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Gaussian Thermal Operations and The Limits of Algorithmic Cooling

Adesso, G.; Serafini, A.; Hsieh, C.-Y.; Lostaglio, M.; Shackerley-Bennett, U.; Longden, S.

Authors

G. Adesso

A. Serafini

C.-Y. Hsieh

M. Lostaglio

U. Shackerley-Bennett

S. Longden



Abstract

The study of thermal operations allows one to investigate the ultimate possibilities of quantum states and of nanoscale thermal machines. Whilst fairly general, these results typically do not apply to continuous variable systems and do not take into account that, in many practically relevant settings, system-environment interactions are effectively bilinear. Here we tackle these issues by focusing on Gaussian quantum states and channels. We provide a complete characterization of the most general Gaussian thermal operation acting on an arbitrary number of bosonic modes, which turn out to be all embeddable in a Markovian dynamics, and derive necessary and sufficient conditions for state transformations under such operations in the single-mode case, encompassing states with nonzero coherence in the energy eigenbasis (i.e., squeezed states). Our analysis leads to a no-go result for the technologically relevant task of algorithmic cooling: We show that it is impossible to reduce the entropy of a system coupled to a Gaussian environment below its own or the environmental temperature, by means of a sequence of Gaussian thermal operations interspersed by arbitrary (even non-Gaussian) unitaries. These findings establish fundamental constraints on the usefulness of Gaussian resources for quantum thermodynamic processes.

Journal Article Type Article
Publication Date Jan 2, 2020
Journal Physical Review Letters
Print ISSN 0031-9007
Electronic ISSN 1079-7114
Publisher American Physical Society
Peer Reviewed Peer Reviewed
Volume 124
Issue 1
Article Number 010602
APA6 Citation Adesso, G., Serafini, A., Hsieh, C., Lostaglio, M., Shackerley-Bennett, U., & Longden, S. (2020). Gaussian Thermal Operations and The Limits of Algorithmic Cooling. Physical Review Letters, 124(1), https://doi.org/10.1103/physrevlett.124.010602
DOI https://doi.org/10.1103/physrevlett.124.010602
Keywords General Physics and Astronomy
Publisher URL https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.124.010602

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