Quantum money

Quantum money is a proposed design of bank notes making them impossible to forge, by using quantum physics. The idea influenced the development of quantum key distribution protocols used in quantum cryptography. Quantum money is a proposed design of bank notes making them impossible to forge, by using quantum physics. The idea influenced the development of quantum key distribution protocols used in quantum cryptography. The idea was put forward in about 1970 by Stephen Wiesner, a graduate student at Columbia University, though it was rejected by a number of scientific journals, meaning that it remained unpublished until 1983. In addition to a unique serial number on each bank note (these notes are actually more like cheques, since a verification step with the bank is required for each transaction), there is a series of isolated two-state quantum systems. For example, photons in one of four polarizations could be used: at 0°, 45°, 90° and 135° to some axis, which is referred to as the vertical. Each of these is a two-state system in one of two bases: the horizontal basis has states with polarizations at 0° and 90° to the vertical, and the diagonal basis has states at 45° and 135° to the vertical.