The idea of zero noise extrapolation relies on the assumption that it is possible to increase the strength of noise in a quantum circuit, e.g., by introducing additional gates.
Since the main errors originate from imperfect CNOT gates, the simplest method is to replace each CNOT gate by 3 CNOT gates.
We will demonstrate the zero noise extrapolation for the HHL-algorithm with 4 qubits, see https://qiskit.org/textbook/ch-applications/hhl_tutorial.html. This algorithms solves a two-dimensional, linear system of equations. The function 𝐹 that we are interested in is the norm of the corresponding solution.
The module algorithm contains the function algo generating the quantum circuit of the HHL algorithm and the function eval_counts corresponding to the above function 𝐹. The module zne contains the class ZNE needed to perform the zero noise extrapolation.
Here or under example_zne.ipynb is an example notebook with further explanations.
