What is Quantum: Definition and 999 Discussions

In physics, a quantum (plural quanta) is the minimum amount of any physical entity (physical property) involved in an interaction. The fundamental notion that a physical property can be "quantized" is referred to as "the hypothesis of quantization". This means that the magnitude of the physical property can take on only discrete values consisting of integer multiples of one quantum.
For example, a photon is a single quantum of light (or of any other form of electromagnetic radiation). Similarly, the energy of an electron bound within an atom is quantized and can exist only in certain discrete values. (Atoms and matter in general are stable because electrons can exist only at discrete energy levels within an atom.) Quantization is one of the foundations of the much broader physics of quantum mechanics. Quantization of energy and its influence on how energy and matter interact (quantum electrodynamics) is part of the fundamental framework for understanding and describing nature.

View More On Wikipedia.org
Recent contents Top users
  1. Ashish Somwanshi

    Measurement problem quantum mechanics

    Is the answer 0.748?
  2. S

    B I have question regarding quantum physics (localizing an electron)

    As QP says it is uncertain that where you found electron. But its not the same phenomena that one fan blade running so fast that you cant see where the blade is. You can only see the blade on a particular position if you use high resulation camera and its position depend on when you take the...
  3. Q

    Quantum Advanced Quantum Mechanics Textbooks: Derivations of Equations

    Hi I’m looking for a textbook that shows the derivations of equations such as the different forms of the schrodinger equation fully and step by step.
  4. I

    Quantum Mechanics problem: Determine the value of the constant

    I have no idea where to start with this problem. I am interested in any hints, or ways to proof this. But i would especially like to know how the commutator is connected to the identity.
  5. hilbert2

    A Changing Hamiltonian with some eigenvalues constant

    Suppose some quantum system has a Hamiltonian with explicit time dependence ##\hat{H} := \hat{H}(t)## that comes from a changing potential energy ##V(\mathbf{x},t)##. If the potential energy is changing slowly, i.e. ##\frac{\partial V}{\partial t}## is small for all ##\mathbf{x}## and ##t##...
  6. B

    A Quantum projection when measuring state population

    Hello! I have two energy levels of opposite parity close by (we can assume they are far from all the other levels in the system) and an off-diagonal term in the 2x2 matrix Hamiltonian that weakly couples them. I initially populate only one parity state, say the positive one, and after a while...
  7. Ashish Somwanshi

    Measurement problem quantum mechanics

    I was not able to attempt since I don't know which formula or method can be used to solve the problem
  8. S

    More Nobel prizes in quantum information?

    Alain Aspect, John Clauser & Anton Zeilinger have rightfully received the Nobel prize for their contributions to quantum information, as they were three of the main pioneers of quantum information. However, is it now impossible or very unlikely that other physicists working on this field (e.g...
  9. T

    I How does a process of a Raman transition break quantum entanglement?

    I'm reading this article about quantum entanglement, and the author writes about a process in a Raman transition which would break the entanglement, and I'm interested about how it breaks the entanglement. So the passage which I'm interested in begins with: "The answer is to do an operation...
  10. H

    I Quantum mechanics stationary state

    Hi, I have hard time to really understand what's a stationary state for a wave function. I know in a stationary state all observables are independent of time, but is the energy fix? Is the particle has some momentum? If a wave function oscillates between multiple energies does it means that the...
  11. G

    I Can I Find Alternative Eyepieces for My Quantum 5 Binocular?

    Hi i have an quantum 5 binocular with 20x and 40x eyepices , is it possible to get other eyepices for this binocular who can fit with some adjustments ?
  12. S

    I Energy from quantum systems in an expanding universe?

    I found a paper (https://arxiv.org/pdf/astro-ph/0411299.pdf) which talks about quantum systems emitting energy due to spacetime expansion. Is this true or only a hypothesis?
  13. Green dwarf

    I Predetermination in quantum theory and information theory

    My understanding of quantum theory and information theory is that, given complete information on the state of the universe at present, it is possible to predict its state at all times in the future and past. 3 questions: 1: is this true? 2: how are quantum-probabilistic outcomes accounted for...
  14. CuriousLearner8

    A Many-Particle Wavefunction Question

    Hello, I hope you are well. I have been doing a lot of readings on the wavefunction and have a question I did not see asked anywhere else in these forums. I was wondering if someone could shed some light on this for me? I know the wavefunction is in 3N coordinate space and could be used to...
  15. Ahmed1029

    Quantum Nolting quantum mechnaics textbook

    I'm curious what you guys think of the Nolting undergraduate physics series, particularly his 2 books on quantum mechanics? Are they sufficient? Are there any errors in them?
  16. lindberg

    I Unruh, Haag et al.: No Room for Particles in Quantum Field Theory?

