Communication Enhancement through Quantum Coherent Control of N Channels in an Indefinite Causal-Order Scenario

In quantum Shannon theory, transmission of information is enhanced by quantum features. Up to very recently, the trajectories of transmission remained fully classical. Recently, a new paradigm was proposed by playing quantum tricks on two completely depolarizing quantum channels i.e., using coherent control in space or time of the two quantum channels. We extend here this control to the transmission of information through a network of an arbitrary number N of channels with arbitrary individual capacity i.e., information preservation characteristics in the case of indefinite causal order. We propose a formalism to assess information transmission in the most general case of N channels in an indefinite causal order scenario yielding the output of such transmission. Then, we explicitly derive the quantum switch output and the associated Holevo limit of the information transmission for N = 2 , N = 3 as a function of all involved parameters. We find in the case N = 3 that the transmission of information for three channels is twice that of transmission of the two-channel case when a full superposition of all possible causal orders is used.

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Performance characterization of Pauli channels assisted by indefinite causal order and post-measurement

Quantum Information and Computation ◽

10.26421/qic20.15-16-1 ◽

2020 ◽

Vol 20 (15&16) ◽

pp. 1261-1280

Author(s):

Francisco Delgado ◽

Carlos Cardoso-Isidoro

Keyword(s):

Quantum Channel ◽

Communication Channel ◽

Quantum Communication ◽

Quantum Channels ◽

Causal Order ◽

Combined Process ◽

Performance Characterization ◽

Output State ◽

Transmission Of Information

Indefinite causal order has introduced disruptive procedures to improve the fidelity of quantum communication by introducing the superposition of { orders} on a set of quantum channels. It has been applied to several well characterized quantum channels as depolarizing, dephasing and teleportation. This work analyses the behavior of a parametric quantum channel for single qubits expressed in the form of Pauli channels. Combinatorics lets to obtain affordable formulas for the analysis of the output state of the channel when it goes through a certain imperfect quantum communication channel when it is deployed as a redundant application of it under indefinite causal order. In addition, the process exploits post-measurement on the associated control to select certain components of transmission. Then, the fidelity of such outputs is analysed to characterize the generic channel in terms of its parameters. As a result, we get notable enhancement in the transmission of information for well characterized channels due to the combined process: indefinite causal order plus post-measurement.

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Quantum capacity analysis of multi-level amplitude damping channels

Communications Physics ◽

10.1038/s42005-021-00524-4 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Stefano Chessa ◽

Vittorio Giovannetti

Keyword(s):

Finite Dimension ◽

Quantum Systems ◽

Capacity Analysis ◽

Quantum Channels ◽

Shannon Theory ◽

Amplitude Damping ◽

Quantum Capacity ◽

Multi Level ◽

Quantum Shannon Theory ◽

Special Case

AbstractEvaluating capacities of quantum channels is the first purpose of quantum Shannon theory, but in most cases the task proves to be very hard. Here, we introduce the set of Multi-level Amplitude Damping quantum channels as a generalization of the standard qubit Amplitude Damping Channel to quantum systems of finite dimension d. In the special case of d = 3, by exploiting degradability, data-processing inequalities, and channel isomorphism, we compute the associated quantum and private classical capacities for a rather wide class of maps, extending the set of models whose capacity can be computed known so far. We proceed then to the evaluation of the entanglement assisted quantum and classical capacities.

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Communication through coherent control of quantum channels

Quantum ◽

10.22331/q-2020-09-24-333 ◽

2020 ◽

Vol 4 ◽

pp. 333

Author(s):

Alastair A. Abbott ◽

Julian Wechs ◽

Dominic Horsman ◽

Mehdi Mhalla ◽

Cyril Branciard

Keyword(s):

Quantum Channel ◽

Coherent Control ◽

Target System ◽

Joint Control ◽

Quantum Channels ◽

Causal Order ◽

Quantum Superposition ◽

Recent Letter ◽

Output State ◽

Specific Implementation

A completely depolarising quantum channel always outputs a fully mixed state and thus cannot transmit any information. In a recent Letter\cite{ebler18}, it was however shown that if a quantum state passes through two such channels in a quantum superposition of different orders---a setup known as the ``quantum switch''---then information can nevertheless be transmitted through the channels. Here, we show that a similar effect can be obtained when one coherently controls between sending a target system through one of two identical depolarising channels. Whereas it is tempting to attribute this effect in the quantum switch to the indefinite causal order between the channels, causal indefiniteness plays no role in this new scenario. This raises questions about its role in the corresponding effect in the quantum switch. We study this new scenario in detail and we see that, when quantum channels are controlled coherently, information about their specific implementation is accessible in the output state of the joint control-target system. This allows two different implementations of what is usually considered to be the same channel to therefore be differentiated. More generally, we find that to completely describe the action of a coherently controlled quantum channel, one needs to specify not only a description of the channel (e.g., in terms of Kraus operators), but an additional ``transformation matrix'' depending on its implementation.

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Quantum Shannon theory with superpositions of trajectories

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.2018.0903 ◽

2019 ◽

Vol 475 (2225) ◽

pp. 20180903 ◽

Cited By ~ 10

Author(s):

Giulio Chiribella ◽

Hlér Kristjánsson

Keyword(s):

Transmission Lines ◽

Internal State ◽

Quantum Systems ◽

Space Time ◽

Shannon Theory ◽

Classical Systems ◽

Theory Of Information ◽

Quantum Shannon Theory ◽

Quantum Counterpart ◽

Multiple Transmission

Shannon's theory of information was built on the assumption that the information carriers were classical systems. Its quantum counterpart, quantum Shannon theory, explores the new possibilities arising when the information carriers are quantum systems. Traditionally, quantum Shannon theory has focused on scenarios where the internal state of the information carriers is quantum, while their trajectory is classical. Here we propose a second level of quantization where both the information and its propagation in space–time is treated quantum mechanically. The framework is illustrated with a number of examples, showcasing some of the counterintuitive phenomena taking place when information travels simultaneously through multiple transmission lines.

