Quantum-cheating in a coin toss? Introducing the Bell state

So, now you have the ability to toss one or more quantum coins and get a probabilistic outcome. That is all well and good, and we could picture ourselves doing some gambling with this new tool of ours, betting money against the outcome of a coin toss. But with a 50/50 outcome, the possibility of earning any real money is limited, unless, of course, we tweak the odds (that is, we cheat).

So how do you cheat in coin tossing? Well, knowing the outcome beforehand would be a clever way. And it turns out this is possible using a quantum phenomenon called entanglement.

By entangling two qubits, we connect them in a way so that they can no longer be described separately. In the most basic sense, if you have two entangled qubits and measure one of them as , the result of measuring the other one will be as.

So, how do we use this to cheat in coin tossing? Well, we create two qubits, entangle them, and then we separate them...