Quantum teleportation is a protocol in quantum information science that allows the transfer of quantum states between two distant qubits. It involves three qubits: the sender's qubit (usually referred to as "Alice's qubit"), the qubit to be teleported (referred to as the "target qubit" or "unknown qubit"), and the receiver's qubit (usually referred to as "Bob's qubit"). The teleportation process itself does not involve the physical transfer of particles or information between qubits.
The actual teleportation process relies on the principles of entanglement and measurement. Initially, Alice and Bob share an entangled pair of qubits, where the state of one qubit is correlated with the other qubit. Alice performs a joint measurement on her qubit and the target qubit, obtaining two classical bits of information. She sends these measurement results to Bob using classical communication channels. Based on Alice's measurement results, Bob applies specific operations on his qubit, thereby reconstructing the unknown state on his qubit.
The key point to note is that the actual quantum state of the target qubit is not instantaneously transferred to Bob's qubit. Instead, the teleportation protocol relies on the classical communication of measurement results to transfer the necessary information to reconstruct the state on Bob's qubit. The process still requires classical communication, which is bound by the limitations of the speed of light.
However, it's important to distinguish between the teleportation of a quantum state and the communication of entanglement itself. While teleportation allows the transfer of quantum states between distant qubits, it does not enable faster-than-light communication. Entanglement, which is the shared correlation between two or more particles, cannot be used to transmit classical information instantaneously. This is due to the no-communication theorem in quantum mechanics, which states that entanglement alone cannot be used for faster-than-light communication or to convey information directly.
In summary, quantum teleportation is a protocol that allows the transfer of quantum states between qubits, but it does not enable instantaneous communication. The principles of entanglement and measurement are utilized in the process, but the transfer of information still relies on classical communication channels.