Motional Broadening in Ensembles With Heavy-Tail Frequency Distribution

Abstract

We show that the spectrum of an ensemble of two-level systems can be broadened through `resetting' discrete fluctuations, in contrast to the well-known motional-narrowing effect. We establish that the condition for the onset of motional broadening is that the ensemble frequency distribution has heavy tails with a diverging first moment. We find that the asymptotic motional-broadened lineshape is a Lorentzian, and derive an expression for its width. We explain why motional broadening persists up to some fluctuation rate, even when there is a physical upper cutoff to the frequency distribution.

6 pages, 4 figures

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• The Quantum Internet
• Long-distance quantum communication with atomic ensembles and linear optics
• Particles and fields in fluid turbulence
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• How to Enhance Dephasing Time in Superconducting Qubits
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