Quantum communication without entanglement

Information in quantum physics is carried in a system’s quantum state, which is basically a list of all the important properties. An atom’s state, for example, contains the relative orientation of the nucleus and electrons, the energy levels the electrons occupy, and the like. Quantum computing manipulates these states in prescribed ways for calculation purposes, but to get the data from one place to another requires communication:

W. J. Munro, A. M. Stephens, S. J. Devitt, K. A. Harrison, and Kae Nemoto have designed a system where quantum bits (qubits) were transferred by individual photons, but interpreted using a special algorithm designed to contain a lot of redundancy and avoid data loss. Since the states of the transmitter and receiver were not entangled (or copied), they don’t need to remain coherent, obviating the need for quantum memory. The actual data transfer could take place over fiber optic cables, and the receiver could itself be used as a transmitter, forming a repeater for larger networks. [Read more….]

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