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Random¹ numbers are hugely important for modern computing². They're used to encrypt credit card numbers and emails. To inject randomness³ into online gaming. And to simulate super complex phenomena⁴, like protein folding or nuclear fission⁵. 

But here's the dirty secret: a lot of these so-called random numbers are not truly random. They're actually what’s known as "pseudo random numbers," generated by algorithms. Think of generating random numbers by rolling dice⁶. If you know the number of dice, it’s simple to figure out something about the realm of possible random numbers—thus putting probabilistic limits on the randomness.

But truly random numbers can be generated through quantum mechanical processes. So researchers built a photonic chip—a computer chip that uses photons instead of electrons. The chip has two lasers: one shoots continuously; the other pulses at regular intervals⁷. Each time the two lasers meet, the interference between the light beams is random, thanks to the rules of quantum mechanics. The chip then digitizes that random signal, and voila: a quantum random number generator⁸. The study is in the journal Optica. [Carlos Abellan et al., Quantum entropy source on an InP photonic integrated circuit for random number generation]

It's not the first time this sort of thing's been built. But compared to old prototypes, this chip is much smaller—a sixth the size of a penny—and works at high speeds. Meaning small and fast enough for a smartphone? The researchers say that's an entirely⁹ predictable outcome.

—Christopher Intagliata