Interpreting Quantum Mechanics

I would like people who take physics seriously (no Usenet crackpots, please,
you know who you are) to comment on the following eight ways that it is
possible to interpret quantum mechanics. In both a famous article and book
("Quantum Reality" Nick Herbert discusses eight now well-know ways of
interpreting QM.

My question is this: Are there any new variants of these ideas that have
appeared in the last 20 years that physicists take seriously? Are there any
totally new ideas, i.e. interpretations of QM that don't fit into any of
these eight ideological boxes?

Are there any experiments which most physicists agree can, or at least in
principle could, show us which interpretations are more true?

Many people talk about decoherence as a solution to the question of how a
wave function collapses. Assuming that this idea is tenable (or possibly
certainly true) would this favor any of the following interpretations, be
neutral to all of them, or perhaps suggest yet a different interpretation of
QM?

I thank you in advance for your consideration and time. If you want to just
briefly mention a possibility and suggest a book to read on that topic, that
would be much appreciated as well!

Thanks,

Robert

----

Nick Herbert talks about "Quantum Reality":

Quantum Reality #1 The Copenhagen Interpretation, Part I - There is no deep
reality.... Everyday phenomena are themselves built not out of phenomena but
out of an utterly different kind of being. Far from being a crank or
minority position, "There is no deep reality" represents the prevailing
doctrine of establishment physics. Because this quantum reality was
developed at Niels Bohr's Copenhagen institute, it is called the "Copenhagen
interpretation." ...



Quantum Reality #2. The Copenhagen interpretation, Part II - Reality is
created by observation....The Copenhagen interpretation properly consists of
two distinct parts: I. There is no reality in the absence of observation; 2.
Observation creates reality . "You create your own reality," is the theme of
Fred Wolf's "Taking the Quantum Leap."

....John Wheeler's memorable maxim for separating what is real in the world
from what is not: "No elementary phenomenon is a real phenomenon until it is
an

observed phenomenon,"



Quantum Reality #3 - Reality is an undivided wholeness. The views of Walter
Heider exemplify a third unusual claim of quantum physicists: that in spite
of its obvious partitions and boundaries, the world in actuality is a
seamless and inseparable whole...

....Heitler accepts an observer-created reality but adds that the act of ob
servation also dissolves the boundary between observer and observed: "The
observer appears, as a necessary part of the whole structure, and in his
full capacity as a conscious being. The separation of the world into an
'objective outside reality' and 'us,' the self-conscious onlookers, can no
longer be maintained. Object and subject have become inseparable from each
other."

Physicist David Bohm of London's Birkbeck College has especially stressed
the necessary wholeness of the quantum world...



Quantum Reality #4 The many-worlds interpretation. Reality consists of a
steadily increasing number of parallel universes.... For any situation in
which several different outcomes are possible some physicists believe that
all outcomes actually occur. In order to accommodate different outcomes
without contradiction , entire new universes spring into being, identical in
every detail except for the single outcome that gave them birth.

....Invented in 1957 by Hugh Everett, a Princeton graduate student, the
many-worlds interpretation is a latecomer to the New Physics scene. Despite
its bizarre conclusion, that innumerable parallel universes each as real as
our own actually exist, Everett's many-worlds picture has gained
Considerable support among quantum theorists...





Quantum Reality #5: Quantum logic (The World obeys a non-human kind of
reasoning.) ...we must scrap our very mode of reasoning, in favor of a new
quantum logic.

For two thousand years, talk about logic (in the West) was cast in the
syllogistic mold devised by Aristotle. In the mid-nineteenth century, George
Boole, an Irish schoolteacher, reduced logical statements to simple
arithmetic by inventing an artificial symbolic language which laid bare the
logical bones of ordinary language.

....a few creative logicians amused themselves by constructing "crazy logics"
using rules other than Boole's, These deviant designs for AND/OR/NOT,
although mathematically consistent, were considered mere curiosities since
they seemed to fit no human pattern of discourse. However, according to some
New Physicists, one of these crazy logics may be just what we need to make
sense out of quantum events. Listen to quantum theorist David Finkelstein
calling for mutiny against the rules of Boole: "Einstein threw out the
classical concept of time; Bohr throws out the classical concept of truth .
.. . Our classical ideas of logic are simply wrong in a basic practical way.
The next step is to learn to think in the right way, to learn to think
quantum-logically."



Quantum Reality #6. Neorealism (The world is made of ordinary objects.) An
ordinary object is an entity which possesses attributes of its own whether
observed or not... The clarity and ubiquity of ordinary reality has seduced
a few physicists - I call them neorealists - into imagining that this
familiar kind of reality can be extended into the atomic realm and beyond.

Neorealists...accuse the orthodox majority of wallowing in empty formalism
and obscuring the world's simplicity with needless mystification. Instead
they preach return to a pure and more primitive faith. Chief among
neorealist rebels was Einstein, whose passion for realism pitted him
squarely against the quantum Orthodoxy...



Quantum Reality #7 Consciousness creates reality... a small faction asserts
that only an apparatus endowed with consciousness (even as you and I) is
privileged to create reality. The one observer that counts is a conscious
observer.

....Eugene Wigner...comments on this ironic turn of events: "It is not
possible to formulate the laws of quantum mechanics in a fully consistent
way with out reference to the consciousness . . . It will remain remarkable
in whatever way our future concepts may develop, that the very study of the
external world led to the conclusion that the content of the consciousness
is an ultimate reality."



Quantum Reality #8. The duplex world of Werner Heisenberg (The world is
twofold, consisting of potentials and actualities.) Most physicists believe
in the Copenhagen interpretation, which states that there is no deep
reality- QR # 1) and observation creates reality QR # 2). What these two
realities have in common is the assertion that only phenomena are real; the
world beneath phenomena is not.

One question which this position immediately brings to mind is this: "if
observation creates reality, what does it create this reality out of? Are
phenomena created out of *** nothingness or out of some more substantial
stuff?" Since the nature of unmeasured reality is unobservable by
definition, many physicists dismiss such questions as meaningless on
pragmatic grounds.

According to Heisenberg, there is no deep reality - nothing down there
that's real in the same sense as the phenomenal facts are real.... "But the
atoms and the elementary particles themselves are not as real; they form a
world of potentialities or possibilities rather than one of things or facts
.. . .

....Heisenberg's two worlds are bridged by a special interaction which
physicists call a "measurement." During the magic measurement act, one
quantum possibility is singled out, abandons its shadowy sisters, and
surfaces in our ordinary world as an actual event. Everything that happens
in our World arises out of possibilities prepared for in that other-the
world of quantum potentia. In turn, our world sets limits on how far crowds
of Potentia can roam. Because certain facts are actual, not everything is
possible in the quantum world. There is no deep reality, no deep
reality-as-we-know-it....



[...cutting towards the end of Nick Herbert's article...]

Since these quantum realities differ SO radically, one might expect them to
have radically different experimental consequences. An astonishing feature
of these eight quantum realities, however, is that they are experimentally
indistinguishable. For all presently conceivable experiments, each of these
realities predicts exactly the same observable phenomena.

....Likewise modern physicists do not know how to determine experimentally
what kind of world they actually live in. However, since "reality has
consequences" we might hope that future experiments, not bound by our
current concepts of measurability, will conclusively establish one or more
of these bizarre pictures as top-dog reality. At present, however, each of
these quantum realities must be regarded as a viable candidate for "the way
the world really is." They may, however, all be wrong.




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