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We consider generalisations of the dense coding protocol with an arbitrary number of senders and either one or two receivers, sharing a multiparty quantum state, and using a noiseless channel. For the case of a single receiver, the capacity…

Quantum theory predicts the existence of genuinely tripartite-entangled states, which cannot be obtained from local operations over any bipartite entangled states and unlimited shared randomness. Some of us recently proved that this feature…

This thesis focuses on the experimental creation and detection of a variety of quantum correlations using nuclear magnetic resonance hardware. Quantum entanglement, being most common and counter-intuitive, is one of the main type considered…

Quantum Physics · Physics 2019-05-16 Amandeep Singh

Ideal deterministic quantum communication tasks require maximally entangled channels. The reality is that the maximally entangled channel is inevitably degraded to a non-maximally entangled one because of various decoherence mechanisms,…

Quantum Physics · Physics 2023-05-17 Xuanxuan Xin , Shiwen He , Yongxing Li , Chong Li

Covert quantum communication is usually analyzed under idealized assumptions that channel parameters, such as transmissivity and background noise, are perfectly known and constant. In realistic optical links, including satellite, fiber, and…

Cryptography and Security · Computer Science 2026-04-16 Abbas Arghavani , Alessandro V. Papadopoulos , Vahid Azimi Mousolou , Giuseppe Nebbione , Shahid Raza

Sharing entanglement across quantum interconnects is fundamental for quantum information processing. We discuss a practical setting where this interconnect, modeled by a quantum channel, is used once with the aim of sharing high fidelity…

Quantum Physics · Physics 2023-10-09 Vikesh Siddhu , John Smolin

Dense coding is the seminal example of how entanglement can boost qubit communication, from sending one bit to sending two bits. This is made possible by projecting separate particles onto a maximally entangled basis. We investigate more…

We provide a purely quantum version of polar codes, achieving the symmetric coherent information of any qubit-input quantum channel. Our scheme relies on a recursive channel combining and splitting construction, where a two-qubit gate…

Quantum Physics · Physics 2021-05-04 Frédéric Dupuis , Ashutosh Goswami , Mehdi Mhalla , Valentin Savin

The squashed entanglement of a quantum channel is an additive function of quantum channels, which finds application as an upper bound on the rate at which secret key and entanglement can be generated when using a quantum channel a large…

Quantum Physics · Physics 2016-04-26 Kaushik P. Seshadreesan , Masahiro Takeoka , Mark M. Wilde

A fully general strong converse for channel coding states that when the rate of sending classical information exceeds the capacity of a quantum channel, the probability of correctly decoding goes to zero exponentially in the number of…

Quantum Physics · Physics 2013-05-29 Robert Koenig , Stephanie Wehner

We explore the classical communication over quantum channels with one sender and two receivers, or with two senders and one receiver, First, for the quantum broadcast channel (QBC) and the quantum multi-access channel (QMAC), we study the…

Quantum Physics · Physics 2017-12-18 Wei Xie , Xin Wang , Runyao Duan

Motivated by quantum network applications over classical channels, we initiate the study of $n$-party resource states from which LOCC protocols can create EPR-pairs between any $k$ disjoint pairs of parties. We give constructions of such…

Quantum Physics · Physics 2024-05-15 Sergey Bravyi , Yash Sharma , Mario Szegedy , Ronald de Wolf

Transmitting unknown quantum states to distant locations is crucial for distributed quantum information protocols. The seminal quantum teleportation scheme achieves this feat while requiring prior maximal entanglement between the sender and…

Quantum Physics · Physics 2025-04-25 Arkaprabha Ghosal , Jatin Ghai , Tanmay Saha , Sibasish Ghosh , Mir Alimuddin

We give the analytic expressions of maximal probabilities of successfully controlled teleportating an unknown qubit via every kind of tripartite states. Besides, another kind of localizable entanglement is also determined. Furthermore, we…

Quantum Physics · Physics 2009-11-13 Ting Gao , Feng-Li Yan , You-Cheng Li

Quantum channel capacities give the fundamental performance limits for information flow over a communication channel. However, the prevalence of superadditivity is a major obstacle to understanding capacities, both quantitatively and…

Quantum Physics · Physics 2025-09-10 Graeme Smith , Peixue Wu

We investigate the effect of noisy channels in a classical information transfer through a multipartite state which acts as a substrate for the distributed quantum dense coding protocol between several senders and two receivers. The…

Quantum Physics · Physics 2015-11-30 Tamoghna Das , R. Prabhu , Aditi Sen De , Ujjwal Sen

We analyse the use of entangled states to perform quantum computations non locally among distant nodes in a quantum network. The complexity associated with the generation of multiparticle entangled states is quantified in terms of the…

Quantum Physics · Physics 2009-10-31 J. I. Cirac , A. Ekert , S. F. Huelga , C. Macchiavello

We provide a versatile upper bound on the number of maximally entangled qubits, or private bits, shared by two parties via a generic adaptive communication protocol over a quantum network when the use of classical communication is not…

Quantum Physics · Physics 2018-01-30 Luca Rigovacca , Go Kato , Stefan Bäuml , M. S. Kim , W. J. Munro , Koji Azuma

Quantum communication enables a host of applications that cannot be achieved by classical communication means, with provably secure communication as one of the prime examples. The distance that quantum communication schemes can cover via…

Quantum Physics · Physics 2020-05-12 Sebastiaan Brand , Tim Coopmans , David Elkouss

We demonstrate a multipartite protocol to securely distribute and reconstruct a quantum state. A secret quantum state is encoded into a tripartite entangled state and distributed to three players. Any two of the three players are able to…

Quantum Physics · Physics 2009-11-10 Andrew M. Lance , Thomas Symul , Warwick P. Bowen , Barry C. Sanders , Ping Koy Lam