Exact interferometers for the concurrence and residual 3-tangle

Abstract

In this paper we describe a set of circuits that can measure the concurrence of a two qubit density matrix without requiring the deliberate addition of noise. We then extend these methods to obtain a circuit to measure one type of three qubit entanglement for pure states, namely the 3-tangle.

arXiv comment7 pages PDFLaTeX (format changed; older versions were in revtex4) 6 figures (now in pdf format, older versions were in encapsulated postscript). v7: small error in circuits corrected, and presentation improved. Old affiliation used in paper as that's where I was at the time. (The date is from the last change to the physics content. The files got lost in the shuffle when moving to a new laptop.)

Cited by in corpus (3)

• Direct method for measuring and witnessing quantum entanglement of arbitrary two-qubit states through Hong-Ou-Mandel interference
• Entangled states in quantum cosmology and the interpretation of Lambda
• Measurable lower bounds on concurrence