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State of the art time-to-digital converter

  • quTAG - state of the art time-to-digital converter

  • Overview
  • Specifications
  • Jitter Measurement
  • Extensions
  • Applications
  • Use cases
  • Downloads

Key Features

Digital resolution 1 ps
Timing jitter down to 3.0 ps (RMS) / 7.0 ps (FWHM)
100 MEvents/s max. rate
Up to 16 stop channels, 1 start channel

The quTAG is a high-end, easy-to-use time-to-digital converter and time tagging device designed for time correlated single photon counting (TCSPC). It is capable of detecting events with a digital resolution of 1 picosecond and a jitter under 10 ps RMS. Its user-adjustable design registers all signals between -3V up to +3 V, like the widely used LVTTL or NIM. It allows capturing up to 100 million time tags per second and uses a USB3.0 connection to transfer the extensive data. It is delivered with software for Windows and Linux with an easy-to-use graphical user interface. It can also be integrated in custom software. Examples for LabView, C/C++ and Python are included.


Two models are available:

  • The basic model
    This model is the entry model for the cost-sensitive customer. It features 1 start and 2 stop channels. The graphical user interface for recording timestamps and the API for your customized solution is included as well. All features of the standard model can be upgraded at your lab.
  • The standard model
    This model features 1 start and 4 stop channels. A separate channel for external clock is available and easily accessible on the front panel. The device allows synchronizing with up to four standard models with all 16 stop channels using the same timebase and clock input. The software includes an analyzing tool for lifetime measurements and correlation functions (e.g. HBT measurements, fluorescence correlation spectroscopy).


Digital resolution1ps
Timing jitter upgrade 2 channels< 3.0
< 4.2
ps RMS /√2 *
ps RMS
Timing jitter< 7.1
< 10
ps RMS /√2 *
ps RMS
Number of stop channelsbasic: 2
standard: 4
(max. 16)
Max event rate100
M/s (per device)
M/s (per channel)
Input signals-3 ... +3
Input connectorsSMA
Connection to PCUSB 3.0
USB 2.0
SoftwareGUI, DLL, LabView, Python, Command line
Windows, Linux
Dimensions44 x 30 x 5cm x cm x cm

All specifications can be found in the datasheet.
* See the tab “Jitter Measurement” for measurement method.

Jitter Measurement

In order to measure the jitter, we generate an electrical pulse with steep edges. This pulse gets split into two by a power splitter and sent into two different inputs of the quTAG (i.e. start and stop-X or stop-X and stop-Y).

Then we use the quTAG software to generate a startstop-histogram. We fit a Gaussian function to this histogram and determine RMS and FWHM. The single channel jitter corresponds to σ / √2 from this two-channel measurement, assuming equal Gaussian contributions from both signals. The FWHM can be obtained by the standard deviation with the relation FWHM = 2 √2 ln 2 σ ≈ 2.35 σ.

The evaluation of the measurements shown above yields the measured jitter and calculated single channel jitter for the different modes:

Jitter upgrade 2 ch. RMS [ps] FWHM [ps]
Measurement 3.28 7.71
Single channel jitter 2.32 5.49
Jitter upgrade 4 ch. RMS [ps] FWHM [ps]
Measurement 4.57 10.74
Single channel jitter 3.23 7.59
Standard RMS [ps] FWHM [ps]
Measurement 8.07 18.96
Single channel jitter 5.70 13.40


Available Extensions standard model basic model
+ Jitter upgrade
This feature allows lower jitter at < 6.4 ps RMS on all four input channels. For lowest jitter of < 4.2 ps RMS, two channels can be combined, leaving two stop-channels of one device for measurements. For optimal jitter results, recalibration with external signals might be necessary. The single channel jitter corresponds to σ / √2 from this two-channel measurement, assuming equal Gaussian contributions from both signals.

Leading to single channel jitter < 3.0 ps RMS/√2 (2 channels) and
< 4.5 ps RMS/√2 (4 channels).

