Re:What are we going to do with quantum computers?
by OscarCunningham on Sunday February 25, 2018 @11:20AM
(#16459597)
>Doesn't quantum transmission infrastructure require direct connections from A to B?
No, the retransmitters can preserve the entanglement (and A and B can verify that this has been done).
In fact (providing qubits can be stored) the transmission can be done indirectly and in advance.
The telecom company produces lots of entangled qubits and gives a bunch to each customer, keeping half of each pair for itself. Then when Alice wants to communicate securely with Bob they ask the telecom company to take the corresponding qubits and perform a joint measurement. This entangles Alice's qubits with Bob's (like making a connection at a telephone exchange). Then Alice and Bob can measure their qubits (in various bases) to create a one-time-pad.
The clever thing is that Alice and Bob can (by checking that on a portion of the qubits their results always matched when they used the same basis) verify that they did indeed have maximally entangled qubits and therefore no one was listening-in.
No, the retransmitters can preserve the entanglement (and A and B can verify that this has been done).
In fact (providing qubits can be stored) the transmission can be done indirectly and in advance.
The telecom company produces lots of entangled qubits and gives a bunch to each customer, keeping half of each pair for itself. Then when Alice wants to communicate securely with Bob they ask the telecom company to take the corresponding qubits and perform a joint measurement. This entangles Alice's qubits with Bob's (like making a connection at a telephone exchange). Then Alice and Bob can measure their qubits (in various bases) to create a one-time-pad.
The clever thing is that Alice and Bob can (by checking that on a portion of the qubits their results always matched when they used the same basis) verify that they did indeed have maximally entangled qubits and therefore no one was listening-in.