scholarly journals Bidirectional coherent classical communication

2005 ◽  
Vol 5 (4&5) ◽  
pp. 380-395
Author(s):  
A.W. Harrow ◽  
D.W. Leung
Keyword(s):  
Quantum Communication ◽  
The Other ◽  
Achievable Rate ◽  
Classical Communication ◽  
Communication Capacity ◽  
Coherent Communication

A unitary interaction coupling two parties enables quantum or classical communication in both the forward and backward directions. Each communication capacity can be thought of as a tradeoff between the achievable rates of specific types of forward and backward communication. Our first result shows that for any bipartite unitary gate, bidirectional coherent classical communication is no more difficult than bidirectional classical communication --- they have the same achievable rate regions. Previously this result was known only for the unidirectional capacities (i.e., the boundaries of the tradeoff). We then relate the tradeoff for two-way coherent communication to the tradeoff for two-way quantum communication and the tradeoff for coherent communication in one direction and quantum communication in the other.

Superdense Coding and Quantum Teleportation

2006 ◽  
Author(s):  
Phillip Kaye ◽  
Raymond Laflamme ◽  
Michele Mosca
Keyword(s):  
Quantum Teleportation ◽  
Communication Channel ◽  
Quantum Communication ◽  
Communication Protocols ◽  
Bell State ◽  
Third Party ◽  
Classical Communication ◽  
Superdense Coding ◽  
Communication Task ◽  
Epr Pair

We are now ready to look at our first protocols for quantum information. In this section, we examine two communication protocols which can be implemented using the tools we have developed in the preceding sections. These protocols are known as superdense coding and quantum teleportation. Both are inherently quantum: there are no classical protocols which behave in the same way. Both involve two parties who wish to perform some communication task between them. In descriptions of such communication protocols (especially in cryptography), it is very common to name the two parties ‘Alice’ and ‘Bob’, for convenience. We will follow this tradition. We will repeatedly refer to communication channels. A quantum communication channel refers to a communication line (e.g. a fiberoptic cable), which can carry qubits between two remote locations. A classical communication channel is one which can carry classical bits (but not qubits).1 The protocols (like many in quantum communication) require that Alice and Bob initially share an entangled pair of qubits in the Bell state The above Bell state is sometimes referred to as an EPR pair. Such a state would have to be created ahead of time, when the qubits are in a lab together and can be made to interact in a way which will give rise to the entanglement between them. After the state is created, Alice and Bob each take one of the two qubits away with them. Alternatively, a third party could create the EPR pair and give one particle to Alice and the other to Bob. If they are careful not to let them interact with the environment, or any other quantum system, Alice and Bob’s joint state will remain entangled. This entanglement becomes a resource which Alice and Bob can use to achieve protocols such as the following. Suppose Alice wishes to send Bob two classical bits of information. Superdense coding is a way of achieving this task over a quantum channel, requiring only that Alice send one qubit to Bob. Alice and Bob must initially share the Bell state Suppose Alice is in possession of the first qubit and Bob the second qubit.

scholarly journals Joint Source and Relay Beamforming Design in Wireless Multi-Hop Sensor Networks with SWIPT

Sensors ◽  
2019 ◽  
Vol 19 (1) ◽  
pp. 182 ◽  
Author(s):  
Xiaoqing Liu ◽  
Zhigang Wen ◽  
Dan Liu ◽  
Junwei Zou ◽  
Shan Li
Keyword(s):  
Energy Harvesting ◽  
Multiple Input Multiple Output ◽  
The Other ◽  
Achievable Rate ◽  
Power Splitting ◽  
Amplify And Forward ◽  
Time Switching ◽  
Multiple Input ◽  
Convex Problem ◽  
Input Multiple Output

We consider a multiple-input multiple-output amplify-and-forward wireless multiple-hop sensor network (WMSN). The simultaneous wireless information and power transfer technology is deployed to potentially achieve an autonomous system. We investigate two practical receiver schemes, which are the power splitting (PS) and the time switching (TS). The power splitting receiver splits received signals into two streams, one for information decoding (ID) and the other for energy harvesting (EH). On the other hand, the time switching receiver only serves in ID mode or energy harvesting mode during a certain time slot. Subject to transmit power constraints and destination harvested energy constraint, we aim to obtain a joint beam-forming solution of source and relay precoders to maximize the maximum achievable rate of the WSN. In order to make the non-convex problem tractable, diagonalization-based alternating optimization algorithms are proposed. Numerical results show the convergence and good performance of the proposed algorithms under both PS and TS protocols.

