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Is Quantum Theory the Last Word?

Sixty years after the famous debate on the nature of Reality between Niels Bohr and Albert Einstein, questions central to their debate are the subject of fascinating experiments. Is Quantum Theory the last word? Have we plumbed the depth and spanned the breadth of scientific inquiry and found that there just simply is no more? Have we come to the "end of the line?" In ancient times, the number of things that could be known was limited and it WAS possible for a single person to know them all. Even as recently as 200 years ago, our range of knowledge was severely circumscribed by our assumptions about the world around us. In the previous century, daring thinkers and observers expanded our understanding of the world in which we live to such a fantastic degree that man's technological progress in the past 100 years has surpassed the previous 2,000 years added all together. Does this acceleration indicate that the end is near? Or, shall we compare such claims to the story about the examiner in the U.S. Patent Office who, at the beginning of this century, suggested that the Patent Office be closed since "everything has already been invented." Well, it clearly wasn't the end in 1901, but perhaps we are approaching it now in the year 2001? Perhaps science, as we know it, has become obsolete because it has explained everything... there is no more "to invent." Does this sound fantastic? Well, one certainly gets this impression when reading some of the recent papers on the subject - a remarkable example being H. P. Stapp's contribution to the X-th Max Born "Quantum Future" Symposium [1], entitled "Quantum Ontology and Mind-Matter Synthesis." [2]

We wish to address Stapp's main theses later on in this section, but before we do, we would like to address the question that certainly deserves an answer if we want to be honest with our audience, to wit: IF quantum theory is NOT The Last Word, if there IS a future, what can it be? It is clear that our answer to this question must be, at present, based on speculation. But, as part of the tradition, once in a while, scientists do speculate! [3]
Our answer, given speculatively remember, is that we believe that quantum theory is an effective and powerful theory of measurements. But, we also believe that it deals only with a particular aspect of reality and that other approaches can, and shall, and must, give us a deeper insight into the complex weavings of Nature.

When we speak about Quantum Theory, we mean its standard and orthodox version which is clearly a linear theory. It is very good for making predictions based on incomplete information. But, it is not suitable for explaining what really happens. It explains the objects and phenomena of our experience, but does NOT explain the underlying reality which we do not experience directly. As Alan Turing succintly stated: "prediction is linear, description is non-linear". There will be more on this subject in Sect. 6, where we will describe in more details a possible scenario for future developments in quantum theory - a "Quantum Future" that we believe is valid and deserving of serious work, even if only to see if Stapp's dark vision of what lies ahead in science is what we must prepare ourselves to face.

Stapp states: "...I propose to break away from the cautious stance of the founders of quantum theory, and build a theory of reality by taking seriously what the incredible accuracy of the predictions of the formalism seems to proclaim, namely that nature is best understood as being built around knowings that enjoy the mathematical properties ascribed to them by quantum theory." According to Stapp, reality should be "recognized to be knowledge, rather than substantive matter... "

Stapp is not the first one to propagate the view that nothing "out there" really exists. Bishop Berkeley, as we know, proclaimed the very same idea long ago when he said: "I have no reason for believing the existence of matter." But Stapp is supporting this view by the practical success of quantum mechanics and failure of "all of our efforts to rid physics of this vile contamination by mind, which quantum theory presses upon us."

Well, let us just point out that the success of quantum theory is not that overhelming!

Meaningless infinities of relativistic quantum field theory tell us that something is seriously wrong with our theoretical assumptions. In our opinion, the value of a theory consists not in that it can explain the technique by which the fabric is woven on the loom of Nature, but that it can explain the patterns of the weaving, the Weaver and perhaps the motivations behind the weaving.

Facts cannot be understood by being crafted into a summary or a formula - they can only be understood by being explained. And, understanding is not the same as "knowing." Quantum Theory, as any other theory, has a finite region of validity - when attempts are made to apply it beyond these limits - we get either nonsense or no answer at all. Quantum theory, in its orthodox version, cannot even be applied to an individual system - like the Universe we live in and experience. We want to discover "why" in addition to "what" regarding the order of the universe in which we find ourselves. We wish to discover why "this" MUST be so, rather than "that;" why Nature does what she does and how. We want to uncover and understand the Laws of Nature, not just the "rules of thumb."

Stapp knows this all too well, but apparently he has lost faith that a better theory can be forthcoming, even if only one small step at a time. Einstein failed, Bohm failed (because his "model has not been consistently extended to the relativistic case of quantum electrodynamics, or to quantum chromodynamics, which are our premiere quantum theories."), Stapp himself, many years ago, tried to advance his own "theory of events" - unsuccessfully it seems. And now, apparently, he is convinced that there is no way out. If he could not do it, it cannot be done. Must it be so? Can it not be that a better explanation is the one that leads to improvements in techniques and concepts and structure?
In his paper The Philosophy of Experiment E. Schrödinger [4] wrote:

The new science (q.m.) arrogates the right to bully our whole philosophical outlook. It is pretended that refined measurements which lend themselves to easy discussions by the quantum mechanical formalism could actually be made. (...) Actual measurements on single individual systems are never discussed in this fundamental way, because the theory is not fit for it.(...) We are also supposed to admit that the extent of what is, or might be, observed coincides exactly with what the quantum mechanics is pleased to call observable.

