26,290 research outputs found
Local Simulation Algorithms for Coulomb Interaction
Long ranged electrostatic interactions are time consuming to calculate in
molecular dynamics and Monte-Carlo simulations. We introduce an algorithmic
framework for simulating charged particles which modifies the dynamics so as to
allow equilibration using a local Hamiltonian. The method introduces an
auxiliary field with constrained dynamics so that the equilibrium distribution
is determined by the Coulomb interaction. We demonstrate the efficiency of the
method by simulating a simple, charged lattice gas.Comment: Last figure changed to improve demonstration of numerical efficienc
Simulating typical entanglement with many-body Hamiltonian dynamics
We study the time evolution of the amount of entanglement generated by one
dimensional spin-1/2 Ising-type Hamiltonians composed of many-body
interactions. We investigate sets of states randomly selected during the time
evolution generated by several types of time-independent Hamiltonians by
analyzing the distributions of the amount of entanglement of the sets. We
compare such entanglement distributions with that of typical entanglement,
entanglement of a set of states randomly selected from a Hilbert space with
respect to the unitarily invariant measure. We show that the entanglement
distribution obtained by a time-independent Hamiltonian can simulate the
average and standard deviation of the typical entanglement, if the Hamiltonian
contains suitable many-body interactions. We also show that the time required
to achieve such a distribution is polynomial in the system size for certain
types of Hamiltonians.Comment: Revised, 11 pages, 7 figure
Simulating Hamiltonian dynamics with a truncated Taylor series
We describe a simple, efficient method for simulating Hamiltonian dynamics on
a quantum computer by approximating the truncated Taylor series of the
evolution operator. Our method can simulate the time evolution of a wide
variety of physical systems. As in another recent algorithm, the cost of our
method depends only logarithmically on the inverse of the desired precision,
which is optimal. However, we simplify the algorithm and its analysis by using
a method for implementing linear combinations of unitary operations to directly
apply the truncated Taylor series.Comment: 5 page
Hamiltonian Simulation Using Linear Combinations of Unitary Operations
We present a new approach to simulating Hamiltonian dynamics based on
implementing linear combinations of unitary operations rather than products of
unitary operations. The resulting algorithm has superior performance to
existing simulation algorithms based on product formulas and, most notably,
scales better with the simulation error than any known Hamiltonian simulation
technique. Our main tool is a general method to nearly deterministically
implement linear combinations of nearby unitary operations, which we show is
optimal among a large class of methods.Comment: 18 pages, 3 figure
Global Demons in Field Theory : Critical Slowing Down in the Xy Model
We investigate the use of global demons, a `canonical dynamics', as an
approach to simulating lattice regularized field theories. This
deterministically chaotic dynamics is non-local and non-Hamiltonian, and
preserves the canonical measure rather than . We apply this
inexact dynamics to the 2D XY model, comparing to various implementations of
hybrid Monte Carlo, focusing on critical exponents and critical slowing down.
In addition, we discuss a scheme for making energy non-conserving dynamical
algorithms exact without the use of a Metropolis hit.Comment: 23 pages text plus 12 figures [Submitted to Nuc. Phys. B, 7/92
Simulating Hamiltonian dynamics using many-qudit Hamiltonians and local unitary control
When can a quantum system of finite dimension be used to simulate another
quantum system of finite dimension? What restricts the capacity of one system
to simulate another? In this paper we complete the program of studying what
simulations can be done with entangling many-qudit Hamiltonians and local
unitary control. By entangling we mean that every qudit is coupled to every
other qudit, at least indirectly. We demonstrate that the only class of
finite-dimensional entangling Hamiltonians that aren't universal for simulation
is the class of entangling Hamiltonians on qubits whose Pauli operator
expansion contains only terms coupling an odd number of systems, as identified
by Bremner et. al. [Phys. Rev. A, 69, 012313 (2004)]. We show that in all other
cases entangling many-qudit Hamiltonians are universal for simulation
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