A Paradox
The “Which Way?”- Question
To make the interpretation problem of Quantum Theory as clear as possible – also to people not so familiar with physics – and to clarify why this is a socio-cultural problem too, here is a typical example: the paradox of the “two ways”, which illustrates the problem vividly.
Let us look at the following experiment:
A light ray (starting top left) passes through the depicted test arrangement. The intensity of the light is chosen so low that almost certainly only one single photon is present within the diagrammed area.
At first the light crosses the semi-permeable mirror SM1. On both paths L and R it is redirected by mirrors M1 and M2 in such a way that the rays are reunited at a second semi-permeable mirror SM2. The lengths of the paths L and R differ, such that at SM2 the phase of the ray propagating along L does not coincide with the phase of the ray propagating along R and one of the two rays disappears due to destructive interference. In both ray paths photon detectors (DL and DR) can be inserted.
The experiment reveals the following (in the common approach unsolvable) absurdity:
If the detectors are not in the light paths, then we observe interference after the second semi-permeable mirror, that is: the photon resp. the light wave must have taken both ways – otherwise interference would not be possible.
This fact deserves particular attention:
There must always be something on the way in both paths – otherwise one could not observe interference after the second semi-permeable mirror if both paths are free.
However if we now insert the detectors into the paths, then in any case only one detector at a time responds: since the photon is indivisible, it can only choose either L or R (with a probability of ½ each).
This fact deserves our particular attention, too:
There can never be anything on the way in both paths at the same time, because the two detectors do never respond simultaneously.
Obviously these two facts contradict each other.
How is this contradiction “solved” within the standard interpretation? In the following way:
If a photon is detected in one of the detectors, the wave phenomenon on the other path vanishes instantaneously – it is considered kind of non existent, it has been nothing but a “probability amplitude”, whatever that means. (This is the so called reduction of the wave function: Only one of the diverging wave-like possibilities – in our example there are only two – becomes real, und all others vanish instantaneously, no matter how distant they may be.)
If these quantum theoretic probability waves only represented probabilities – as is the case with dices, then there wouldn’t be a problem: nothing would vanish because in any case there exists but one reality: namely the dice on its way, from the very beginning of the cast, and because the probability of one sixth for each option only points to the fact that we simply don’t know the definite path.
Quantum Theoretic possibilities however cannot be interpreted like that: They interfere – there is interference if the detectors do not stop the light rays. This must imply that something exists in both paths. And something that exists cannot just vanish!
Still, it does vanish. And we have to resign to this fact – at least according to the general conviction. Indeed, this paradox is not conceived to explain anything but rather to demonstrate that nature behaves in a way which is totally incomprehensible to us.
But hold on! Perhaps the photon “knows”, what we are doing? If the information whether the detectors are inserted or not existed in some way at the first semi-permeable mirror SM1, then the photon could decide whether to take one way or both.
But even this conjecture – which itself does not seem very plausible – does not offer a solution to the problem, because we can defer the decision whether or not to insert the detectors into the light paths up to the moment when the light already has passed the first semi-permeable mirror, that is: until the decision whether it has taken only one or both ways already has been made. Also in this case the experiment proceeds in the same way: Without the detectors we observe interference, but when the detectors are inserted, no simultaneous response but a random sequence of alternating events in both detectors occurs. However, since the decision whether the light took one or both paths already must have been made, we seem to be able to determine retroactively what it does resp. has done.
The standard interpretation doesn’t offer here anything but fine words. E.g. it is stated: “The events cannot be described isolated from each other. They form an single entity which is broken only by measurement.”
If this should mean anything, I have missed this meaning up to now. Phrases like: “Nothing is an event as long as it is not observed” are indeed nothing else than smokescreens upon the unacceptable absurd fact that in this paradox – just as in all quantum theoretic descriptions – something which gives proof of its existence by interference is vanishing, and that this disappearance happens without any physical causation.
And, at that, this disappearance is supposed to happen simultaneously with the measurement, that is at any given distance without any delay, and in this context, too, it is unclear what that means: In the case of observers moving relative to each other – would there occur a difference of the time points where all probability waves disappear, which do not become real?
