Classical information channel
Encyclopedia
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:
Quantum information science
Quantum information science is an area of study based on the idea that information science depends on quantum effects in physics. It includes theoretical issues in computational models as well as more experimental topics in quantum physics including what can and cannot be done with quantum...
, 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
Quantum channel
In quantum information theory, a quantum channel is a communication channel which can transmit quantum information, as well as classical information. An example of quantum information is the state of a qubit...
which can transmit quantum information
Quantum information
In quantum mechanics, quantum information is physical information that is held in the "state" of a quantum system. The most popular unit of quantum information is the qubit, a two-level quantum system...
). 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 teleportationQuantum teleportationQuantum teleportation, or entanglement-assisted teleportation, is a process by which a qubit can be transmitted exactly from one location to another, without the qubit being transmitted through the intervening space...
, a classical channel together with a previously prepared entangledQuantum entanglementQuantum entanglement occurs when electrons, molecules even as large as "buckyballs", photons, etc., interact physically and then become separated; the type of interaction is such that each resulting member of a pair is properly described by the same quantum mechanical description , which is...
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 cryptographyQuantum cryptographyQuantum key distribution uses quantum mechanics to guarantee secure communication. It enables two parties to produce a shared random secret key known only to them, which can then be used to encrypt and decrypt messages...
, 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).