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Photon Turnstile Improves Cryptography

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In pursuit of more reliable quantum cryptography systems, a team at Stanford University in California and NTT Basic Research Laboratories in Atsugi, Japan, has demonstrated a system that incorporates a photon turnstile, which enables it to support 28-dB channel losses. Using an attenuated laser in place of the turnstile device, the system fails at a channel loss of 23 dB.

As reported in the Dec. 19/26 issue of Nature, the turnstile comprised a quantum dot in a micropost cavity optically excited by 3-ps pulses from a Ti:sapphire laser. To implement the BB84 quantum cryptography protocol, the photons from the turnstile passed through an electro-optic modulator with a 4-ns switching time that rotated the polarization into one of four states. Passive polarization and avalanche photodiodes detected the photons at the receiving end, one meter away.

Photonics Spectra
Jan 2003
As We Go To Pressattenuated laserBreaking Newsphoton turnstilePresstime Bulletinquantum cryptography systemlasers

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