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Quantum Cryptography With Ordinary Equipment

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Artist's representation of quantum keys.

A new approach to quantum cryptography could work with commercially available equipment and use less bandwidth than current methods, according to Japanese researchers.

Credit: iStockphoto

Japanese researchers have proposed an approach to quantum cryptography they say would theoretically work with commercially available equipment and consume less bandwidth than existing methods.

The technique would transmit photons over an optical fiber using ordinary lasers, which would discharge a photonic train while a phase modulator imparts a phase on them. The receiver divides the transmission into two separate signals with a randomly produced delay between them, and then those signals are superimposed and detected on the receiving end. The integrated waves could be out of phase and cancel each out, or they could be in phase and generate a bigger wave, and the phase difference between pulses can function as bits that constitute a key to decrypt the message.

The researchers say the technique does not depend on the Heisenberg uncertainty principle and does not require regular transmission measurements to detect key tampering, unlike existing quantum key distribution systems.

University of Tokyo researcher Masato Koashi says the technique would substantially lower the communications overhead needed, which is critical in scenarios in which communication channels are noisy.

From IEEE Spectrum
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