Quantum Analyzer Setup Tab
The Quantum Analyzer Setup is the main control panel for the qubit measurement unit on the Instrument (see Functional Overview for an overview block diagram). It is available on all SHFQA Instruments.
Features

2 Application modes

Readout up to 16 qubits

Up to 16 customized integration weights

Qubit state discrimination

Graphic representation of data processing
Description
Control/Tool  Option/Range  Description 

QA Setup 
Configure the Qubit Measurement Unit 
The Quantum Analyzer Setup tab is divided into 2 subtab groups for resonator spectroscopy (see Figure 1) and qubit readout (see Figure 2) application. By selecting Application Mode, Spectroscopy or Readout, the corresponding subtabs provide all configuration of readout pulse generation and acquired data processing (see Table 2). All readout and integration weight waveforms or spectroscopy envelop saved in the waveform memories can be displayed by the Waveform Viewer subtab of the Readout Pulse Generator tab (see Figure 3).
Spectroscopy Mode
The SHFQA has 1 Digital Oscillator per channel. In Spectroscopy mode, the Digital Oscillator is used for readout waveform generation and integration. There are 2 operation modes for readout waveform generation, Continuous and Pulse.
In Continuous mode, the output signal on the front panel is a continuous wave. The frequency of the output signal is configured by the center frequency of the frequency upconversion chain and the offset frequency of the Digital Oscillator. The amplitude of the output signal is configured by the output range of the frequency upconversion chain and the amplitude gain of the Digital Oscillator. The SHFQA Sweeper class (API) is the central controller in the Spectroscopy mode. The simplified measurement flow in Continuous mode is shown in Figure 4 (see tutorial Continuous Resonator Spectroscopy).

Configure parameters for frequency sweep and integration

Sweeper sets the start frequency to the Digital oscillator

Sweeper waits for a trigger signal from a Hardware Trigger Engine to start integration

after the integration is finished the Sweeper set a new frequency and continue the measurement
The complex signal generated by the Digital Oscillator is
where \(g_{\mathrm{osc}}\ (0\le g_{\mathrm{osc}}\le1)\) is the amplitude gain of the Digital Oscillator, \(f_{\mathrm{IF}}\) is the frequency of the oscillator. The signal is then filtered and upconverted by a 2 GHz digital oscillator on the signal output path, and reaches the Digital To Analog Converter (DAC) as \(g_{\mathrm{osc}}e^{i 2\pi (f_{\mathrm{IF}}+f_{\mathrm{2\ GHz}})t_n}\). After the ADC and analog frequency upconversion, the output signal on the front panel is
where \(C = 10^{\frac{P_{\mathrm{range,\ out}}10}{20}}\) is a factor converting the power range of the output signal in units of dBm to the amplitude in units of V, \(f_{\mathrm{RF}} = f_0 + f_{\mathrm{IF}}\), \(f_0\) is the center frequency. The output power calculation is detailed in Inputs/Outputs Tab.
The frequency downconversion and integration data processing of the input signal in both Spectroscopy and Readout mode is detailed in Quantum Analyzer Result Tab.
In Pulse mode, the output signal on the front panel is pulsed. The readout pulse is generated by an uploaded waveform envelope modulated by the Digital Modulator. In this mode the readout amplitude is also controlled by the amplitude of the waveform envelope. The simplified measurement flow in Pulse mode is the following (see Figure 4 and tutorial Pulsed Resonator Spectroscopy).

Configure Sweeper parameters for frequency sweep and integration

Upload readout pulse envelope

Sweeper sets the start frequency to the Digital oscillator,

Sweeper waits for a trigger signal from the Hardware Trigger Engine to playback a readout pulse and start integration,

after the integration is finished the Sweeper set a new frequency and continue the measurement.
Please note that there is a delay between the starting time of pulse generation and integration due to the Instrument’s internal delay and the physical system’s external delay. The delay can be measured and compensated by setting the integration delay.
The results after integration in both Continuous and Pulse mode are saved in the result logger, and the power and phase can be calculated and plotted with the Sweeper.
Output Signal
The complex signal generated by the Digital Oscillator and the Envelope is
where \(A_n\) is the complex envelope and \(A_n\le 1\). The output signal on the front panel is
where \(A_{\ \mathrm{real}}(t)\) (\(A_{\ \mathrm{imag}}(t)\)) is the real (imaginary) part of the envelope.
Readout Mode
The SHFQA has 8 or 16 readout waveform memory slots, and 8 or 16 integration weights memory slots per channel. In readout mode, these memory slots are used for readout pulse generation and weighted integration. The SHFQA Readout Pulse Generator is the central controller in Readout mode. The simplified measurement flow is shown in Figure 5 (see tutorial Multiplexed Qubit Readout).

