Specifications

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:

Extensions

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.

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

Publications

• Time-of-arrival detection for time-resolved scanning transmission X-ray microscopy imaging
  S. Finizio et al., Journal of Synchrotron Radiation (2020)
• Performance Optimization and Real-Time Security Monitoring for Single-Photon Quantum Key Distribution
  T. Kupko et al., arXiv preprint (2019)
• Hong-Ou-Mandel interference between independent III-V on silicon waveguide integrated lasers
  C. Agnesi, et al., arXiv preprint (2019)
• Sub-ns timing accuracy for satellite quantum communications
  C. Agnesi et al., arXiv preprint (2019)
• Experimental demonstration of quantum advantage for one-waycommunication complexity
  N. Kumar et al., arXiv preprint (2018)
• A photonic quantum walk with a four-dimensional Coin
  L. Lorz et al., arXiv preprint (2018)
• Towards quantum communication from global navigation satellite system
  L. Calderaro et al., IOP Publishing (2018)

General Applications

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..

Results:
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.

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

Overview of quick and easy Python Coding Examples

Python is a popular coding language for labs and institutes. Therefore, qutools created a Python file to wrap all the DLL or SO (Win/Linux) functions to gain quick and easy control of the hardware.

The following list shows the different examples using this wrapper. An explanation is added to each code.

• Retrieve Countrates and Coincidences
• Live Plotting of Countrates with matplotlib
• Create and retrieve a histogram of two channels
• Live Plotting of the histogram with a changing channel delay
• Retrieve timestamps
• Write timestamps to a file on the PC
• Change different settings of the quTAG

First Coding Example: How to retrieve Countrates

The following codes show how to quickly connect to the quTAG via Python. The quTAG.py file wraps all DLL functions to get simple access via your own code.

In the first example qutag-GetCoincCounter-starter_example.py we are retrieving countrates and coincidences of the quTAG and its input channels.

# quTAG Python example codes based on the quTAG Python wrapper.
# Run with Python 3.7.3 (32bit), numpy-1.13.3 and Windows 7 (64bit)

# Import the python wrapper which wraps the DLL functions.
# The wrapper should be in the same directory like this code in the folder '../QUTAG-V1.5.0/userlib/src'.
try:
	import QuTAG
except:
	print('Time Tagger wrapper QuTAG.py is not in the search path.')
	
	
#Initialize the quTAG device
qutag = QuTAG.QuTAG()
# Set the exposure time (or integration time) of the internal coincidence counters in milliseconds, range = 0...65535
qutag.setExposureTime(1000) # 1000 ms exposure time
# Give some time to accumulate data
time.sleep(1) # 1 second sleep time with 100ms exposure time would give ~10 times data we don't get

# Now let's retrieve the most recent values of the built-in coincidence counters from quTAG.
# The array contains count rates for all 5 channels and rates for coincidences of events detected on different channels. Events are coincident if they happen within the coincidence window (qutag.setCoincidenceWindow).
# The coincidence counters are not accumulated, i.e. the counter values for the last exposure (see setExposureTime ) are returned.
data,updates = qutag.getCoincCounters()
print('Updates since last call: ', updates, '| latest Data: ', data)
# updates	Output: Number of data updates by the device since the last call. Pointer may be NULL.
# data	        Output: Counter Values. The array must have at least 31 elements.
#                       The Counters come in the following channel order with single counts and coincidences:
#                       0(5), 1, 2, 3, 4, 1/2, 1/3, 2/3, 1/4, 2/4, 3/4, 1/5, 2/5, 3/5, 4/5, 1/2/3, 1/2/4, 1/3/4, 2/3/4, 1/2/5, 1/3/5, 2/3/5, 1/4/5, 2/4/5, 3/4/5, 1/2/3/4, 1/2/3/5, 1/2/4/5, 1/3/4/5, 2/3/4/5, 1/2/3/4/5 
### see 'tdcbase.h' file reference for more info: function TDC_getCoincCounters(Int32 *data, Int32 *updates)

Datasheets

Manuals

Software

quTAG software V1.5.3*	12/2019	25.1 MB	exe
quTAG software V1.5.3*	12/2019	20.9 MB	zip
64bit library win V1.5.3*	12/2019	0.4 MB	zip
64bit software linux V1.5.3*	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!