Proof-of-concept system could lead to ultra-secure international communication. Entangled photons of light could help to create ultra-secure communication systems.Punhstock Physicists have built a communication network, secured by quantum cryptography, that could one day work on a global scale. Quantum cryptography scrambles data using the laws of quantum mechanics, relying on a concept known as entanglement to ensure absolutely security. Entanglement allows two particles to be quantum-mechanically connected even when they are physically separated. Although the specific condition of either particle cannot be precisely known, taking measurements of one will instantly tell you something about the other. The trick can't be...