# Quantum Mechanical Conceptual Problems

• DMuitW
In summary, the conversation discusses some problems encountered in quantum mechanics, including the concept of wave/particle duality and the collapse of the wave function. The discussion also touches on the relationship between quantum states and classical systems, and the role of measurement in this relationship. Ultimately, the conversation highlights the need for a better understanding of how quantum states can be converted into observable classical systems.

#### DMuitW

Some straightforward problems I have encountered in QM; i'll post them gradually, otherwise it 'd be a little long, thanks

1a) Wave/particle Duality: A quantum wave as stated through Dirac and von Neumann is a probability wave expressed by Schrödinger equation and thus here implying a superimposed state. A first conceptual problem I encounter here is that the very being of superposition can never be observed. It can be derived from the interference of for example the double slit experiment. Logically, the superimposed wave function has encountered a "wave collapse" due to a certain form of measurement. Due to this wave collapse, the former probability wave will act as a single vector in Hilbert space, containing finite energy, thus being a point in Hilbert space.
If we keep on using this definition of the quantum properties, I am very curious what that exactly causes the wave collapse.

1b) The notion of the "particle"- being of the quantum as a single vector in Hilbert space with finite energy thus implies a major problem explaining classical "rest mass". Thus if a classical observable particle,if being fundamentally different in some way of the quantum vector,is observed, it could never generate an interference pattern (if we do a gedankenexperiment containing two slits and bowling balls), just because the quantum properties of the propability wave needed for interference avoid the classical notion of matter.
IF! on the other hand you don't make a difference of fundamental level between a single quantum system and a classical system, -what- does then "convert" your theoretical vector in Hilbert space to a classical observable system having a structural rest mass, in which E=mc² must play a major role?

1c) If indeed, you don't make a fundamental difference between a single quantum state and a "classical" system (as being build up by single quantum states), then what contains the information to collapse the wave function of a whole system, thus creating a logically structured classical system??

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DMuitW said:
Some straightforward problems I have encountered in QM; i'll post them gradually, otherwise it 'd be a little long, thanks

1a) Wave/particle Duality: A quantum wave as stated through Dirac and von Neumann is a probability wave expressed by Schrödinger equation and thus here implying a superimposed state. A first conceptual problem I encounter here is that the very being of superposition can never be observed. It can be derived from the interference of for example the double slit experiment. Logically, the superimposed wave function has encountered a "wave collapse" due to a certain form of measurement. Due to this wave collapse, the former probability wave will act as a single vector in Hilbert space, containing finite energy, thus being a point in Hilbert space.
If we keep on using this definition of the quantum properties, I am very curious what that exactly causes the wave collapse.

I'm going to risk sounding like a broken record (broken CD?), but here goes.

The consequences of superposition CAN be observed. When you make a measurement, you are only forcing a definite state only on that corresponding to the commuting observable. It means that the observable that do NOT commute will still be represented by a superposition of states. For example, when you make a measure of Lz, the other two orthorgonal observables, Lx and Ly, REMAINS in indefinite state. Lz do not commute with both Lx and Ly. This means that a measurement of Lz does NOT remove the superposition of states that may be describing Lx and Ly.

Thus, if something is in a superposition of states, if I can find a non-commuting observable, I can make that measurement and see if so-and-so values reflect the fact that there is some form of superposition going on. This is what has been observed in the Stony Brook/Delft SQUID experiment (I have made repeated references to this here and in my Journal entry).

Thus, you can still detect the effect of such superposition without causing a total "collapse" of the wavefunction.

Zz.

Ok, so according to that paper superposition also is also noted in macroscopic distant states. Thats a clear and straight answer , thanks.

But that leaves most of my other questions unanswered. I still have conceptual problems on how a dimensionless "energy" vector such as stated by Quantum Mechanics can in some way or another be altered and be converted in a "particle" observable in 3D, and Above all, can be combined in such a way that they form logically structured systems.
In other words, how a single quantum state can be collapsed in some way or another and form with numerous other similarly collapsed functions a "classical system".

Thank you

1c) If indeed, you don't make a fundamental difference between a single quantum state and a "classical" system (as being build up by single quantum states), then what contains the information to collapse the wave function of a whole system, thus creating a logically structured classical system??
Maybe this will help.

DECOHERENCE, EINSELECTION,. AND THE
QUANTUM ORIGINS OF THE CLASSICAL. Wojciech Hubert Zurek.

http://

Regards

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There is no wave particle duality.

The superposition is just a description of the space/time distribution of some of the particle or system's properties.These properties constitute a partial description of the particle and its fields.

There is no real collapse. There is just redistribution of particle or system properties over space/time.

juju

## 1. What is quantum mechanics?

Quantum mechanics is a branch of physics that studies the behavior of particles at the atomic and subatomic level. It explains how particles such as electrons and photons behave and interact with each other.

## 2. What are quantum mechanical conceptual problems?

Quantum mechanical conceptual problems refer to theoretical issues and paradoxes that arise when trying to understand and explain the behavior of particles at the quantum level. These problems challenge our understanding of the physical world and the basic principles of quantum mechanics.

## 3. How do quantum mechanical conceptual problems impact science and technology?

Quantum mechanical conceptual problems have had a significant impact on science and technology. They have led to the development of new technologies such as transistors, lasers, and computer systems. They have also helped us understand the fundamental principles of the universe, leading to advancements in fields such as chemistry, biology, and materials science.

## 4. What are some examples of quantum mechanical conceptual problems?

One example of a quantum mechanical conceptual problem is the wave-particle duality of light, which states that light can behave as both a wave and a particle. Another example is the uncertainty principle, which states that the more precisely we know the position of a particle, the less we know about its momentum, and vice versa.

## 5. How do scientists approach solving quantum mechanical conceptual problems?

Scientists use a combination of mathematical equations, experimental data, and theoretical models to approach and solve quantum mechanical conceptual problems. They also collaborate with other scientists and conduct experiments to test and validate their theories and hypotheses.