Geometric phases for mixed states in interferometry

E Sjoqvist, A K Pati, A Ekert, J S Anandan, M Ericsson, D K L Oi, V Vedral

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We provide a physical prescription based on interferometry for introducing the total phase of a mixed state undergoing unitary evolution, which has been an elusive concept in the past. We define the parallel transport condition that provides a connection form for obtaining the geometric phase for mixed states. The expression for the geometric phase for mixed state reduces to well known formulas in the pure state case when a system undergoes noncyclic and unitary quantum evolution.

Original languageEnglish
Pages (from-to)2845-2849
Number of pages5
JournalPhysical Review Letters
Issue number14
Publication statusPublished - 2 Oct 2000


  • quantum physics
  • neutrons
  • interferometry
  • geometric phases

Cite this

Sjoqvist, E., Pati, A. K., Ekert, A., Anandan, J. S., Ericsson, M., Oi, D. K. L., & Vedral, V. (2000). Geometric phases for mixed states in interferometry. Physical Review Letters, 85(14), 2845-2849.