The interpretation of quantum mechanics looks like today not as a physical, but rather as a social problem. In some sense this situation is similar to the one that was in astronomy during the time of Galileo and Copernicus. At that time it was thought that the Earth is flat, and the Sun rotates around it. But people have seen the round Sun, the round Moon, and at sufficiently frequent lunar eclipses - the round Earth's shadow. It was not very difficult to understand that the Earth is also round and rotates. But the process of recognition by society of this fact was, as you know, very long and dramatic. And it is not because people were stupid but because there were for this case social reasons. In Russian there is a short and exact description of this situation poetically:
«Учёный, сверстник Галилея,
был Галилея не глупее.
Он знал, что вертится Земля,
но у него была семья» (Е. Евтушенко, 1957)
The Inquisition now is absent, but other quite strong social reasons remain. These social reasons change consciousness of scientists in such a way that they lose ability adequately to perceive even the simple and obvious experimental facts.
Many years in quantum physics delusion exists that “all known laws of physics are invariant under time reversal”. But today we have several direct and great number of indirect experimental proofs that it not so.
First of all it is the experiments on splitting and mixing of photons in nonlinear crystals. Here at first stage the narrow laser radiation is split on wide signal and idler beams which then are mixed up in other nonlinear crystal. We should expect emergence of wider radiation, but experiments show preferred regeneration of initial narrow radiation [arXiv:quant-ph/0302038]. Other fact is the well known Bloch oscillations of cold atoms in vertical optical lattice. Here the atoms fall down and then return in the initial point due to highly asymmetrical light scattering.
You don't need to be Einstein to understand that these facts are the direct sign of inequality of forward and reversed processes in quantum physics. The reversed process, which returns the quantum system into the initial state, has much greater differential crosssection than any other processes. Recognition of the fact of inequality of forward and reversed processes in quantum physics directly leads to the conclusion that the Bohm theory is the most correct interpretation of quantum mechanics [arXiv:0706.2488v6].
We need now a detailed experimental study of differential cross-sections of the forward and reversed processes. But in the beginning it is necessary to convince the scientific community to recognize the Bohm theory and the fact of time reversal noninvariance in quantum physics. However, it is absolutely unclear today how physicists must solve this mainly social problem in quantum physics. Or perhaps we have to wait a hundred years, when new physicists will be born (without social complexes).
We knew already from the old greeks that the Earth is round. There was still some popular belief at the time of Colombus, by the geocentric system implies that the Earth is round. Although the heliocentric system is highly conterintuitive, only the religious people sticked to the Bible. At the time of Galileo, most scientists, including Descartes, adopted it, even if covertly.
Claude , you practically characterize the present day situation in quantum physics. Many years later you can say:” We knew already from the Bohm about hidden variables. Only orthodox zealots rejected it. However, most scientists, including myself, adopted it, even if covertly” :)
Unfortunately, such religiosity (as a social phenomenon) leads to deep stagnation in experimental quantum physics. Although a lot of experiments are carried out, but in wrong direction. We need in experimental study of differential cross-sections of forward and reversed processes.
Bohm theory entails a non local potential, thus it meets the same conceptual difficulties as orthodox quantum mechanics. It gives the same predictions, it is then only a further interpretation, but is not as handy for calculations, and in particular doesn't lead to quantum field theory. It is not true that the scientists rejet it, they don't use it, that's all.
Non invariance under time reversal is another issue. There are scientists who advocates it uncovertly, especially the Nobel prize winner Prigogine. Another Nobel prize winner, 't Hooft, thinks that quantum mechanics emerges from deterministic and time asymmetric processes at the Plank scale, through information loss. On the other hand, irreversibilty is well understood in the framework of statistical mechanics
Vladimir, time asymmetry easily creeps into the laboratory and further detailed exploration is needed to recognize that the process that violated it was actually time symmetric at a more fundamental level.
This is only the words.
In contrast, we have direct experimental proofs. This is, for example, widely known phenomenon of Bloch oscillations of cold atoms in vertical optical lattice. Here the atoms are freely falling in optical field. At strictly certain moment of time the atom absorbs and emits (scatters) the photon in the strictly defined direction. As a result, the atom returns exactly into the initial point of space. This is simple and clean experimental fact. It directly demonstrates extremely high degree of spatial asymmetry of light scattering.
