1/f noise in experimental Sinai quantum billiards

It was recently conjectured that 1/f noise is a fundamental characteristic of spectral fluctuations in chaotic quantum systems. In this Letter we show that the level fluctuations of experimental realizations of the Sinai billiard exhibit {\em 1/f} noise, corroborating the conjecture. Assuming that the statistical properties of these systems are those of the Gaussian orthogonal ensemble (GOE), we compare the experimental results with the universal behavior predicted in the random matrix framework, and find an excellent agreement. The deviations from this behavior observed at low frequencies can be easily explained with the semiclassical periodic orbit theory. In conclusion, it is shown that the main features of the conjecture are affected neither by non-universal properties due to the underlying classical dynamics nor by the uncertainties of the experimental setup.