scholarly journals A new exponential separation between quantum and classical one-way communication complexity

2011 ◽  
Vol 11 (7&8) ◽  
pp. 574-591
Author(s):  
Ashley Montanaro
Keyword(s):  
Fourier Analysis ◽  
Boolean Function ◽  
Communication Complexity ◽  
Quantum Communication ◽  
Membership Problem ◽  
Classical Communication ◽  
Exponential Separation ◽  
Quantum Communication Complexity ◽  
Natural Generalisation ◽  
Subgroup Membership Problem

We present a new example of a partial boolean function whose one-way quantum communication complexity is exponentially lower than its one-way classical communication complexity. The problem is a natural generalisation of the previously studied Subgroup Membership problem: Alice receives a bit string $x$, Bob receives a permutation matrix $M$, and their task is to determine whether $Mx=x$ or $Mx$ is far from $x$. The proof uses Fourier analysis and an inequality of Kahn, Kalai and Linial.

scholarly journals Multipoint-Interconnected Quantum Communication Networks

2021 ◽  
Author(s):  
Qingcheng Zhu ◽  
Yazi Wang ◽  
Lu Lu ◽  
Yongli Zhao ◽  
Xiaosong Yu ◽  
...  
Keyword(s):  
Communication Networks ◽  
Network Architecture ◽  
Quantum Teleportation ◽  
Secure Communication ◽  
Quantum Communication ◽  
Optimization Methods ◽  
Distribution Networks ◽  
Computational Power ◽  
Classical Communication ◽  
Promising Solution

As quantum computers with sufficient computational power are becoming mature, the security of classical communication and cryptography may compromise, which is based on the mathematical complexity. Quantum communication technology is a promising solution to secure communication based on quantum mechanics. To meet the secure communication requirements of multiple users, multipoint-interconnected quantum communication networks are specified, including quantum key distribution networks and quantum teleportation networks. The enabling technologies for quantum communication are the important bases for multipoint-interconnected quantum communication networks. To achieve the better connection, resource utilization, and resilience of multipoint-interconnected quantum communication networks, the efficient network architecture and optimization methods are summarized, and open issues in quantum communication networks are discussed.

Dynamics of multi-qubit states in non-inertial frames for quantum communication applications

2014 ◽  
Vol 14 (3&4) ◽  
pp. 255-264
Author(s):  
Alaa Sagheer ◽  
Hala Hamdoun
Keyword(s):  
Degradation Rate ◽  
Quantum Communication ◽  
Ghz State ◽  
The Other ◽  
W State ◽  
Entangled States ◽  
Inertial Frames ◽  
Qubit States ◽  
Degree Of Entanglement ◽  
Accelerated Frames

In this paper, some properties of multi-qubit states traveling in non-inertial frames are investigated, where we assume that all particles are accelerated. These properties are including fidelities, capacities and entanglement of the accelerated channels for three different states, namely, Greeberger-Horne-Zeilinger (GHZ) state, GHZ-like state and W-state. It is shown here that all these properties are decreased as the accelerations of the moving particles are increased. The obtained results show that the GHZ-state is the most robust state comparing to the others, where the degradation rate is less than that for the other states particularly in the second Rindler region. Also, it is shown here that the entangled property doesn't change in the accelerated frames. Additionally, the paper shows that the degree of entanglement decreases as the accelerations of the particles increase in the first Rindler region. However in the second region, where all subsystems are disconnected at zero acceleration, entangled states are generated as the acceleration increases.

scholarly journals Quantum communication complexity advantage implies violation of a Bell inequality

2016 ◽  
Vol 113 (12) ◽  
pp. 3191-3196 ◽  
Author(s):  
Harry Buhrman ◽  
Łukasz Czekaj ◽  
Andrzej Grudka ◽  
Michał Horodecki ◽  
Paweł Horodecki ◽  
...  
Keyword(s):  
Communication Complexity ◽  
Quantum Communication ◽  
Bell Inequality ◽  
Main Tool ◽  
Classical Communication ◽  
Quantum Communication Complexity ◽  
Bell Nonlocality ◽  
Large Quantum ◽  
General Connection ◽  
Inputs And Outputs

We obtain a general connection between a large quantum advantage in communication complexity and Bell nonlocality. We show that given any protocol offering a sufficiently large quantum advantage in communication complexity, there exists a way of obtaining measurement statistics that violate some Bell inequality. Our main tool is port-based teleportation. If the gap between quantum and classical communication complexity can grow arbitrarily large, the ratio of the quantum value to the classical value of the Bell quantity becomes unbounded with the increase in the number of inputs and outputs.

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