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

  • Spectroscopy mode and readout mode

  • Continuous or pulsed resonator spectroscopy

  • Power spectral density

  • Weighted integration

  • Readout up to 16 qubits per channel

  • 2-state and multistate discrimination

Description

Table 1. App icon and short description
Control/Tool Option/Range Description

QA Setup

btn mnu quantum analyzer um

Configure the Qubit Measurement Unit

The Quantum Analyzer Setup tab is divided into 2 sub-tab groups for resonator spectroscopy (see Figure 1) and qubit readout (see Figure 2) application. By selecting Application Mode, Spectroscopy or Readout, the corresponding sub-tabs provide all configurations of readout pulse generation and acquired data processing (see Table 5). The main differences of the Application Modes are listed in Table 2.

shfqa qa setup tab spectroscopy
Figure 1. LabOne GUI: QA Setup Tab - Spectroscopy Mode
shfqa qa setup tab readout
Figure 2. LabOne GUI: QA Setup Tab - Readout Mode
shfqa generator tab waveform viewer
Figure 3. LabOne GUI: Readout Pulse Generator Tab - Waveform Viewer
Table 2. Main differences of Spectroscopy and Readout mode
Parameters Spectroscopy mode Readout mode

Waveform generation

Digital oscillator and envelope

Sample by Sample

Waveform output mode

Continuous or pulsed

Pulsed

Waveform length

Continuous
or up to 16 μs or 32 μs

Up to 2 μs

Number of qubits per channel

1

Up to 8 or 16

Integration length

Up to 16.7 ms

Up to 2 μs

Integration weight unit per channel

Not applicable

Up to 8 or 16

Real-time state discrimination

Not applicable

Yes

Multistate discrimination

Not applicable

Qubits, qutrits and ququads

Spectroscopy Mode

Spectroscopy mode is mainly used for resonator spectroscopy and power spectral density measurement. The SHFQA has 1 Digital Oscillator per channel. In Spectroscopy mode, the Digital Oscillator is used for readout waveform generation and integration. The SHFQA Sweeper class (API) is the central controller for the Spectroscopy mode, see tutorial Continuous Resonator Spectroscopy and Pulsed Resonator Spectroscopy.

There are 2 operation modes for readout waveform generation, Continuous and Pulsed. In Continuous mode, signal from the Digital Oscillator is routed to the digital IQ mixing stage (see Functional Overview) for readout waveform generation in the output path, and to multiply the input signal for readout waveform integration in the input path, see Figure 4. In Pulsed mode, signal from the Digital Oscillator modulates the envelope from the Waveform Memory and then is routed to the output and input paths same as in Continuous mode. The pulse envelope can be displayed on the Waveform Viewer sub-tab of the Readout Pulse Generator tab. The main differences of the 2 operation modes are listed in Table 3.

functional description setup spectroscopy
Figure 4. Readout waveform generation and integration in Spectroscopy mode
Table 3. Main differences of Continuous and Pulsed mode in Spectroscopy mode.
Parameters Continuous mode Pulsed mode

Readout pulse length

Continuous wave

Up to 16 μs or 32 μs
(up to 32 kSa or 64 kSa)

Envelope delay

Not applicable

Up to 131.1 μs

Readout pules amplitude

Controlled by output range and gain factor of the Digital Oscillator

Controlled by output range, gain factor of the Digital Oscillator and the envelope

Readout Waveform Output In Spectroscopy Mode

The readout waveform on the Instrument output can be expressed as

\[\begin{equation}\tag{1} \begin{aligned} E_{\mathrm{output}}(t) & = C_{P\rightarrow A}A(t)g_{\mathrm{osc}}e^{i2\pi (f_0 + f_{\mathrm{osc}}) t + i\phi_{\mathrm{output}}},\\ \end{aligned} \end{equation}\]

where \(C_{P\rightarrow A} = 10^{\frac{P_{\mathrm{range,\ output}}-10}{20}}\) is the conversion factor converting the power range \(P_{\mathrm{range,\ output}}\) of the output signal in units of dBm to the amplitude in units of V, , \(A(t)\) is the complex readout envelope in Pulsed mode and \(A(t) = 1\) in Continuous mode, \(g_{\mathrm{osc}}\) is the amplitude gain factor of the Digital Oscillator, \(f_0\) is the center frequency set in the Input/Output tab, \(f_{\mathrm{osc}}\) is the offset frequency set by the Digital Oscillator, \(\phi_{\mathrm{output}}\) is the global phase can be reset by resetting the phase of the Digital Oscillator.

