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 ...

learn more… | top users | synonyms (3)

3
votes
0answers
20 views

Resource cost and noise effects in quantum teleportation of multible (entangled) qbits

Suppose you have n qubits that are in an unknown state (may be entangled, etc). Can you teleport this state by teleporting each qubit individually (using a Bell state and a classical channel)? If ...
0
votes
1answer
27 views

How to determine whether an eigenstate of total spin is symmetric or antisymmetric?

Here we have two identical paticles with spin $I$, integer or half-integer, and there are $(2I+1)^2$ states. Each one of them can be uniquely determined by total spin and its orientation, we can use ...
-5
votes
2answers
57 views

Proving (instead of discovering) the laws of quantum mechanics

A single toss of a fair coin cannot be predicted. But if we observe a large number of tosses, we can prove mathematically the law that roughly half of them will show up heads. The movements of ...
3
votes
2answers
56 views

What's the true reason behind thermal expansion?

Thermal expansion is a normal concept everyday. There are 2 explanations: 1, thermal expansion result in stress, then result in deformation 2, thermal expansion result in deformation, then result in ...
1
vote
3answers
93 views

Do electrons pop into and out of existence around the nucleus of an atom?

What surrounds the nucleus is the probability wave. But are the electrons constantly popping in and out of existence around the nucleus in the cloud?
2
votes
1answer
41 views

What is the energy of a Gaussian wave packet?

Suppose we have a potential barrier situation, that is $V(x)$ is zero everywhere except on the interval $[-a,a]$, where it is equal to some $V_0 > 0$. Introduce some Gaussian shaped wave packet to ...
0
votes
1answer
43 views

What does vector space and bra/ket space mean? [on hold]

I wonder What are the similarities and dissimilarities between a vector space and bra/ket space?
0
votes
0answers
26 views

Determining Parity of Decaying Quantum System

Show that a particle of spin $1$ cannot decay into two identical particles of spin $0$. The $\rho$-meson has spin $1$ and can decay into two spinless (spin-$0$) $\pi$-mesons, or pions, with ...
2
votes
6answers
396 views

On the foundations of quantum physics

Quantum physics has to be validated by experiments. But experiments are to be interpreted in the context of quantum physics. Isn'it like a snake biting its own tail? For example, using a scanning ...
5
votes
3answers
262 views

Entanglement and simultaneity

According to the special theory of relativity, distant simultaneity depends on the observer's reference frame. And, according to the quantum theory, in the case of two entangled particles, a measure ...
1
vote
0answers
53 views

A problem with the Gamow state

Consider a form of potential $U(r)$ as follows $$ U(r)=\begin{cases}0 & 0<r\leq a \\ U_0 & a<r\leq b \\ 0 &r>b\end{cases} $$ In this problem $r$ is the distance from the origin, ...
0
votes
1answer
17 views

In what order will the magnetic quantum number be filled

For example, the electron configuration for Cu(II) ion is [Ar]3d9. So only the 3d shell matters to the total orbital angular momentum of the ion. For 3d shell there are 5 possible values of $m_l : ...
1
vote
1answer
44 views

Does a static electric field act continuously?

Electromagnetic radiation is emitted and absorbed in discrete units, photons. One photon's energy is described by the well known $E = hf$ formula. Now, if you a have static electric field that ...
4
votes
0answers
74 views

Are there any proposed alternatives to quantum mechanics as there are alternatives to general relativity?

There are a lot of alternatives to general relativity and one of the motivations is attempting to formulate a working theory of quantum gravity. In some limit they reduce to general relativity. But ...
-4
votes
0answers
30 views

Show that a barrier which is forbidden for a classical particle can have a finite probability for a quantum particle [on hold]

Show that a barrier which is forbidden for a classical particle can have a finite probability for a quantum particle.
5
votes
1answer
105 views

Should the differential of a wavefunction have a time partial derivative?

