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 UHFQA instruments.
Features

Raw signal deskew

Signal rotation in I/Q plane

10×10 crosstalk suppression matrix

Threshold operation

Qubitqubit correlation analysis
Description
Control/Tool  Option/Range  Description 

QA Setup 
Configure the Qubit Measurement Unit 
The Quantum Analyzer Setup tab (see Figure 1) is divided into different sections each representing a signal processing step starting from raw signal deskew to the final threshold operation that transforms an analog I/Q signal into a discrete qubit state. This tab represents the interface to the following functional blocks: the integration units, the internal oscillator, the crosstalk suppression matrix, the deskew matrix, the correlation unit, the statistics unit, and the thesholding unit. A block diagram representing the flow of data and trigger signals between the functional blocks is found in Architecture and Signalling .
Twoelement vectors of samples arrive at 1.8 GSa/s from Signal Inputs 1 and 2. In the Deskew section, at this rate, each sample vector is multiplied by a 2×2 Rotation/Gain matrix. The default value is the identity matrix [1, 0; 0, 1] which leaves both input signals unchanged. Changing this to a different value allows the user to compensate for signal imperfections such as analog linear crosstalk, or mixer amplitude imbalance.
In the Integration section, each of the two input signals is demodulated by multiplying with a reference signal and the product is integrated over a fixed time T after reception of a trigger. The user can choose the mode of operation of the weighted integration. In Standard mode, the reference signal is given by the Integration Weights programmed to the instrument memory using the Quantum Analyzer Input Tab . This mode offers the full flexibility to define a custom integration weight to realize a matched filter. In Spectroscopy mode, the reference signal is given by sine and cosine signals generated by the internal digital oscillator controlled from the Inputs/Outputs Tab , which allows for longer integration times and thus higher frequency resolution than the Standard mode. The input signals V~Sig In 1~(t) and V~Sig In 2~(t) of duration T are reduced to a single pair of voltages V_{I} and V_{Q}. Since there are 10 separate qubit measurement units, there can be up to 10 pairs (V~I, q~, V~Q, q~ for q=1…10), each corresponding to one frequency component of the signals V~Sig In 1~(t) and V~Sig In 2~(t).
The Rotation section rotates and scales the signal in the complex plane after integration. For each of the 10 channels, the rotation is characterized by a complex number z_{q} = x_{q}+iy_{q} = r_{q}×exp(iθ_{q}). The demodulated signal is multiplied with z_{q}: V'~I, q~ + iV'~Q, q~ = (V~I, q~ + iV~Q, q_{)×z}q~. The user may specify z_{q} in polar coordinates in the form "r @ θ" or in Cartesian coordinates in the form "x + y i". Examples are "[email protected]" for a 45 degree rotation, or "0.0 + 1.0 i" for a 90 degree rotation. The purpose of the rotation step is to ensure that the readout contrast is shifted into the inphase signal component, i.e., that the state of qubit q only affects V'~I, q~ but not V'~Q, q~.
The Crosstalk section is a graphical representation of the 10×10 crosstalk suppression matrix C that supports systematic minimization of the influence of one qubit’s state on another qubit’s readout signal. The signal processing up to after the rotation step can be abstracted as a 10×10 matrix M that transforms the vector of qubit states (s_{1},…,s_{10}), with s_{q} = 0 or 1, into the vector of signals (V'~I, 1~, … V'~I, 10~). This matrix can be measured systematically by preparing the qubit system in different states of the form (0,…, 0, 1, 0,…, 0), and measuring the resulting signal. Using the Crosstalk Suppression optimally relies on finding the matrix C such that C×M is diagonal. Due to the complexity of this method, setting the elements of the crosstalk suppression matrix C from the graphical UI would be impractical, and its elements can only be set from the API. We denote the signals after crosstalk suppression with a double prime as (V''~I, 1~, … V''~I, 10~) = C×(V'~I, 1~, … V'~I, 10~).
The Correlation section optionally enables the outputs of two readout channels to be multiplied prior to averaging, logging, etc. When enabled, the corresponding channel is multiplied with another channel selected as the Source.
The Thresholds section allows one to define a voltage threshold to transform the inphase quadrature V''~I, q~ of the readout signal into a discrete qubit state, 0 or 1.
Functional Elements
Control/Tool  Option/Range  Description 

Rotation/Gain Matrix 
Implements a 2×2 matrix multiplication. The two input signals are treated as a vector with two elements and the result is a vector as well. 

InPhase Gain 
Gain of inphase branch 

Quadrature Gain 
Gain of quadrature branch 

InPhase Phase 
Phase of inphase branch 

Quadrature Phase 
Phase of quadrature branch 

Mode 
Application mode. 

Standard 
The integration weights are given by the userprogrammed filter memory. 

Spectroscopy 
The integration weights are generated by a digital oscillator. This mode offers enhanced frequency resolution. 

