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We consider a line with noise in the simplest case. Loss does not add noise. Amplification via phase insensitive amplifiers do add noise. A lower bound of this capacity is the quantum analog to the Shannon capacity of a linear channel with…

Quantum Physics · Physics 2013-03-05 Antonio Mecozzi

Quantum communication is an important branch of quantum information science, promising unconditional security to classical communication and providing the building block of a future large-scale quantum network. Noise in realistic quantum…

Quantum Physics · Physics 2020-01-24 Kyungjoo Noh , Stefano Pirandola , Liang Jiang

The quantum capacity of thermal noise channel is studied. The extremal input state is obtained at the postulation that the coherent information is convex or concave at its vicinity. When the input energy tends to infinitive, it is verified…

Quantum Physics · Physics 2007-05-23 Xiao-yu Chen

The communication complexity of a quantum channel is the minimal amount of classical communication required for classically simulating a process of state preparation, transmission through the channel and subsequent measurement. It…

Quantum Physics · Physics 2012-09-14 Alberto Montina

We investigate the capacity of three symmetric quantum states in three real dimensions to carry classical information. Several such capacities have already been defined, depending on what operations are allowed in the sending and receiving…

Quantum Physics · Physics 2007-05-23 Peter W. Shor

We show that when coherent-state encoding is employed in conjunction with coherent detection, the Bosonic broadcast channel is equivalent to a classical degraded Gaussian broadcast channel whose capacity region is dual to that of the…

Quantum Physics · Physics 2007-05-23 Saikat Guha , Jeffrey H. Shapiro

We consider classical-quantum (cq-)channels with memory, and establish that Ar{\i}kan-constructed polar codes achieve the classical capacity for two key noise models, namely for (i) qubit erasures and (ii) unital qubit noise with channel…

Quantum Physics · Physics 2025-12-03 Jaswanthi Mandalapu , Vikesh Siddhu , Krishna Jagannathan

We investigate the limits of communication over the discrete-time Additive White Gaussian Noise (AWGN) channel, when the channel output is quantized using a small number of bits. We first provide a proof of our recent conjecture on the…

Information Theory · Computer Science 2008-05-15 Jaspreet Singh , Onkar Dabeer , Upamanyu Madhow

Two new classes of quantum channels, which we call more capable and less noisy, are introduced. The more capable class consists of channels such that the quantum capacities of the complementary channels to the environments are zero. The…

Quantum Physics · Physics 2012-01-26 Shun Watanabe

A long-standing problem on the classical capacity of bosonic Gaussian channels has recently been resolved by proving the minimum output entropy conjecture. It is also known that the ultimate capacity quantified by the Holevo bound can be…

Quantum Physics · Physics 2015-05-07 Jaehak Lee , Se-Wan Ji , Jiyong Park , Hyunchul Nha

The capacity of multiple-input multiple-output additive white Gaussian noise channels is investigated under peak amplitude constraints on the norm of the input vector. New insights on the capacity-achieving input distribution are presented.…

Information Theory · Computer Science 2021-05-06 Antonino Favano , Marco Ferrari , Maurizio Magarini , Luca Barletta

A classification of one-mode Gaussian channels is given up to canonical unitary equivalence. A complementary to the quantum channel with additive classical Gaussian noise is described providing an example of one-mode Gaussian channel which…

Quantum Physics · Physics 2010-12-30 A. S. Holevo

We give a capacity formula for the classical information transmission over a noisy quantum channel, with separable encoding by the sender and limited resources provided by the receiver's pre-shared ancilla. Instead of a pure state, we…

Quantum Physics · Physics 2017-05-22 Quntao Zhuang , Elton Yechao Zhu , Peter W. Shor

We addressed the question of optimality of private quantum channels. We have shown that the Shannon entropy of the classical key necessary to securely transfer the quantum information is lower bounded by the entropy exchange of the private…

Quantum Physics · Physics 2009-11-13 Jan Bouda , Mario Ziman

We propose and experimentally demonstrate an efficient framework for the quantum simulation of quantum channels in NMR. Our approach relies on the suitable decomposition of non-unitary operators in a linear combination of $d$ unitary ones,…

Quantum Physics · Physics 2017-12-19 Tao Xin , Shi-Jie Wei , Julen S. Pedernales , Enrique Solano , Gui-Lu Long

The simplest building blocks for quantum computations are the qubit-qubit quantum channels. In this paper, we analyze the structure of these channels via their Choi representation. The restriction of a quantum channel to the space of…

Mathematical Physics · Physics 2023-07-24 Attila Lovas , Attila Andai

Evaluating the quantum capacity of quantum channels is an important but difficult problem, even for channels of low input and output dimension. Smith and Smolin showed that the quantum capacity of the Clifford-twirl of a qubit amplitude…

Quantum Physics · Physics 2021-10-12 Yingkai Ouyang

Two partial orderings among communication channels, namely, `being degradable into' and `being less noisy than,' are reconsidered in the light of recent results about statistical comparisons of quantum channels. Though our analysis covers…

Quantum Physics · Physics 2016-12-01 Francesco Buscemi

The quantum analog of the classical erasure channel provides a simple example of a channel whose asymptotic capacity for faithful transmission of intact quantum states, with and without the assistance of a two-way classical side channel,…

Quantum Physics · Physics 2008-11-26 Charles H. Bennett , David P. DiVincenzo , John A. Smolin

We consider ergodic causal classical-quantum channels (cq-channels) which additionally have a decaying input memory. In the first part we develop some structural properties of ergodic cq-channels and provide equivalent conditions for…

Quantum Physics · Physics 2016-11-18 Igor Bjelakovic , Holger Boche