# Tag: Quantum Computing

## Quantum Dollars use Uncertainty to Create Certainty

By Eric Wolff | December 13, 2010 4:29 am

Without getting into the ethics of WikiLeak’s activities, I’m disturbed that Visa, MasterCard and PayPal have all seen fit to police the organization by refusing to act as a middleman for donations.  The whole affair drives home how dependent we are on a few corporations to make e-commerce function, and how little those corporations guarantee us anything in the way of rights.

In the short term, we may be stuck, but in the longer term, quantum money could help solve the problems by providing a secure currency that can be used without resort to a broker.

Physicist Steve Wiesner first proposed the concept of quantum money in 1969. He realized that since quantum states can’t be copied, their existence opens the door to unforgeable money.

Here’s how MIT computer scientist Scott Aaronson explained the principles:

Heisenberg’s famous Uncertainty Principle says you can either measure the position of a particle or its momentum, but not both to unlimited accuracy. One consequence of the Uncertainty Principle is the so-called No-Cloning Theorem: there can be no “subatomic Xerox machine” that takes an unknown particle, and spits out two particles with exactly the same position and momentum as the original one (except, say, that one particle is two inches to the left). For if such a machine existed, then we could determine both the position and momentum of the original particle—by measuring the position of one “Xerox copy” and the momentum of the other copy. But that would violate the Uncertainty Principle.

…Besides an ordinary serial number, each dollar bill would contain (say) a few hundred photons, which the central bank “polarized” in random directions when it issued the bill. (Let’s leave the engineering details to later!) The bank, in a massive database, remembers the polarization of every photon on every bill ever issued. If you ever want to verify that a bill is genuine, you just take it to the bank”

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