Coded messages can keep your secrets safe, but you also might prefer to conceal the fact that you’re communicating at all. Now, scientists are working to make even the whispers of top-secret communications completely undetectable by eavesdroppers. And the methods for sending such stealthy dispatches are being extended from ordinary “classical” messages to quantum ones.
The typical method for sending secret messages is encryption, which allows two parties to exchange coded information that a bystander can’t interpret. But if you want to send a message that no one can even tell you’re sending, you need something else: covert communication. “What covertness gives you is a much more secure way of communicating,” says quantum information researcher Boulat Bash of Raytheon BBN Technologies in Cambridge, Mass.
Scientists have already demonstrated covert communication in the classical realm. But a paper posted April 19 on arXiv.org shows that covert communication can be expanded to the quantum world, opening up the possibility of covertly exchanging quantum bits, or qubits.
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