Readout Trigger Selection 
Selects the trigger source for the sequencer from the Hardware Trigger Engine. 

Readout Trigger Selection 
Select the source for triggering the readout. 

Trigger In 1 
Use the Trigger In 1 as the trigger signal. 

Trigger In 2 
Use the Trigger In 2 as the trigger signal. 

Trigger In 3 
Use the Trigger In 3 as the trigger signal. 

Trigger In 4 
Use the Trigger In 4 as the trigger signal. 

AWG Integration Trigger 
Use the AWG Integration Trigger as the trigger signal. 

Spectroscopy Trigger Selection 
Selects the source for triggering the spectroscopy. 

Trigger In 1 
Use the Trigger In 1 as the trigger signal. 

Trigger In 2 
Use the Trigger In 2 as the trigger signal. 

Trigger In 3 
Use the Trigger In 3 as the trigger signal. 

Trigger In 4 
Use the Trigger In 4 as the trigger signal. 

AWG Integration Trigger 
Use the AWG Integration Trigger as the trigger signal. 

Integration Length 
The integration time of all weighted integration units specified in units of samples. In Standard mode, a maximum of 4096 samples can be integrated, which corresponds to 2.3 µs. In Spectroscopy mode, a maximum of 16.7 MSa can be integrated, which corresponds to ~10 ms. 

Errors 
Number of holdoff violations detected in the INTEGRATION unit since last reset. 

Delay 
A delay time in units of samples that adjusts the time at which the integration starts in relation to the trigger signal of the weighted integration units. 

Source 
Controls the routing of the input signals to the INTEGRATION units. 

1 → Real, 2 → Imag 
Signal input 1 to real part, Signal input 2 to imaginary part. 

2 → Real, 1 → Imag 
Signal input 2 to real part, Signal input 1 to imaginary part. 

1 → Real, 1 → Imag 
Signal input 1 to real part, Signal input 1 to imaginary part. 

2 → Real, 2 → Imag 
Signal input 2 to real part, Signal input 2 to imaginary part. 

Rotation 
Complex rotation coefficient applied to the signals after integration. 

Representation 
Select between Cartesian and polar representation of the complex rotation coefficient. Cartesian coordinates are entered in the format "x+iy", polar coordinates in the format "[email protected]" where x, y, r, and a are real numbers. 

Crosstalk 
Graphical representation of the 10×10 crosstalk suppression matrix. Positive values are black, negative values are red. 

Bypass Crosstalk 
Bypass the Crosstalk matrix in order to reduce the latency through the system. 

Bypass Rotation 
Bypass Rotation in order to reduce the latency through the system. 

Bypass Deskew 
Bypass Deskew in order to reduce the latency through the system. 

En 
Enable the correlation mode for the given channel. 

Source 
Controls the channel with which correlation should be made. Selecting the same channel as the readout channel number corresponds to selfcorrelation. 

Level 
The discretization level applied to the output of the Crosstalk Suppression matrix. 

Length 
Sets the integration length in spectroscopy mode in number of samples. A maximum of 33.5MSa (2^25 samples) can be integrated, which corresponds to 16.7ms. 

Delay 
Sets the delay of the start of the integration in spectroscopy mode with respect to the Trigger Signal. 

Offset Frequency 
Sets the digital oscillator frequency. The sum of the Offset Frequency and the Center Frequency correspond to the frequency of the microwave tone at the Out connector. 

Output Frequency 
Displays the carrier frequency of the microwave signal at the Out connector. This frequency corresponds to the sum of the Center Frequency and the Offset Frequency. 

Amplitude 
Amplitude of the microwave signal relative to the range of the Output. 

Set Mode 
Set Generator Waveform by parametric generation or CSV Upload. 

Parametric 
Generator Waveform are generated by defining sine wave parameters. 

Upload 
Generator Waveform are uploaded by the user in a form of a CSV file. 

Frequency 
Frequency of the complex exponential function. 

Window Type 
Window function to be applied to the complex exponential function. 

Window Length 
Length of the selected window in samples, starting from 0. 

Waveform Memory 
Selects the waveform memory for parametric or arbitrary waveform upload. 

Set To device 
Write the real and imaginary part of the Waveform to the selected Waveform Memory. 

Set To Device 
Write the real and imaginary part of the Waveform to the selected Waveform Memory. 

CSV File 
Drag and drop CSV file containing columns of Sequencer Waveform. 

Amplitude 
Amplitude of the complex exponential function. 

Sequencer 
Runs the Sequencer. 

Status 
Running, Idle, Waiting 
Displays the status of the sequencer on the instrument. Off: Ready, not running. Green: Running, not waiting for any trigger event. Yellow: Running, waiting for a trigger event. Red: Not ready (e.g., pending elf download, no elf downloaded) 