title: Observation of geometric phases for mixed states using NMR interferometry.
abstract: Examples of geometric phases abound in many areas of physics. They offer both fundamental insights into many physical phenomena and lead to interesting practical implementations. One of them, as indicated recently, might be an inherently fault-tolerant quantum computation. This, however, requires one to deal with geometric phases in the presence of noise and interactions between different physical subsystems. Despite the wealth of literature on the subject of geometric phases very little is known about this very important case. Here we report the first experimental study of geometric phases for mixed quantum states. We show how different they are from the well-understood, noiseless, pure-state case.
authors.affiliation: Structural Research Laboratory, University of Science and Technology of China, Hefei, 230027, People's Republic of China. djf@ustc.edu.cn
authors.forename: Jiangfeng
authors.initials: J
authors.lastname: Du
authors.forename: Ping
authors.initials: P
authors.lastname: Zou
authors.forename: Mingjun
authors.initials: M
authors.lastname: Shi
authors.forename: Leong Chuan
authors.initials: LC
authors.lastname: Kwek
authors.forename: Jian-Wei
authors.initials: JW
authors.lastname: Pan
authors.forename: C H
authors.initials: CH
authors.lastname: Oh
authors.forename: Artur
authors.initials: A
authors.lastname: Ekert
authors.forename: Daniel K L
authors.initials: DK
authors.lastname: Oi
authors.forename: Marie
authors.initials: M
authors.lastname: Ericsson