Quantum mechanics describes the microscopic properties of nature in a regime where classical mechanics no longer applies. It explains phenomena such as the wave-particle duality, quantization of energy and the uncertainty principle and is generally used in single body systems. Use the quantum-field-...

learn more… | top users | synonyms (4)

1
vote
3answers
451 views

Compatibility of economics and physics? [closed]

This is an open-ended and broad and multi-part question; but I would be willing to accept an answer that simply corrects my misconceptions. I am sorry if it is inappropriate or too soft for this site....
3
votes
2answers
145 views

In the dual-slit experiment, can the time it takes for a photon to arrive reveal the path it took?

It seems like this experiment is possible: Fire a photon, and start a timer The photon travels through the slit(s) The photon strikes a plate -- the timer is stopped. Based on where on the plate ...
14
votes
9answers
59k views

What's the standard “roadmap” to learning quantum physics? [closed]

I'm really interested in quantum physics and would like to learn more. However, I don't know where to start and in what order I should learn things. So, ideally I'm looking for some sort of roadmap of ...
3
votes
1answer
6k views

What does $\Psi^*$ mean in Schrodinger's formulation of Quantum Mechanics?

I am not a physics student. In one of my courses, some fundamental concepts of Quantum mechanics were needed, so I was going through them when I stumbled upon this. It says $$\text{probability} = \...
1
vote
1answer
383 views

A quantum particle in a box (with a catch)

I am reading Shankar's Quantum Mechanics and I am looking at the case where there is one particle inside a box, where the potential is zero inside the wall and abruptly goes to infinity outside the ...
2
votes
1answer
462 views

Is it a total or an explicite time derivative in the Schrödinger equation?

I am always dubious when I need write Schrödinger equation: do I write $\partial / \partial t$ or $d/dt$ ? I suppose it depends on the space in which it is considered. How?
3
votes
1answer
2k views

What is “Quantum Levitation”?

I just found this video Controlled Quantum Levitation on a WipeOut Track and I'm having a hard time finding the term "Quantum Levitation" used except in reference to the video. What is the proper ...
4
votes
1answer
167 views

Are energies non-transferable in the Born-Oppenheimer approximation, and when does it apply?

Adiabatic approximation or the Born-Oppenheimer approximation is used whenever the electronic motion is too fast that the electrons effectively see static nuclei and the nuclei, in turn, see an ...
6
votes
2answers
761 views

What is the symmetry that corresponds to conservation of position?

We know that conserved quantities are associated with certain symmetries. For example conservation of momentum is associated with translational invariance, and conservation of angular momentum is ...
1
vote
1answer
903 views

Conjugate Variables and Fourier Transforms in Classical Physics

Let q be a generalized coordinate with a conjugate momentum p and a potential resulting in a periodic motion of q. What is the meaning of the Fourier transform of q(t) over its period? Can this be ...
9
votes
2answers
635 views

Regularisation of infinite-dimensional determinants

Can a regularisation of the determinant be used to find the eigenvalues of the Hamiltonian in the normal infinite dimensional setting of QM? Edit: I failed to make myself clear. In finite dimensions,...
4
votes
3answers
1k views

Nanorobots. What stops us from producing them yet?

If we can already predicts accuratelly motion on molecular levels, what stops us from developing small robots to, for instance, navigate through our blood vessels looking for cancerous cells and ...
13
votes
1answer
6k views

What inspired Schrödinger to derive his equation?

I have almost no background in physics and I had a question related to Schrodinger's Equation. I think, it is not really research level so feel free to close it, but I would request you to kindly ...
4
votes
2answers
3k views

Software to simulate and visualize atoms?

Not sure if this is a physics or chemistry question. But if the motion of atoms and it's particles can be described by quantum mechanics, then is there a software that simulate full atoms and it's ...
6
votes
6answers
1k views

Which physically acceptable quantum interpretations do not require the existence of any observer at all?

Some interpretations of quantum mechanics — like the Copenhagen interpretation in particular — require the existence of an observer. The role of the observer is a bit mysterious. After all,...
7
votes
2answers
2k views

Careers in physics that are related to quantum mechanics or relativity? [closed]

Personally I learned Physics in high-school and found it very interesting, I read up a lot about physics in my free time. Personally I am also a programmer which I think is also good when it comes to ...
7
votes
2answers
840 views

Why don't quantum effects invalidate the speed of light barrier?

