The compression of 2 qubits into a single ququart and generating an ancilla

Despite promising proof of concept demonstrations, currently available quantum hardware suffers from fundamental scalability limitations. The field is relatively new and it is imperative to consider emerging technologies in the space and evaluate their unique tradeoff spaces to determine how to best close the gap between current devices and target applications. Here, we explore three recent developments on this front. First, we consider extensions to currently available hardware, which allow the use of higher level states, beyond the usual binary, which when used temporarily can confer circuit-level advantage. Second, we consider the use of superconducting resonant cavities to reduce hardware requirements to implement quantum error correction protocols. Finally, we consider the use of neutral atoms, which offer unique strengths and weaknesses. It is valuable to evaluate new technology early and often to determine the best path toward scalability. doi 10.1109/MM.2021.3099139

Jonathan M. Baker and Frederic T. Chong