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Title: Low depth quantum circuits for Ising models

A scheme for measuring complex temperature partition functions of Ising models is introduced. Two applications of this scheme are presented. First, through appropriate Wick rotations, those amplitudes can be analytically continued to yield estimates for partition functions of Ising models. Bounds on the estimated error are provided through a central-limit theorem whose validity extends beyond the present context; it holds for example for estimations of the Jones polynomial. The kind of state preparations and measurements involved in this application can be made independent of the system size or the parameters of the system being simulated. Second, the scheme allows to accurately estimate non-trivial invariants of links. Another result concerns the computational power of estimations of partition functions for real temperature classical ferromagnetic Ising models. We provide conditions under which estimating such partition functions allows to reconstruct scattering amplitudes of quantum circuits, making the problem BQP-hard. We also show fidelity overlaps for ground states of quantum Hamiltonians, which serve as a witness to quantum phase transitions, can be estimated from classical Ising model partition functions. Finally, we discuss how accurate corner magnetisation measurements on thermal states of two-dimensional Ising models lead to fully polynomial random approximation schemes (FPRAS) for the partitionmore » function.« less
Authors:
 [1] ;  [2] ;  [3] ;  [2]
  1. Dept. Estructura i Constituents de la Matèria, Universitat de Barcelona, 08028 Barcelona (Spain)
  2. Centre for Engineered Quantum Systems, Department of Physics and Astronomy, Macquarie University, North Ryde, NSW 2109 (Australia)
  3. Physics of Information Group, Instituto de Telecomunicações, P-1049-001 Lisbon (Portugal)
Publication Date:
OSTI Identifier:
22224288
Resource Type:
Journal Article
Resource Relation:
Journal Name: Annals of Physics (New York); Journal Volume: 340; Journal Issue: 1; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; APPROXIMATIONS; ATOMS; DEPTH; ERRORS; GROUND STATES; HAMILTONIANS; ISING MODEL; MAGNETIZATION; PARTITION FUNCTIONS; PHASE TRANSFORMATIONS; POLYNOMIALS; QUANTUM INFORMATION; RANDOMNESS; ROTATION; SCATTERING AMPLITUDES; SIMULATION