[FDE] Toshiba solves the multi-photon problem in QKD (Quantum Key Distribution)

[Saqib Ali]

http://www.assodigitale.it/content/view/5354/74/
Toshiba has demonstrated two ways of solving the multi-photon problem
in the Quantum Key Distribution (QKD):

1) "decoy pulses". These decoy pulses are weaker on average and so
very rarely contain two or more photons. If an eavesdropper attempts a
pulse-splitting attack, she will transmit a lower fraction of these
decoy pulses than signal pulses. Thus by monitoring the transmission
of the decoy and signal pulses separately this type of intervention
can be detected.

2) single photon diode based on nano-technology. Yes they have created
a diode that is capable of emitting just a single photon. This will
not only solve the multi-photon problem but will also improve the
bit-rate drastically.

Why are multi-photon pulses such a problem in QKD?
The eavesdropper can split the multi-photon pulse, measuring one
photon and letting the other one go. Thus the eavesdropper can
determine part of the key. Even more, the attacker can stop all single
photon pulses, and allow only multi-photon pulses, thus gaining access
to the whole key.

http://www.assodigitale.it/content/view/5354/74/