Understanding Quantum Physics: An Advanced Guide for the Perplexed

not
inert but active; it moves purely by its own "free will". Maybe God
does play dice in the atomic world. I finally broke loose the tightest shackles
of continuous motion with the help of inspiration. After this event, the
outcome seems very natural from a logical point of view. If a particle cannot
move continuously, it must move in a discontinuous way. How deep-rooted the
prejudice of the uniqueness of continuous motion is!
    If an atom moves
in a random and discontinuous way, then it can easily pass through two slits at
the same time. But why does a ball appear to move in a contrary way? Moreover,
why on earth does God play dice? These puzzles further haunted me. After
graduated from the Institute of Electronics, I decided to be an independent
theoretical physicist, or more accurately, a natural philosopher who aims at
understanding the mysterious universe. Life was not easy. But I never gave up
my research, and I never stop thinking. It had become the theme of my life.
    As time went on,
the picture of random discontinuous motion became clearer and clearer in my
mind. When I took a walk one afternoon in June 2001, I suddenly had another
inspiration after long reflection in solitude and meditation. I realized that
motion has no cause in reality, and thus it must be essentially random, i.e.,
God must play dice. Moreover, the familiar phenomenon of inertia has already
revealed that a ball also jumps in a random and discontinuous way just like an
atom. This is another new idea. Maybe the path to truth is always devious in
order that surprise can hide at the turn waiting for persevering seekers. God
also plays dice in our everyday world. He actually plays dice with the whole
universe. What a harmonic world!
    I simply want to
know the answer of a naive question. I simply think on it continually. But the
exploration has completely changed my life. It shapes my way through the world
and finally leads me to God, the ultimate reality. As Trinity said in The
Matrix , "It’s the question that brought you here… The answer is out
there, Neo, and it’s looking for you, and it will find you if you want it
to."
     

 
    Chapter 1
    How Can We Understand Quantum Mechanics?
    I think I can safely say that nobody
understands quantum mechanics... Do not keep saying to yourself, if you can
possible avoid it, “But how can it be like that?” because you will get ‘down
the drain’, into a blind alley from which nobody has escaped. Nobody knows how
it can be like that.
    —Richard
Feynman
    Quantum mechanics,
according to its Schrödinger picture, is a non-relativistic theory about the
wave function and its evolution. There are two main problems in the conceptual
foundations of quantum mechanics. The first one concerns the physical meaning
of the wave function in the theory. It has been widely argued that the
probability interpretation is not wholly satisfactory because of resorting to
the vague concept of measurement - though it is still the standard
interpretation in textbooks nowadays. On the other hand, the meaning of the
wave function is also in dispute in the alternative formulations of quantum
mechanics such as the de Broglie-Bohm theory and the many-worlds
interpretation. Exactly what does the wave function describe then?
    The second problem
concerns the evolution of the wave function. It includes two parts. One part
concerns the linear Schrödinger evolution. Why does the linear nonrelativistic
evolution of the wave function satisfy the Schrödinger equation? It seems that
a satisfactory derivation of the equation is still missing. The other part
concerns the collapse of the wave function during a measurement, which is
usually called the measurement problem. The collapse postulate in quantum
mechanics is ad hoc, and the theory does not tell us how a definite measurement
result emerges. Although the alternatives to quantum mechanics already give
their respective solutions to this problem, it has been a hot topic of debate
which solution is right or in the right direction. In the final analysis, it is
still unknown whether the wavefunction collapse is real or not. Even if the
wave function does collapse under some circumstances, it remains unclear
exactly why and how the wave function collapses. The measurement problem has
been widely acknowledged as one of the hardest and most important problems in
the foundations of quantum mechanics.
    Let’s illustrate
these problems with a typical double-slit experiment with single