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:
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—W. T. Lhamon, U.S. educator, critic. “Material Differences,” Deliberate Speed: The Origins of a Cultural Style in the American 1950s, Smithsonian (1990)
“I have all my life been on my guard against the information conveyed by the sense of hearing—it being one of my earliest observations, the universal inclination of humankind is to be led by the ears, and I am sometimes apt to imagine that they are given to men as they are to pitchers, purposely that they may be carried about by them.”
—Mary Wortley, Lady Montagu (1689–1762)
“Eddie did not die. He is no longer on Channel 4, and our sets are tuned to Channel 4; he’s on Channel 7, but he’s still broadcasting. Physical incarnation is highly overrated; it is one corner of universal possibility.”
—Marianne Williamson (b. 1953)