Quantum Analyzer Result Tab¶

The Quantum Analyzer Result tab is the interface to the Result Logger unit of the instrument and displays processed data after the qubit measurement unit (see functional overview for an overview block diagram). It is available on all UHFQA instruments.

Features¶

Acquisition and display of measurement data
Multiple probe points: after Rotation, Crosstalk Suppression, Threshold, Correlation
Multi-qubit state statistical analysis

Description¶

The Quantum Analyzer Result tab (see LabOne UI: Quantum Analyzer Result tab) is divided into a display section on the left and a configuration section on the right.

Figure 1: LabOne UI: Quantum Analyzer Result tab

This tool allows you to acquire, average, and analyze, large sets of data sourced at various points of the signal processing chain. The Source setting in the Control sub-tab lets you choose the probe point. The available sources are:

After Rotation: voltages V'_{I, q} after rotation in the complex plane
After Crosstalk Suppression: voltages V''_{I, q} after application of the Crosstalk Suppression matrix C
After Voltage Correlation: product of voltages V''_{I, q}×V''_{I, q'} corresponding to two qubits q and q'
After Threshold: discretized states s_q
After State Correlation: product of discretized states s_q×s_q' corresponding to two qubits q and q'
Statistics, before State Correlation: result of the Statistics Unit
Statistics, after State Correlation: result of the Statistics Unit

The data are stored in a vector with a length of up to 10₆ points and displayed in the plot area on the left once the acquisition is complete. The Result Logger subports averaging of multiple vectors which is enabled by setting the Averages to any number higher than 1.

The Statistics sub-tab allows one to compress the information from many measurements into just a few numbers. The Statistics Unit measures the states s_q after the threshold operation and determines three values for each readout channel q:

The number of times the result of the measurement was a logic ‘1’. This value is called Ones.
The number of times the result of the measurement differed from the result of the previous measurement. This value is called Flips.
Number of state errors. A state error occurs when there is a discrepancy between the measured state of this channel and the state that is predicted based on the configured multi-qubit state table.

The Length setting determines the number of measurements s_q to take into account to determine these values.

The statistics values are best explained with an example. Consider that on channel 1 we read the sequence of results "0101001010", which contains four ones and eight flips, and for channel 2 we read the sequence of results "0011000110". Consider that we have set the state map to the array (1, 2, 3, 0), or (0b01, 0b10, 0b11, 0b00) in binary notation. The state map is set using the API. This state map defines what we expect for the next two-qubit state based on the current two-qubit state in the sequence according to the following table.

Table 2: Qubit state map example
Current two-qubit state	Expected next two-qubit state
00	01
01	10
10	11
11	00

The actual measured state sequence is 00, 01, 10, 11, 00, 00, 01, 10, 11, 00. From this sequence and the state map we can see that there is an error on channel 1 between the fifth and sixth measurement. Measurement five and six both result in the state 00 being measured. However, according to the state table, we expect the state 01 to follow the state 00. Therefore, there is a state error on channel 1. The user interface also reports the total number of state errors for the whole measurement, which is 1.

Functional Elements¶

Table 3: Quantum Analyzer Result tab
Control/Tool	Option/Range	Description
Run/Stop		Run the Result Logger.
Reset		Clear the Result Logger.
Acquired		Indicates when data point is recorded.
Display Source		Selects the signal source for the Result Logger.
	Crosstalk	Result after crosstalk unit.
	Threshold	Result after Threshold unit.
	Rotation	Result after Rotation unit.
	Crosstalk Correlation	Correlation unit after the Crosstalk unit.
	Threshold Correlation	Correlation unit after the Threshold unit.
Length		Number of data points to record. One data point corresponds to a single averaged output of the selected source.
Averages		Number of averages per recorded data point.
Acquired		Indicate the index of the data point that will be recorded next.
Mode		Defines the averaging mode of the Result Logger.
	Cyclic	The first point of the Result vector is the average of the results number 1, M+1, 2M+1, and so forth, where M is equal to the Length setting. The second point is the average of the results number 2, M+2, 2M+2, and so forth.
	Sequential	The first point of the Result vector is the average of the first N results, where N is equal to the Averages setting. The second point of the Result vector is the average of the following N results, and so forth.
Rotation		Rotation angle applied to the recorded complex values.
Shift I		Translation shift applied to the I component of the recorded data points.
Shift Q		Translation shift applied to the Q component of the recorded data points.
Scaling I		Scaling factor applied to the I component of the recorded data points.
Scaling Q		Scaling factor applied to the Q component of the recorded data points.
Enable		Enable the Statistics Unit.
Reset		Clear the Statistics Unit.
Length		Number of measurements over which the Statistics Unit should operate.
Total Errors		Total number of state errors. The total number of state errors is incremented if any of the measured bits show a state error. The value will be identical for all channels.
Ones		Number of logical ones measured for this channel.
Flips		Number of flips measured for this channel. A flip is defined as a change in qubit state from one measurement to the next.
Errors		Number of state errors measured for this channel. A state error occurs when there is a discrepancy between the measured state of this channel and the state that is predicted based on the configured state table.
Plot Type		Switch between complex wave dot plot and complex wave components (X, Y, Amplitude and Phase) plot.