But, instead of correct physical explanation, we have a good mathematical description of the phenomenon, which is based on the Gross–Pitaevskii equation, and interpretation, which includes the so-called Brillouin zones. The mathematical description itself nothing says about physical nature of phenomenon. The existing physical explanation, which is based on the assumption of existence of potential barriers in an optical lattice, badly agrees with the mathematical description: it demands introduction of the artificial concept of the superfluid regime when atoms tunnel through the potential barriers.
The actual physical nature of the phenomenon is that the differential cross section of reversed process (which returns a quantum system in the initial state) is considerably larger than the differential cross section of any other forward or partially reversed processes. Despite the fact that the integral cross section of forward and reversed processes are identical (Einstein coefficients for absorption and stimulated emission of photons are equal). Inequality of differential cross sections of forward and reversed processes is a real physical base of whole nonlinear optics (this is a concrete example of the so-called hidden variables). Our scientific community many years tries to ignore the direct experimental facts of such kind. Until now, it has in this task a success.
Vladimir,
Every experiment I have conducted or watched others conduct displayed a strong arrow of time. So what? When you tell me about your arrows of time in your experiments you are not saying anything new or surprising. That's what we generally expect because we live in a Universe with a strong entropy gradient. You are simply ignoring the question I asked. Again, what about your experiments suggests that you are experiencing Nature at the fundamental level?
Sorry Peter but the impression is that you guys don't actually understand the subject.
Dear David.
You have to explain what sense you put in the term "fundamental level". I discuss the problem of inequality of forward and reversed processes in quantum physics. I think that this is a quite fundamental property of quantum physics (time reversal noninvariance). The arrow of time and the entropy look like as simple and obvious results of this property.
Vladimir,
If you are referring to wave function collapse quantum mechanics, then I agree that there is an asymmetry at the fundamental level. However, there are good reasons to think that wavefunction collapse does not occur. The Schrodinger equation and its solutions are time reversal invariant and the simplest way of understanding the experiments is in terms of "apparent" collapse due to decoherence.
Let me comment on your question about what I mean by “fundamental level” by appealing to the notion of isolated. For example, if I want to uncover the time reversal symmetry of a harmonic oscillator or pendulum, I can’t simply go into my lab, pull the bob to one side, and let the pendulum swing, because the disturbance from air resistance will introduce a time asymmetry into my results. I will discover, in fact, that the amplitude of the swing is getting smaller in one direction of time, and, therefore, larger in the other. That is due, of course, to the fact that my experiment began in a low entropy configuration (all the energy in the pendulum bob) and by the second law, will very likely evolve into lower entropy configurations (those with smaller swing amplitudes). Therefore, I must work hard to isolate my pendulum bob so that I don’t disturb the physical process whose time asymmetry or lack of, I wish to explore. This means that I need to produce a vacuum. And, as you well know, I can’t produce a perfect vacuum, which means that I can reduce the time asymmetry in my results, but cannot as a matter of practical issue, remove it completely. But that doesn’t mean that the physics of the pendulum or harmonic oscillator is not time reversal invariant. The solution, in fact, is time reversal invariant despite the fact that from an experimental perspective I ultimately fail to show that.
In short, it is your job to identify the aspects of your experiment that are the equivalent to air resistance in the pendulum example. But, if you want to convince people of the time irreversibility of your process, what you cannot do is to appeal to collapse of the wavefunction without explaining the physical process of collapse, which remains unexplained to this day. Ultimately, if in fact you can show that the entire physical process occurring in your lab inherently violates time reversal symmetry, then that would be very important. Why don’t you write that up and submit to Physical Review instead of complaining about the culture of physics on ResearchGate?
Dear David.
Thanks for the detailed comment. The situation becomes more clear. We have typical dialogue of the theorist and experimenter who do not understand each other. We have different language and background. I discuss a physical nature of the processes in quantum physics, but you, mainly, discuss its mathematical description: the Schrodinger equation and wavefunction collapse. There will be 100 years soon as theorists excitedly discuss the problem of collapse of wave function. Obviously, it is important for the mathematical description, but has little to do with understanding the physical nature of the processes.
The phenomenon of Bloch oscillations of cold atoms in vertical optical lattice is not my experimental result. It is widely known for many years. This phenomenon is really on the fundamental level (in your interpretation). It directly demonstrates extremely high degree of spatial asymmetry of light scattering. But, till now it does not have correct physical interpretation mainly because of the physical explanation in quantum physics, is widely replaced with the mathematical description. Referees in Phys. Rev. are same theorists who do not approve such discussions and watch over the purity of the doctrine. I do not know how long this situation will last. However, as we say: “сколько верёвочке не виться, а конец будет” (in Russian :)
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