Qubit Measurement Unit

The Qubit Measurement Unit is the central data analysis tool of the SHFQA. Its main purpose: correlating the Input Signal with the Output Signal in Spectroscopy Mode, or the Reference traces stored in the Integration Weights and then discriminating a qubit state from the correlated signal.

Features Overview

  • High-fidelity single-shot readout

  • Real-time state discrimination with low latency for fast feedback

  • Correlation of up to 16 reference traces stored in up to 16 Integration Weights.

  • Powerful Result Logger with real-time result averaging, and access to all results in the analysis chain.

Description

The Qubit Measurement Unit consists of three elements: Integration, Discrimination and Result Logging which we will explain in the following. All relevant nodes of the Qubit Measurement Unit are accessible through the /DEV…​./QACHANNELS/n/READOUT/…​ node tree.

Integration

The correlation with a reference signal is achieved by first multiplying the Input Signal with the content of the Integration Weights using a complex-valued multiplication. The result of each multiplication is then integrated for the length of the longest Integration Weight (max. 4096 samples). All relevant nodes of the Integration Unit can be accessed through the /DEV…​./QACHANNELS/n/READOUT/INTEGRATION/…​ node tree.

State Discrimination

State Discrimination considers the real part of the complex-valued integration result and discriminates using a user-definable threshold. Thanks to the complex treatment of the data, the rotation of the results in the complex plane is as simple as multiplying a complex number \(A*exp(i\phi)\) to the Integration Weights. All relevant nodes of the State Discrimination Unit can be accessed through the /DEV…​./QACHANNELS/n/READOUT/DISCRIMINATORS/…​ node tree.

Result Logger

The Result Logger is a powerful tool to visualize and acquire the correlated and discriminated results. Because of it advanced averaging features it can display the measurement results of a full experiment, e.g. a Rabi or Ramsey experiment without any additional post-processing and as soon as the experiment has terminated. All relevant nodes of the Result Logger can be accessed through the /DEV…​./QACHANNELS/n/READOUT/RESULT/…​ node tree.