Jump-Starting Quantum Error Correction with Entanglement
Daniel Gottesman · Science · 2006
Today's communications networks are filled with Web pages, e-mails, telephone conversations, video clips, financial transactions, and more, all encoded digitally as bursts of light flashing through fiber-optic cables. All of these messages can be boiled down to sequences of bits, 0's and 1's—usually long sequences, measured in kilobits, megabits, or sometimes even gigabits. But light, like everything else, behaves according to the laws of quantum mechanics, and a sequence of bits is not a good way to describe the properties of a quantum object. Instead, we should turn to quantum bits, or “qubits,” and someday, perhaps, today's network traffic will be supplemented by streams of such quantum information. Quantum transmissions would enable cryptographic systems to detect attempted eavesdropping, and quantum computers capable of manipulating quantum information could solve some problems far more rapidly than any conceivable classical computer. Just as classical information is encoded today in error-correcting codes to protect it against errors in transmission, quantum information will need to be encoded in quantum error-correcting codes in order to reliably reach its destination. Indeed, quantum information is more sensitive to errors than is classical information, so error correction will be even more important. On page 436 of this issue, Brun et al. (1) show how it is possible to improve the performance of quantum error-correcting codes, using a quantum state previously shared between the sender and receiver.