As we have stressed elsewhere [6]

J.S. Bell [7, 8] deplored the misleading use of the term measurement in quantum theory. He opted for banning this word from our quantum vocabulary, together with other vague terms such as macroscopic, microscopic, observable and several others. He suggested that we ought to replace the term measurement with that of experiment, and also not to even speak of observables (the things that seem to call for an observer) but to introduce instead the concept of beables- the things that objectively happen-to-be (or not-to-be).gif

But there is no place for events or for beables in ordinary quantum theory. That is because each event must have three characteristic features:

If just one of these three features is relaxed, then what we have is not an event.
It must be classical, because it must obey the classical yes-no logic; it must never be in a superposition of it being "happened and/or unhappened." Otherwise it would not be an event.
It must be discrete. It must happen wholly. An event that approximately happened is not an event at all.
It must be irreversible, because it can not be made to be undone. This feature distinguishes real events from the virtual ones. Once something has happened - it has happened at a certain instant of time. It must have left a trace. Even if this trace can be erased, the very act of erasing will change the future - not the past. Something else may happen later, but it will be already a different event. We believe that events, and nothing but events, are pushing forward the arrow of time.

German philosopher E. Bloch expressed the very same idea succintly: Zeit ist nur dadurch, daß etwas geschieht und nur dort wo etwas geschiecht. But Stapp will say: "where are these events if not in our minds alone?" Our answer is: every energy transfer from one place to another is an event. Do such energy transfers happen? We speculate that they do. Our engineering and technology stands as proof. But then, one could inquire, where precisely do we think these events happen? We answer: they are localized neither in space nor in time. But, in our simplified mathematical models of reality we associate events with particular pieces of our experimental setup, mainly with perceivable or recordable changes of macroscopic bodies.gif

This is not to deny the existence or importance of "mental events" or "knowing," or the part that "mind" plays in the observing/measuring process - but these are only part of the answer. We agree with Stapp in one (but only one) point: the orthodox quantum theory is about measurements rather than about the real world that is being measured. The orthodox quantum theory is about predictions based on "knowledge of the observer." But orthodox quantum theory is not the only theory in existence, and it grasps only a piece of what can be grasped. It explains only part of the problem of how and why Nature weaves as she does. It comes nowhere close, in our opinion, to explaining everything that can be understood.

If knowledge, this thing that Stapp considers so highly, is to continue to grow, then the depth and breadth of the theory must expand as well. Stapp says: "This structure evolves the knowledge created by earlier knowings into the makings of later knowings" and "It is rather the knowings that are the basic irreducible units: they enter as entire units into a dynamic structure that carries forward the facts fixed by past knowings to produce the possibilities for future knowing" which actually amounts to the same "clockwork theory" of classical physics only at a greatly reduced scale and with the locus of manifestation reversed! One thing he says with which we agree up to a point: "Orthodox quantum theory is pragmatic; it is a practical tool based on human knowing."

But we seek to bridge the gap between "knowing" and understanding. Event Enhanced Quantum Theory, or EEQT as we denote it - cf. [16, 17, 18, 19] - is a minimal extension of quantum theory that accounts for events. It is a minimal extension of quantum theory that unifies continuous evolution of "wave function" with quantum jumps that accompany real world events. We do not pretend that EEQT is a fundamental theory. It is semi-phenomenological in its nature. But it shows that one can go beyond linear quantum theory, that one can predict more than the standard formalism would allow, that new questions can be asked, new horizons opened against the gloomy fog of the "nothing but knowings" landscape of future physics.

In the eighties fundamental concepts of quantum theory:

wave particle duality
quantum state vectors
back-action in quantum measurement
uncertainty limits
Schrödinger cats (S. Haroche [20])

gradually became accessible to experimentalists. The practical questions of controlling fundamental quantum phenomena have surfaced in the domains of quantum optics and applied physics. Quantum optics, in particular, has a special fascinating flavor as it deals with
  1. Squeezing
  2. Quantum Non-Demolition
  3. Quantum State Reconstruction
  4. Cavity Quantum Electrodynamics; Quantum Optics of Single Atoms (S. Haroche[20], H. Walther[21])
  5. Quantum Information:
  6. Spatial Quantum Structures

New technologies and new experiments need a new theory that will allow for simulation of real-time behaviour of individual quantum systems communicating with external control devices. EEQT is such a theory - it was created just for this purpose.
In Section 2 we will describe the mathematical formalism of EEQT and in Section 3 we will list its main results, in particular application of EEQT to the problem of relativistic quantum measurements. The main point made there is: the decision mechanism for events in EEQT is non-local in space. In a relativistic theory it must also be non-local in time. This implies that, once in a while, the effect will precede its cause. We expect to see events that can be interpreted in terms of superluminal propagation. The probabilistic character of such a propagation, as described in our model, prevents anti-telephone paradoxes from taking place.
It is to be noted that superluminality is a question that continues to fascinate physicists and laymen alike. Recently, with a new generation of tunneling time experiments, it has become a laboratory experimental question. The concept of tunneling time is well posed in EEQT - cf. [24, 25]

It is also to be noted that our relativistic model lives in a five-dimensional space-time, with Schwinger-Fock "proper time" as the fifth coordinate, and also that we are using indefinite-metric Hilbert space. This last property does not contradict positive definiteness of probabilities in our model.

It should be stressed that in EEQT all the probablistic interpretations of quantum theory are derived from the dynamics! In particular, it makes no sense to ask the question "what would be a distribution of observed values of an observable" without adding the appropriate terms to the evolution equation. In this respect EEQT embodies in its dynamics much more of the spoken philosophical language of Bohr and Heisenberg, quoted so freely by Stapp, than Standard Quantum Theory. There is a price that we must pay for this: the dynamical equations of EEQT are harder to solve. But, on the other hand, EEQT makes it possible to analyze experimental situations that the Standard Quantum Theory seems to exclude from its consideration - like simultanous measurement of several noncommuting observables. In this case, as explained in more detail in Section 3, measurement results exhibit chaotic and fractal behaviour.

In Section 5 we will attempt to answer frequently asked questions and objections against EEQT. In Section 6, we will sketch possible future developments of EEQT, while Section 7 will summarize our paper.

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