Quantum entanglement is a phenomenon in which two or more particles become interconnected in such a way that the state of one particle instantaneously influences the state of the other, regardless of the distance separating them. This unique property of entangled particles is what underpins the principles of quantum communication. In practical terms, when two qubits are entangled, measuring the state of one qubit will instantly reveal the state of the other, thanks to their interconnected nature. This correlation occurs even if the particles are light years apart, which challenges our classical understanding of communication and information transfer.
In quantum communication systems, entanglement is primarily used for secure data transmission. For instance, in quantum key distribution (QKD), two parties can use pairs of entangled particles to generate shared encryption keys. If one party measures their particle, the results will directly affect the corresponding particle held by the other party. Any attempt by an eavesdropper to intercept these particles would disturb the entangled state, making it evident that the security of the communication has been compromised. This feature makes quantum communication more secure than traditional methods, as it allows users to detect any unauthorized access to their data.
Another practical application of quantum entanglement in communication is teleportation, which allows the transfer of quantum information from one location to another without moving the particles themselves. Teleportation does not entail physical travel; instead, it requires classical communication alongside entangled particles. If two parties share entangled particles, one can send the complete state of their quantum system to the other party through a combination of measurement results and classical messages. Although still in the experimental phase, these concepts hold promise for developing future communication networks that are significantly more secure and efficient than current technologies.