Conveyor-belt superconducting quantum computer
Francesco Cioni, Roberto Menta, Riccardo Aiudi, Marco Polini, Vittorio Giovannetti · Physical Review A · 2026
The processing unit of a solid-state quantum computer consists of an array of coupled qubits, each driven with on-chip microwave lines that route control signals to the qubits in order to perform logical operations. This approach to quantum computing comes with two major problems. On the one hand, it greatly hampers scalability towards fault-tolerant quantum computers, which are estimated to need a number of qubits—and therefore driving lines—on the order of 10 6 . On the other hand, these lines are a source of electromagnetic noise, exacerbating frequency crowding and crosstalk, while also contributing to power dissipation inside the dilution fridge. We here tackle these two challenges by presenting a quantum processing unit (QPU) for a universal quantum computer which is (rather than ) driven. Our QPU relies on a closed loop of superconducting qubits with always-on ZZ interactions which we dub the “conveyor belt.” Notably, this architecture requires only O ( N ) physical qubits to run a computation on N computational qubits, in contrast to previous O ( N 2 ) proposals for global quantum computation. Universality is achieved via the implementation of single-qubit gates and a Toffoli gate. The ability to perform multiqubit operations in a single step could vastly improve the fidelity and execution time of many algorithms.