SHFQA Mode Configuration And Setup

The SHFQA can be operated in two modes, the Spectroscopy and the Qubit Readout mode. For each mode, the digital connectivity of the instrument is reconfigured, i.e. different functionality blocks are enabled and connected with each other. This reduces complexity, the need for the user to (re)configure the functionality units in the correct way each time the application is changed, and reduces the chance of wrong block configuration as interdependencies between the different possible mode settings are removed.

Features Overview

  • Configure the operation mode of the SHFQA

  • Obtain a fast overview over the readout Channel configuration

  • Gain fast access to the most important settings for Spectroscopy and Qubit Readout mode


The SHFQA can be configured in two operation modes: Spectroscopy and Qubit Readout mode. The mode can be switched using the high-level node /DEV…​./QACHANNELS/n/MODE and its typically the first node that needs to be set at the beginning of an experiment.

The Spectroscopy mode is functionally set up around the Sweeper. The Sweeper controls the offset frequency (from the Center Frequency of the Channels analysis band) and amplitude of the digital Oscillator, that is output in continuous mode operation at the Signal Output. The signal at the Channels Input is then downconverted using the same digital Oscillator signal as a reference before integration. The resulting integrated quadrature signals are then provided by the Sweeper module as a function of the varied parameters.

An external Trigger from the hardware trigger engine may be provided to trigger the acquisition of the result integration in the sweeper. That way, even a pulsed resonator spectroscopy - e.g. following qubit state preparation - can be performed.

The Output Signal of the Spectroscopy mode is always continuous wave.

functional description setup spectroscopy
Figure 1. Instrument connectivity in Spectroscopy mode

The Qubit Readout mode is functionally set up around the Readout Pulse Generator including the Sequencer and its intended use is to perform high-fidelity single-shot qubit, qutrit or ququad readout. In the Qubit Readout mode, the Sequencer controls playback of frequency-multiplexed readout pulses stored in the Waveform Memory. After passing throught the setup and following digitization, the pulses are correlated with references traces. The correlation, performed through a Sequencer-timed integration with the Reference traces stored in the complex-valued Integration Weights, results in a single, complex data point for each defined Reference trace (Integration Weight) - or readout resonator, respectively. These data points can then be classified corresponding to a specific qubit state in the Threshold unit. The Result Logger can both access the integrated data after correlation, or the discriminated results after the Threshold unit.

functional description setup readout
Figure 2. Instrument connectivity in Qubit Readout mode

Functional Elements

The following Table 1 summarizes all relevant settings to navigate the different nodes. The modes are all accessible through the first level of the QAChannels branch: /DEV…​./QACHANNELS/n/…​. More functional elements for the specific modules can be found in the corresponding chapters.

Table 1. Input and Output Settings
Control/Tool Option/Range Description



Selects between Spectroscopy and Qubit Readout mode.