Enough with these absurdities! – To everyone with at least the tiniest devotion to reason it should be clear that things cannot behave in the just described manner. Thus the one and only task is to discover where in the apparently unbreakable chain of physical evidences there are hidden weak links and, accordingly, to find how things really work.
Thus at the time, when interpretation problems of this kind became apparent, the following should have happened:
Each of these paradoxes – all of which are of the same kind as the one discussed above – should have been considered as reductio ad absurdum which definitely reveals that this way of interpreting the physical facts is not possible, alas that is: the very way which physics has actually chosen and which has become dogmatic meanwhile.
Instead physicists plunged head first into a swamp of unsolvable confusion. They themselves felt compelled by a net of physical facts – however I think that this imperative was not based on facts but has to be seen – as is the case with all the other disintegration processes of society taking place at this time – as a historical inevitability. A culture in demise defined the laws of thinking and acting, and everybody obeyed – based on good reasons in their opinion – but actually as unconscious executors of the ineluctable: politicians, artists, scientists.
In the area where indeed factual necessity was the guiding principle, in the Quantum Theoretical formalism itself which had to stand thousand of tests, the physical world is not just in good order – it is great! However in the area of interpretation it is nothing but another symptom of the general cultural decline.
Thus it is left to us, the inheritors of the intellectual disaster, to catch up on the interpretations that were impossible at that time and to base the scientific view of the world on a reasonable fundament.
However these comments are not just pretty colourful speech bubbles and cheap declarations! A proposal for the solution of the two-way paradox already exists. As had to be expected, the solution requires far reaching changes of the established interpretation scheme of Quantum Theory, indeed of physics in total. Shortly outlined, it reads as follows:
There are no photons in the usual sense, i.e. as particles. Photons are just names for the transitions between two electron states, which are caused by continuous accumulation of light waves. In this model it is evident that there must always be light waves on the way in both paths, so that there always occurs interference at the second semi-permeable mirror SM2, if both paths are free. However it has to be shown, why always only one detector responds, if both detectors are inserted. As it turns out, this follows from the characteristics of the division of the light waves at the first semi-permeable mirror SM1 – i.e. the very light waves that subsequently cause the transitions interpreted as photons. In this explanation, all facts which previously seemed contradicting each other, can be understood as consequences of continuous, objective and local processes, and the absurdity, which could not be eliminated within the usual description, disappears completely.
The solution of the paradox is executed in the paper Local and objective Interpretation of Quantum Theory (p 64ff). It is an adaptation of a concept, which I developed for the local description of entangled photons (in the same paper, p 50ff).
The above definition of photons seems to be in contradiction with the description of interaction between light and matter, which has its origin in Einstein’s model of the Photoelectric Effect. This Einstein model, however, can also be reduced to continuous wave phenomena. (See Photoelectric Effect.)
If the scheme of the solution of the two-way paradox is generalized and applied to the interpretation of Quantum Theory, then all absurdities disappear. Well known facts seem so clear and self-evident that – from the new point of view – it seems very strange how things could develop so extremely wrong. If you want to know more of the basic ideas of the alternative interpretation, I recommend the Local and objective Interpretation of Quantum Theory; It contains a simple presentation of the conception, together with some basic arguments.
The chances of this new concept, however, will probably not depend on its qualification but on the contemporary status of the civilization. Is it better than at the beginning of the twentieth century?
This assumption seems unrealistic. After a destruction process that lasted more than a hundred years, the cultural landscape is devastated. The principle anything goes reigns. In physics this shows up in the form of concepts like dark matter or dark energy, which are used in cosmology quite unscrupulously, although they are physically hardly justifiable ad hoc constructions. The further development of the theoretical foundations of physics – unguided due to the interpretation vacuum – has degenerated into an affected artistry. Advanced physical theories can only be compared with late scholastic debates, testifying in this way the decline of theoretical physics, which considers itself – blind to the dubiousness of its fundaments – being near to perfection.
Is it possible to bring a world to reason by virtue of reason? This seems unlikely. Still, what has to be done has to be done.