Low-frequency noise in transport through quantum pOint contacts

We report the noise characteristics of quantum point contacts between 100 Hz and 100 kHz at 4.2 K. The noise consists of a 111 component on top of a white background. The 1I/noise increases as the contact width decreases and shows peaks between the quantized resistance plateaus. The white noise background increases with current but is much lower than the fuB shot noise level, suggesting that shot noise is not generated in an ideal quantum point oontact, where the electrons do not suffer backscattering as they enter and traverse the contact.