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This paper investigates the design of the capacity-achieving input distribution for the discrete-time Poisson channel (DTPC) under dark current effects with low-precision analog-to-digital converters (ADCs). This study introduces an…

Signal Processing · Electrical Eng. & Systems 2025-09-23 Qianqian Li , Lintao Li , Lixiang Liu , Lei Yang , Caihong Gong , Hua Li , Shiya Hao , Xiaoming Dai

We consider the task of estimating the expectation value of an $n$-qubit tensor product observable $O_1\otimes O_2\otimes \cdots \otimes O_n$ in the output state of a shallow quantum circuit. This task is a cornerstone of variational…

Quantum Physics · Physics 2021-03-11 Sergey Bravyi , David Gosset , Ramis Movassagh

We improve the space complexity of Karatsuba multiplication on a quantum computer from $O(n^{1.427})$ to $O(n)$ while maintaining $O(n^{\lg 3})$ gate complexity. We achieve this by ensuring recursive calls can add their outputs directly…

Quantum Physics · Physics 2019-04-17 Craig Gidney

The aim of this work is to study the zero-error capacity of pure-state classical-quantum channels in the setting of list decoding. We provide an achievability bound for list-size two and a converse bound holding for every fixed list size.…

Quantum Physics · Physics 2026-04-17 Marco Dalai , Filippo Girardi , Ludovico Lami

We apply numerical optimization and linear algebra algorithms for classical computers to the problem of automatically synthesizing algorithms for quantum computers. Using our framework, we apply several common techniques from these…

Numerical Analysis · Mathematics 2025-09-16 Yuxin Huang , Benjamin E. Grossman-Ponemon , David A. B. Hyde

Recently the theory of communication developed by Shannon has been extended to the quantum realm by exploiting the rules of quantum theory. This latter stems on complex vector spaces. However complex (as well as real) numbers are just…

Information Theory · Computer Science 2018-04-23 Samad Khabbazi Oskouei , Stefano Mancini

We present quantum algorithms to efficiently perform discriminant analysis for dimensionality reduction and classification over an exponentially large input data set. Compared with the best-known classical algorithms, the quantum algorithms…

Quantum Physics · Physics 2016-07-12 Iris Cong , Luming Duan

We show that entirely quantum Shannon theoretic methods, based on von Neumann entropies and their properties, can be used to derive Singleton bounds on the performance of entanglement-assisted hybrid classical-quantum (EACQ) error…

Quantum Physics · Physics 2024-09-25 Manideep Mamindlapally , Andreas Winter

The present work continues investigation of the capacities of measurement (quantum-classical) channels in the most general setting, initiated in~\cite{HCT}. The proof of coding theorems is given for the classical capacity and…

Quantum Physics · Physics 2014-08-15 A. A. Kuznetsova , A. S. Holevo

The entanglement-assisted classical capacity of a noisy quantum channel is the amount of information per channel use that can be sent over the channel in the limit of many uses of the channel, assuming that the sender and receiver have…

Quantum Physics · Physics 2007-05-23 Charles H. Bennett , Peter W. Shor , John A. Smolin , Ashish V. Thapliyal

Variational quantum algorithms are the centerpiece of modern quantum programming. These algorithms involve training parameterized quantum circuits using a classical co-processor, an approach adapted partly from classical machine learning.…

Quantum Physics · Physics 2022-11-09 V. Akshay , H. Philathong , E. Campos , D. Rabinovich , I. Zacharov , Xiao-Ming Zhang , J. Biamonte

We generalize the Approximate Quantum Compiling algorithm into a new method for CNOT-depth reduction, which is apt to process wide target quantum circuits. Combining this method with state-of-the-art techniques for error mitigation and…

The classical product state capacity of a noisy quantum channel with memory is investigated. A forgetful noise-memory channel is constructed by Markov switching between two depolarizing channels which introduces non-Markovian noise…

Quantum Physics · Physics 2009-06-23 Jeroen Wouters , Ismail Akhalwaya , Mark Fannes , Francesco Petruccione

The recent paper (IEEE Trans. IT 69, 1680) introduced an analytical method for calculating the channel capacity without the need for iteration. This method has certain limitations that restrict its applicability. Furthermore, the paper does…

Information Theory · Computer Science 2024-03-15 Masahito Hayashi

Estimating the unitarity of an unknown quantum channel $\mathcal{E}$ provides information on how much it is unitary, which is a basic and important problem in quantum device certification and benchmarking. Unitarity estimation can be…

Quantum Physics · Physics 2026-02-23 Kean Chen , Qisheng Wang , Peixun Long , Mingsheng Ying

The classical capacity of a quantum channel with arbitrary Markovian correlated noise is evaluated. For the general case of a channel with long-term memory, which corresponds to a Markov chain which does not converge to equilibrium, the…

Quantum Physics · Physics 2015-05-13 Nilanjana Datta , Tony Dorlas

Determining the optimal fidelity for the transmission of quantum information over noisy quantum channels is one of the central problems in quantum information theory. Recently, [Berta-Borderi-Fawzi-Scholz, Mathematical Programming, 2021]…

Quantum Physics · Physics 2026-04-21 Yeow Meng Chee , Hoang Ta , Van Khu Vu

We consider process tomography for unitary quantum channels. Given access to an unknown unitary channel acting on a $\textsf{d}$-dimensional qudit, we aim to output a classical description of a unitary that is $\varepsilon$-close to the…

Quantum Physics · Physics 2024-07-31 Jeongwan Haah , Robin Kothari , Ryan O'Donnell , Ewin Tang

We study optimal rates for quantum communication over a single use of a channel, which itself can correspond to a finite number of uses of a channel with arbitrarily correlated noise. The corresponding capacity is often referred to as the…

Quantum Physics · Physics 2010-03-19 Francesco Buscemi , Nilanjana Datta

An important distinction in our understanding of capacities of classical versus quantum channels is marked by the following question: is there an algorithm which can compute (or even efficiently compute) the capacity? While there is…

Quantum Physics · Physics 2026-03-31 Archishna Bhattacharyya , Arthur Mehta , Yuming Zhao