Witnessing entanglement by proxy

Stefan Bäuml, Dagmar Bruß, Marcus Huber, Hermann Kampermann, Andreas Winter

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Entanglement is a ubiquitous feature of low temperature systems and believed to be highly relevant for the dynamics of condensed matter properties and quantum computation even at higher temperatures. The experimental certification of this paradigmatic quantum effect in macroscopic high temperature systems is constrained by the limited access to the quantum state of the system. In this paper we show how macroscopic observables beyond the mean energy of the system can be exploited as proxy witnesses for entanglement detection. Using linear and semi-definite relaxations we show that all previous approaches to this problem can be outperformed by our proxies, i.e. entanglement can be certified at higher temperatures without access to any local observable. For an efficient computation of proxy witnesses one can resort to a generalised grand canonical ensemble, enabling entanglement certification even in complex systems with macroscopic particle numbers.

Original languageEnglish
Article number015002
JournalNew Journal of Physics
Issue number1
StatePublished - 1 Jan 2016
Externally publishedYes


  • entanglement
  • entropy
  • thermodynamics


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