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The sender Alice based on entangled photon-pair source

The big blue-shining pile of optics is a parametric down conversion photon-pair source, producing two entangled 813 nm photons from a 406.5 nm pump photon. One photon of the pair is sent down a fiber-optic cable to the receiver Bob (or to Eve as has been the case in our eavesdropping experiment), the other photon is detected locally. The local detection happens in the little thing with a fan grille (in the foreground), which is a miniature four-state polarization analyzer with four single-photon detectors. The timing of photon detection events is recorded by a timestamp unit synchronized from a rubidium clock (both at the right side of the image).
All this hardware, except perhaps the rubidium clock, has been built at the Centre for quantum technologies, Singapore.

This picture from Full eavesdropping on quantum cryptography gallery and Quantum hacking lab gallery is included in Picture Collection (ref. nr. a294-4) on Photo Pages.

Taken on July 5, 2009 at the Centre for quantum technologies, Singapore.
Fujichrome Sensia 100 film, Canon EOS-3, EF 75–300 1:4–5.6 II lens at 85 mm, 81A filter, f/18 14 min, tripod. Scanned on Nikon LS-2000 scanner.

How you can use this image. ©2009 Vadim Makarov