A laser that usually produces a steady beam starts to tremble near its threshold, like a string about to sound. This trembling is not a defect but quantum noise: atoms inside the laser emit light randomly, without any external cause. Engineers captured this noise using an optical fiber delay (light travels through the fiber, and its early and late versions are compared) and turned it into a stream of random bits — two billion per second.
But the raw stream is slightly uneven: some bit combinations occur a bit more often than others. So it is passed through a "randomness squeezer"—an algorithm that shuffles the bits and makes their distribution perfectly uniform. After this, the rate drops to a billion bits per second, but each bit passes rigorous statistical tests. The device already works as a prototype for real tasks: generating encryption keys, simulating random processes, and protecting communication channels.
A laser's quantum noise arises from spontaneous emission — the same process that makes fireflies flicker unpredictably rather than in sync.
In the series "Westworld," quantum random number generators are used to create unpredictable storylines for androids.