Noiseless Output Extrapolation (NOX)

See make_nox() for API documentation.

NOX is an error mitigation protocol for estimating correct outputs from noisy circuits []. Given an input circuit, it produces new circuits that amplify the noise afflicting individual cycles via identity insertion methods. The correct outputs from the given circuit are then extrapolated from the noisy estimates produced by these new circuits.

A simplified diagram of the NOX protocol. The noise in different cycles of the bare input circuit is amplified. The correct output of the circuit (green dot) is extrapolated from noisy estimates produced by the bare circuit (pink dot) and the circuits with amplified noise (red dots).

Examples of terms that may be returned from the analysis are as follows. These descriptions are also available via mouse-overs when running True-Q™ in a Jupyter or Colab notebook.

Estimated Parameters

\(ev_\texttt{ZZIZ}\) -

The mitigated expectation value of an output string, such as 0000, of a Weyl observable, such as ZZIZ for qubits and W00W02W01W00 for qutrits, or of a mixed string, such as 0Z1X.