# cirq.DepolarizingChannel¶

class cirq.DepolarizingChannel(p)[source]

A channel that depolarizes a qubit.

__init__(p) → None[source]

The symmetric depolarizing channel.

This channel applies one of four disjoint possibilities: nothing (the
identity channel) or one of the three pauli gates. The disjoint
probabilities of the three gates are all the same, p / 3, 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

$$\rho \rightarrow (1 - p) \rho + (p / 3) X \rho X + (p / 3) Y \rho Y + (p / 3) Z \rho Z$$

Parameters: p – The probability that one of the Pauli gates is applied. Each of the Pauli gates is applied independently with probability p / 3. ValueError – if p is not a valid probability.

Methods

 controlled_by(*control_qubits) Returns a controlled version of this gate. num_qubits() The number of qubits this gate acts on. on(*qubits) Returns an application of this gate to the given qubits. on_each(*targets) Returns a list of operations apply this gate to each of the targets. validate_args(qubits) Checks if this gate can be applied to the given qubits. wrap_in_linear_combination(coefficient, …)