Dr Shields's photon detector, however, permits cryptographers to use a phenomenon called quantum entanglement to make a repeater that does not destroy quantum states.
The Bombe was developed by a team including mathematician Alan Turing, which enabled cryptographers to decode more than 3, 000 German messages in a day.
The MIT mathematicians, that is, sidestepped a weak spot that had plagued cryptographers ever since the days of the ancient Greeks: How do sender and receiver hand off a key without risking that their communication channel or their courier will be compromised in some way?