Cross-correlated noise measurements are performed in etched AlxGa1xAs/GaAs based quantum rings in equilibrium at a bath temperature of Tbath=4.2K. The measured white noise exceeds the thermal (Johnson–Nyquist) noise expected from the measured electron temperature Te and the electrical resistance R. This excess part of the white noise decreases as Tbath increases and vanishes for Tbath12K. Excess noise is neither observed if one arm of a quantum ring is depleted of electrons nor in one-dimensional-constrictions that have a length and width comparable to the quantum rings. A model is presented that suggests that the excess noise originates from the correlation of noise sources, mediated by phase-coherent propagation of electrons.

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