Observation of an enhanced Aharonov-Bohm effect

A new measurement scheme to investigate the Aharonov-Bohm (AB) effect is proposed. We have found that the AB amplitude relative to the total signal becomes much more enhanced in a non-local four-terminal configuration than that obtained in the conventional four-terminal configuration and the AB phase can be continuously controlled electrostatically. It is shown that the Landauer-Buttiker formula explains these results. What is more important, the coherence of electron measured in the non-local setup is found to survive at higher temperature than that in the conventional one. The present result indicates that decoherence is affected by way of measurement and poses an important question on the mechanism of quantum decoherence. (C) 2002 Published by Elsevier Science Ltd.