Quantum communication

Abstract

The communication of information between two spatially separated parties requires a directed resource, such as a bit or qubit, that is naturally constrained by the speed of light and, in the case of the quantum information, is subject to the constraints of the no-cloning theorem. Several specifically quantum-mechanical protocols are discussed in this chapter that illustrate different uses of the combination of resources available to support communication and information processing when quantum resources are available. It is important to note that, despite the value of entanglement for communication, classical communication cannot be simulated by the resource of shared quantum entanglement alone in an attempt to circumvent this speed-of-light constraint, due to the undirected nature of entanglement.¹

For more on the “peaceful coexistence” of quantum mechanics and relativity, see Ch. 8 of [384].