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Title: Defects in Quantum Computers

The shift of interest from general purpose quantum computers to adiabatic quantum computing or quantum annealing calls for a broadly applicable and easy to implement test to assess how quantum or adiabatic is a specific hardware. Here we propose such a test based on an exactly solvable many body system–the quantum Ising chain in transverse field–and implement it on the D-Wave machine. An ideal adiabatic quench of the quantum Ising chain should lead to an ordered broken symmetry ground state with all spins aligned in the same direction. An actual quench can be imperfect due to decoherence, noise, flaws in the implemented Hamiltonian, or simply too fast to be adiabatic. Imperfections result in topological defects: Spins change orientation, kinks punctuating ordered sections of the chain. Therefore, the number of such defects quantifies the extent by which the quantum computer misses the ground state, and is imperfect.
Authors:
 [1] ;  [2] ;  [3] ;  [3]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of Silesia, Katowice (Poland). Inst. of Physics; Jagiellonian Univ., Krakow (Poland). Inst. of Physics
  2. Jagiellonian Univ., Krakow (Poland). Inst. of Physics
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Report Number(s):
LA-UR-17-24558
Journal ID: ISSN 2045-2322
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 8; Journal Issue: 1; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA); The National Science Centre (Poland)
Country of Publication:
United States
Language:
English
Subject:
97 MATHEMATICS AND COMPUTING; Atomic and Nuclear Physics
OSTI Identifier:
1427373

Gardas, Bartłomiej, Dziarmaga, Jacek, Zurek, Wojciech H., and Zwolak, Michael. Defects in Quantum Computers. United States: N. p., Web. doi:10.1038/s41598-018-22763-2.
Gardas, Bartłomiej, Dziarmaga, Jacek, Zurek, Wojciech H., & Zwolak, Michael. Defects in Quantum Computers. United States. doi:10.1038/s41598-018-22763-2.
Gardas, Bartłomiej, Dziarmaga, Jacek, Zurek, Wojciech H., and Zwolak, Michael. 2018. "Defects in Quantum Computers". United States. doi:10.1038/s41598-018-22763-2. https://www.osti.gov/servlets/purl/1427373.
@article{osti_1427373,
title = {Defects in Quantum Computers},
author = {Gardas, Bartłomiej and Dziarmaga, Jacek and Zurek, Wojciech H. and Zwolak, Michael},
abstractNote = {The shift of interest from general purpose quantum computers to adiabatic quantum computing or quantum annealing calls for a broadly applicable and easy to implement test to assess how quantum or adiabatic is a specific hardware. Here we propose such a test based on an exactly solvable many body system–the quantum Ising chain in transverse field–and implement it on the D-Wave machine. An ideal adiabatic quench of the quantum Ising chain should lead to an ordered broken symmetry ground state with all spins aligned in the same direction. An actual quench can be imperfect due to decoherence, noise, flaws in the implemented Hamiltonian, or simply too fast to be adiabatic. Imperfections result in topological defects: Spins change orientation, kinks punctuating ordered sections of the chain. Therefore, the number of such defects quantifies the extent by which the quantum computer misses the ground state, and is imperfect.},
doi = {10.1038/s41598-018-22763-2},
journal = {Scientific Reports},
number = 1,
volume = 8,
place = {United States},
year = {2018},
month = {3}
}