Building your own noise model

There may be times where you wish to build your own custom noise models. Whether it's to generate specific errors to test your error-mitigation methods or to create something resembling a specific device, having the ability to customize your own noise model is a handy feature to have available.

In the following steps, we will create single- and multi-qubit errors, along with readout errors. The single-qubit error will have an amplitude dampening error, the multi-qubit error will have a depolarizing error, and the readout error will be applied to one of the two qubits in the circuit:

1. We'll begin by defining the single- and multi-qubit probability error values, followed by initializing and setting the depolarizing errors. First to the single qubit, and then to the multi-qubit error:

   # Import the error classes and methods
   from qiskit.providers.aer.noise import depolarizing_error
   from qiskit.providers.aer.noise import ReadoutError
   # Single...