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

  • Qubit-qubit correlation analysis

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 (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 .

functional qasetup
Figure 1. LabOne UI: Quantum Analyzer Setup tab

Two-element 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 VI and VQ. 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 zq = xq+iyq = rq×exp(iθq). The demodulated signal is multiplied with zq: V'~I, q~ + iV'~Q, q~ = (V~I, q~ + iV~Q, q)×zq~. The user may specify zq 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 in-phase 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 (s1,…,s10), with sq = 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 in-phase quadrature V''~I, q~ of the readout signal into a discrete qubit state, 0 or 1.

Functional Elements

Table 2. Quantum Analyzer Setup tab
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.

In-Phase Gain

Gain of in-phase branch

Quadrature Gain

Gain of quadrature branch

In-Phase Phase

Phase of in-phase branch

Quadrature Phase

Phase of quadrature branch

Mode

Application mode.

Standard

The integration weights are given by the user-programmed 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 hold-off 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 self-correlation.

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)