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Part of: A Science Kit for Quantum Physics.

  • Overview
  • Sample Experiments
  • Add-Ons
  • System Includes
  • Variants
  • Downloads


One of the most popular industrial applications for quantum phenomena right now is quantum cryptography, or better, quantum key distribution. With the  the quED and this add-on, you can use weak coherent pulses to demonstrate realistically how a secure communication between two parties (Alice and Bob) is made possible by the BB84 protocol in a real environment. Additionally, a pulse with average photon numbers from 0.1 to 100 can be generated by the click of a button, which can be useful for showing the particle nature of light or quantum randomness.

Disclaimer: This is a QKD demonstration experiment kit. It shows and teaches the fundamental protocol (without cheating), but it is NOT a QKD device that can be used in a real-world scenario. The distance between Alice and Bob is only a few centimeters and this amongst other aspects renders it absolutely useless for real applications.

Sample Experiments

Here is a list of the experiments where the quED-QKD is involved or can enhance the experience.

Single Photon Experiments without Interference
Particle Nature of Photons
Quantum Random Bit Generation
Quantum cryptography: The BB84 protocol
Single Photon Experiments with Interference
  • Interaction-Free Measurement (Bomb Test)

These are the experiments we have come up with so far and found interesting enough to put them here. Do you have more ideas? Please let us know!

Other Add-Ons

Here are more add-ons designed to be extend the functionality of the quED:

+ quED-MI Michelson Interferometer

Demonstrate the wave nature of single photons through their interference or build a quantum eraser.

Single Photon Michelson Interferometer Add-On for the quED.

  • Single Photon Michelson Interferometer Add-On for the quED.

Interference is generally considered to be a wave phenomenon. Curiously it also works with single quantum objects. Use the quED-MI Michelson Interferometer add-on together with the quED to show that this is the case. (The photograph shows the motorised version.)

Read more about the quED-MI Michelson Interferometer.

+ quED-HBT Hanbury Brown Twiss Add-On

Perform the “Grangier Experiment”, explore the particle nature of single photons with a Hanbury Brown & Twiss setup and build a quantum random bit generator.

Hanbury Brown & Twiss Setup for Heralded Single Photon Sources.

  • Hanbury Brown-Twiss setup Add-On for the quED

Photons (or generally quantum objects) sometimes also behave like particles. With this add-on you can show that photons can not be split up. You can also explore a simple quantum random bit/number generator and use it in combination with the quED-MI to show wave and particle nature of photons in one experiment.

Read more about the quED-HBT.

+ quED-HOM Hong–Ou–Mandel Effect

Experience the purely quantum 2-photon interference effect by revealing the Hong-Ou-Mandel dip.

Hong-Ou-Mandel Interferometer Demonstrating 2-Photon Interference.

  • Hong-Ou-Mandel effect Add-On for the quED

When you have two indistinguishable photons and each of them hit one input of a beam splitter, they exit the beam splitter together in one output port. This is an effect you cannot demonstrate with bright light, but with this add-on you can.

Read more about the quED-HOM.

System Includes

The quED-QKD is an add-on to the quED and consists of the following parts:

  • Hard- and Software support for pulsed operation of the quED (the control unit is upgraded)
  • Half-wave plate (Alice)


There are two variants of the quED-QKD:

  • Manual: The half-wave-plate and the polarizer have to be set manually, the results are also taken by hand.
  • Motorized: Random numbers can be used to automatically set the half-wave-plate and the polarizer. The resulting key can be measured and refined further automatically in the control unit.


quED-QKD manual 02/2019 1.4 MB pdf
quED-QKD sample solution 02/2019 0.7 MB pdf