In quantum information science, classical information channel (often called simply classical channel) is a communication channel that can be used to transmit classical information (as opposed to quantum channel which can transmit quantum information). An example would be a light travelling over fiber optics lines or electricity travelling over phone lines.
Although classical channels cannot transmit quantum information by themselves, they can be useful in combination with quantum channels. Examples of their use are:
- In quantum teleportation, a classical channel together with a previously prepared entangled quantum state are used to transmit quantum information between two parties. Neither the classical channel nor the previously prepared quantum state alone can do this task.
- In quantum cryptography, a classical channel is used along with a quantum channel in protocols for quantum key exchange.
- In quantum communication, the information rate of a noisy quantum channel can be increased when used together with a noise-free classical channel. In particular, some very noisy quantum channels cannot transmit quantum information if used alone but can transmit it if used together with a classical channel (which is not capable of transmitting quantum information by itself).
Famous quotes containing the words classical, information and/or channel:
“Compare the history of the novel to that of rock ‘n’ roll. Both started out a minority taste, became a mass taste, and then splintered into several subgenres. Both have been the typical cultural expressions of classes and epochs. Both started out aggressively fighting for their share of attention, novels attacking the drama, the tract, and the poem, rock attacking jazz and pop and rolling over classical music.”
—W. T. Lhamon, U.S. educator, critic. “Material Differences,” Deliberate Speed: The Origins of a Cultural Style in the American 1950s, Smithsonian (1990)
“When action grows unprofitable, gather information; when information grows unprofitable, sleep.”
—Ursula K. Le Guin (b. 1929)
“How old the world is! I walk between two eternities.... What is my fleeting existence in comparison with that decaying rock, that valley digging its channel ever deeper, that forest that is tottering and those great masses above my head about to fall? I see the marble of tombs crumbling into dust; and yet I don’t want to die!”
—Denis Diderot (1713–1784)