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PicoQuant - It's about time

Quantum Optics

Coincidence Correlation

Determine the presence of a single quantum system

Coincidence correlation with picosecond timing can be used to determine if one is actually observing a single quantum system in the form of a single photon emitter. Here one employs the knowledge that such a system can only emit one photon at a time. This is because in typical quantum systems such as single molecules or defect centers in diamond there is a characteristic average lifetime of the excited state that must pass before the system can be excited again. If one finds that two detectors observing the source „click“ simultaneously (with statistical significance) then obviously the source cannot be a single photon emitter.

In case of experiments dealing with photon entanglement one effectively tries to prove or disprove correlations between measurement outcomes using some kind of correlator.
In the case of experiments with photons one may, for instance, employ polarizers to filter out quantum states of interest and then use photon detectors to determine whether or not they occurred correspondingly at both parts of the entangled pair. Now, given that photon detectors are not 100% efficient (and actually neither is the creation of entangled pairs and their transmission) one typically must repeat the experiment many times in order to arrive at a statistically reliable answer. Since there can also be unwanted photons from background radiation or detector artifacts it is a smart common practice to perform the coincidence correlation with picosecond timing. The correlations can then be determined for narrow time windows where the knowledge of the time the photons travel can be used to eliminate background.


Setup for coincidence correlationIn a coincidence correlation setup, the photons emitted by the systems are split using, e.g. a 50 / 50 beamsplitter or a polarization splitter and send onto two single photon sensitive detectors. The output of these detectors is then fed into a time tagging unit with high temporal resolution that allows not only to detect coincidences in a certain time window but obtain the full second or higher oder correlations.

PicoQuant offers several instruments such as time-tagging units and single photon sensitive detectors that can be used to perform coincidence correlation:

Time-tagging Units

HydraHarp 400 - multichannel time tagging moduleHydraHarp 400

Multichannel Picosecond Event Timer

  • Up to 8 independent input channels and common synch channel (up to 150 MHz)
  • Time channel width of 1 ps
  • Time tagging with sustained count rates up to 40 Mcps
  • USB 3.0 connection

PicoHarp300 - time tagging unitPicoHarp 300

Compact Dual-Channel Picosecond Event Timer

  • Two identical synchronized but independent input channels
  • Time channel width of 4 ps
  • Time tagging with sustained count rates up to 5 Mcps
  • USB 2.0 connection

TimeHarp260 - time tagging moduleTimeHarp 260

Dead-time Free Coincidence Correlation

  • One or two independent input channels and common synch channel (up to 84 MHz)
  • Two models with either 25 ps (PICO model) or 1 ns (NANO model) base resolution
  • Ultra short dead time (< 25 ns for PICO model, < 1 ns for NANO model)
  • PCIe interface

Single Photon Detectors

PDM SPAD - single photon sensitive detectorPDM Series

Single Photon Avalanche Diodes

  • Timing resolution down to < 50 ps (FWHM)
  • Detection efficiency up to 49%
  • Different active areas: 20, 50, and 100 µm
  • Ultra stable at high count rates

Latest 10 publications related to Antibunching

The following list is an extract of 10 recent publications from our bibliography that either bear reference or are releated to this application and our products in some way. Do you miss your publication? If yes, we will be happy to include it in our bibliography. Please send an e-mail to info@picoquant.com containing the appropriate citation. Thank you very much in advance for your kind co-operation.