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We compute entanglement cost and distillable entanglement of states supported on symmetric subspace. Not only giving general formula, we apply them to the output states of optimal cloning machines. Surprisingly, under some settings, the…

Quantum Physics · Physics 2007-08-24 Keiji Matsumoto

One of the most important questions in quantum information theory is the so-called separability problem. It involves characterizing the set of separable (or, equivalently entangled) states among mixed states of a multipartite quantum…

Quantum Physics · Physics 2014-12-16 Michał Oszmaniec

The rate at which quantum communication tasks can be performed using direct transmission is fundamentally hindered by the channel loss. Quantum repeaters allow, in principle, to overcome these limitations, but their introduction necessarily…

Quantum Physics · Physics 2021-03-24 Kenneth Goodenough , David Elkouss , Stephanie Wehner

We study the capacity of d-dimensional quantum channels with memory modeled by correlated noise. We show that, in agreement with previous results on Pauli qubit channels, there are situations where maximally entangled input states achieve…

Quantum Physics · Physics 2007-05-23 E. Karpov , D. Daems , N. J. Cerf

We study the problem of universal quantum cloning -- taking several identical copies of a pure but unknown quantum state and producing further copies. While it is well known that it is impossible to perfectly reproduce the state, how well…

Quantum Physics · Physics 2016-08-09 Alastair Kay

Local unitary operations allow for a unifying approach to the quantification of quantum correlations among the constituents of a bipartite quantum system. For pure states, the distance between a given state and its image under…

Quantum Physics · Physics 2015-10-23 M. Cianciaruso , S. M. Giampaolo , W. Roga , G. Zonzo , M. Blasone , F. Illuminati

Quantum state discrimination is one of the most fundamental problems studied in quantum information theory. Applications range from channel coding to metrology and cryptography. In this work, we introduce a new variant of this task: Local…

Quantum Physics · Physics 2024-05-20 Christian Majenz , Maris Ozols , Christian Schaffner , Mehrdad Tahmasbi

We address the problem of coding for classical broadcast channels, which entails maximizing the success probability that can be achieved by sending a fixed number of messages over a broadcast channel. For point-to-point channels, Barman and…

Information Theory · Computer Science 2024-12-10 Omar Fawzi , Paul Fermé

Coherent information quantifies the achievable rate of the reliable quantum information transmission through a communication channel. Use of the correlated quantum states instead of the factorized ones may result in an increase in the…

Quantum Physics · Physics 2022-06-28 Sergey N. Filippov

We report on experimental implementation of the optimal universal asymmetric 1->2 quantum cloning machine for qubits encoded into polarization states of single photons. Our linear optical machine performs asymmetric cloning by partially…

Quantum Physics · Physics 2015-05-14 Antonin Cernoch , Jan Soubusta , Lucie Celechovska , Miloslav Dusek , Jaromir Fiurasek

We build a machine learning model to detect correlations in a three-qubit system using a neural network trained in an unsupervised manner on randomly generated states. The network is forced to recognize separable states, and correlated…

Quantum Physics · Physics 2024-08-20 Mateusz Krawczyk , Jarosław Pawłowski , Maciej M. Maśka , Katarzyna Roszak

Distributed quantum computing supports combining the computational power of multiple quantum devices to overcome the limitations of individual devices. Circuit cutting techniques enable the distribution of quantum computations via classical…

Quantum Physics · Physics 2024-08-06 Marvin Bechtold , Johanna Barzen , Frank Leymann , Alexander Mandl

We compare entanglement with quantum nonlocality employing a geometric structure of the state space of bipartite qudits. Central object is a regular simplex spanned by generalized Bell states. The Collins-Gisin-Linden-Massar-Popescu-Bell…

Quantum Physics · Physics 2015-03-13 Christoph Spengler , Marcus Huber , Beatrix C. Hiesmayr

We investigate the conditions under which a set $\SC$ of pure bipartite quantum states on a $D\times D$ system can be locally cloned deterministically by separable operations, when at least one of the states is full Schmidt rank. We allow…

Quantum Physics · Physics 2015-03-17 Vlad Gheorghiu , Li Yu , Scott M. Cohen

Shared entanglement is a resource available to parties communicating over a quantum channel, much akin to public coins in classical communication protocols. Whereas shared randomness does not help in the transmission of information, or…

Quantum Physics · Physics 2018-03-22 Ashwin Nayak , Julia Salzman

We prove that the correlations present in a multipartite quantum state have an \emph{operational} quantum character as soon as the state does not simply encode a multipartite classical probability distribution, i.e. does not describe the…

Quantum Physics · Physics 2008-05-09 Marco Piani , Pawel Horodecki , Ryszard Horodecki

In an entanglement swapping scenario, if two sources sharing entangled states between three parties are independent, local correlations lead to a different kind of inequalities than the standard Bell inequalities, known as network local…

Quantum Physics · Physics 2022-11-23 Pritam Halder , Ratul Banerjee , Shiladitya Mal , Aditi Sen De

We investigate optimal discrimination between two projective single-qubit measurements in a scenario where the measurement can be performed only once. We consider general setting involving a tunable fraction of inconclusive outcomes and we…

Quantum Physics · Physics 2014-12-01 M. Mikova , M. Sedlak , I. Straka , M. Micuda , M. Ziman , M. Jezek , M. Dusek , J. Fiurasek

Maximally entangled states--a resource for quantum information processing--can only be shared through noiseless quantum channels, whereas in practice channels are noisy. Here we ask: Given a noisy quantum channel, what is the maximum…

Quantum Physics · Physics 2018-07-17 Rajarshi Pal , Somshubhro Bandyopadhyay , Sibasish Ghosh

Effective information transmission is a central element in quantum information protocols, but the quest for optimal efficiency in channels with symmetrical characteristics remains a prominent challenge in quantum information science. In…

Quantum Physics · Physics 2023-11-02 Atta ur Rahman , S. M. Zangi , Ma-Cheng Yang , Cong-Feng Qiao