Mitigating Superconducting Qubit Crosstalk via Optimal Control

Current superconducting quantum computing experiments have reached a level of complexity where two-dimensional lattices of quantum bits (qubits) comprising on the order of 50 qubits can be fabricated and operated. Such architectures are necessary to both implement quantum error correcting codes as well as to perform quantum simulations and machine learning experiments. However, a rectangular qubit arrangement necessarily requires each individual qubit to be coupled to 4 neighbors (qubits or resonators), leading to unwanted interactions or crosstalk. In fact, this frequency crowding often results in qubits idling within 200 MHz of each other, causing conventional single qubit gates to incur errors as large as 2%. By means of numerical simulations, we systematically analyze crosstalk in various physical configurations, and show that pulses generated via GRAPE can eliminate it.