Quantum superdense coding
In quantum teleportation, we saw that two classical bits are used to transfer a quantum state from Alice to Bob. In superdense coding, we use a single quantum state to send two classical bits.
There are two classical bits, which means a total of 4 combinations. Now, depending on Alice and what she wants to send to Bob, she will apply one of the following gate operations:
- If Alice wants to send
00, then nothing is done. - If Alice wants to send
01, then a Z gate is applied. - If Alice wants to send
10, then an X gate is applied. - If Alice wants to send
11, then ZX is applied.
Figure 3.15 shows the circuit for the superdense coding:
Figure 3.15 – Superdense coding circuit
From Figure 3.15, you can see that Alice generates a shared entanglement between qubits a and b and, to encode her secret message, she uses the X gate, which means she is sending value with 10 as information to Bob. Bob then undoes the...
