Experimental Realization of Topological Floquet Models in Circuit QED

Topological band structures are well known to produce symmetry-protected chiral edge states which transport particles unidirectionally. These same effects can be harnessed in the frequency domain using a spin-1/2 system subject to periodic drives [1]. Previously, the topological regime of such models was thought to be experimentally inaccessible due to a need for ultrastrong coupling; however, recent results have shown that the desired Hamiltonian is achievable in a rotating frame and can give rise to "boosting" of non-classical states of light in a cavity [2]. We show that the rotating magnetic field required for boosting can be achieved by combining an oscillatory flux bias with an amplitude modulated microwave drive in quadrature. Field amplitudes exceeding 100 MHz in both the X and Z axes have been achieved, surpassing the intrinsic qubit-cavity g of 30 MHz. The spatial profiles of the drive and boost cavities are used to design a low crosstalk chip with drive to boost isolation exceeding 40 dB. We present preliminary characterization of the cavity state boosting protocol.

[1]: I. Martin, G. Refael, and B. Halperin, Phys. Rev. X 7, 041008 (2017)

[2]: D. M. Long, P. J. D. Crowley, A. J. Kollár, and A. Chandran, Phys. Rev. Lett. 128, 183602 (2022).