While proving that no matter can reach the speed of light (a fact which I call the kinetic energy barrier), Einstein uses the fact that he can calculate the velocity and position of an electron. ...
2
votes
3answers
220 views

What are local electrons in a crystal?

I am reading Pekar's "Research in Electron Theory of Crystals" and I came across a passage I find a bit unclear: The theory developed below takes into account the dielectric polarization of a an ...
1
vote
1answer
147 views

What kind of interactions denote 'observation'?

I'm quite perplexed by the notion of 'observation' in regards to the collapse of a particle's probability wave. Does a particle's wave only collapse when it is involved in a strong interaction (such ...
6
votes
4answers
952 views

Locality in Quantum Mechanics

We speak of locality or non-locality of an equation in QM, depending on whether it has no differential operators of order higher than two. My question is, how could one tell from looking at the ...
7
votes
6answers
359 views

Why quantum states are classified using only conserved quantities?

While studying quantum mechanics from standard textbooks I always felt some conceptual gap that was never mentioned or explained. In what follow I tried to formulate my question, please be patient ...
3
votes
3answers
1k views

Can actual quantum effects occur on a macro scale?

I apologize if this question is posted on the wrong portion of the website, but I knew no better place to ask. I've come to see that some effects, such as super-conduction may happen at either ...
10
votes
1answer
154 views

Consideration of static atomic displacements in electronic structure calculations

I am hoping to discuss some details of electronic structure calculations. I am not an expert on this topic, so please forgive any abuse of terminology. It is my understanding that first principles ...
2
votes
3answers
1k views

J.J. Sakurai book on Q.Mech [closed]

I just want to ask how recommended is the book on quantum mechanics by J.J. Sakurai. Is it any good as an introductory text? And are there better suggestions (substitutes)?
8
votes
1answer
89 views

Relativistic corrections to quantum mechanics of Coloumb potential

Systems of charged particles (such as atomic nuclei and electrons) can be described by nonrelativistic quantum mechanics with the Coloumb interaction potential. A fully relativistic description is ...
4
votes
5answers
724 views

Do we really know which slit the photon passed through in Afshar's experiment?

The plain old double slit experiment displays interference when we don't measure which slit the photon passed through, and no interference when it is measured. Let's turn our attention to the case ...
1
vote
2answers
252 views

Puzzled by $\mathrm p = -i\hbar \nabla = m \dot{\mathrm r}$?

I'm working on Physics of Atoms and Molecules by Bransden and Joachain. And I've come across the following statement, which I don't understand (p.195, ch. 4.3, "The dipole approximation") ... In ...
18
votes
7answers
3k views

Good book on the history of Quantum Mechanics?

Can anyone recommend a good book on the history of Quantum Mechanics, preferably one that is technical and not afraid to explain the maths (I did a degree in Physics many years ago) and also that ...
4
votes
2answers
311 views

Mass of the particle and gravitational field

Which mass of the particle is the source of gravitational field? If we define mass as a pole of the propagator, and calculate loop corrections to the pole we get infinities. Now the way we get rid of ...
0
votes
2answers
370 views

The Lorentz Transformations in the Micro-World

Two particles[or micro-observers] A and B are in relative uniform motion wrt each other in the x-x’ direction. The “observer” A decides to deduce[or interpret] the Lorentz Transformations wrt to B. ...
1
vote
1answer
170 views

Do interaction-free measurements require a physical collapse or splitting in order to be truly interaction free?

Interaction-free quantum experiments like Renninger's experiment or the Elitzur-Vaidman bomb tester are often taken to be examples of interaction-free measurements of a system. Unfortunately, such ...
8
votes
4answers
2k views

Variation of delayed choice quantum eraser

Let me base the discussion on the pictorial description of the delayed choice quantum eraser experiment on wikipedia. First suppose that we do precisely the same thing with the lower parts of the ...
7
votes
8answers
3k views

What exactly is the 'observer' in physics and/or quantum mechanics? [duplicate]

Possible Duplicate: nature of an observer For instance, in the double slit experiment, what is exactly defined as an observer? I remember from somewhere, light is also an observer?
2
votes
1answer
131 views

Cross sections and renormalization scheme

Can the result on cross section of some process be dependent on the renormalization scheme used?
21
votes
8answers
4k views

Deterministic quantum mechanics

I came across a very recent paper by Gerard 't Hooft The abstract says: It is often claimed that the collapse of the wave function and Born's rule to interpret the square of the norm as a ...
13
votes
3answers
16k views

What exactly is a quantum of light?

