Intensive temperature and quantum correlations for refined quantum measurements

Alessandro Ferraro*, Artur Garcia-Saez, Antonio Acin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)

Abstract

We consider the concept of temperature in a setting beyond the standard thermodynamics prescriptions. Namely, rather than restricting to standard coarse-grained measurements, we consider observers able to master any possible quantum measurement -a scenario that might be relevant at nanoscopic scales. In this setting, we focus on quantum systems of coupled harmonic oscillators and study the question of whether the temperature is an intensive quantity, in the sense that a block of a thermal state can be approximated by an effective thermal state at the same temperature as the whole system. Using the quantum fidelity as figure of merit, we identify instances in which this approximation is not valid, as the block state and the reference thermal state are distinguishable for refined measurements. Actually, there are situations in which this distinguishability even increases with the block size. However, we also show that the two states do become less distinguishable with the block size for coarse-grained measurements -thus recovering the standard picture. We then go further and construct an effective thermal state which provides a good approximation of the block state for any observables and sizes. Finally, we point out the role that entanglement plays in this scenario by showing that, in general, the thermodynamic paradigm of local intensive temperature applies whenever entanglement is not present in the system. Copyright (C) EPLA, 2012

Original languageEnglish
Article number10009
Number of pages6
JournalEurophysics Letters (EPL)
Volume98
Issue number1
DOIs
Publication statusPublished - Apr 2012

Keywords

  • ENTANGLEMENT

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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