Quantum Superdense Coding Protocol

One of the most basic applications of quantum algorithms is superdense coding. It is a simple protocol, but it is also an important protocol. Now let's take a detailed look.

The setup of the protocol is as follows:

Alice wants to send 2-qubit information to Bob, but she can only send a single-qubit due to her possibilities. But how does Bob get a 2-qubit of information from Alice?

This is where Caren comes in. Caren entanglements 2 qubits through Hadamard and CNOT. It sends one of the entangled particles to Alice and the other to Bob. Alice and Bob have no information as they do not measure which particle has come to them.

From here on, Alice will be able to send the qubits she wants to Bob. Let's examine them all in turn.

Let Alice wants to send the 00 qubits. In this case, it will use the I gate.

Let Alice wants to send the 01 qubits. In this case, it will use the X gate.

Let Alice wants to send the 10 qubits. In this case, it will use the Z gate.

Let Alice wants to send the 11 qubits. In this case, it will use the iY gate.

As can be seen, Bob finds the qubit information sent by Alice in the measurement results with 100% probability.

Let's focus on the important point above. For this protocol to work correctly, the qubits to be created must be entangled. Otherwise, if they are not entangled, Bob will get different results with different probabilities.

The entangled states you see above are called Bell States. As I mentioned before, in order to obtain an accurate measurement result with a 100% probability of the quantum superdense coding protocol, it is necessary to start the process with one of the Bell entanglement states.

I will write about different protocols in my future articles.

Stay with physics. :)

Reference

https://www.youtube.com/watch?v=3wCW4x51Blo&list=PLqNc_xpYGu77u6dI_RijjCLd-nP8p_4pI&index=22

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