I am currently trying to learn some basic quantum mechanics and I am a bit confused. Wikipedia defines a photon as a quantum of light, which it further explains as some kind of a wave-packet. What ...
0
votes
2answers
144 views

How do you properly analyze decoherence when the system-environment interaction is strong?

The standard decoherence analyses work something like this. Split the universe into a system and its environment, and split the Hamiltonian as the sum of the system Hamiltonian, environment ...
2
votes
6answers
3k views

What does a unitary transformation mean in the context of an evolution equation?

Let be the unitary evolution operator of a quantum system be $U(t)=\exp(itH)$ for $t >0$. Then what is the meaning of the equation $$\det\bigl(I-U(t)e^{itE}\bigr)=0$$ where $E$ is a real ...
0
votes
0answers
207 views

Semiclassical approximation for the exponential sum (partition function)

For any real and positive $s$ and in the sense of semiclassical approximation, is this valid? $ \sum_{n}exp(-sE_{n})\sim \iint_{C}dxdpe^{-s(p^{2}+V(x))}$ valid for every $s$ Here simply both the sum ...
20
votes
10answers
14k views

Does the Pauli exclusion principle instantaneously affect distant electrons?

According to Brian Cox in his A night with the Stars lecture$^1$, the Pauli exclusion principle means that no electron in the universe can have the same energy state as any other electron in the ...
6
votes
2answers
958 views

Assumptions in Heisenberg's 1925 paper

I am not entirely clear as to what were the bases for Heisenberg's assumptions in his 1925 paper. He claims that one cannot consider relations between quantities that are unobservable "in principle", ...
4
votes
3answers
2k views

Index Manipulation and Angular Momentum Commutator Relations

I have been trying for hours and cannot figure it out. I am not asking anyone to do it for me, but to understand how to proceed. We have the relations $$[L_i,p_j] ~=~ i\hbar\; \epsilon_{ijk}p_k,$$ ...
1
vote
5answers
960 views

Observable: possible outcome of measurement vs (linear) transformation

One of the postulates of quantum mechanics is that every physical observable corresponds to a Hermitian operator $H$, that the possible outcomes of the measurements are eigenvalues of the operator, ...
1
vote
3answers
483 views

Is energy conserved in decay of hydrogen atom in superposed state?

This looks like a paradox. Let's say we have an hydrogen atom. Superposition of states could be possible for electrons. But if an electron is in a superposition, I guess it could decay into a lower ...
8
votes
1answer
460 views

Physical interpretation of Wheeler - Dewitt equation

What is the mainstream ( if there is one ) interpretation of the Wheeler - Dewitt equation $\hat{H}\Psi =0$ ?
1
vote
4answers
765 views

Atom Theory vs Quantum Physics

This never really occurred to me until now, so maybe it does not categorize as a really important question, but, according to Quantum Mechanics, anything that is not observed exists as a probability ...
1
vote
2answers
257 views

Reconstruction of information stored in an evaporating black hole from the emission spectrum?

For simple setups, where the radiation field deviates not too far from thermodynamic equilibrium (< 10 %), corrections to the Planckian thermal emission spectrum can be calculated (and measured) ...
14
votes
1answer
6k views

Can you magnetize iron with a hammer?

We know that a piece of ferromagnet, such as iron, can be magnetized by putting in a strong magnetic field to get domains parallel to the field grow. I also remember from pop. culture and MacGyver ...
3
votes
2answers
267 views

Can the Heisenberg interpretation or path integrals apply to open quantum systems?

It has been claimed by some people that Schrödinger's picture is more misleading compared to the Heisenberg principle or path integrals, and that we would be better off abandoning the Schrö...
5
votes
1answer
1k views

The implication of anti-commutation relations in quantum mechanics

All the textbooks I saw are very clear about the implications of commutating operators in quantum mechanics. However, much less is said about anti-commutation relations. Does it have a general ...