Hi Dmitri

This is a very interesting, complex and still open question about the nature of reality in quantum mechanics, if it exists or not until we measure it.

Recently one student asked me (in simple words): "if an object behaves as wave and particle, when the object "decides" to assume the particle or wave behavior..."?

I understood his question despite the simplicity of the words used by him. And it poses in my mind once more a special attention to this topic and on the real meaning on the act of measurement in quantum mechanics. I thank you to address such interesting question.

By the way I told the student that, according to quantum mechanics, the revelation of his quantum nature, wave-like or particle-like, depends HOW the corresponding measurement is made. Some experiments will reveal its wave-like nature and others its particle-like nature...this explanation in fact is a bit far from the expectations of people in general. I understand.

Andrew Truscott said recently, refering to this topic, that "measurement is everything". He said also that "reality does not exist until we measure it". Very interesting and profound statement.

Dear Professor Vasconcellos, please write me in [email protected]

Let us talk via emails. I was unable to talk private in researchgate.

Be best,

Dmitri.

Believing in "observer" and "function wave" is pecular to the Göttingen-København tribe and their heirs. Nothing such is shared in transactional microphysics.

We recall the six postulates practiced in transactional microphysics:

Then the moral principle: we refrain from censuring the experimental results that embarrass the doctrine in power.Hiding so many experimental facts to the students is wrong, and it violates the scientific deontology.

Sure, so many experimental results embarrass the copenhaguists:All the spectral absorptions, all the interferences as the anti-reflective coatings, quarter-wave plates, interferential colors, Goos-Hänchen effect in plane polarization, Imbert-Fedorov in circular polarization, all proofs of the non-negligible width of each photon. A very long list!

They hid from you the transparency effect Ramsauer-Townsend, which is strictly undulatory. But if the electron is strictly undulatory, how will they continue to impress the gullible public, by their mystic “wave-corpuscle dualism”? Many other everyday experimental results are incompatible with the corpuscular ideation of the Göttingen-Københavnists.

The economy of postulates and concepts is on our side. No more need to erect the properties of the Fourier transform as a new postulate: they are simply inherited. The magical concepts of “superposition of (corpuscular) states”, “intrication (of supposed theoretical and corpuscular states), measurement, psychism and consciousness of the observer”, all that is dropped: Your Majesty, I did not need that hypothesis!

about the relation of nature and observer. while God created the world (big bang=fiat lux), He must have seen the very little universe... and- like physicists claim- influenced it.

Hi Dmitri

Coming back to science, and to your very interesting quastion, Gedankenexperiments have played an important role in the development of quantum theory specially on the topic of quantum reality. A paradigmatic example: John Wheeler’s delayed-choice gedankenexperiment, in which the wave-particle duality of a test particle cannot be fully understood using only classical concepts. See for instance:

REAL AND UNREAL

In Physics by Brian Koberlein

Quantum theory is strange, but very real. Through countless experiments we’ve found that quantum objects have both particle-like and wave-like properties. In some experiments the particle nature dominates, while in others the wave nature dominates. Some experiments can even show the effects of both properties. This duality between particles and waves in quantum theory is deeply counterintuitive, which means often the results of quantum experiments are interpreted incorrectly.

Take, for example, recent claims that reality doesn’t exist until we measure it. The claims arise from a recent experiment published in Nature that uses a single atom to perform what is known as the delayed-choice experiment. This experiment was first proposed as a thought experiment (gedanken experiment) by John Wheeler as a way of exploring the counterintuitive aspects of particle-wave duality.

Wheeler’s idea was to imagine a “cosmic interferometer.” Suppose light from a distant distant quasar were to be gravitationally lensed by closer galaxy. As a result, light from a single quasar would appear as coming from two slightly different locations. Wheeler then noted that this light could be observed in two different ways. The first would be to have a detector aimed at each lensed image, thus making a particle measurement. The second would be to combine light from these two images in an interferometer, thus making a wave measurement. According to quantum theory, the results of these two types of experiments (particle or wave) would be exactly as we’ve observed in their standard form. But the light began its journey billions of years ago, long before we decided on which experiment to perform. Through this “delayed choice” it would seem as if the quasar light “knew” whether it would be seen as a particle or wave billions of years before the experiment was devised.

Although the quasar experiment Wheeler proposed isn’t practical, modern experimental equipment allows us to perform a similar experiment in the lab, where the decision to measure a particle or wave is done at random after the quantum system is “committed.” For example, in 2007 a delayed-choice experiment was made using laser light to create a delayed-choice double slit experiment. In this new paper, the team used an ultracold helium atom to do a similar delayed-choice interference experiment. With both experiments the results were exactly as predicted by quantum theory. So both matter and light exhibit this strange quantum effect.

While this is great work, the result isn’t unexpected. Quantum theory made a very clear prediction about this kind of experiment, and its prediction has been confirmed. Where things get fuzzy is in the interpretation. One popular way to interpret quantum theory is to presume quanta have a potential wavefunction, which then collapses into a definite state when observed. In this view the act of measurement gives reality to the quantum. In the delayed-choice experiment that would mean the quantum doesn’t become “real” until you measure it, which could be billions of years after its origin in the case of quasar light. But this is an overly simplistic take on things. Quantum objects are real, but simply have indefinite properties. These properties are defined by the experiments we do. What the delayed choice experiments really show is that quanta don’t exist as particles or waves, but are truly unique objects which can exhibit particle and wave properties in certain experiments.

While that might seem strange, it isn’t magical or mystical. The Moon wouldn’t vanish from existence if everyone closed their eyes, and reality isn’t dependent upon us observing it.

Paper: A. G. Manning, et al. Wheeler’s delayed-choice gedanken experiment with a single atom. Nature Physics, DOI: 10.1038/nphys3343 (2015)

Paper: Jacques, V. et al. Experimental realization of Wheeler’s delayed-choice gedanken experiment. Science 315, 966–968 (2007).