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As we enter the era of useful quantum computers we need to better understand the limitations of classical support hardware, and develop mitigation techniques to ensure effective qubit utilisation. In this paper we discuss three key…

Quantum Physics · Physics 2020-09-21 James R. Cruise , Neil I. Gillespie , Brendan Reid

For a continuous-input-continuous-output arbitrarily distributed quantum channel carrying classical information, the channel capacity can be computed in terms of the distribution of the channel envelope, received signal strength over a…

Information Theory · Computer Science 2022-06-09 Mouli Chakraborty , Harun Siljak , Indrakshi Dey , Nicola Marchetti

We address the issue of improving the quality of the joint remote preparation of an arbitrary two-qubit in case four qubits of the quantum channel which consists of a GHZ state and a GHZ-like one are subjected to noises. Two controlling…

Quantum Physics · Physics 2017-03-21 Thanh Dat Le , Van Hop Nguyen

We develop a device-independent framework for testing quantum channels. That is, we falsify a hypothesis about a quantum channel based only on an observed set of input-output correlations. Formally, the problem consists of characterizing…

Quantum Physics · Physics 2017-03-17 Michele Dall'Arno , Sarah Brandsen , Francesco Buscemi

Quantum technologies rely on the ability to coherently manipulate, process and transfer information, encoded in quantum states, along quantum channels. Decoherence induced by the environment introduces errors, thus setting limits on the…

Quantum Physics · Physics 2013-01-14 Bogna Bylicka , Dariusz Chruściński , Sabrina Maniscalco

The quantum channel capacity gives the ultimate limit for the rate at which quantum data can be reliably transmitted through a noisy quantum channel. Degradable quantum channels are among the few channels whose quantum capacities are known.…

Quantum Physics · Physics 2011-03-31 Markus Grassl , Zhengfeng Ji , Zhaohui Wei , Bei Zeng

To avoid prohibitive overheads in performing fault-tolerant quantum computation, the decoding problem needs to be solved accurately and at speeds sufficient for fast feedback. Existing decoding systems fail to satisfy both of these…

The concept of negative probabilities can be used to decompose the interaction of two qubits mediated by a quantum controlled-NOT into three operations that require only classical interactions (that is, local operations and classical…

Quantum Physics · Physics 2009-06-16 Holger F. Hofmann

Superdense Coding is a cornerstone in secure quantum communication, exploiting pre-shared entanglement to encode two classical bits within a single qubit. However, noise and decoherence deteriorate entanglement quality, restricting both…

Quantum Physics · Physics 2025-04-18 Syed Emad Uddin Shubha , Tasnuva Farheen

Non-local quantum computation (NLQC) replaces a local interaction between two systems with a single round of communication and shared entanglement. Despite many partial results, it is known that a characterization of entanglement cost in at…

Quantum Physics · Physics 2025-06-02 Andreas Bluhm , Simon Höfer , Alex May , Mikka Stasiuk , Philip Verduyn Lunel , Henry Yuen

It is well-known that simulating quantum circuits with low but non-zero hardware noise is more difficult than without noise. It requires either to perform density matrix simulations (coming with a space overhead) or to sample over "quantum…

Quantum Physics · Physics 2025-02-28 Etienne Granet , Kévin Hémery , Henrik Dreyer

In the current quantum computing paradigm, significant focus is placed on the reduction or mitigation of quantum decoherence. When designing new quantum processing units, the general objective is to reduce the amount of noise qubits are…

Quantum Physics · Physics 2026-02-17 Viacheslav Kuzmin , Wilfrid Somogyi , Ekaterina Pankovets , Alexey Melnikov

We consider fault-tolerant quantum computation in the context where there are no fresh ancilla qubits available during the computation, and where the noise is due to a general quantum channel. We show that there are three classes of noisy…

Quantum Physics · Physics 2013-01-11 Michael Ben-Or , Daniel Gottesman , Avinatan Hassidim

It has been more than 20 years since Deutsch and Hayden demonstrated that quantum systems can be completely described locally -- notwithstanding Bell's theorem. More recently, Raymond-Robichaud proposed two other approaches to the same…

Quantum Physics · Physics 2021-02-25 Charles Alexandre Bédard

Quantum computers have enabled solving problems beyond the current computers' capabilities. However, this requires handling noise arising from unwanted interactions in these systems. Several protocols have been proposed to address efficient…

Quantum Physics · Physics 2021-09-14 Ali Shaib , Mohamad H. Naim , Mohammed E. Fouda , Rouwaida Kanj , Fadi Kurdahi

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

We show that a local channel cannot create quantum discord (QD) for zero QD states of size $d\geq3$ if and only if either it is a completely decohering channel or it is a nontrivial isotropic channel. For the qubit case this propertiy is…

Quantum Physics · Physics 2013-04-01 Yu Guo , Jinchuan Hou

We propose a scheme to implement quantum computation in decoherence-free subspace with superconducting devices inside a cavity by unconventional geometric manipulation. Universal single-qubit gates in encoded qubit can be achieved with…

Quantum Physics · Physics 2009-09-08 Zheng-Yuan Xue , Shi-Liang Zhu , Z. D. Wang

Noise and errors are unavoidable in any realistic quantum process, including processes designed to reduce noise and errors in the first place. In particular, quantum thermodynamical protocols for cooling can be significantly affected,…

Quantum Physics · Physics 2026-01-26 Jian Li , Xiaoyang Wang , Marcus Huber , Nicolai Friis , Pharnam Bakhshinezhad

Quantum machine learning models have the potential to offer speedups and better predictive accuracy compared to their classical counterparts. However, these quantum algorithms, like their classical counterparts, have been shown to also be…

Quantum Physics · Physics 2021-05-27 Maurice Weber , Nana Liu , Bo Li , Ce Zhang , Zhikuan Zhao