### Published in Science, 29 Aug 2013

In theory, so-called quantum cryptography provides a totally secure way of sending information. In practice, maybe not. But now physicists have demonstrated how to close a technological loophole that could have left secrets open to eavesdroppers.

Suppose Alice wants to send Bob a secret message. In ordinary cryptography, she can convert the message to binary numbers—i.e., a string of 0s and 1s—and then scramble it by combining it mathematically with another string of random 0s and 1s, which serves as the key. Bob then uses this key to undo the scrambling and read the message. Of course, to make the scheme work, Alice must pass the key to Bob without letting it be intercepted by an eavesdropper, Eve. […]

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