Origin of Q-Cryptography: quantum money
Now that you have learned about the fundamentals of Q-Mechanics, we will talk about Q-Cryptography. The curious story of its first application began in the 70s, when a Ph.D. candidate, Stephen Wiesner from Columbia University, had an idea. He invented a special kind of money that (theoretically) couldn’t be counterfeited: quantum money. Wiesner’s quantum money mostly relied on quantum physics regarding photons.
Suppose that we have a group of photons traveling all in the same direction on a predetermined axis. Moving in space, a photon has a direction of vibration known as the polarization of the photon. The following diagram shows what we are talking about:
Figure 9.7 — Photon polarization
As you can see, photons spin their polarization in all directions, including diagonals, as the initial state of an unpolarized photon is the superposition of oscillating horizontally and vertically. However, if we place...
