Figure 1

Scanning electron micrograph of a cantilever with a single ring similar to the ones used in the experiment. Inset: magnified view of the ring. These images show the cantilever and ring prior to their release from the underlying ${\mathrm{SiO}}_2$ layer.Reuse & Permissions

Figure 2

Typical measurements of the persistent current in a single ring. (a) A small section of $I(B)$, the persistent current as a function the applied magnetic field. The oscillations are due to the Aharonov-Bohm effect, while the aperiodic modulation arises from flux inside the metal of the ring. (b) Red curve: $I(B)$ over a broader range of magnetic field. Blue curve: the envelope of $I(B)$. (c) The quadrature amplitudes $I^{(+)}$ (black) and $I^{(-)}$ (pink). The envelope in (b) and the quadratures in (c) were extracted by applying the Hilbert transform to the red trace in (b), as described in the Supplemental Material [27].Reuse & Permissions

Figure 3

Autocorrelation of the persistent current in a single ring. The blue curve is the normalized autocorrelation of the $I(B)$ data from ring #6, while the red curve is a fit to theory. Only data with $\Delta B<0.3$ was used for the fit. The expected error in the autocorrelation (due to the finite size of the data set) is indicated by the dashed horizontal lines. Similar behavior was observed in all eight rings.Reuse & Permissions

Figure 4

The measured distribution of persistent current. (a) Cumulants of the persistent current distribution, calculated from the combined data for all eight rings. Blue circles are the measured cumulants, and black circles are the cumulants expected for a Gaussian distribution. Black error bars: statistical uncertainty from the finite sample size. Blue error bars: statistical uncertainty from the finite signal-to-noise ratio. (b) Histogram of the observed persistent currents. To reduce oversampling artifacts, the data is first binned to give data points that are approximately independent. The solid line is the no-free-parameters prediction.Reuse & Permissions