Editing Quantum channel (section)

== In the experimental setting ==

Experimentally, a simple implementation of a quantum channel is [[fiber optic]] (or free-space for that matter) transmission of single [[photon]]s.  Single photons can be transmitted up to 100&nbsp;km in standard fiber optics before losses dominate.{{cn|date=December 2024}}  The photon's time-of-arrival (''time-bin entanglement'') or [[Polarization (waves)|polarization]] are used as a basis to encode quantum information for purposes such as [[quantum cryptography]].  The channel is capable of transmitting not only basis states (e.g. <math>|0\rangle</math>, <math>|1\rangle</math>) but also superpositions of them (e.g. <math>|0\rangle+|1\rangle</math>).  The [[quantum coherence|coherence]] of the state is maintained during transmission through the channel. Contrast this with the transmission of electrical pulses through wires (a classical channel), where only classical information (e.g. 0s and 1s) can be sent.