.This paper introduces the definition and calculating nature of two integral frequently used in Quantum Mechanics,and presents the methods and formularized results of Quantum Mechanics by using integral.
A kink-based expression for the canonical partition function is developed using Feynman’s path integral formulation of quantum mechanics and a discrete basis set. The approach is exact for a complete set of states. The method is tested on the 3×3 Hubbard model and overcomes the sign problem seen in traditional path integral studies of fermion systems. Kinks correspond to transitions between different N-electron states, much in the same manner as occurs in configuration interaction calculations in standard ab initio methods. The different N-electron states are updated, based on which states occur frequently during a Monte Carlo simulation, giving better estimates of the true eigenstates of the Hamiltonian.
The Path-Integral Formulation of Quantum Mechanics is introduced
along with a detailed mathematical description of how it is
used in quantum computations. The important concept of the kernel
is explained, along with the free particle and harmonic oscillator as
examples. Furthermore, the method for calculating expectation values
of quantum operators is explained.
The expectation values are naturally calculated by importance
sampled Monte Carlo integration and by use of the Metropolis algorithm.
This is due to the discretization of the path integral results
in an integral with a high number of integration variables. The mathematical
concepts of this calculation are explained. Also, a method for
obtaining the probability density of the treated system is presented.
The calculations are performed by a GPU, due to its high capabilities
for numerical operations. This requires the mathematical
computations to be parallelized and is done by use of the free software
PyOpenCL. A thorough introduction to these concepts are given.
The resulting ground state energies and probability densities for
many particle systems interacting with harmonic as well as attractive
and repulsive gaussian potentials are presented. The calculations
worked exceedingly well for many particle systems.
Source code is available at https://sourceforge.net/projects/
feynmangpu/files/
I show that frequentism, as an explanation of probability in classical statistical mechanics, can be extended in a natural way to a decoherent quantum history space, the analogue of a classical phase space. The result is a form of finite frequentism, in which the Gibbs concept of an infinite ensemble of gases is replaced by the quantum state expressed as a superposition of a finite number of decohering microstates. It is a form of finite and actual (as opposed to hypothetical) frequentism insofar as all the microstates exist, even though they may differ macroscopically, in keeping with the decoherence-based Everett interpretation of quantum mechanics.