The main problem that we find strange with quantum particles is that they are considered as classical particles while they behave in a very non-classical way. (Or, the problem is to think of quantum particles as “objects,” a term first coined by Michael Brooks.) Many examples of “weirdness” arising from quantum nature stem from this fact — or at least from the many different interpretations of quantum mechanics that bring about these weirdnesses. However, regardless of what quantum physicists are dealing with, the objects that require quantum physical description are not equivalent to classical objects, or even to or similar to things like dust, sand, or glass.
Quantum particles are much smaller than the classical particles we normally see, so much so that they are incredibly small. Because of this, almost (in the words of Philip Ball) “everything is different on the quantum scale” (i.e., not just strange). This means that using words like “object” and “particle” in the context of classical physics is problematic. Even the word “wave” in quantum mechanics is often misleading. This is mainly because quantum wave functions are merely mathematical objects represented by equations — strictly speaking, they do not correspond exactly to descriptions of reality.
More specifically, if particles were waves, then wave interference would be less strange, and wave superposition less strange. (That is, it is also problematic to consider quantum x as a wave – as just described.)
Technically speaking, quantum x (i.e., something that has not yet been named, and for lack of a suitable word, is represented by a letter) and quantum y interfere with each other — just like waves on the ocean. Thus, when quantum x and quantum y interfere, they are superimposed on each other. Of course, a classical object cannot interfere with another classical object — at least not in the same way as a quantum object interferes with each other. Nor can classical x and classical y be in superposition.
However, we are not talking about a classical object here, not even a classical particle!
Therefore, why does quantum x not behave like a classical object, or even like a classical particle? Conversely, if a classical object behaved like a quantum x, it would also look strange. But this does not happen. Many people think quantum phenomena are strange mainly because they treat them as classical phenomena, but they behave very non-classically. In fact, we only have quantum phenomena that behave in a quantum way — just as classical phenomena behave in a classical way.
When Michael Brooks uses the term “a single positive nuclear charge, or proton,” he again shows us the problem with the word “particle. Here we can certainly arrive at a definition, which is.
"Proton = (single) positive nuclear charge
"
Thus, in this case, the particle is simply a positive charge. Now, positive (or negative) charges are hardly particle-like — at least when they exist in isolation, because they always exhibit wave characteristics. Even if a proton (or another particle) contains other properties besides charge (e.g. spin, mass, size, etc.), the word “particle” still doesn’t seem appropriate …… but it is useful!
If we go back to the description of quantum objects as waves, one way to show the implausibility of this description (among many others) is to clarify the de Broglie wavelength of a fullerene molecule (composed of 60 carbon atoms). A fullerene is a huge quantum “object” measuring about a meter, or a trillionth of a meter! How exactly does this relate to waves on the ocean or any other type of classical (or macroscopic) wave?
The following discussion is as close as possible to classical particles in quantum mechanics.
When a wave becomes a particle
As already mentioned, when two quantum waves meet, they superimpose. This superposition is the sum of two waves at any given position. Moreover, this “sum” can behave more like a particle than the two waves alone. (This is in general agreement with Max Born’s position in the 1920s/30s – see “Born’s Law” for details). This particle-like thing is the result of the superposition of two or more quantum waves. In other words, if you put a wave trough with another wave trough (or a wave peak with another wave peak), then you get something like a particle or a solid. In other words, when waves are squeezed, fused or mixed together, it becomes more like a hard entity ……
Of course, all these words and descriptions are similar in nature!
In other words, we are still using “wave” and “particle” here (as well as “trough” and “crest”, not to mention “squeeze”). Not to mention the words “squeeze”, “fusion” and “mix”). This is mainly because I had no choice but to do so.
In fact, all these words belong to the interpretation of quantum mechanics. This means that simply using the monotonic variables x, y, etc. is not very helpful when interpreting quantum mechanics. Of course, this is not helpful to any interested layman.
The body of a smoke gargoyle
Although the article opens with a quote from Michael Brooks, he also writes elsewhere in the same book:
"According to Bohr, the ultimate entity behind Schrödinger's fluctuation equation is neither a wave nor a particle, and therefore it cannot be described in any terms we can deal with."
Of course, the fact that Brooks merely quotes Niels Bohr does not mean that he agrees with Bohr. Nevertheless, Bohr does raise a question that needs to be addressed — even if one does not need to accept his overall position or interpretation. (Many people do disagree with Bohr — especially physicists such as Albert Einstein and later David Bohm.)
John Wheeler (John Archibald Wheeler, 1911-2008)
The American theoretical physicist John Archibald Wheeler has also studied these problems, or at least similar ones. He used the image of a “smoke dragon” to make his point. He pointed out that between experimental input and experimental output (or observation), “we have no right to talk about what exists”. Thus, words like “particle” and “wave” are naturally suspect — at least when used in the context of experimental processes (i.e., the hypothetical “reality” of the dragon’s body). “realness”) is the case.
Thus, there is a difference between describing quantum x as a “particle” or “wave” before the output (i.e., as it exists and occurs before the actual experiment or observation) and describing quantum x in this way after the experimental or observational output. However, even when experiments (or observations) have been performed, i.e. when the quantum wave function has “collapsed”, the use of these classical terms may still be problematic.
Again, Bohr is quoted. According to Brooks, Bohr believed that
"Once a measurement is made, the type of measurement will determine what we can see."
more importantly,
"For example, if you use an instrument to detect the position of an object in space, you will see objects that have a definite position in space—that is, entities we call particles."
The point here is that the use of the word “particle” to refer to something on the dragon’s body, and to refer to something after the “spatial location of the object detected by the instrument”, is suspicious. So this (ontological?) x is not only not a particle before measurement or observation, but also not a particle after measurement (or observation).
In conclusion: the classical term “particle” is problematic in all quantum cases.
Note.
If it is problematic to consider quantum particles as particles (or objects), then it is also problematic to consider atoms as particles.
Perhaps an atom cannot be considered as an “object” at all. After all, if the nucleus of a helium atom is considered to be the size of a lemon, then the edge of the atom (defined by the outer orbit of its electron) would be 2.5 miles in diameter. Thus, proportionally speaking, the nucleus is extremely out of proportion to the entire atom. Each electron in the atom is even smaller than the atom to which it belongs, which is incredibly small. (It is the equivalent of a dot on a circle of 2.5 miles in diameter. Even smaller! There is no accurate statement about the size of the electron.)
Of course, most if not all (classical) entities are also made up of individual atoms of elements, so this is not a problem in itself.
Link to the original article: Quantum Particles are Neither Classical Particles Nor Weird Objects
The translated content represents the author’s opinion only and does not represent the position of the Institute of Physics, Chinese Academy of Sciences.
