Quantum communication networks show great promise in becoming a highly secure communications system. By carrying information with photons or atoms, which are entangled so that the behavior of one affects the other, the network can easily detect any eavesdropper who tries to tap the system.
Physicists at the Georgia Institute of Technology have just reached an important milestone in the development of these systems by entangling a photon and a single atom located in an atomic cloud. Researchers believe this is the first time an entanglement between a photon and a collective excitation of atoms has passed the rigorous test of quantum behavior known as a Bell inequality violation. The findings are a significant step in developing secure long-distance quantum communications. They appear in the July 29, 2005 edition of the Physical Review of Letters.
Relying on photons or atoms to carry information from one place to another, network security relies on a method known as quantum cryptographic key distribution. In this method, the two information-carrying particles, photonic qubits or atomic qubits, are entangled. Because of the entanglement and a rule in quantum physics that states that measuring a particle disturbs that particle, an eavesdropper would be easily detected because the very act of listening causes changes in the system.
David Terraso | EurekAlert!
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