Concept of pulse extraction methods

General description

The extraction methods take a 1D (for continuous counting) or 2D (for gated counting) integer array representing the count trace as input together with method specific parameters. In case of gated counting, the first dimension of the count array is the gate index and the second dimension is the time bin index of the corresponding time trace.

Based on these inputs it will extract the actual laser-on part of the timetrace for each laser pulse. So the returned object will be a 2D integer numpy array with the first dimension being the index of the laser pulse and the second dimension being the count trace of the corresponding laser pulse.

Architecture

Each extraction method is a bound method of a child class of PulseExtractorBase. This base class provides read-only access to important attributes of PulsedMeasurementLogic via properties. (see ./logic/pulsed/pulse_extractor.py) For the extraction you can therefore access all the information contained in PulsedMeasurementLogic, namely:

• is_gated (bool indicating if the fast counter is gated or not)
• measurement_settings (dict containing the parameters to define the current measurement)
• sampling_information (dict containing information about the discretization of the currently loaded waveform/sequence)
• fast_counter_settings (dict containing the current settings for the fast counter hardware)

If you need access to another attribute of the logic module simply add it as property to PulseExtractorBase but make sure to protect it properly against changes to the logic module.

In addition the base class provides access to the qudi logger which can be used just like in any other qudi module, e.g. `self.log.warning('I am a warning!')`

All parameters needed for the pulse extraction that can not be provided by the logic module need to be handed over to the extraction method directly as keyword arguments with default value.

When activating the PulsedMeasurementLogic, an instance of PulseExtractor will be created. This class finds and imports all child classes of PulseExtractorBase from the default directory ./logic/pulsed/pulse_extraction_methods/. It will also inspect the extraction methods and create two dictionaries. One is holding references to the method itself and the other contains the keyword arguments together with the currently set values for each extraction method. In both cases the dictionary keys are the method names excluding the "analyse_" naming prefix. Those two dictionaries can be accessed via properties of PulseExtractor. The property holding the extraction parameters is masked in order to only return or set the parameter set for the currently selected extraction method.

Method signature

Each extraction method must meet the following requirements:

• Is bound instance method of a PulseExtractorBase child class
• Method name starts with prefix gated_ for extraction of gated counter timetraces or ungated_ for extraction of continuous counter timetraces.
• First argument (after self) must be named count_data
• Additional parameters must be defined as optional keyword arguments
• Default values for additional arguments must be of type int, float, str or bool. Depending on the default argument type the GUI will automatically create the proper input widget.

Adding new methods procedure

1. Define a class with PulseExtractorBase as the ONLY parent class.
2. Make sure the base class gets initialized with: ```python def init(self, *args, **kwargs): super().__init__(*args, **kwargs) ```
3. Define extraction methods in new class. (see section "Method signature")
4. Place the module containing your class definition in the default directory to import from (./logic/pulsed/pulse_extraction_methods/) or put it in a custom directory and specify the path in your config for the PulsedMeasurementLogic as ConfigOption "additional_extraction_path".

You can also simply add your extraction method to an already existing PulseExtractorBase child class. In that case you just need to follow step 3.

By default qudi ships with the default methods defined in ./logic/pulsed/pulse_extraction_methods/basic_extraction_methods.py. This module should not be altered unless you intend to contribute your methods to the qudi repository.

A template for a new PulseExtractor class could look like:

class MyPulseExtractor(PulseExtractorBase):
    """ Description goes here """
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

    def gated_my_method_name1(self, count_data, my_float_param=42.0, my_int_param=42):
        # Do something
        pass

    def ungated_my_method_name2(self, count_data, my_str_param='derp', my_bool_param=True):
        # Do something
        pass

    def _some_helper_method(self):
        pass