The readout waveform envelope \(A(t)\) in Pulsed mode can be displayed on the Waveform Viewer, see Figure 3.

Readout Results In Spectroscopy Mode

The readout input signal after analog frequency down-conversion before the ADC is

\[\begin{equation}\tag{2} \begin{aligned} E_{\mathrm{before\ ADC}}(t) & = \operatorname{Re}(A_{\mathrm{input}}(t)e^{i2\pi f_{\mathrm{before\ ADC}} t + i\phi_{\mathrm{input}}})\\ & = A_{\mathrm{input}}(t)\cos({2\pi f_{\mathrm{before\ ADC}} t + \phi_{\mathrm{input}}})\\ & = A_{\mathrm{input}}(t)\frac{e^{i2\pi f_{\mathrm{before\ ADC}} t + i\phi_{\mathrm{input}}} + e^{-i2\pi f_{\mathrm{before\ ADC}} t - i\phi_{\mathrm{input}}}}{2}, \end{aligned} \end{equation}\]

where \(A_{\mathrm{input}}(t)\) is the amplitude of input signal on the front panel of the instrument, \(f_{\mathrm{before\ ADC}}\) is the frequency of the input signal before ADC, \(\phi_{\mathrm{input}}\) is the global phase of the input signal on the front panel of the instrument. After the ADC, it becomes

\[\begin{equation}\tag{3} \begin{aligned} E_{i,\ \mathrm{after\ ADC}} & = C_{\mathrm{scaling}}A_{i,\ \mathrm{input}}(t)\frac{e^{i2\pi f_{\mathrm{after\ ADC}} t_i + i\phi_{\mathrm{input}}} + e^{-i2\pi f_{\mathrm{after\ ADC}} t_i - i\phi_{\mathrm{input}}}}{2}\\ & = \frac{C_{\mathrm{scaling}}A_{i,\ \mathrm{input}}(t)}{2}(e^{i2\pi f_{\mathrm{after\ ADC}} t_i + i\phi_{\mathrm{input}}} + e^{-i2\pi f_{\mathrm{after\ ADC}} t_i - i\phi_{\mathrm{input}}}), \end{aligned} \end{equation}\]

where \(C_{\mathrm{scaling}}\) is the conversion factor depending on gain factor, ADC range and bit resolution, \(f_{\mathrm{after\ ADC}}\) is the frequency after the ADC, \(i\) means the \(i\)-th sample. The signal \(E_{i,\ \mathrm{after\ ADC}}\) is then down-converted by a digital oscillator at 1 GHz and filtered the high frequency components, as

\[\begin{equation}\tag{4} \begin{aligned} E_{i,\ \mathrm{before\ integration}} & = E_{i,\ \mathrm{after\ ADC}}e^{-i2\pi f_{\mathrm{after,\ LO2}}t}\\ & = \frac{C_{\mathrm{scaling}}A_{i,\ \mathrm{input}}(t)}{2}(e^{i2\pi f_{\mathrm{after\ ADC}} t_i + i\phi_{\mathrm{input}}} + e^{-i2\pi f_{\mathrm{after\ ADC}} t_i - i\phi_{\mathrm{input}}})e^{-i2\pi f_{\mathrm{input,\ LO2}}t},\\ & = \frac{C_{\mathrm{scaling}}A_{i,\ \mathrm{input}}(t)}{2}(e^{i2\pi f_{\mathrm{baseband}} t_i + i\phi_{\mathrm{input}}} + e^{-i2\pi f_{\mathrm{sum}} t_i - i\phi_{\mathrm{input}}})\\ & \stackrel{\mathrm{filter}}{=} \frac{C_{\mathrm{scaling}}A_{i,\ \mathrm{input}}}{2}e^{i2\pi f_{\mathrm{baseband}} t_i + i\phi_{\mathrm{input}}},\\ \end{aligned} \end{equation}\]