Upload or parametrically generate readout pulse and integration weights

Configure integration parameters

Upload and compile a measurement sequence in a sequencer of the SHFQA Readout Pulse Generator

Configure a digital trigger if a trigger is desired to run the sequence

Run the measurement sequence
The last 3 steps are configured in the SHFQA Readout Pulse Generator Tab. Please note that overflow of output (OVO) could happen if the amplitude setting or the overshoot of the readout waveform exceeds 1. The readout pulse playback and weighted integration are both started with startQA command, and the measurement results are saved in the SHFQA result logger and displayed in the Quantum Analyzer Result Tab. If Integration is selected as the result source, the returned data is complex data with I as real part and Q as imaginary part. If Thresholding is selected, the real part of the complex data will be compared with a threshold on the Thresholding subtab, and the result will be either 0 or 1.
Output Signal
The complex data uploaded from a CSV file or APIs, or parametrically generated by using LabOne UI saved in a single waveform memory slot is
where \(A_n \le 1\) (\(n\) means the nth sample) is the amplitude, \(f_{\mathrm{IF}}\) is the offset frequency, \(\phi\) is the phase. In case of parametric waveform generation, \(A_n\) is constant. Please note that the maximum amplitude of sum of all waveforms in use should not exceed 1. The output signal on the front panel is
where \(C\) is a conversion factor depending on selected output power range. For multiqubit readout in the same readout line, the output signal is
where \(i\) indicates ith waveform memory slot.
Integration weights
The complex integration weight can be uploaded from a CSV file or APIs, or parametrically generated by using LabOne GUI and saved into a single integration weight memory slot as
where \(A_{\mathrm{weight},\ n} \le 1\) is the amplitude of the integration weight, \(f_{\mathrm{weight}}\) is the frequency of the integration weight, \(\phi_{\mathrm{weight}}\) is the phase of the integration weight. The integration result is then calculated by multiplying the frequency downconverted complex input signal by the conjugate of the integration weight.
In order to achieve the highest possible resolution in the signal after integration, it’s advised to scale the dimensionless readout integration weights with a factor so that their maximum absolute value is equal to 1. 
Functional Elements
Control/Tool  Option/Range  Description 

Application Mode 
Spectroscopy 
Using internal digital oscillator for waveform generation and integration. 
Readout 
Using uploaded waveform for output signal generation and customized weights for integration. 

Errors 
Number 
Number of holdoff errors detected since last reset. 
Spectroscopy 

Trigger Signal 
Selects the source of the trigger for the integration and envelope in Spectroscopy mode. 

Integration Length 
\(2^2\) to \(2^{25}\) 
Sets the integration length in Spectroscopy mode in number of samples. Up to 33.5 MSa (2^25 samples, with granularity of 4 Samples ) can be recorded, which corresponds to 16.7 ms. 
Integration Delay 
4 ns to 131.1 μs 
Sets the delay of the integration in Spectroscopy mode with respect to the trigger signal. The resolution is 2 ns. 
Operation Mode 
Continuous 
The output of the internal digital oscillator is used directly for frequency upconversion. 
Pulse 
The waveform envelope is modulated by the internal digital oscillator before frequency upconversion. 

Length 
4 to 32 k (SHFQA2 without 16W option) or 64 k 
Indicate the length of uploaded envelope waveform in units of Samples. The granularity is 4 Samples. 
Delay 
0 ns to 131.1 μs 
Set a delay between readout pulse playback trigger and the first sample of the readout pulse (in Pulsed mode). The resolution is 2 ns. 
File Upload 
CSV file 
Drop CSV file to upload the envelope waveform. 
Center Frequency 
1  8 GHz 
Display center frequency in Spectroscopy mode. 
Offset Frequency 
 1 to +1 GHz 
Set offset frequency to the internal digital oscillator in Spectroscopy mode. 
Output Frequency 
0.5 to 8.5 GHz 
Display frequency of the output signal in Spectroscopy mode. 
Amplitude 
0 to 1 
Set gain of the internal digital oscillator in Spectroscopy mode. The recommended range is from 0.01 to 1 in pulsed mode. 
Readout 

Integration Length 
4 to 4096 
Sets the length of all Integration Weights in number of samples. A maximum of 4096 samples can be integrated, which corresponds to 2.05 us. The granularity is 4 Samples. 
Integration Delay 
0 ns to 131.1 μs 
Sets a common delay for the start of the readout integration for all Integration Weights with respect to the time when the trigger is received. The resolution is 2 ns. 
Sequencer Run/Stop 
Run or Stop 
Enables the Sequencer. 
Waveforms Clear 
Empty all readout Waveform Memory slots or Integration weight Units. 

Waveform Generation 
Parametric or Upload 
Select the way to generate waveform. 
Parametric Amplitude 
0 to 1 
Set amplitude factor for parametric readout pulse and integration weight generation. 
Parametric Frequency 
1 to +1 GHz 
Set offset frequency for parametric readout pulse or integration weight generation. 
Parametric Phase 
180 to 180 degree 
Set phase for parametric readout pulse and integration weight generation. 
Parametric Window Type 
Rectangular 
Display window function to be applied in complex exponential function for parametric readout pulse and integration weight generation. 
Parametric Window Length 
4 to 4096 
Length of the selected window in samples for parametric readout pulse and integration weight generation. 
Parametric Set To Device 
Yes or No 
Set parametrically generated readout pulse and integration weight to waveform memory slot and integration memory slot, respectively. 
Thresholding 
14.51 kV to 14.51 kV 
Set threshold for quantum state discrimination. Note that the data before thresholding is not normalized by the integration length. 