    In a paper by Bain (2011), particles are left with little ontological value because of the Reeh-Schlieder theorem, the Unruh effect and Haag's theorem. The author claims (and here I am copying his conclusion): First, the existence of local number operators requires the absolute temporal metric...
  17. sol47739

    I Exploring Electromagnetism & Quantum Mechanics

    In classical electromagnetism I think I have understood the following(please correct me if something is wrong): A charge produces an electric field, a charge moving with constant velocity produces a magnetic field, an accelerating charge emits electromagnetic radiation. In radio antennas this is...
  18. G

    I Quantum events near a black hole

    I apologise for my very limited understanding of quantum physics: my background is in General Relativity. A wave function is said to represent the probability of a particle being at some point in space/time, and I take that to mean that the probability of a quantum event is a density on...
  19. Hakimderubeis

    I Understanding Planck's Quantum of Action: A Guide for Beginners

    So, I am doing a Uni project with Planck's constant. What I need to do is determine Planck´s "quantum action" with help from the Photo effect and reverse voltage method. The thing is that I have never learned Quantumphysics or stuff like that. So, what and where should I begin to learn? (Sorry...
  20. sol47739

    I Polarization of photons quantum mechanically

    What is it of the photon that gets polarized from a quantum mechanical perspective? In the classical perspective it is often thought that it is the oscillating electric field that gets polarized. But in the quantum case: Is it the de Broglie wave function? Or is it the spin and in case it is the...
  21. Demystifier

    I Nature Physics on quantum foundations

    The editors of high impact journal Nature Physics explain why the field of quantum foundations is important for physics. https://www.nature.com/articles/s41567-022-01766-x
  22. E

    I Understanding No Energy Degeneracy in Sakurai's Quantum Mechanics

    Hello, I'm hoping someone can help me understand a statement in Sakurai Modern Quantum Mechanics (3rd edition). In particular, in the section that describes free particle in infinite spherical well (page 198, section 3.7.2), after the text has shown that for a given ##l## value, the energy...
  23. Graham87

    Quantum Mechanics - Matrix representations

    I have found J^2 and Jz, but I am not sure how to find Jx and Jy. I’m thinking maybe use J+-=Jx+-iJy ? But I get unclear results. Thanks!
  24. E

    I Wondering why quantum entanglement occurs

    hi there I am an engineer but have a huge interest in physics and wanted to ask anyone who has any knowledge of why quantum entanglement occurs?
  25. Graham87

    Intro to quantum mechanics - Spin and linear algebra

    So this expression is apparently in Sz basis? How can you see that? How would it look in Sy basis for example? The solution is following. They are putting Sz as a basis, bur how do you know that Sz is the basis here? Thanks
  26. fresh_42

    B Positive Definite Cartan Matrices in Quantum Physics

    As I was looking for an example for a metric tensor that isn't among the usual suspects, I observed that the Cartan matrix I wanted to use is positive definite (I assume all are), but not symmetric. Are the symmetry breaks in quantum physics related to this fact?
  27. Graham87

    Intro to Quantum Mechanics - Formalism normalisation

    I can't figure out how they get i/sqrt(2) for normalisation of c1. Why is it a complex number? If I normalise c1 I just get 1/sqrt(2) because i disappears in the absolute value squared. Thanks
  28. ramana3797

    I need help to fix a Quantum Espresso installation error in Linux

    I'm a M.Sc physics student and I need to use quantum espresso for my research project . I tried the same procedure I used to install it on the system at home as I did for the one at the College but i keep getting the same error . I can't find why . I'm also new to linux . I'm using ubuntu and I...
  29. C

    B Is the probability of a quantum outcome ever zero such as with....

    Greetings, Given an infinite universe or an infinite number of universes? - Regarding the location of an electron around an atom, is there a tiny volume in which finding the electron 100%? Or is there a possibility, no matter how remote, it might be found a meter away or a kilometer away? -...
  30. G

    I At which point is gravity inconsistent with quantum mechanics?

    I'd like to understand how gravity does not combine with quantum mechanics. At least there is no accepted theory of quantum gravity, so I assume it is not solved? I'm only starting to learn QFT and eventually GR. Maybe, someone can already outline where those theories fail to combine and comment...
  31. P

    I Does chaos amplify inherent quantum level randomness?