where \(f_{\mathrm{input,\ LO2}}\) is the frequency of the digital oscillator, \(f_{\mathrm{baseband}} = f_{\mathrm{after\ ADC}}-f_{\mathrm{input,\ LO2}} = f_{\mathrm{osc}}\) is the differential frequency, \(f_{\mathrm{sum}} = f_{\mathrm{before\ ADC}}+f_{\mathrm{input,\ LO2}}\) is the sum frequency. The signal at \(f_{\mathrm{sum}}\) is filtered out by the digital filter. By multiplying a factor of \(\sqrt{2}/C_{\mathrm{scaling}}\) the units of the signal is converted to Vrms, and it can be monitored by the SHFQA Scope in a loopback configuration. After the filter the signal is then integrated with the signal from the Digital Oscillator \(e^{-i2\pi f_{\mathrm{osc}} t}\) and normalized by the number of integration samples \(N\),

\[\begin{equation}\tag{5} \begin{aligned} E_{\mathrm{after\ integration}} & = \frac{1}{N}\sum_{i = 1}^{N}E_{i,\ \mathrm{before\ integration}}e^{-i2\pi f_{\mathrm{osc}} t_i},\\ & = \frac{C_{\mathrm{scaling}}}{2N}\sum_{i = 1}^{N} A_{i,\ \mathrm{input}}e^{i2\pi f_{\mathrm{osc}} t_i + i\phi_{\mathrm{input}}}e^{-i2\pi f_{\mathrm{osc}} t_i},\\ & = \frac{C_{\mathrm{scaling}}}{2N}\sum_{i = 1}^{N} A_{i,\ \mathrm{input}}e^{i\phi_{\mathrm{input}}}. \end{aligned} \end{equation}\]

If \(A_{i,\ \mathrm{input}} = A_{\mathrm{input}}\) is constant, then

\[\begin{equation}\tag{6} \begin{aligned} E_{\mathrm{after\ integration}}=\frac{C_{\mathrm{scaling}}A_{\mathrm{input}}}{2}e^{i\phi_{\mathrm{input}}}. \end{aligned} \end{equation}\]

By multiply the factor of \(\sqrt{2}/C_{\mathrm{scaling}}\), the units of the results is converted to Vrms, and then can be downloaded from the instrument via the Instrument node /DEV…/QACHANNELS/n/SPECTROSCOPY/RESULT/DATA/WAVE, see Device Node Tree. The power of input signal can then be derived as

\[\begin{equation}\tag{7} \begin{aligned} P_{\mathrm{input}} & = 10\log_{10}\frac{|E_{\mathrm{after\ integration}}|^2}{50} + 30. \\ \end{aligned} \end{equation}\]

The power and phase of the input signal can also be calculated and plotted using the Sweeper class.

Power spectral density

Power Spectral Density (PSD) measurements are generally required to characterize an amplification chain. In Spectroscopy mode, a PSD measurement can be performed using the SHFQA Sweeper, see GitHub zhinst-toolkit example or zhinst-toolkit Online Documentation, or using instrument nodes, see Device Node Tree.

Here, the PSD is calculated on the hardware as \(S_{xx}(f) = \lim_{N\to\infty} \frac{(\Delta t)^2}{T}|\sum_{n = -N}^{n = N} x_ne^{-i2\pi f_n\Delta t}|^2\) (see Spectral density Wikipedia), where \(\Delta t = 1/f_\mathrm{s}\) is the time step, \(f_\mathrm{s}\) is the sampling rate, \(T = (2N+1)\Delta t\) is the integration length in seconds, \(2N+1\) is the integration length in samples, \(x_ne^{-i2\pi f_n\Delta t}\) is the \(n\)-th complex data of the input signal. This calculation is done by the Instrument, and it returns the real-valued PSD in units of \(\mathrm{Vrms}^2/\mathrm{Hz}\). The applicable ranges of the PSD measurement are listed in Table 4.

Note that the measurement bandwidth is determined by the inverse of integration time, and the frequency step should be less than or equal to the measurement bandwidth. Typically, the PSD measurement requires many averages to be accurate. Setting the number of averages to a number larger than or equal to 1000 is recommended.

Table 4. Applicable ranges of PSD measurements
Parameters Values

LabOne version

≥ 23.02

Number of channels

2 or 4 for SHFQA;
1 for SHFQC

Input frequency range

0.5 - 8.5 GHz

Input power

up to +10 dBm

Input waveform length

continuous or pulsed (> 2 ns)

Measurement bandwidth (1 / integration time)

60 Hz to 500 MHz (16.7 ms to 2 ns)

Number of averages

1 to 131k

Input voltage noise density

see Specifications

Input spurious free dynamic range (excluding harmonics)

see Specifications

Readout Mode

Readout mode is mainly used for multi qubit readout. The SHFQA has 8 or 16 readout Waveform Memory slots, and 8 or 16 integration weight units 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, see Figure 5 and tutorial Multiplexed Qubit Readout.

functional description setup readout
Figure 5. Readout waveform generation, integration and discrimination in Readout mode.

