Tuning

Tuning quantum dots is a process roughly consisting of two parts. First, puddles of electrons are formed within an electron gas by finding appropriate voltages for all electrostatic gates nearby. The second step optimizes the voltages of a small subset of these gates to adjust the number of charges within each dot and the couplings between them. The figure below illustrates the entire tuning process on a nanowire, where both steps have been performed.

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The general goal of dot tuning illustrated on a nanowire: by setting voltages to all electrostatic gates, well-defined quantum dots with specific tunnel couplings can be formed.

A manual approach to tuning consists of a sequence of measurements iteratively narrowing down the voltage range of each gate, outlined in Manual tuning. nanotune applies this approach to the first step, also referred to as coarse tuning. By automating some of the most common measurements and replacing the experimenter’s decision making by binary classifiers, it implements the device characterization and dot-tuning procedures outlined in the workflow diagram in Fig. 2.

Both device characterization and dot tuning is covered by the tuning module, whose main components are the Tuner base class and its two subclasses Characterizer and DotTuner, described in Device tuner. Tuning results are saved in an instance of a TuningHistory, which holds instances of MeasurementHistory and TuningResult, described in Results saving.