrate our ideas with a number of examples, including classical-quantum channels and Weyl diagonal channels, and close with an extensive discussion of open questions.10abipartite equivocation graph10aBipartite graph10aCapacity planning10aChoi-Kraus operators10acoding theorem10acommutative bipartite graph10aElectronic mail10aencoding10aentanglement-assisted capacity10afeedback10afeedback-assisted capacity10afeedback-assisted zero-error capacity10ainformation theory10anoiseless feedback channel10aquantum channels10aquantum communication10aquantum entanglement10aQuantum information10aReceivers10aShannon's zero-error communication10atelecommunication channels10aunlimited quantum capacity10azero-error capacity1 aDuan, R.1 aSeverini, S.1 aWinter, A uhttps://grupsderecerca.uab.cat/giq/node/87000472nas a2200157 4500008003900000022001400039245004900053210004500102260001200147300001400159490000800173100001400181700001500195700001400210856009000224 2013 d a0018-944800aThe structure of Renyi entropic inequalities0 astructure of Renyi entropic inequalities c10/2013 a20120737 0 v4691 aLinden, N1 aMosonyi, M1 aWinter, A uhttps://grupsderecerca.uab.cat/giq/publications/structure-renyi-entropic-inequalities