Crosstalk and drift-detection on the IBM Quantum Experience

A wide variety of noise processes can corrupt the performance of a quantum information processor (QIP). Certain noise processes can be caused by changing external variables that should not (but do) affect the quantum computation; such noise makes the QIP’s behavior context dependent. Two examples of context-dependent noise are drift (behavior changing with time) and crosstalk (behavior changing with operations on, and states of, other qubits). We used a unified framework for context dependence detection to look for both drift and crosstalk on IBM’s publicly accessible Quantum Experience devices. Small but detectable levels of both drift and crosstalk for certain single-qubit operations were found, while two-qubit CNOT gates induced crosstalk with a much stronger signal. We conclude that our method of context dependence detection is suitable for use in currently extant quantum information processor systems.