Simulating sparse Hamiltonians with star decompositions

  • Authors:
  • Andrew M. Childs;Robin Kothari

  • Affiliations:
  • Department of Combinatorics & Optimization, University of Waterloo and Institute for Quantum Computing, University of Waterloo;David R. Cheriton School of Computer Science, University of Waterloo and Institute for Quantum Computing, University of Waterloo

  • Venue:
  • TQC'10 Proceedings of the 5th conference on Theory of quantum computation, communication, and cryptography
  • Year:
  • 2010

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Abstract

We present an efficient algorithm for simulating the time evolution due to a sparse Hamiltonian. In terms of the maximum degree d and dimension N of the space on which the Hamiltonian H acts for time t, this algorithm uses (d2(d+log* N) ∥Ht∥)1+o(1) queries. This improves the complexity of the sparse Hamiltonian simulation algorithm of Berry, Ahokas, Cleve, and Sanders, which scales like (d4(d+log* N) ∥Ht∥)1+o(1) To achieve this, we decompose a general sparse Hamiltonian into a small sum of Hamiltonians whose graphs of non-zero entries have the property that every connected component is a star, and efficiently simulate each of these pieces.