TY - JOUR
T1 - Every entangled state provides an advantage in classical communication
JF - Journal of Mathematical Physics
Y1 - 2019
A1 - Bäuml, S.
A1 - Winter, A.
A1 - Yang, D.
VL - 60
UR - http://aip.scitation.org/doi/10.1063/1.5091856http://aip.scitation.org/doi/pdf/10.1063/1.5091856
JO - Journal of Mathematical Physics
ER -
TY - JOUR
T1 - Classical capacities of quantum channels with environment assistance
JF - Problems of Information Transmission
Y1 - 2016
A1 - Karumanchi, S.
A1 - Mancini, S.
A1 - Winter, A.
A1 - Yang, D.
AB - A 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.
VL - 52
UR - https://link.springer.com/article/10.1134/S0032946016030029
ER -
TY - JOUR
T1 - Entanglement and Coherence in Quantum State Merging
JF - Physical Review Letters
Y1 - 2016
A1 - Streltsov, A.
A1 - Chitambar, E.
A1 - Rana, S.
A1 - Bera, N.
A1 - Winter, A.
A1 - Lewenstein, M.
VL - 116
UR - http://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.116.240405
JO - Phys. Rev. Lett.
ER -
TY - JOUR
T1 - On {Zero}-{Error} {Communication} via {Quantum} {Channels} in the {Presence} of {Noiseless} {Feedback}
JF - IEEE Transactions on Information Theory
Y1 - 2016
A1 - Duan, R.
A1 - Severini, S.
A1 - Winter, A.
KW - bipartite equivocation graph
KW - Bipartite graph
KW - Capacity planning
KW - Choi-Kraus operators
KW - coding theorem
KW - commutative bipartite graph
KW - Electronic mail
KW - encoding
KW - entanglement-assisted capacity
KW - feedback
KW - feedback-assisted capacity
KW - feedback-assisted zero-error capacity
KW - information theory
KW - noiseless feedback channel
KW - quantum channels
KW - quantum communication
KW - quantum entanglement
KW - Quantum information
KW - Receivers
KW - Shannon's zero-error communication
KW - telecommunication channels
KW - unlimited quantum capacity
KW - zero-error capacity
AB - We 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.
VL - 62
ER -
TY - JOUR
T1 - The structure of Renyi entropic inequalities
JF - Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
Y1 - 2013
A1 - Linden, N.
A1 - Mosonyi, M.
A1 - Winter, A.
VL - 469
IS - 2158472222
JO - Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
ER -