cirq.depolarize

Returns a DepolarizingChannel with given probability of error.

cirq.depolarize(
    p: float, n_qubits: int = 1
) -> cirq.DepolarizingChannel

Used in the notebooks

Used in the tutorials

This channel applies one of \(4^n\) disjoint possibilities: nothing (the identity channel) or one of the \(4^n - 1\) pauli gates. The disjoint probabilities of the non-identity Pauli gates are all the same, \(p / (4^n - 1)\), and the identity is done with probability 1 - p. The supplied probability must be a valid probability or else this constructor will raise a ValueError.

This channel evolves a density matrix via

\[ \rho \rightarrow (1 - p) \rho + p / (4^n - 1) \sum _i P_i \rho P_i \]

where \(P_i\) are the \(4^n - 1\) Pauli gates (excluding the identity).

p The probability that one of the Pauli gates is applied. Each of the Pauli gates is applied independently with probability \(p / (4^n - 1)\), where \(n\) is n_qubits.
n_qubits The number of qubits.

ValueError if p is not a valid probability.