Can you think of other protocols or synchronization functionalities that could have a solution in quantum networks that are impossible to solve using a classical internet?
Clock synchronization and position verification amongst others.
Imagine there are four robots on the mountain, all of them well-behaving. Can you come up with how they will agree on the attack? Can you write down the quantum state that needs to be distributed?
Let’s say all four robots share a quantum state, and we are going to suppose that all of the robots measure their state in the same basis. Previously they have agreed that if they measure 0 they will retreat and if they measure 1 they will attack. Since the four robots are well-behaving they need to always agree. Thus the state that they will share will be a state of the following form if they are measuring in the Z basis:
Also called a GHZ state.