In quantum computing, size isn’t the only thing that matters

Currently, a popular way to demonstrate a computational advantage in optical quantum computing is boson sampling. This technique is quite difficult to grasp for the uninitiated, but it’s useful to think of it as a simple marble run. Balls are inserted on top, run down a track and at the bottom, ‘randomly’ end up in one of several holes with scores attached to them. The distribution of the balls is a straightforward statistical matter.

Now think of boson sampling as a highly advanced marble run, in which photons are injected into the device and also ‘land’ in one of many output slots. Calculating the output distribution from a given input configuration is hard to do classically because of the quantum mechanical weirdness happening inside the device. Inter-particle interference produces a kind of randomness that has proven hard to deal with using conventional computers.