All-to-all parametric control of a SNAIL-based quantum module

For superconducting quantum computers, the most commonly used architecture is a 2D-lattice architecture with between 2.5 and 4 nearest-neighbors. NISQ algorithms on these machines suffer as the large number of SWAP operations needed to link distant qubits cause long delay, and hence large amounts of decoherence across the processor. An alternate architecture is a modular architecture based on quantum modules and routers. A modular architecture increases the efficiency of NISQ algorithms by using a more flexible and denser network of qubit connection which reduces the SWAP operation count when distant qubits interact. In this talk, we present our work on the basic building block for our modular approach, a 4-qubit module with all-to-all qubit connectivity, controlled with parametric driving. A central SNAIL mode acts as the coupler, creating three-wave couplings among all qubits. Two-qubit gates are realized by driving the SNAIL at the difference frequency of a given qubit pair. Two qubit gates with several hundred ns gate times can be performed between all pairs of qubits. We will present our experiment results on calibrating high fidelity iSWAP gate family on all pairs of qubits in this module and exploring the possibility of implementing more novel types of gates that can improve efficiency at compiling quantum algorithms. We will also discuss the prospects for combining our module with other modules via quantum state routers [1] to build a larger quantum computer.

[1] C. Zhou, et al. arXiv: 2109.06848 (2021).