Avoided crossing and sub-Fourier-sensitivity in driven quantum systems

Cubero, David and Robb, Gordon R.M. and Renzoni, Ferruccio (2018) Avoided crossing and sub-Fourier-sensitivity in driven quantum systems. Physical Review Letters, 121 (21). 213904. ISSN 1079-7114 (https://doi.org/10.1103/PhysRevLett.121.213904)

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The response of a linear system to an external perturbation is governed by the Fourier limit, with the inverse of the interaction time constituting a lower limit for the system bandwidth. This does not hold for nonlinear systems, which can thus exhibit sub-Fourier-behavior. The present Letter identifies a mechanism for sub-Fourier-sensitivity in driven quantum systems, which relies on avoided crossing between Floquet states. Features up to three orders of magnitude finer than the Fourier limit are presented.