A Robust Modular Quantum Processor

Abstract: We explore the concept of redundancy of critical elements in a quantum computing architecture to circumvent disruption of quantum operations due to a failure of such an element, for example, from a catastrophic cosmic ray event. We illustrate this concept with reference to a recently proposed superconducting modular quantum architecture with a star-like configuration, which has a router at the center that enables superconducting qubit interactions across various modules. Regarding this router as a vital element, we propose a double-star configuration, where a loss of one router is backed by the second one. We also examine the usefulness of this double-star configuration under normal conditions, namely, when the quantum hardware has been rendered safe against cosmic rays due to other mitigating actions like shielding or movement to an underground facility. Simultaneous two qubit-pair interactions like two simultaneous CZ gates and multiqubit gates like CCZS are then easily facilitated.