There are 2 state discrimination modes, 2-state discrimination (default, see tutorial Multiplexed Qubit Readout and multistate discrimination (see tutorial Multistate discrimination). Both modes are based on the linear Support Vector Machine and one versus one classification. Note that multistate discrimination can only be configured via LabOne APIs.

Readout Waveform Generation In Readout Mode

The readout waveform can be generated parametrically by LabOne GUI and APIs, and then uploaded and saved in the Waveform Memory. All readout waveforms saved in the Waveform Memory can be erased by clicking Clear on LabOne GUI or using LabOne APIs. Each readout waveform can be used for a single qudit readout, and up to 8 or 16 qubits can be readout simultaneously using a sum of the readout waveforms saved in the Waveform Memory. The Readout Waveform Generator controls which and how readout waveforms are played, see the Readout Pulse Generator Tab.

The readout waveform saved in the \(j\)-th Waveform Memory slot is complex data, can be expressed as

\[\begin{equation}\tag{8} \begin{aligned} E_{i,\ j,\ \mathrm{readout}} & = A_{i,\ j,\ \mathrm{readout}}e^{i2\pi f_{j,\ \mathrm{offset}}t_{i,\ j} + i\phi_{j,\ \mathrm{readout}}}\\ & = (A_n\cos{(\phi)} + i A_n\sin{(\phi)})e^{i2\pi f_{\mathrm{IF}}t_n}\\ & = (A_{n,\ \mathrm{real}} + i A_{n,\ \mathrm{imag}})e^{i2\pi f_{\mathrm{IF}}t_n},\\ \end{aligned} \end{equation}\]

where \(A_{i,\ j,\ \mathrm{readout}}\ (0\le A_{i,\ j,\ \mathrm{readout}}\le 1)\) is the amplitude factor of the readout waveform at the \(i\)-th sample, \(f_{j,\ \mathrm{offset}}\) is the offset frequency, \(\phi_{j,\ \mathrm{readout}}\) is the global phase. The output signal on the front panel is

\[\begin{equation}\tag{9} \begin{aligned} E_{\mathrm{output}}(t) & = \sum_j A_{j,\ \mathrm{readout}}(t)e^{i2\pi (f_{j,\ \mathrm{offset}}+f_0)t + i\phi_{j,\ \mathrm{readout}}}\\ & = C(A_{\ \mathrm{real}}(t)\cos(2\pi f_{\mathrm{RF}}t) - A_{\ \mathrm{imag}}(t)\sin(2\pi f_{\mathrm{RF}}t)),\\ \end{aligned} \end{equation}\]

where the sum depends on number of qudits readout in parallel. Note that the maximum amplitude factor of the sum of all waveforms in use should not exceed 1.

Integration Weights

The integration weights can be parametrically generated or measured with the SHFQA Scope for the best SNR (see tutorial Integration Weights Measurement), and uploaded to the integration weight units. All integration weights saved in the memory can be erased by clicking Clear on LabOne GUI Integration Weights sub-tab or using LabOne APIs. The length of the integration weight is automatically extended to 4096 Samples once it’s uploaded, and integration length is used to configure how long it integrates. The Readout Waveform Generator controls which and how integration weights are used, see Readout Pulse Generator Tab.

The integration weights saved in the \(k\)-th integration weight unit is complex data, can be expressed as

\[\begin{equation}\tag{10} \begin{aligned} E_{i,\ k,\ \mathrm{weights}} & = A_{i,\ k,\ \mathrm{weight}}e^{-i2\pi f_{k,\ \mathrm{weight}}t_{i,\ k} - i\phi_{k,\ \mathrm{weight}}}\\ & = (A_{\mathrm{weight},\ n}\cos{(\phi_{\mathrm{weight}})} + i A_{\mathrm{weight},\ n}\sin{(\phi_{\mathrm{weight}})})e^{i2\pi f_{\mathrm{weight}}t_n}\\ & = (A_{\mathrm{weight,\ real},\ n} + i A_{\mathrm{weight,\ imag},\ n})e^{i2\pi f_{\mathrm{weight}}t_n},\\ \end{aligned} \end{equation}\]

where \(A_{i,\ k,\ \mathrm{weight}}\ (0\le A_{i,\ k,\ \mathrm{weight}}\le 1)\) is the amplitude factor of the integration weight at \(i\)-th sample, \(f_{k,\ \mathrm{weight}}\) is the frequency of the integration weight, \(\phi_{k,\ \mathrm{weight}}\) is the global phase of the integration weight.

