Megascopic Quantum Phenomena
301
Process 2: The continuous, deterministic change of state of an isolated system with
time according to a wave equation ∂ψ/∂t = Aψ, where A is a linear operator. This
formulation describes a wealth of experience. No experimental evidence is known
which contradicts it.”
Everett questioned the whole process of measurement—the problem already wellknown at the time—namely the fact that the von Neumann view did only fit a certain
type of measurement but is not able the explain all of them: “Von Neumann showed
how to treat a special class of approximate measurements by the method of projection
operators. However, a general treatment of all approximate measurements by the
method of projections operators can be shown to be impossible… von Neumann’s
example is only a special case of a more general situation. Consider any measuring
apparatus interacting with any object system. As a result of the interaction the state
of the measuring apparatus is no longer capable of independent definition. It can be
defined only relative to the state of the object system. In other words, there exists
only a correlation between the two states of the two systems. It seems as if nothing
can ever be settled by such a measurement” [17].
Furthermore Everett concentrated only on a set of measurement problems that
differs from the von Neumann class, i.e. those excluding observers with a conscious
mind and taking only into the consideration devices in the role of “observers”. Quoting: “Not all conceivable situations fit the framework of this mathematical formulation. Consider for example an isolated system consisting of an observer or measuring
apparatus, plus an object system. Can the change with time of the state of the total
system be described by Process 2? If so, then it would appear that no discontinuous
probabilistic process like Process 1 can take place. If not, we are forced to admit
that systems which contain observers are not subject to the same kind of quantummechanical description as we admit for all other physical systems. The question
cannot be ruled out as lying in the domain of psychology. Much of the discussion of
“observers” in quantum mechanics has to do with photoelectric cells, photographic
plates, and similar devices where a mechanistic attitude can hardly be contested.
For the following one can limit himself to this class of problems, if he is unwilling
to consider observers in the more familiar sense on the same mechanistic level of
analysis” [17].
Up to this point the Everett’s conclusion is certainly correct. But what about his
proposal for a generalization of von Neumann’s method based on projection operators? One should perhaps anticipate some generalizations where observers with a
conscious mind together with the devices in the role of “observers” should be put
side by side in some wider context. But in contrast he simply attempts to remove
“Process l” from the Copenhagen postulates. In consequence it means to get rid of
two axioms, i.e. the Born rule and the von Neumann–Wigner rule, downgrading the
Born rule, not as an axiom but as an emergent rule from “Process 2”. Everett finally
arrives at his own eccentric and surreal interpretation of quantum mechanics, known
now as the MWI (many-worlds interpretation): “We thus arrive at the following picture: Throughout all of a sequence of observation processes there is only one physical
system representing the observer, yet there is no single unique state of the observer
301
Process 2: The continuous, deterministic change of state of an isolated system with
time according to a wave equation ∂ψ/∂t = Aψ, where A is a linear operator. This
formulation describes a wealth of experience. No experimental evidence is known
which contradicts it.”
Everett questioned the whole process of measurement—the problem already wellknown at the time—namely the fact that the von Neumann view did only fit a certain
type of measurement but is not able the explain all of them: “Von Neumann showed
how to treat a special class of approximate measurements by the method of projection
operators. However, a general treatment of all approximate measurements by the
method of projections operators can be shown to be impossible… von Neumann’s
example is only a special case of a more general situation. Consider any measuring
apparatus interacting with any object system. As a result of the interaction the state
of the measuring apparatus is no longer capable of independent definition. It can be
defined only relative to the state of the object system. In other words, there exists
only a correlation between the two states of the two systems. It seems as if nothing
can ever be settled by such a measurement” [17].
Furthermore Everett concentrated only on a set of measurement problems that
differs from the von Neumann class, i.e. those excluding observers with a conscious
mind and taking only into the consideration devices in the role of “observers”. Quoting: “Not all conceivable situations fit the framework of this mathematical formulation. Consider for example an isolated system consisting of an observer or measuring
apparatus, plus an object system. Can the change with time of the state of the total
system be described by Process 2? If so, then it would appear that no discontinuous
probabilistic process like Process 1 can take place. If not, we are forced to admit
that systems which contain observers are not subject to the same kind of quantummechanical description as we admit for all other physical systems. The question
cannot be ruled out as lying in the domain of psychology. Much of the discussion of
“observers” in quantum mechanics has to do with photoelectric cells, photographic
plates, and similar devices where a mechanistic attitude can hardly be contested.
For the following one can limit himself to this class of problems, if he is unwilling
to consider observers in the more familiar sense on the same mechanistic level of
analysis” [17].
Up to this point the Everett’s conclusion is certainly correct. But what about his
proposal for a generalization of von Neumann’s method based on projection operators? One should perhaps anticipate some generalizations where observers with a
conscious mind together with the devices in the role of “observers” should be put
side by side in some wider context. But in contrast he simply attempts to remove
“Process l” from the Copenhagen postulates. In consequence it means to get rid of
two axioms, i.e. the Born rule and the von Neumann–Wigner rule, downgrading the
Born rule, not as an axiom but as an emergent rule from “Process 2”. Everett finally
arrives at his own eccentric and surreal interpretation of quantum mechanics, known
now as the MWI (many-worlds interpretation): “We thus arrive at the following picture: Throughout all of a sequence of observation processes there is only one physical
system representing the observer, yet there is no single unique state of the observer