What is Quantum effects: Definition and 35 Discussions

Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, quantum field theory, quantum technology, and quantum information science.
Classical physics, the description of physics that existed before the theory of relativity and quantum mechanics, describes many aspects of nature at an ordinary (macroscopic) scale, while quantum mechanics explains the aspects of nature at small (atomic and subatomic) scales, for which classical mechanics is insufficient. Most theories in classical physics can be derived from quantum mechanics as an approximation valid at large (macroscopic) scale.Quantum mechanics differs from classical physics in that energy, momentum, angular momentum, and other quantities of a bound system are restricted to discrete values (quantization), objects have characteristics of both particles and waves (wave-particle duality), and there are limits to how accurately the value of a physical quantity can be predicted prior to its measurement, given a complete set of initial conditions (the uncertainty principle).
Quantum mechanics arose gradually from theories to explain observations which could not be reconciled with classical physics, such as Max Planck's solution in 1900 to the black-body radiation problem, and the correspondence between energy and frequency in Albert Einstein's 1905 paper which explained the photoelectric effect. These early attempts to understand microscopic phenomena, now known as the "old quantum theory", led to the full development of quantum mechanics in the mid-1920s by Niels Bohr, Erwin Schrödinger, Werner Heisenberg, Max Born and others. The modern theory is formulated in various specially developed mathematical formalisms. In one of them, a mathematical entity called the wave function provides information, in the form of probability amplitudes, about what measurements of a particle's energy, momentum, and other physical properties may yield.

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  1. nomadreid

    I Quantum effects near 0 Kelvin

    In https://phys.org/news/2016-09-cold-black-holes.html it is stated that a supermassive black hole interior could be 10^-14 degrees Kelvin. Is there a limit, perhaps due to quantum effects, below which a temperature (in a black hole or elsewhere) can go? Or do the possibilities approach 0...
  2. A

    A What quantum effects that involve gravity can be studied without QFT?

    So there is no a full quantum theory of gravitation. However, there are instances where quantum effects due to gravitation have been studied. Like Gravitational neutron interferometry https://arxiv.org/pdf/1701.00259.pdf or maybe gravitational decoherence...
  3. S

    Forward light-cones and special relativity

    Homework Statement How can we tell that quantum effects do not propagate along forward light-cones that represent two separate events? How do light-cones demonstrate this notion of quantum effects? Homework EquationsThe Attempt at a Solution We don't know which events occur first given...
  4. P

    B Why do quantum effects arise due to microscopic size?

    First, in quantum mechanics, space is not quantized. So, you can have particles of any size. It's not like the minimum size should be a space quantum. If there's no absolute 'huge' and no absolute 'microscopic', just relative sizes, then there should be no reason to assume that we follow general...
  5. K

    Quantum Effects in MOSFET

    Hello to all ! In MOSFET at strong inversion electrons confined to triangular quantum well, electrons occupy only 1 or 2 lowest subbands. and the Van Dort model gives the quantum mechanical intrinsic carrier density in inversion channel via increased energy band-gap(ΔE). NQM = NCL× Exp(-ΔE/2kt)...
  6. durant35

    Relativistic quantum effects

    Do effects like velocity time dilation and gravitational time dilation occur in probabilistic QM, are SR and GR compatible with QM?
  7. entropy1

    Cause of quantum effects on small and large scales

    If I understand correctly, quantum effects become very small as the object in consideration becomes larger. My question: what causes this? For instance: does it have to do with the relation between the quantum objects in the macro object, or does the math show that quantum effects become...
  8. A

    Quantum effects caused by our mathematics?

