quantumcrypto

random number generator

one of the key ingredients of the bb84 protocol are true random number generators. we have the perfect solution beeing 4 colors of m&m‘s in an opaque bag. but don‘t forget to put back the m&m‘s after drawing one!!!

polarized photons

here are the four polarized photons, which are send out by alice and measured by bob and eve. eve has a copy of this set of photons to send out duplicates of her measurement.

polarization resolved detectors

eve and bob have two polarization resolved detectors for measuring the polarization of the photons. each of the detectors corresponds to a polarization basis ⊕ or ⊗. the polarization basis is determined with our biological random number generator.

this is a pictorial of our experimental verification of the BB84 quantum cryptography transmission in the seminar of our photonics lectures.

Bob

1/2 Alice

Bob / Eve

1/2 Alice

here are the brave men and woman, who have carried out the difficult task of cryptography

... from the scence

polarization measurement

I don‘t know their problem?!

a random number and its corresponding photon

drawing a random number

the first 14 bits of the alice‘s key

the first 14 bits of the bob‘s key

all 50 bits of the bob‘s key

alice‘s and bob‘s bits and the marked coincidences which form the final quantum key (21 out of 50 bases coincidence)

the quantum key erasor

eval eve

bobs key with eavesdropping

alice‘s key with eavesdropping

alice and bob recognized that some of their bits which should aggree do not aggree, so somebody was listening, (26 out of 50 bases coincidence, 19 bits OK, but 7 bits wrong)