Yes, the Nobel Prize was awarded to three men who played a game.
This is a game that can only be won by breaking the laws of reality.
The setup
The setup is simple. You and your twin love matching colors. You each wake up in the morning and put on either red or blue, and you want to match.
Except: you guys are pretty moody. You each have a 50% chance of waking up happy or grumpy.
The rules:
Both happy: you want to match colors.
Both grumpy: you definitely do not want to match.
One happy, one grumpy: the happy one cheers the other up, you want to match.
Each of the four mood combinations is equally likely (25% each). You wake up and only know your own mood, not your twin's. What color should you wear to maximize the chances of getting it right?
The best classical strategy
It turns out that a very simple strategy already lets you win 75% of the time:
Always wear red.
Think through it. Three of the four mood combinations want you to match, and if you both always wear red, you always match. Only the “both grumpy” case (which wants you to not match) loses. That's 3 out of 4. 75%.
Can we do better?
No. Since you can't know if your twin is happy or grumpy, the “both grumpy” case is a 50/50 guess at best, and the math works out so that 75% is the best any classical strategy can achieve. Any agreed-upon plan, any private information, any randomness you share ahead of time, none of it gets you above 75%.
That's an upper bound. It's been proven impossible.
With entanglement
What if you and your twin shared an entangled pair of qubits? It turns out you can win ~85% of the time.
That's shocking. We know no information can be sent over entanglement. Yet entangled qubits beat the classical limit by 10 percentage points. Something real is being shared between you and your twin that can't be reduced to any pre-shared classical strategy.
That gap, between 75% and 85%, is what John Clauser, Alain Aspect, and Anton Zeilinger spent their careers measuring. They showed that real entangled qubits really do beat the classical bound. That's what won them the 2022 Nobel Prize in Physics.
Let's see how it works.
Hold them
Two qubits you can hold in your hands.
Qubi is a model qubit. Pair them up, run the gates, build the intuition that this guide just laid out, by touch.