In chapter 1 of Griffths' QM text, he shows that $\frac{\mathrm{d}}{\mathrm{d}t}\int_{-\infty}^{\infty}|\Psi|^2\,\mathrm{d}x=0$ by noting $$\begin{align} ...
1
vote
1answer
34 views

How does observer affects the wave-particle nature ? (and related questions: part 2)

Following comments I split my question in to two parts which are independent. The questions are about double slit experiment with an observer(s). Suppose electrons are being used in the experiment ...
1
vote
1answer
70 views

Degrees of freedom in Quantum Mechanics

If we look at a particle in classical mechanics, the degrees of freedom increase as its size decreases like the degrees of freedom of an atom is more than that of molecule, and subsequently, the ...
0
votes
0answers
47 views

How does an observer affect the wave-particle nature? [on hold]

I have heard about the double slit experiment and the effect the observer has on the outcome, mostly in documentaries. I have few questions about what they mean by an observer. I will assume the ...
0
votes
0answers
27 views

The energy of an electron in a time-dependent electric field

Is energy of an electron in a time-dependent electric field any different from the one in a static field? Why did D.Griffith state in his "Intro to QM"( when he discussed the perturbation of EM waves ...
0
votes
0answers
38 views

What is the form of the Hamiltonian for periodic boundary conditions? [on hold]

What would the potential term be for a system with periodic boundary conditions? I know the simple harmonic Hamiltonian, but what about a general system such as a wire? I'm trying to solve the ...
2
votes
0answers
52 views

Wave/particle-duality as result of taking different limits of a QFT

There is an account on dualities in quantum field theories and string theories by Polchinski from last week http://arxiv.org/abs/1412.5704 At the end of page 4, he writes the wave/particle ...
1
vote
0answers
16 views

Sufficient criterion for su(2) invariant spin-1*spin_s bipartite density matrix

SU(2) invariant spin-1 and spin-S bipartite density matrix is given by $\rho ^{1,S}=\frac1{3*(2S+1)}[1+\alpha {S^A_i\times S^B_i}+\beta S^A_{ij}\times S^B_{ij}]$, i j varies from ...
0
votes
2answers
82 views

How can the electron be a wave? [duplicate]

I read about Rutherford's failed attempt to describe the atomic model. Then I read about Bohr's model and his postulates. Ok, that was fine. But then I read in my book a statement that shocked me: ...
6
votes
4answers
162 views

Difference between spin and polarization of a photon

I understand how one associates the spin of a quantum particle, e.g. of a photon, with intrinsic angular momentum. And in electromagnetism I have always understood the polarization of an EM wave as ...
0
votes
1answer
41 views

Quantum cloning of orthonormal states

If I understand correctly, for two orthonormal states $\left|\psi_1\right\rangle$ and $\left|\psi_2\right\rangle$ in the Hilbert space H, there must exist a unitary transformation $U$, such that: ...
1
vote
1answer
116 views

Are wave functions real physical objects? [duplicate]

Are wave functions (ex. electron waves) real physical objects or just mathematical tools?. Some researchers say that they have proof that they are real objects. Here's [the link] ...
3
votes
1answer
54 views

What topics do I need to study electromagnetism on the quantum scale? [on hold]

What topics do I need to study (in order) so that I can study electromagnetics on the quantum scale? What is the name of the discipline studying electromagnetism on the quantum scale? Do I need to ...
1
vote
0answers
57 views

What does the relation between mass and energy of a free particle mean?

What does the Hamiltonian for a free particle mean? Does it mean that the kinetic energy of the particle is in reverse relation with mass? $H$ or $E=\hbar^{2}k^{2}/2m$. Or better to ask: what's the ...
2
votes
4answers
526 views

Exploring beyond event horizons

In the expanding universe the velocity of separation between galaxies depends upon how far they are. If they are much far away will they have relative velocity of separation greater than speed of ...
5
votes
2answers
269 views

Wave function in quantum mechanics

I was wondering about something while studying quantum mechanics. If the wave function collapses when measuring a particle and assumes a single position, how do we know that it was a wave in the first ...
1
vote
1answer
39 views

Why two-particle wavefunctions are separable and their corresponding particles are indistiguishable at the same time?

