Multipartite-entanglement tomography of a quantum simulator

Year: 2019

Authors: Gabbrielli M., Lepori L., Pezzè L.

Autors Affiliation: CNR, INO, QSTAR, Largo Enrico Fermi 2, I-50125 Florence, Italy; LENS, Largo Enrico Fermi 2, I-50125 Florence, Italy; Univ Aquila, Dipartimento Sci Fis & Chim, Via Vetoio, I-67010 Laquila, Italy; INFN, Lab Nazl Gran Sasso, Via Giovanni Acitelli 22, I-67100 Laquila, Italy; Ist Italiano Tecnol, Graphene Labs, Via Morego 30, I-16163 Genoa, Italy.

Abstract: Multipartite-entanglement tomography, namely the quantum Fisher information (QFI) calculated with respect to different collective operators, allows to fully characterize the phase diagram of the quantum Ising chain in a transverse field with variable-range interaction. In particular, it recognizes the phase stemming from long-range (LR) antiferromagnetic interaction, a capability also shared by the spin squeezing. Furthermore, the QFI locates the quantum critical points, both with vanishing and nonvanishing mass gap. In this case, we also relate the finite-size power-law exponent of the QFI to the critical exponents of the model, finding a signal for the breakdown of conformal invariance in the deep LR regime. Finally, the effect of a finite temperature on the multipartite entanglement, and ultimately on the phase stability, is considered. In light of the current realizations of the model with trapped ions and of the potential measurability of the QFI, our approach yields a promising strategy to probe LR physics in controllable quantum systems.

Journal/Review: NEW JOURNAL OF PHYSICS

Volume: 21 (3)      Pages from: 033039-1  to: 033039-17

More Information: We warmly thank Nicolo Defenu, Fabio Ortolani, Simone Paganelli, Augusto Smerzi, Luca Tagliacozzo, Andrea Trombettoni, and Davide Vodola for useful discussions and for the help with numerics. The authors also acknowledge the participation to the workshop ´Entanglement in Quantum Systems´, held at the Galileo Galilei Institute for Theoretical Physics, Firenze, 21th May-13th July 2018, where part of this work has been performed. This work has been supported by the QuantEra ERA-NET cofund project ´Q-Clocks´ and EURAMET Empir project ´USOQS´.
KeyWords: entanglement; spin chain; long-range interaction; quantum phase transitions
DOI: 10.1088/1367-2630/aafb8c

Citations: 22
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