In 2-state discrimination mode, 1 qubit requires 1 integration weight, i.e. the conjugated difference of readout input signal while qubit is prepared in state |0> and |1>, see Figure 6. In multistate discrimination mode, 1 qudit with \(n\) states requires \(n(n-1)/2\) integration weighs (one vs one classification), i.e. the conjugated differences of any 2 readout input signal while qudit is prepared in state |\(i\)> and |\(j\)>, where \(i\ (0\le i\le n-2)\) and \(j\ (1\le j\le n-1)\) are integer and \(i\neq j\). Only \(n-1\) integration weights need to be uploaded, and the integration results from the rest of integration weights are calculated by the Instrument automatically, see Figure 7 and Figure 8.

All integration weights saved in the integration weight units can be displayed on the Waveform Viewer, see Figure 3.

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.

Thresholding

Thresholding sub-tab is used to configure thresholds for state discrimination in 2-state discrimination mode. In multistate discrimination mode, thresholds and assignment matrix are configured by LabOne APIs.

The readout input signal in Readout mode may include different frequencies for multiplexed readout, as

\[\begin{equation}\tag{11} \begin{aligned} E_{i,\ \mathrm{before\ integration}} &= C_{\mathrm{scaling}}\sum_j \frac{A_{i,\ j,\ \mathrm{input}}}{2}e^{i2\pi f_{j,\ \mathrm{baseband}}t_i+\phi_{j,\ \mathrm{input}}}\\ \end{aligned} \end{equation}\]

where \(j\) is the \(j\)-th component of the readout input signal. By multiplying a conversion factor \(\sqrt{2}/C_{\mathrm{scaling}}\), the units of the signal is converted to Vrms, then the signal can be downloaded and monitored by the Scope. This signal is then integrated with different integration weights \(A_{j,\ \mathrm{weight}}(t)e^{-i2\pi f_{j,\ \mathrm{baseband}}t-i\phi_{j,\ \mathrm{weight}}}\) simultaneously. The integration result after 1 weighted integration unit is

\[\begin{equation}\tag{12} \begin{aligned} E_{j,\ \mathrm{after\ integration}} & = \frac{C_{\mathrm{scaling}}}{N}\sum_{i=1}^N \frac{A_{i,\ j,\ \mathrm{input}}}{2}e^{i2\pi f_{j,\ \mathrm{baseband}}t_i+\phi_{j,\ \mathrm{input}}}A_{i, j,\ \mathrm{weight}}e^{-i2\pi f_{j,\ \mathrm{baseband}}t_i-i\phi_{j,\ \mathrm{weight}}}\\ & = \frac{C_{\mathrm{scaling}}}{N}\sum_{i=1}^N \frac{A_{i,\ j,\ \mathrm{input}}A_{i, j,\ \mathrm{weight}}}{2}e^{i(\phi_{j,\ \mathrm{input}}-\phi_{j,\ \mathrm{weight}})}, \end{aligned} \end{equation}\]

where \(A_{i, j,\ \mathrm{weight}}\) is the amplitude of the integration weight, \(\phi_{j,\ \mathrm{weight}}\) is the phase of the integration weight. The result after integration is complex data, and can be downloaded and displayed on the Quantum Analyzer Result Tab after multiplying the conversion factor of \(\sqrt{2}/C_{\mathrm{scaling}}\). For the best SNR, the integration weight is configured such that \(\phi_{j,\ \mathrm{input}}=\phi_{j,\ \mathrm{weight}}\), therefore the imaginary part of the result is 0, as

\[\begin{equation}\tag{13} \begin{aligned} E_{j,\ \mathrm{after\ integration}} & = \frac{C_{\mathrm{scaling}}}{2N}\sum_{i=1}^N A_{i,\ j,\ \mathrm{input}}A_{i, j,\ \mathrm{weight}}. \end{aligned} \end{equation}\]

In 2-state discrimination mode, all integration weights can be uploaded via LabOne GUI and APIs, and all integration results saved in the result logger can be displayed on the Quantum Analyzer Result Tab if integration is selected as result source. In multistate discrimination mode, all integration weights can only be uploaded via LabOne APIs, and only \(n-1\) integration results are saved in the result logger if integration is selected as result source, the rest are calculated automatically in the pairwise difference units.

