depolarizing_error

depolarizing_error(param, num_qubits)

Return a depolarizing quantum error channel.

The depolarizing channel is defined as:

\[E(ρ) = (1 - λ) ρ + λ \text{Tr}[ρ] \frac{I}{2^n}\]

with \(0 \le λ \le 4^n / (4^n - 1)\)

where \(λ\) is the depolarizing error param and :math`n` is the number of qubits.

• If \(λ = 0\) this is the identity channel \(E(ρ) = ρ\)

• If \(λ = 1\) this is a completely depolarizing channel \(E(ρ) = I / 2^n\)

• If \(λ = 4^n / (4^n - 1)\) this is a uniform Pauli error channel: \(E(ρ) = \sum_j P_j ρ P_j / (4^n - 1)\) 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.