Applied Physics

Quantum Phone Calls

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Science  01 May 2009:
Vol. 324, Issue 5927, pp. 568-569
DOI: 10.1126/science.324_568d

Certain conversations or transactions are meant to be private. Yet despite the encryption of digital communication in one form or another, information theory presents a loophole whereby such encrypted messages can be compromised, if only in principle (in practice it may be extremely difficult to do so). Quantum mechanics closes that loophole altogether. Sharing quantum mechanically—entangled photons can provide a secure key with which to encrypt and send a message, safe in the knowledge that the message cannot be opened by an eavesdropper, at least not without alerting you to the breach. Chen et al. demonstrate a quantum key distribution protocol in a real-world application scenario, with the quantum key distributed over a network consisting of three stations linked by 20 km of commercial optical fiber. The generated keys can be used immediately in the context of encrypted real-time telephone conversations between the separated stations. With such a demonstration, quantum privacy in your own home may not be a too distant prospect.

Opt. Express 17, 6540 (2009).

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