TITLE:
How Does Wave Packet of a Free Particle Yield?
AUTHORS:
Tianhai Zeng
KEYWORDS:
Superposition of Eigenstates, Interaction, Entangled State, Conservation Law, Double-Slit Experiment, Tunnel Phenomenon
JOURNAL NAME:
Journal of Modern Physics,
Vol.6 No.7,
June
11,
2015
ABSTRACT: Preparing
a particle in a superposition or a wave packet of eigenstates of a physical quantity
is to let it interact with a large object. The composite system composed of the
particle and the large object evolves into an entangled state. When the state
of the large object is considered to be approximately unchanged, the entangled
state can be approximately considered as a product state, and then the particle
is prepared in an approximate superposed state. We consider the Schrodinger
equation for a composite system with interactions between subsystems as a
fundamental postulate and a single particle’s Schrodinger equation must be
approximately obtained from it. We argue that superposition of states exists
only in composite systems. Interaction exchanging some quantities between
subsystems makes conservation laws strictly hold, and no wave packet of a free
particle yields. With this point, we can also understand the double-slit
experiment and the tunnel phenomenon.