Modular Quantum Computing with Three-wave Parametric Gates

Parametric driving has long been used in weakly nonlinear superconducting circuits to create nearly quantum-limited ‘parametric’ amplifiers, which are in wide use for the readout of superconducting qubits. However, our and others’ recent work show that we can extend parametric pumping schemes to create a variety of other vital components of quantum computers. These parametric controls are extremely flexible, coupling both linear cavities and qubits, and are currently in use in our laboratory for a variety of applications including qubit bath engineering, single- and two-qubit gates as well as controlled, coherent links between qubits in multiple quantum modules. In each experiment the key source of nonlinearity is a so-called SNAIL device whose three-wave couplings we exploit to controllably couple quantum modes. More, by applying multiple, simultaneous drives we can drive both parallel operations between multiple pairs of modes and three or more body interactions and gates. In this talk I will review our recent experimental efforts, especially our realization of four transmon all-to-all quantum modules and a quantum state router [1] which can link four modules with highly coherent operations, as well as the prospects for scaling to larger modular quantum processors.
[1] A modular quantum computer based on a quantum state router C. Zhou, P. Lu, M. Praquin, T.-C. Chien, R. Kaufman, X. Cao, M. Xia, R. Mong, W. Pfaff, D. Pekker, M. Hatridge. arXiv:2109.06848 (2021).