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gate_error(channel, target=None, require_cp=True, require_tp=False)

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Return the gate error of a noisy quantum channel.

The gate error EE is given by the average gate infidelity

E(E,U)=1Fave(E,U)E(\mathcal{E}, U) = 1 - F_{\text{ave}}(\mathcal{E}, U)

where Fave(E,U)F_{\text{ave}}(\mathcal{E}, U) is the average_gate_fidelity() of the input quantum channel E\mathcal{E} with a target unitary UU.


  • channel (QuantumChannel) – noisy quantum channel.
  • target (Operator or None) – target unitary operator. If None target is the identity operator [Default: None].
  • require_cp (bool) – check if input and target channels are completely-positive and if non-CP log warning containing negative eigenvalues of Choi-matrix [Default: True].
  • require_tp (bool) – check if input and target channels are trace-preserving and if non-TP log warning containing negative eigenvalues of partial Choi-matrix Trout[E]ITr_{\text{out}}[\mathcal{E}] - I [Default: True].


The average gate error EE.

Return type



QiskitError – if the channel and target do not have the same dimensions, or have different input and output dimensions.

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