cirq.ops.depolarize

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Returns a DepolarizingChannel with given probability of error.

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

Used in the notebooks

This channel applies one of 4n disjoint possibilities: nothing (the identity channel) or one of the 4n - 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).