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Experimental Observation of Lee-Yang Zeros

Xinhua Peng, Hui Zhou, Bo-Bo Wei, Jiangyu Cui, Jiangfeng Du, and Ren-Bao Liu
Phys. Rev. Lett. 114, 010601 – Published 5 January 2015
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Abstract

Lee-Yang zeros are points on the complex plane of physical parameters where the partition function of a system vanishes and hence the free energy diverges. Lee-Yang zeros are ubiquitous in many-body systems and fully characterize their thermodynamics. Notwithstanding their fundamental importance, Lee-Yang zeros have never been observed in experiments, due to the intrinsic difficulty that they would occur only at complex values of physical parameters, which are generally regarded as unphysical. Here we report the first observation of Lee-Yang zeros, by measuring quantum coherence of a probe spin coupled to an Ising-type spin bath. The quantum evolution of the probe spin introduces a complex phase factor and therefore effectively realizes an imaginary magnetic field. From the measured Lee-Yang zeros, we reconstructed the free energy of the spin bath and determined its phase transition temperature. This experiment opens up new opportunities of studying thermodynamics in the complex plane.

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  • Received 11 September 2014

DOI:https://doi.org/10.1103/PhysRevLett.114.010601

© 2015 American Physical Society

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Imaginary Magnetic Fields in the Real World

Published 5 January 2015

Imaginary magnetic fields predicted by the fundamental theory of phase transitions can be realized experimentally.

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Authors & Affiliations

Xinhua Peng1,*, Hui Zhou1, Bo-Bo Wei2, Jiangyu Cui1, Jiangfeng Du1,†, and Ren-Bao Liu2,‡

  • 1Hefei National Laboratory for Physical Sciences at Microscale, Department of Modern Physics, and Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei 230026, China
  • 2Department of Physics, Centre for Quantum Coherence, and Institute of Theoretical Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China

  • *xhpeng@ustc.edu.cn
  • djf@ustc.edu.cn
  • rbliu@phy.cuhk.edu.hk

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Issue

Vol. 114, Iss. 1 — 9 January 2015

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