Readout Calibration

Readout calibration is a technique used to mitigate SPAM errors. To implement readout calibration, a circuit with an identity gate on every qubit and a second circuit with an X gate on every qubit is used to profile the SPAM error on a system in order to correct for SPAM errors when running subsequent circuits. Due to the dynamic nature of quantum devices, the error profile will evolve continuously, so it is important that readout calibration be performed regularly to maximize the overlap between the error profile and the correction.

True-Qᵀᴹ performs readout calibration automatically for circuits in a circuit collection containing one of True-Qᵀᴹ’s diagnostic protocols whenever readout calibration circuits are included therein; the actual correction is performed when the fit function is called for a given circuit collection.

Readout Calibration in Circuit Batches

Readout calibration circuits can be automatically added to each batch when circuits are partitioned into batches (see trueq.CircuitCollection.batch()); for example, circuits submitted to an IBMQ device using the trueq.interface.qiskit.Executor() can have readout correction automatically applied.

Providing readout calibration circuits as extra_circuits when calling trueq.CircuitCollection.batch() will cause the batcher to add a copy of the readout calibration circuits at the start of each batch.