Energy cost of entanglement extraction in complex quantum systems

• Published in: Nature communications 2018-09, Vol.9 (1), p.3792-9, Article 3792
• Main Authors: Bény, Cédric, Chubb, Christopher T., Farrelly, Terry, Osborne, Tobias J.
• Format: Article
• Language: English
• Subjects: 639/766/483/481; 639/766/483/640; Energy; Energy costs; Field theory; Humanities and Social Sciences; multidisciplinary; Price increases; Quantum entanglement; Quantum field theory; Quantum theory; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-018-06153-w

What is the energy cost of extracting entanglement from complex quantum systems? Operationally, we may wish to actually extract entanglement. Conceptually, we may wish to physically understand the entanglement distribution as a function of energy. This is important, especially for quantum field theory vacua, which are extremely entangled. Here we build a theory to understand the energy cost of entanglement extraction. First, we consider a toy model, and then we define the entanglement temperature, relating energy cost to extracted entanglement. Next, we give a physical argument quantifying the energy cost of entanglement extraction in some quantum field vacua. There the energy cost depends on the spatial dimension: in one dimension, for example, it grows exponentially with extracted entanglement. Next, we provide approaches to bound the energy cost of extracting entanglement more generally. Finally, we look at spin chain models numerically to calculate the entanglement temperature using matrix product states. Understanding the energy cost of entanglement extraction has fundamental implications, in particular for quantum field theory and condensed matter. Here, the authors analyse how the optimal energy cost scales with the number of extracted EPR pairs, when local operations and classical communication are allowed.