Fifteen Eighty Four

Academic perspectives from Cambridge University Press


Myths and Open Questions of Quantum Mechanics

David W, Snoke

After a hundred years, the field of quantum mechanics still has much to cause us to ponder. Nevertheless, science has progressed, and we know more than we used to know.  Among the things that have progressed are the modern understandings of past experiments in the context of quantum field theory.  Some of the things we now know are:

  • The Planck radiation spectrum and the photoelectric effect tell us nothing at all about whether particles like little billiard balls exist. Both experiments are well understood as wave phenomena.
  • Although quantum jumps can be very fast, there is no evidence that they are ever instantaneous.  Straightforward calculations give the time scale for quantum transitions.
  • Some definite, physical measurements can be made that require a system to be in a superposition of different particle numbers.

The above, and other considerations discussed in the book, lead to the view of particles as “epi-phenomena,” that is, concepts derivable from a deeper underlying reality, namely the quantum field. Therefore, the common dichotomy of “wave-particle duality” is wrongheaded.

While “wave-particle duality” is not a fundamental mystery, there is still much that is mysterious. In particular, how do we account for non-local correlations, when a detection event at one location seems to influence what happens at another detector far away? In the book, I review in depth some of the major rival interpretations of quantum mechanics, namely the Copenhagen interpretation, the many-worlds (Everett-Wheeler) interpretation, and spontaneous collapse. 

The Copenhagen interpretation has received much critique over the decades, which I review.  However, the many-worlds view seems to be rising in influence, without the same degree of critique—it seems that the main critique is often simply that it has bizarre implications. In this book I offer an extended discussion of problems of the many-worlds from a scientific perspective.  Among other things, I argue that the many-worlds approach doesn’t actually help with the nonlocality problem.  Instead of the results of specific outcomes of detection events having nonlocal effects, in the many-worlds approach the definition of a set of basis states by a detector (called “einselection” by Zurek) is propagated nonlocally.

Spontaneous collapse theories are often not taken seriously, but they are still viable. In the book I present a new version that is consistent with experiments, which ends up looking just like a set of weak measurements.  While extended critique of this model has not yet occurred, it has been fleshed out enough to not be obviously wrong.

Overall, the book takes the perspective that the quantum field is real (as real, say, as water waves), and not just a construct. The first 120 pages of the book have no equations and can be read by a non-physicist.  Several of the later chapters require only freshman/sophomore-level physics. I also include a basic introduction to quantum field theory for the non-expert, and several results of modern decoherence theory, which relates to measurement theory.

Title: Interpreting Quantum Mechanics

Author: David W, Snoke

ISBN: 9781009261555

About The Author

David W, Snoke

David Snoke leads a laboratory at the University of Pittsburgh studying fundamental optical effects. In 2006 he was elected a Fellow of the American Physical Society 'for his pione...

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