Random, but not by chance: A quantum random-number generator for encryption, security

Researchers have devised a new kind of random number generator, for encrypted communications and other uses, that is cryptographically secure, inherently private and - most importantly - certified random by laws of physics.

That is important because randomness is surprisingly rare. Although the welter of events that transpire in the course of daily life can certainly seem haphazard and arbitrary, none of them is genuinely random in the sense that they could not be predicted given sufficient knowledge. Indeed, true randomness is almost impossible to come by.

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Now, however, a team of experimentalists from the Joint Quantum Institute (JQI) , in partnership with European quantum information scientists, has demonstrated a method of producing a certifiably random string of numbers based on fundamental principles of quantum mechanics. They report their results in the 15 April 2010 issue of Nature.

Clipped from: Randomness is no lottery thanks to entangled ions - physicsworld.com

Randomness is no lottery thanks to entangled ions

Monroe's team employed a method known as a Bell test, named after the late physicist John Bell who invented it in 1964. They placed two atomic ions in separate enclosures one metre apart, and then "entangled" them by passing single photons through them. Once entangled, the state of one atom is inextricably linked to the superposed state of the other, so that a measurement of one – in this case, a measurement made by recording the emission of light – causes the states of both atoms to collapse.

Over the course of a month, the researchers measured the states of more than 3000 entangled atomic ion pairs, generating a string of 42 binary digits. Because the correlations between the measured states were less than a certain value, as given by Bell's famous "inequality", they were – according to quantum mechanics – certifiably random.

Clipped from: Random Numbers -- But Not By Chance

Random Numbers -- But Not By Chance
April 2010

Every time their apparatus signaled that entanglement had been achieved, the researchers rotated each atom on its axes according to a random schedule and then took a measurement of each atom’s emitted light. [See Figure 1.] The value from each of two atoms was then used to generate a binary number. [See animation.]