    Forgive me if I sound ignorant, but is it possible that quantum affects (value of h, why physical dimensions appear to come in discreet chuncks, etc) all stem from our mathematics (which originated as counting numbers -quantum steps). I do understand that calculus was invented to help remedy...
  9. L

    Do the quantum effects we observe in visible light occur in all wave

    Hello everyone, I'd like to start off by expressing my appreciation for the existence of this forum to begin with. I majored in Sociology, yet classical and quantum physics has grasped my attention to a whole new level. Basically, I have a very elementary understanding in the subject, which is...
  10. michael879

    Quantum effects from an imperfect absorber

    I've had this idea stuck in my head ever since I read up on the Feynman-Wheeler formulation of classical E&M (absorber theory), and I was wondering if anyone here had any comments on it. For those who aren't familiar with it, it is a slight modification of the well-known E&M theory that makes...
  11. G

    Why quantum effects disappear at the classical level

    I forget where I read it but one author said that mountains of ink have been spilled debating why quantum effects disappear at the quantum level. I don't understand why this is a problem, I think the answer is rather obvious. One poster on another thread wrote: "Technically - classical physics...
  12. D

    Condensed matter - Is quantum effects relevant.

    a) Are quantum effects relevant for the air around us? "Formulas": The Fermi energy of athmosperic air: \epsilon_F = \dfrac{\hbar^2}{2m_{air}}(3\pi^2C)^{2/3} Attempt to solve: I calculated the fermi energy to : \epsilon_F = 1\times 10^{-25}\,\text{J} And k_bT = k_b 293\,\text{K} = 4\times...
  13. StevieTNZ

    Quantum Effects Brought to Light

    "Quantum Effects Brought to Light" Have had this article for a while now - http://www.nature.com/news/2011/110428/full/news.2011.252.html - but I was wondering why you wouldn't expect Bell's inequality to be violated had the entanglement been broken before amplification. The results, prior to...
  14. T

    Lack of quantum effects at higher temperatures

    I readhttp://www.learner.org/courses/physics/unit/text.html?unit=6&secNum=6" article and started wondering: What is the real reason for classical behavior of liquids gases at room temp? I have always thought that it is because of the deBroigle wavelength relation. At room T particles have a...
  15. P

    Exploring the Classical Wave Effects of Square Holes in Bamboo Slats

    The house where I live has a wall made of bamboo slats. There are small square holes between the slats, but when light shines through the square holes onto a surface the shape is always round. Why is that?
  16. K

    Impact of quantum effects on macro scale objects

    Not long ago I was arguing with someone on the Internet (where everyone is wrong) about impact of quantum effects on macro scale objects. Imagine ice-hockey table (one with almost no friction) with number of pucks on it. If you'll hit one of them it is safe to say that pucks' paths are very...
  17. wolram

    Exploring Dark Energy and Quantum Gravity with Atom Interferometry

    arXiv:1101.4890 (cross-list from gr-qc) [pdf, ps, other] Title: On the quantitative interpretation of dark energy by quantum effect of gravity and experimental scheme with atom interferometer II: the inclusion of general relativity Authors: Hongwei Xiong Comments: 18 pages, 3 figures...
  18. U

    Quantum effects in a single-slit experiment

    The famous double-slit-experiment has been widely discussed just about everywhere, but I'm wondering about seeing wave-particle duality with a single-slit experiment. This experiment would consist of a source of particles, a screen with a single slit, and a second screen with some sort of...
  19. A

    When do quantum effects become important?

    At what length scale do quantum effects become important in gravitational calculations??
  20. O

    Quantum effects Photosynthesis

    I would like to hear some thoughts about the quantum effects that seem to be an important part of the photosynthesis (http://www.lbl.gov/Science-Articles/Archive/PBD-quantum-secrets.html" ). According to the scientists who made this discovery it seems that the photon tests all possible paths...
  21. bcrowell

    Alcubierre drive has trouble with quantum effects

    A recent paper says that Alcubierre's warp drive probably won't work due to quantum effects: http://www.technologyreview.com/blog/arxiv/23292/ -- nontechnical summary http://arxiv.org/abs/0904.0141 -- paper Speaking as a non-specialist, it seems hard to tell which predictions about the...
  22. S