+ Stop channel extension
The quTAG basic features two stop channels that can be extended by up to two more flexible stop channels. The quTAG standard has all 4 stop channels enabled by default.
+ Lifetime software
This software addon enables the user to analyze lifetime measurements on the fly. It calculates the histograms, fits exponential decreases and takes response function of the system into account.
+ Correlation software
This software extension is intended for calculating the correlation function, as needed for example in Hanbury Brown-Twiss experiments or fluorescence correlation spectroscopy. Standard functions can be fitted to assess the relevant parameters.
+ Clock Input
The quTAG can be synchronized to an external clock of 10 MHz to allow more precise long-term accuracy.
+ Synchronization between devices
This extension allows you to synchronize up to 4 quTAG devices. By this, up to 16 equal stop channels are offered and behave like one device – all sharing the same clock input and time base.
+ Marker Input
This extension allows the use of additional input channels with less resolution that can be used for your trigger signals (e.g. pixel clock, line clock). These inputs are included in your timeline and help you sorting and assigning your timestamps.
+ Filters / Virtual Channels
This extension allows you to enable user-defined filters or virtual channels (e.g. coincidence and sync filters or artificial dead time). This filtering happens inside the device so that you save bandwith on your USB connection.

+ User-defined Clock frequency
Allow to use any frequency between 1-100 MHz as clock input for long-term accuracy.
+ Start Channel as Input
The start channel can be converted to another stop channel allowing the device to have 5 completely equal input channels with 1 ps resolution.
+ Divider for stop channels
This option allows you to enable a divider on all stop channels. This allows higher (periodic) frequencies to be recorded.
– included
– upgradeable

Additional extensions are available upon request. Customized solutions, e.g. signal outputs, are possible. Contact us for details!


General Applications

Time-Correlated Single Photon Counting (TCSPC)
Fluorescence/Phosphorescence Lifetime Measurements / Imaging (FLT / FLIM)
Fluorescence (Lifetime) Correlation Spectroscopy (FCS / FLCS)
Foerster Resonance Energy Transfer (FRET)
Single Photon Emitter Characterisation
We used the quTAG for two experiments together with the superconducting nanowire single photon detector (SNSPD) from our long-time collaborators at Single Quantum. The results proved the efficiency and speed that we expected as we engineered the quTAG.

Laser trigger as Start, Single Quantum SNSPD as Stop

We measured a time difference histogram between the trigger pulse from the laser as start and the SQ detector signal as stop.
This is basically the setup for a Fluorescence Lifetime Imaging (FLIM) measurement..

Whole system response function (blue, measured with quTAG): Timing jitter 17.8 ps RMS, 35.9 ps FWHM
For comparison: Detector response function (red, measured with fast oscilloscope): Timing jitter 14.5 ps RMS, 26.1 ps FWHM.


One SQ Detector as Start, another one as Stop

Here, we measured the time difference histogram between one of the two SQ SNSPDs as Start and the other one as Stop pulse.

Timing jitter of 2 SQ SNSPDs measured with the quTAG (blue): 21.6 ps RMS, 45.6 ps FWHM.


quTAG datasheet 02/2019 0.3 MB pdf
quTAG HR datasheet 03/2020 0.4 MB pdf
quTAG MC datasheet 03/2020 0.4 MB pdf


quTAG brochure 03/2019 2.4 MB pdf
quTAG manual V1.4.0 05/2019 0.9 MB pdf
quTAG software manual V1.5.0 10/2019 0.3 MB pdf


quTAG software V1.5.2* 12/2019 25.1 MB exe
quTAG software V1.5.2* 12/2019 20.9 MB zip
64bit library win V1.5.2* 12/2019 0.4 MB zip
64bit library linux V1.5.2* 12/2019 7.7 MB tgz
FTDI driver V1.2 10.4 MB exe
Python examples 06/2020 0.4 MB zip

* Note! This software is compatible only with serial number T 01 0012 and newer! Please contact us if you own an older device!