What is Quantum basics: Definition and 83 Discussions
Quantum mechanics is the study of very small things. It explains the behavior of matter and its interactions with energy on the scale of atomic and subatomic particles. By contrast, classical physics explains matter and energy only on a scale familiar to human experience, including the behavior of astronomical bodies such as the Moon. Classical physics is still used in much of modern science and technology. However, towards the end of the 19th century, scientists discovered phenomena in both the large (macro) and the small (micro) worlds that classical physics could not explain. The desire to resolve inconsistencies between observed phenomena and classical theory led to two major revolutions in physics that created a shift in the original scientific paradigm: the theory of relativity and the development of quantum mechanics. This article describes how physicists discovered the limitations of classical physics and developed the main concepts of the quantum theory that replaced it in the early decades of the 20th century. It describes these concepts in roughly the order in which they were first discovered. For a more complete history of the subject, see History of quantum mechanics.
Light behaves in some aspects like particles and in other aspects like waves. Matter—the "stuff" of the universe consisting of particles such as electrons and atoms—exhibits wavelike behavior too. Some light sources, such as neon lights, give off only certain specific frequencies of light, a small set of distinct pure colors determined by neon's atomic structure. Quantum mechanics shows that light, along with all other forms of electromagnetic radiation, comes in discrete units, called photons, and predicts its spectral energies (corresponding to pure colors), and the intensities of its light beams. A single photon is a quantum, or smallest observable particle, of the electromagnetic field. A partial photon is never experimentally observed. More broadly, quantum mechanics shows that many properties of objects, such as position, speed, and angular momentum, that appeared continuous in the zoomed-out view of classical mechanics, turn out to be (in the very tiny, zoomed-in scale of quantum mechanics) quantized. Such properties of elementary particles are required to take on one of a set of small, discrete allowable values, and since the gap between these values is also small, the discontinuities are only apparent at very tiny (atomic) scales.
Many aspects of quantum mechanics are counterintuitive and can seem paradoxical because they describe behavior quite different from that seen at larger scales. In the words of quantum physicist Richard Feynman, quantum mechanics deals with "nature as She is—absurd".For example, the uncertainty principle of quantum mechanics means that the more closely one pins down one measurement (such as the position of a particle), the less accurate another complementary measurement pertaining to the same particle (such as its speed) must become.
Another example is entanglement, in which a measurement of any two-valued state of a particle (such as light polarized up or down) made on either of two "entangled" particles that are very far apart causes a subsequent measurement on the other particle to always be the other of the two values (such as polarized in the opposite direction).
A final example is superfluidity, in which a container of liquid helium, cooled down to near absolute zero in temperature spontaneously flows (slowly) up and over the opening of its container, against the force of gravity.
I'm trying to make sure I understand the g-factor of the electron, so if my question is flawed please don't just point out my flaws, but help me correct my understanding
If I understand correctly the magnetic moment of an object depends on it charge, its mass and its momentum
$$
\mu =...
I'm trying to fill a conceptual gap I have in the history of physics
In 1922 Stern and Gerlach make their experiment, proving that electrons have intrinsic angular momentum, however it takes a while for people to understand this. At first they think this is somehow caused by quantization of...
Hi everyone,
I need some help getting the gist of Bell’s theorem and his notion of inequalities.
How would you explain it to someone with limited knowledge of mathematics?
What are the potential implications?
Im trying to learn QM on my own and I just want to clear some things up. I feel dumb writing some out but Id rather clear my confusion than believe im interpreting what I read correctly.
From what I've read, every measurement of a system gives us values that are the eigenvalues of a certain...
hello i would to get some help with my homework.
1. true
2. i dont know
3. true
4. i dont know
5, false
6. i dont know
about 2,4,6 i really have know idea what to think I really appreciate help
As per my name, I am Quantum Newbie. I am I am exactly that. I'm interested more specifically in the following:
mandella effect, butterfly effect, alternate universes, mirror worlds, bubble worlds, quantum mortality, crossovers, multiple paths on the same frequency, dementions, universe A and...
Let E be a fixed immutable quantity. E can be freely exchanged between T and V, as long as $$T + V = E$$
1. What does the quantity $$\int_x T - V $$ signify? What is the importance of this quantity?
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Let E now be the budget of a factory. E can either be spent on T or V in...
