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

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.

scholarly journals Communication through coherent control of quantum channels

Quantum ◽  
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.

scholarly journals NUMERICAL CHARACTERIZATION OF ATMOSPHERIC EFFECTS ON AN EARTH–SPACE QUANTUM COMMUNICATION CHANNEL

2007 ◽  
Vol 05 (01n02) ◽  
pp. 241-248 ◽  
Author(s):  
N. ANTONIETTI ◽  
M. MONDIN ◽  
G. BRIDA ◽  
M. GENOVESE
Keyword(s):  
Free Space ◽  
Communication Channel ◽  
Quantum Communication ◽  
Single Photon ◽  
Atmospheric Effects ◽  
Single Photons ◽  
Atmospheric Conditions ◽  
Numerical Characterization ◽  
Simulation Results

Quantum communication in free space is the next challenge of telecommunications. Since we want to determine the outcome of a quantum communication by means of single photons, we must understand how a single photon interacts with the atmosphere. In this brief article, some simulation results for realistic and generic atmospheric conditions are reported and discussed.

AUTHENTICATED QUANTUM KEY DISTRIBUTION WITHOUT CLASSICAL COMMUNICATION

2007 ◽  
Vol 17 (03) ◽  
pp. 323-335 ◽  
Author(s):  
NAYA NAGY ◽  
SELIM G. AKL
Keyword(s):  
Quantum Channel ◽  
Quantum Key Distribution ◽  
Communication Channel ◽  
Quantum Communication ◽  
Key Distribution ◽  
Secret Key ◽  
Classical Communication ◽  
Quantum Communication Channel ◽  
High Security ◽  
Public Keys

The aim of quantum key distribution protocols is to establish a secret key among two parties with high security confidence. Such algorithms generally require a quantum channel and an authenticated classical channel. This paper presents a totally new perception of communication in such protocols. The quantum communication alone satisfies all needs of array communication between the two parties. Even so, the quantum communication channel does not need to be protected or authenticated whatsoever. As such, our algorithm is a purely quantum key distribution algorithm. The only certain identification of the two parties is through public keys.

scholarly journals Towards joint reconstruction of noise and losses in quantum channels

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
F. Piacentini ◽  
A. Avella ◽  
P. Traina ◽  
L. Lolli ◽  
E. Taralli ◽  
...  
Keyword(s):  
Quantum Channel ◽  
Quantum Communication ◽  
Photon Number ◽  
Practical Implementation ◽  
Quantum Metrology ◽  
Quantum Channels ◽  
Transmission Losses ◽  
Single Measurement ◽  
Joint Reconstruction

AbstractThe calibration of a quantum channel, i.e. the determination of the transmission losses affecting it, is definitely one of the principal objectives in both the quantum communication and quantum metrology frameworks. Another task of the utmost relevance is the identification, e.g. by extracting its photon number distribution, of the noise potentially present in the channel.Here we present a protocol, based on the response of a photon-number-resolving detector at different quantum efficiencies, able to accomplish both of these tasks at once, providing with a single measurement an estimate of the transmission losses as well as the photon statistics of the noise present in the exploited quantum channel.We show and discuss the experimental results obtained in the practical implementation of such protocol, with different kinds and levels of noise.

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

Entropy ◽  
2019 ◽  
Vol 21 (10) ◽  
pp. 1012 ◽  
Author(s):  
Lorenzo M. Procopio ◽  
Francisco Delgado ◽  
Marco Enríquez ◽  
Nadia Belabas ◽  
Juan Ariel Levenson
Keyword(s):  
Information Transmission ◽  
Coherent Control ◽  
Quantum Channels ◽  
New Paradigm ◽  
Causal Order ◽  
Shannon Theory ◽  
Information Preservation ◽  
Transmission Of Information ◽  
Individual Capacity ◽  
Quantum Shannon Theory

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.

