### Superquantum Quoins

*Totally Random* invites the reader to imagine a superquantum correlation produced by tossing a pair of "quoins", which the reader creates by putting two ordinary quarters through a device called the Super Quantum Entrangler, or SQE-PR01 for short. When tossed starting both heads-up, the quoins will always land opposite (one heads and one tails). When tossed starting any other way, they will always land the same (both heads or both tails). *Totally Random* unpacks the devastating significance of this seemingly innocuous correlation.

### Superquantum vs Quantum

Our hypothetical quoins' landings are correlated in this way (see above) 100% of the time. In the real world, entangled quantum particles behave very much like entangled quoins. You can get correlations between the polarizations of entangled photons, or the spins of entangled electrons, that are like the correlation between quoin landings about 85% of the time.

### The PR-Box

The idea of thinking about quantum mechanics in terms of a superquantum correlation comes from two physicists, Sandu Popescu and Daniel Rohrlich. The *Totally Random* quoin correlation is the same as the correlation between inputs and outputs of their "nonlocal box", now referred to as a PR-box. What’s nice is that the correlation exhibits all the conceptually puzzling features of quantum correlations. It gets right to the heart of what's so weird about entanglement, while being easily understandable without the mathematical complexities of quantum mechanics. The PR-box has turned out to be a crucial tool in investigating the possibilities and limitations of quantum entanglement.