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Coherence and decoherence in the Harper-Hofstadter model



Ian Spielman, Qiyu Liang, Dimi Trypogeorgos, Ana Valdes-Curiel, Junheng Tao, Mingshu Zhao


We quantum simulated the 2D Harper-Hofstadter (HH) lattice model in a highly elongated tube geometry—three sites in circumference—using an atomic Bose-Einstein condensate. In addition to the usual transverse (out-of-plane) magnetic flux, piercing the surface of the tube, we threaded a longitudinal flux Φ L down the axis of the tube. This geometry evokes an Aharonov-Bohm interferometer, where noise in Φ L would readily decohere the interference present in trajectories encircling the tube. We observe this behavior only when transverse flux is a rational fraction of the flux quantum and remarkably find that for irrational fractions the decoherence is absent. Furthermore, at rational values of transverse flux, we show that the time evolution averaged over the noisy longitudinal flux matches the time evolution at nearby irrational fluxes. Thus, the appealing intuitive picture of an Aharonov-Bohm interferometer is insufficient. Instead, we quantitatively explain our observations by transforming the HH model into a collection of momentum-space Aubry-André models.
Physical Review Research


BEC, localization, coherence


Spielman, I. , Liang, Q. , Trypogeorgos, D. , Valdes-Curiel, A. , Tao, J. and Zhao, M. (2021), Coherence and decoherence in the Harper-Hofstadter model, Physical Review Research, [online], (Accessed June 14, 2024)


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Created May 19, 2021, Updated October 14, 2021