scholarly journals On the one-shot zero-error classical capacity of classical-quantum channels assisted by quantum non-signalling correlations

2017 ◽  
Vol 17 (5&6) ◽  
pp. 380-398
Author(s):  
Ching-Yi Lai ◽  
Runyao Duan
Keyword(s):  
Quantum Channel ◽  
Quantum Communication ◽  
Semidefinite Program ◽  
Circulant Graph ◽  
Quantum Channels ◽  
Kraus Operator ◽  
Cyclotomic Cosets ◽  
Classical Capacity ◽  
Classical Quantum ◽  
The One

Duan and Winter studied the one-shot zero-error classical capacity of a quantum channel assisted by quantum non-signalling correlations, and formulated this problem as a semidefinite program depending only on the Kraus operator space of the channel. For the class of classical-quantum channels, they showed that the asymptotic zero-error classical capacity assisted by quantum non-signalling correlations, minimized over all classicalquantum channels with a confusability graph G, is exactly log ϑ(G), where ϑ(G) is the celebrated Lov´asz theta function. In this paper, we show that the one-shot capacity for a classical-quantum channel, induced from a circulant graph G defined by equal-sized cyclotomic cosets, is logbϑ(G)c, which further implies that its asymptotic capacity is log ϑ(G). This type of graphs include the cycle graphs of odd length, the Paley graphs of prime vertices, and the cubit residue graphs of prime vertices. Examples of other graphs are also discussed. This gives Lov´asz ϑ function another operational meaning in zero-error classical-quantum communication.

REMOTE STATE PREPARATION IN NON-MARKOVIAN ENVIRONMENT

2012 ◽  
Vol 10 (03) ◽  
pp. 1250030 ◽  
Author(s):  
YANLIANG ZHANG ◽  
QINGPING ZHOU ◽  
GUODONG KANG ◽  
FANG ZHOU ◽  
XIAOBO WANG
Keyword(s):  
Quantum Channel ◽  
Communication Channel ◽  
Quantum Communication ◽  
Remote State Preparation ◽  
Entangled States ◽  
Particle State ◽  
Noisy Environments ◽  
Initial State ◽  
State Preparation ◽  
Over Time

We present a scheme for remote preparing a general two-particle state by two entangled states serving as the quantum communication channel. In this scheme, it is possible for the receiver to perfectly reconstruct the initial state that the sender hopes to prepare with the method of introducing an auxiliary qubit and postselection measurements in the situation of non-maximal entangled quantum channel. Furthermore, we investigate the influence of the dissipation factors on the processing of the remote state preparation when the entangled resources are in the Markovian and non-Markovian noisy environments. It is shown that the fidelity of remote state preparation is decreasing exponentially over time in Markovian environments and attenuating oscillatorily in non-Markovian. However, when the non-Markovian and the detuning conditions are satisfied simultaneously, the fidelity can be preserved at comparative high levels, effectively.

scholarly journals Device-independent tests of quantum channels

2017 ◽  
Vol 473 (2199) ◽  
pp. 20160721 ◽  
Author(s):  
Michele Dall’Arno ◽  
Sarah Brandsen ◽  
Francesco Buscemi
Keyword(s):  
Closed Form ◽  
Quantum Channel ◽  
Arbitrary Dimension ◽  
Quantum Channels ◽  
Input Output ◽  
Amplitude Damping ◽  
Universal Cloning

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 the set of input–output correlations compatible with any arbitrary given quantum channel. For binary (i.e. two input symbols, two output symbols) correlations, we show that extremal correlations are always achieved by orthogonal encodings and measurements, irrespective of whether or not the channel preserves commutativity. We further provide a full, closed-form characterization of the sets of binary correlations in the case of: (i) any dihedrally covariant qubit channel (such as any Pauli and amplitude-damping channels) and (ii) any universally-covariant commutativity-preserving channel in an arbitrary dimension (such as any erasure, depolarizing, universal cloning and universal transposition channels).

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