    Does chaos amplify inherent quantum level randomness/uncertainty to macroscopic level?
  32. Graham87

    Plot the Expectation Value of Spin - Intro to Quantum Mechanics Homework

    I have found an answer to all of them (a-e) but I don’t know how to plot the function. Thanks!
  33. TheHeraclitus

    I Carlo Rovelli, loop quantum gravity and point particles

    I am reading a popular-science book Reality Is Not What It Seems by Carlo Rovelli, one of the founders of loop quantum gravity. He writes: and and So basically, space (spacetime) is just another quantum field like all the others, and the quanta of this field is the nod. Nods have volume...
  34. D

    Quantum computer storage capacity

    I have a question regarding the storage capacity of quantum computers. I read that 32 qubits (4 "quantum bytes" if you will - not sure if that's an actual term or not yet) can store the equivalent of 500mb of data. Is this directly proportional? I.e., would 8 qubits store the equivalent of...
  35. Graham87

    Intro Quantum Mechanics - Dirac notations

    I am learning Dirac notations in intro to quantum mechanics. I don’t understand why the up arrow changes to down arrow inside the equation in c). My own calculation looks like this:
  36. Graham87

    Quantum mechanics - Find S_x and S_y

    I have a lecture slide that shows how to find S_x and S_y. I get all the steps except the last row. Where did 1/2 come from? I think my linear algebra needs polishing. Thanks!
  37. Delta2

    I Entanglement and FTL signaling in professional scientific literature

    According to professional scientific literature and to our best understanding, are there any suggestions that entanglement might imply some sort of faster than light signaling between the entangled particles? I know that according to relativity nothing can travel faster than light, but what...
  38. H

    A Is there a lost information paradox for quantum physics?

    Hi Pfs, When Stephen Hawking proposed the idea of black hole information it appeared that information could be lost. it was a problem in GR which is a dererminitic theory. Knowing initial data and Hamiltonian tells you what was and will be. It is not the case in quantum physics. things evolve...
  39. A

    I Counterfactual quantum computation on interferometer

    I watched a video on the topic by Sabine Hossenfelder. Now it is said by many that this proves the photon "knows" something in advance because a certain state of a certain beam splitter can be probed in theory without the photon ever encountering that beam splitter because it took another path...
  40. Javelin

    A Quantum Properties of Quasi Static Electric Fields

    Assume I could produce a stream of calcium ions from a 2nm diameter nanotube by pushing them through the nanotube using coulomb repulsion. Assuming these coulomb repulsed ions produce a stream of entangled ions which then create a slowly emitting quasi static electric (near) field. Even if...
  41. LCSphysicist

    Courses Quantum optics for graduate students

    I have just finished my course on electromagnetism. Due to my performance, the professor has contact me for congratulations and asking, if i want, to join his quantum optics course for graduate students. Even so i think it is interesting to follow the advice, i am a little afraid if this...
  42. C

    What is the mechanism behind Quantum Entanglement?

    What is the mechanism behind Quantum Entanglement? Why do only subatomic particles exhibit Quantum Entanglement?
  43. D

    I Decoherence and Quantum tunnelling

    A macroscopic object has the order of Avogadro’s number of particles. That’s over 10^23. So the probability of all of them tunneling, at the same time, is on the order of that original small probability, to the 10^23 power. And then on top of that, you have to factor in the chances of it...
  44. H

    A Loop quantum gravity and General relativity

    Hi PFs, I am reading this paper written by carlo Rovelli: https://arxiv.org/abs/1010.1939 there are many things that i fail to understand, but i would like to begin with a simple thing. Rovelli write that: It is locally Lorentz invariant at each vertex, in the sense that the vertex amplitude...
  45. A

    I Quantum computation and entropy

    Quantum gates must be reversible. The usual justification for this is that in QM the time evolution of a system is a unitary operator which, by linear algebra, is reversible (invertible). But I am trying to get a better intuition of this, so I came up with the following explanation: In order to...
  46. J

    I Black hole singularity vs. quantum mechanics

    I'm wondering about some aspects about black holes (BH) and singularities, but since all my questions have to do mostly with quantum mechanics, I placed this thread in here. OK, let's assume there IS a singularity in the middle of a BH. A) Pauli exclusion principle (PEP) says no two fermions...
  47. D

    I Does Heisenberg Have Ontological Commitments to Quantum Theory?

    Heisenberg is regarded as a major figure of the Copenhagen interpretation. In a certain degree, he is influenced by Logical positivism. Despite of that, has he any ontological commitments regarding the Quantum theory? Or, he considers the Quantum theory merely as calculation procedure for...
  48. H

    A In What Space Does Quantum Spin Take Place

    Quantum spin is orientable so it takes place in a space with an even number of dimensions. What is that space? If the space had an odd number of dimensions, then spin in that space wouldn't be orientable. But quantum spin is orientable. We could say that it is Minkowski space, but that space...
  49. M

    Let's build a quantum radio receiver

    Homework Statement:: I would like to write a science fiction story on how alien quantum communication could work and how scientist on Earth build the first "radio" receiver, entangling Quantums over big distances randomly. Relevant Equations...
  50. D

    I "No objective reality" in quantum mechanics?

    As per title and the TL;DR, I'm curious if there could be some truth in these statements of the headlines I had read recently or are they just sensationalist fluff. Personally, I find these statements very hard to believe. In fact, impossible to believe. But I'm not a QM expert, not even an...
Back
Top