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Following on from my question on educational quantum computing toys, I was wondering whether it is possible to implement the BB84 key distribution protocol with easily-obtained consumer hardware - lasers, fiber-optic cables, optical filters, etc. Does anyone know of any papers detailing this, or simple demonstrations, or whether it's theoretically possible? I did find an article detailing an experiment from the University of Waterloo.

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I am glad you enjoyed my experiments! :) I'd be happy to talk more about how I ran that project --- dm me at twitter.com/crazy4pi314.

To your question, I don't know of any good papers or articles on the setup, but you can get a pretty reasonable demo of polarization-encoded BB84 with a few pretty common components:

  • polarized laser pointer
  • some half wave plates
  • polarizers to represent Eve
  • a 50:50 beam splitter
  • 2 polarizing beam splitters
  • 2 photo detectors

It is not really quantum key distribution (consumer grade single photon sources aren't really a thing, sadly) but it worked well in a number of outreach events I have done with middle schoolers -> undergrads. We just had a bunch of ThorLabs "Legos" and let them in two teams try to assemble a working Alice and Bob. Then, if there was an odd number someone got to be eve with a polarizer between. We had some very simple displays on a computer showing where signal was being received at the detectors.

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