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Individual Differences and Reliability of Information Transmission in Absolute Judgments of Loudness, Brightness and Line Lengths

Perceptual and Motor Skills ◽

10.2466/pms.1974.39.1.239 ◽

1974 ◽

Vol 39 (1) ◽

pp. 239-246 ◽

Cited By ~ 2

Author(s):

Stephen G. Landau ◽

Monte S. Buchsbaum ◽

Richard Coppola ◽

Miriam Sihvonen

Keyword(s):

Central Nervous System ◽

Nervous System ◽

Information Transmission ◽

Digit Span ◽

Line Length ◽

Intelligence Scale ◽

Transmission Of Information ◽

Processing Facility ◽

The Central Nervous System ◽

The Mean

Information transmission, as estimated from absolute judgments of loudness, brightness and line length, was measured in 35 normal Ss. Each S was tested on all modalities on each of three days. Individuals varied widely in their ability to transmit information and were consistent across modalities and days; reliabilities for loudness, brightness and line length between Days 2 and 3 were 0.72, 0.81, and 0.89 respectively. The mean intercorrelation between modalities was 0.40. WAIS Digit Span but no other intelligence scale was positively correlated with transmission of information. The results suggest the existence of a single information-processing facility in the central nervous system.

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Asymptotic Performance of Port-Based Teleportation

Communications in Mathematical Physics ◽

10.1007/s00220-020-03884-0 ◽

2020 ◽

Author(s):

Matthias Christandl ◽

Felix Leditzky ◽

Christian Majenz ◽

Graeme Smith ◽

Florian Speelman ◽

...

Keyword(s):

Matrix Theory ◽

Building Blocks ◽

Convergence Result ◽

Dirichlet Eigenvalue ◽

Shannon Theory ◽

Optimal Protocol ◽

Local Quantum ◽

Non Local ◽

Fixed Input ◽

Quantum Shannon Theory

AbstractQuantum teleportation is one of the fundamental building blocks of quantum Shannon theory. While ordinary teleportation is simple and efficient, port-based teleportation (PBT) enables applications such as universal programmable quantum processors, instantaneous non-local quantum computation and attacks on position-based quantum cryptography. In this work, we determine the fundamental limit on the performance of PBT: for arbitrary fixed input dimension and a large number N of ports, the error of the optimal protocol is proportional to the inverse square of N. We prove this by deriving an achievability bound, obtained by relating the corresponding optimization problem to the lowest Dirichlet eigenvalue of the Laplacian on the ordered simplex. We also give an improved converse bound of matching order in the number of ports. In addition, we determine the leading-order asymptotics of PBT variants defined in terms of maximally entangled resource states. The proofs of these results rely on connecting recently-derived representation-theoretic formulas to random matrix theory. Along the way, we refine a convergence result for the fluctuations of the Schur–Weyl distribution by Johansson, which might be of independent interest.

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Substantiation of Vulnerabilities in Various Secure Routing Protocols of MANET

Forensic Investigations and Risk Management in Mobile and Wireless Communications - Advances in Wireless Technologies and Telecommunication ◽

10.4018/978-1-5225-9554-0.ch007 ◽

2020 ◽

pp. 168-194

Author(s):

Sherin Zafar ◽

Samia Khan ◽

Nida Iftekhar ◽

Siddhartha Sankar Biswas

Keyword(s):

Information Transmission ◽

Routing Protocols ◽

Ad Hoc ◽

Secure Routing ◽

Network Layer ◽

Transmission Of Information ◽

Secure Routing Protocols ◽

Remote System

This chapter overviews and characterizes the protected steering convention in MANET, and furthermore, it discusses the proposed technique for alleviating those assaults. In the directing convention of the MANET while sending information bundles to different hubs, some middle hubs remove helpful data parcels and can't advance the parcel to the following hub. Some hubs may change the substance of bundles amid the information transmission session. In this way, secured transmission of information and different security administrations are the first necessity of MANET like some other foundation remote system. Ad-hoc arranges face different assaults like detached listening (passive eavesdropping) and dynamic obstruction, limiting source hub from finding the goal and system parcel. Ensuring the network layer usefulness is the most significant objective of system layer security plan for MANET, which prompts verified conveyance of bundles between the versatile hubs through multi-bounce sending.

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Improving the quality of noisy spatial quantum channels

Quantum Information and Computation ◽

10.26421/qic15.7-8-3 ◽

2015 ◽

Vol 15 (7&8) ◽

pp. 568-581

Author(s):

Ning Tang ◽

Zi-Long Fan ◽

Hao-Sheng Zeng

Keyword(s):

Information Transmission ◽

Quantum Channel ◽

Physical Mechanism ◽

Time Dependent ◽

Quantum Channels ◽

Markovian Model ◽

Quality Of Information

We show, for the non-Markovian or time-dependent Markovian model of noise, by breaking the noisy spatial quantum channel (SQC) into a series of periodically arranged sub-components, that the quality of information transmission described by the purity, fidelity and concurrence of the output states can be improved. The physical mechanism and possible implementation of the idea have been discussed.

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