Phase-coherent transport probed by noise measurements in quantum rings

Voltage noise measurements are performed in an etched Al
0.35
Ga
0.65
As/GaAs-based quantum ring structure using a cross-correlation technique at 4.2 K. Additional noise, exceeding the thermal noise expected from the conductance, is observed and earlier findings are confirmed [1]. Here, we identify phase-coherent transport in the quantum ring as cause for additional correlated noise, denoted as quantum-coherent network noise (QCNN), and determine a correlation coefficient in different contact configurations. Aharonov-Bohm magnetoresistance oscillations prove quantum interference at 15 mK. Our experiments show that voltage noise measurements are sensitive probes of quantum transport and may become relevant for investigations in closed-loop quantum networks.