Quantum entanglement,the real-time synchronization between two coupled quanta distributed afar,has intrigued physicists for a long time as a "spooky action" described by Albert Einstein.How the quanta of the coherent pair"interact"with each other despite the long distance remains a mystery,but the theoretically perfect security promised by the inherent physics encourages scientists to explore possible ways to utilize it for information encryption-After all,a message sealed by quantum cryptography would be totally immune to hackers.