Device challenges for near term superconducting quantum processors: frequency collisions

The outstanding progress in experimental quantum computing with superconducting Josephson-junction based qubits over the past few decades has pushed coherence times many orders of magnitude above that of the first measured. We are also in the midst of scaling towards complex architectures of multi-qubit processors where maintaining very low gate error rates at the limits supported by coherence times is extremely important. Here we will review some of the critical materials and device challenges for superconducting qubits from the perspective of improved coherence and improved error rates. In particular we will focus on the problem of frequency allocations in order to target multi-qubit lattices for fixed-frequency microwave-based gates.