Before state discrimination, thresholds for each qudit have to be estimated and uploaded to the Instrument, see tutorial Multistate discrimination). During thresholding, the real part of the result after integration is compared with a threshold, and it returns 0 or 1. Qubit state discrimination can be done in both 2-state and multistate discrimination modes. The readout result of qubit after thresholding is

\[\begin{equation}\tag{14} \begin{aligned} E_{j,\ \mathrm{after\ thresholding}}= \begin{cases} 0 & \mathrm{Re}[E_{j,\ \mathrm{after\ integration}}] \le T_j,\\ 1 & \mathrm{Re}[E_{j,\ \mathrm{after\ integration}}] \gt T_j,\\ \end{cases} \end{aligned} \end{equation}\]

where \(T_j\) is the threshold of the \(j\)-th qubit, see Figure 6. The result after thresholding can represent qubit state directly.

shfqa qa setup tab data processing qubit
Figure 6. Readout data processing for qubits. The green blocks are used for both state discrimination modes and the blue blocks are used for multistate discrimination mode only configured by LabOne APIs. \(x_i\) is the readout input signal at the \(i\)-th sample, \(w_{1,\ i}\) is the optimal integration weight calculated from the difference while qubit is prepared in state |0> and |1>, \(T_1\) is the threshold for the integrated result.

For a qutrit, 3 thresholds are used, 2 for the integration results in the weighted integration units and 1 for the integration result in the pairwise difference units, see Figure 7. After thresholding, the 3-bit data is assigned to 0, 1 or 2 by the assignment matrix, and the discriminated results can be displayed in the Quantum Analyzer Result Tab. The discriminated result represented by 2-bit data can be transferred to control instruments via DIO and ZSync for feedback experiment.

shfqa qa setup tab data processing qutrit
Figure 7. Readout data processing for qutrits. The green blocks are used for both state discrimination modes and the blue blocks are used for multistate discrimination mode only configured by LabOne APIs. \(x_i\) is the readout input signal at the \(i\)-th sample,\(w_{1,\ i}\) and \(w_{2,\ i}\) are the integration weights measured by calculating the readout pulse difference when the qutrit is prepared in state |0> and |1>, and state |0> and |2>, respectively. "a - b" is the pairwise difference of the integration results. The pairwise difference is equivalent to having the third weighted integration \(\sum (w_{1,\ i} - w_{2,\ j}) \cdot x_i\). \(T_1\), \(T_2\) and \(T_3\) are the thresholds for the 3 integration results.

For a ququad, 6 thresholds are used, 3 for the integration results in the weighted integration units and 3 for the integration results in the pairwise difference units, see Figure 8. After thresholding, the 6-bit data is assigned to 0, 1, 2 or 3 by the assignment matrix, and the discriminated results can be displayed in the Quantum Analyzer Result Tab. The discriminated result represented by 2-bit data can be transferred to control instruments via DIO and ZSync for feedback experiment.

shfqa qa setup tab data processing ququads
Figure 8. Readout data processing for ququads. \(x_i\) is the readout input signal at the \(i\)-th sample, \(w_{1,\ i}\), \(w_{2,\ i}\) and \(w_{3,\ i}\) are the integration weights measured by calculating the readout pulse difference when the ququad is prepared in state |0> and |1>, state |0> and |2>, and state |0> and |3>, respectively. "a - b" are the pairwise differences of the integration results. These pairwise differences are equivalent to having 3 more weighted integration \(\sum (w_{1,\ i} - w_{2,\ j}) \cdot x_i\), \(\sum (w_{1,\ i} - w_{3,\ j}) \cdot x_i\) and \(\sum (w_{2,\ i} - w_{3,\ j}) \cdot x_i\). \(T_1\), \(T_2\), \(T_3\), \(T_4\), \(T_5\) and \(T_6\) are the thresholds for 6 integration results.

Functional Elements

Table 5. QA setup settings
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 hold-off 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 up-conversion.

Pulse

The waveform envelope is modulated by the internal digital oscillator before frequency up-conversion.

Length

4 to 32 k (SHFQA 2 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 μs. 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.