depolarizing_error

depolarizing_error(param, num_qubits)

Return a depolarizing quantum error channel.

The depolarizing channel is defined as:

$$E(\rho )=(1-\lambda )\rho +\lambda \text{Tr}[\rho ]\frac{I}{2^n}$$

with $0\le \lambda \le 4^n/(4^n-1)$

where $\lambda$ is the depolarizing error param and $n$ is the number of qubits.

• If $\lambda =0$ this is the identity channel $E(\rho )=\rho$

• If $\lambda =1$ this is a completely depolarizing channel $E(\rho )=I/2^n$

• If $\lambda =4^n/(4^n-1)$ this is a uniform Pauli error channel: $E(\rho )=\sum _j{P}_j\rho P_j/(4^n-1)$ for all $P_j!=I$.

Parameters:

• param (double) – depolarizing error parameter.

• num_qubits (int) – the number of qubits for the error channel.

Returns:

The quantum error object.

Return type:

QuantumError

Raises:

NoiseError – If noise parameters are invalid.