    At what temperature do quantum effects become significant for a gas

    Hi, I was wondering how to calculate a rough estimate of the temperature at which quantum effects begin to become important for a gas of interacting particles. Let's say the particles interact via a spherically symmetric potential with an equilibrium distance R and a well-depth E (such as the...
  23. Truecrimson

    Macroscopic quantum effects and gravitational wave detector

    My first thread here. Please bear with my lack of knowledge. I talked to a physics grad student about whether it's fair to describe QM as a theory applied only to microscopic objects. Although the definition of "fair" is ambiguous, at least he told me that, from his understanding, he wouldn't...
  24. F

    Exploring the Planck Length & Quantum Effects

    "The Planck length is the scale at which classical ideas about gravity and space-time cease to be valid, and quantum effects dominate. This is the ‘quantum of length’, the smallest measurement of length with any meaning." What I am wondering about this description is the word "dominate"...
  25. R

    Quantum effects at the neurological level

    I had read that Roger Penrose and others (like Hameroff and Chalmers from Arizona) have been studying the possibility that quantum events may influence the way our nerves fire and our brains develop thought. Can anyone comment on the scientific progress of these studies?
  26. M

    Dynamics of charged particles and quantum effects

    Why do we not consider quantum effects when we deal with motion of electrons in a Cathode Ray Oscilloscope, or in a cyclotron? We derive various relations using classical physics which turn out to be quite accurate in the laboratory.How is this possible when it is expressly known that classical...
  27. K

    Can Quantum Mechanics Explain Biology?

    In my biology class, I've learned that most of the fundamental processes of genetics occur on an atomic level (i.e. DNA, RNA, etc.). Can quantum mechanics be applied?
  28. I

    Are neurons sensitive to quantum effects?

    How sensitive are neurons and chemical receptors like olfactory receptors to the chemicals that stimulate them? Can a single molecule stimulate a nerve? How many photons does it take to stimulate a rod or a cone in the eye? I ask because I'm curious as to whether or not human thought and...
  29. X

    Quantum effects in biological systems

    I am going into my fourth year of studying physics and math as an undergrad. So I'm starting to think about what I want to research after I graduate. So far I'm pretty sure I want to go into biophysics. Specifically, I'm interesting in studying quantum mechanical effects in biological or organic...
  30. N

    Quantum Effects Negligible in Diffraction, Tunneling & Zero-Point Oscillation

    Homework Statement I am to show that quantum effects are negligible in: (i) The diffraction of a tennis ball of mass m=0.1 kg moving at a speed of 0.5 m/s by a window of size 1X1.5 m^2 (ii)The tunneling probability for a marble of mass m=5 g moving at a speed of 10 cm/s against a...
  31. J

    Free-Air Transmission and Quantum Effects?

    Why does the double-slit experiment with a laser work properly in an atmosphere? Likewise, I've seen news reports of entangled photons transmitted in a fiber or in open-air used to generate a shared secret. So, both superposition and entanglement works. But, the fact that the speed of the...
  32. D

    Symmetry in quantum effects.

    As someone returning to a study of physics after many years, I would appreciate any help and comments on my unresolved questions after reading “popular science” type information regarding quantum effects. In considering (that old chestnut!) the “twin slit” experiment to demonstrate the quantum...
  33. G

    Under what conditions will quantum effects become important for gravity?

    I have to write a short essay answering this question (1st year university level). I am finding it very hard to get any decent info on the net at all. If someone could help me out with this I would be very appreciative. Thanks. Regards Graeme
  34. J

    Under what conditions will quantum effects become important for gravity?

    Under what conditions will quantum effects become important for gravity?
  35. T

    Quantum effects in very small scale numerical modelling

    For those of you familiar with numerical modelling of various phenomena, you will know about work like the various discretisation schemes, stability/gradient limiters for high order schemes and so on. The most broad sweeping improvement to the field of numerical modelling would ultimately be...