cirq.ops.depolarize

Returns a DepolarizingChannel with given probability of error.

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).

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).
n_qubits The number of qubits.

ValueError if p is not a valid probability.