If I understand it correctly, the Hamiltonian represents the total energy of the system. Can it be non-local? If yes, doesn't this contradict relativistic locality?
What I did was first noting that ##\hat{\vec{S}}_1\cdot\hat{\vec{S}}_2=\frac{1}{2}(\hat{\vec{S}}^2-\hat{\vec{S}}_1^2-\hat{\vec{S}}_2^2)##, but these operators don't commute with ##\hat{S}_{1_z}## and ##\hat{S}_{2_z}##, this non the decoupled basis ##\ket{s_1,s_2;m_1,m_2}## nor the coupled one...
Recall that in the semi-classical Bohr-Sommerfeld quantization scheme from the early days of quantum mechanics, bound orbits were quantized according to the value of the action integral around a single loop of a closed path. Clearly this only makes sense if the orbits in question permit closed...
Please explain in simple words, the meaning of the Schrodinger wave equation in the quantum mechanics model of atom. $$\frac{\partial^{2} \psi}{\partial x^{2}}+\frac{\partial^{2} \psi}{\partial y^{2}}+\frac{\partial^{2} \psi}{\partial z^{2}}+\frac{8 \pi^{2} m}{h^{2}}(E-U) \psi=0$$
How do the Pauli spin matrices transform under an inversion ? I think I mean to say the 3 dimensional improper rotation which is just in 3 dimensional matrix notation minus the identity - so exactly how are the 2 dimensional Pauli spin matrices changed. And under a 180 rotation do the 'y' and...
Dear experts,
I'm currently working my way through the paper Masanes, Galley, Müller, https://arxiv.org/abs/1811.11060.
On page 3, they define what they call a bi-local measurement: If we have two systems a and b and we define an outcome probability function for some measurement f on system a...
Hey all! I'm Alexander, after all of the exposure quantum physics is getting in these Marvel movies I decided to study up and I must say Quantum Physics just doesn't set well with me. I'm very interested in what has been made capable due to the math involved with quantum physics. I have a large...
Homework Statement
Find the noralization constant ##A## of the function bellow: $$ \psi(x) = A e^\left(i k x -x^2 \right) \left[ 1 + e^\left(-i \alpha \right) \right], $$ ##\alpha## is also a constant.
Homework Equations
##\int_{-\infty}^{\infty} e^\left(-\lambda x^2 \right) \, dx = \sqrt...
Hi everybody,
I've read some pages in Nielsens "Quantum Computing" book, it's very interesting, but especially at Grover's algorithm, there occurs a question for me. It is said that a phase shift is performed, which is defined as follows:
##|0\rangle \rightarrow |0\rangle \\ |x\rangle...
The question is as follows:
A particle of mass m has the wave function
psi(x, t) = A * e^( -a ( ( m*x^2 / hbar) +i*t ) )
where A and a are positive real constants.
i don't know how to format my stuff on this website, so it may be a bit harder to read. Generally when i write "int" i mean the...
I am still confused about the difference between measurement and interaction. I mean when electrons are traveling from source to the screen through the slits, there are air molecules in their way. And even if the electron double slit experiment is carried out in total vacuum in a completely...
Have thought about this for sometime but couldn't get deeper.
I have speculated that wave-particle duality is a direct result of the relativity theory. Especially it could arise from the factor of length contraction (dimensionality reduction). So far, the particle reality is based on various...
Homework Statement
Does the n = 2 state of a quantum harmonic oscillator violate the Heisenberg Uncertainty Principle?
Homework Equations
$$\sigma_x\sigma_p = \frac{\hbar}{2}$$
The Attempt at a Solution
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I worked out the solution for the second state of the harmonic oscillator...
Homework Statement
Hi, guys. The question is: For a 3-state system, |0⟩, |1⟩ and |2⟩, write the matrix representation of the raising operators ## \hat A, \hat A^\dagger ##, ## \hat x ## and ##\hat p ##.
Homework Equations
I know how to use all the above operators projecting them on...
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All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
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All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
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All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
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All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/
All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence.
Course Website: http://www.nptel.ac.in/courses/115104096/