Dr. Thomas Jennewein (co-founder of UQD) has a strong interest in the development and building of instruments for research.

Development expertise in:

  • single-photon detectors, such as avalanche photo-diodes (Geiger mode) and photo-multiplier tubes
  • electronics for operating APD in Geiger mode, both active quenching and passive quenching
  •  high-speed coincidence and gating electronics
  • thermal control circuits, in particular thermo-electric cooler
  • quantum sources for quantum communications
  • weak-coherent pulse quantum sources based on integrated optical modulators
  • quantum random number generators
  • photo-diode circuitry (non Geiger-mode)
  • programmable logic (CPLD based) experiment control: examples include digital signal delay, Pockels-cell sequence driver, pseudo-random signal generator, photon detector gating.



Coincidence logic examples:

Throughout his career in experimental quantum optics, Dr. Jennewein designed and built various circuits analyzing the signals in time or correlation. One of the most important type of electronics he worked on are circuits for coincidence logics, with several of his earlier designs included high-speed TTL and ECL, even discrete transistors. He later built a programmable logic based logic which was synchronized by the pulsed pump laser.

A Versatile Coincidence Logic in ACT-TTL

This is a very versatile and simple coincidence logic. It is based on the very cost effective ACT-TTL (=Advanced CMOS – Transistor-Transistor Logic compatible) logic family. These parts are available off-the shelf for a few 10s of dollars.

This circuit works as follows: the (relatively) long input TTL signals (input X1 and input X2) are first received in a Flip-Flop, which is actually a Data-Flip-Flop (D-FF) configured as a mono-Flop. The pulse width is as short as about 3 ns (which is approximately the gate propagation duration). These short pulses are then combined on a AND gate. The resulting signal will only be logic-HIGH if there is an overlap of the two input pulses.

In practice, it is advisable to also send the coincidence signal into a Flip-Flop, which is configured has the feedback to the reset coupled with an RC element from the /Q output. This effectively slows down the reset of the D-FF, which in turn leads to  a longer output pulse (such as 100 ns) for each coincidence signal. These can easily be counted with a general event counter.

Multi Photon Coincidence Logic in CPLD for Quantum Teleportation

Setup of entanglement-swapping experiment using optimal Bell-state analysis. The two photon pairs are produced by spontaneous parametric down conversion in Barium-borate pumped by UV-laser pulses (wavelength = 384 nm, width = 200 fs)

    Multi-Photon Entanglement



Ultra-fast Coincidence Logic ECL for Cluster State Quantum Computing



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