Nature plays dice with at least 11 faces

Researchers at Heriot-Watt and Glasgow University, part of SUPA, have shown that nature plays dice with at least 11 faces, using light that looks like pasta spirals!

An experiment using light with orbital angular momentum, featured on the cover of the September issue of Nature Physics, has proved that such light indeed posesses high-dimensional quantum entanglement.

Such "supercorrelated" quantum states with high entanglement can be useful for ultrasensitive quantum metrology, secure quantum communication, and ultimately for quantum computers.

Predictions  versus probabilities

Quantum mechanics is a strange theory. It would seem reasonable that if we specify the initial conditions well enough, then we can predict exactly what should happen in any situation. For example, it is very difficult to predict the Scottish weather, but if we knew the exact position and velocity of every air molecule, and same for the clouds, sea etc., then we should in principle be able to predict the weather with certainty. It is only because we cannot possibly collect this sheer volume of data, never mind run the calculations even on a supercomputer, that we can't predict the weather. And same thing for any other process.

Quantum mechanics says that this is fundamentally not the case. It only gives probabilities for events to occur, no matter how well we know the initial conditions. "Quantum weather" is fundamentally unpredictable. Einstein was uncomfortable with this, and famously said "God does not play dice".

Proving  that nature plays dice

This work proves that nature plays dice with at least 11 faces each. This was achieved by using photons, or particles of light, that twist like pasta spirals, as the "dice". Exactly how the photons twisted was the different "faces" of the "dice". Previously, the record was "dice" with 2 and 3 "faces". Most experiments use the polarisation of light, that is, what direction the electromagnetic field is oscillating in. This gives a die with two faces. But the "twist" this experiment used, just like pasta, comes in inifinitely many shapes, so one can have dice with arbitrarily many faces.

The team from Heriot-Watt consisted of PhD student Adetunmise Dada, Dr Erika Andersson and Prof. Gerald Buller.  The University of Glasgow research team was Dr Jonathan Leach and Prof. Miles Padgett.