If the wavefunction $\psi(r_1,r_2)$ doesn't represents an entangled state, it is separable: $$\psi(r_1,r_2)=\psi_a(r_1)\psi_b(r_2)$$ In this treatment, we ignore the interaction between two particles ...
0
votes
0answers
18 views

Energy eigen value for a perturbed free particle system

Suppose we have a one-dimensional free particle system and we introduce a perturbation like $V(x)=V_{0} \cos(Gx)$, where $G$ is the reciprocal lattice vector (it's a periodic perturbation, I think) ...
1
vote
0answers
13 views

How come plasmon resonances of metals are capable of being tuned to different wavelengths?

I read in this article that plasmon resonances though being a pre-determined property of a metal are capable of being tuned to other wavelengths when these same metals are made into tiny ...
1
vote
0answers
59 views

Quantum Simple Harmonic Oscillator Interpretation

I am just wondering what does the SHO system from quantum mechanics actually physically represent? Is it just a SHO of a quantum particle, seems a little too obvious for quantum theory? I'm from a ...
0
votes
0answers
50 views

What collapsed the wave function of organic molecules for life to form? [on hold]

The wave function only collapses when it is measured by an observer. So, before life came into the universe, I'm guessing that everything existed in superposition. We are told life was formed as a ...
1
vote
1answer
64 views

Is nature quantized?

I was reading Planck's postulate the other day on Wikipedia and couldn't help but noticing the sentence: "...is the postulate that the energy of oscillators in a black body is quantized..." ...
0
votes
0answers
27 views

In MWI, how to make sense of the nonuniqueness of decomposing mixed states into pure states?

It's well known that in quantum mechanics, a generic mixed state can be decomposed into pure states in infinitely many different ways. While this property is kind of understandable if quantum states ...
-1
votes
1answer
25 views

What is trivial and non-trivial gate in computing?

My question seems like it should be posted in Computer Engineering section, but below is how I found this word. I was reading the textbook: Quantum Computation And Quantum Information - by Michael A. ...
-1
votes
0answers
50 views

Double slit experiment setup which resolves dualism

Suppose we have the following setup of double-slit experiment: A point source of coherent photons emits them so that they fall onto a non-transparent panel D ...
1
vote
1answer
41 views

Delayed Choice Quantum Eraser [duplicate]

All delayed choice quantum eraser experiments I've seen record the signal photons reaching detector D0 and then use the data of the idler photons recorded at detectors D1, D2, D3, D4 to "filter out" ...
0
votes
0answers
27 views

Best book for learning Quantum Communication [duplicate]

I am new in Quantum physics. I want to do my BSc thesis on Quantum Communication. My major is Communication. So I want to learn fast. I have little idea about quantum computing. So please suggest me ...
6
votes
3answers
735 views

Does quantum entanglement arise from quantum theory or is it merely an experimental observation?

I assume that entanglement emerges from quantum mechanics because the idea was around before experimental verification (e.g the EPR paper). How then does entanglement emerge from the theory (please ...
-1
votes
1answer
39 views

Quantum Physics, Energy States [closed]

Which of the following transitions in a hydrogen atom absorbs a photon of the highest energy? a.) $n=2\hspace{1cm}to\hspace{1cm}n=3$ b.) $n=3\hspace{1cm}to\hspace{1cm}n=2$ c.) ...
0
votes
0answers
29 views

How to minimize the wavepacket dispersion?

This is a final exam problem. Here is what I can remember: We know that if an electron's wavefunction starts out as a narrow wavepacket, and moving in a region of constant potential, then the ...
0
votes
3answers
140 views

About the double orthogonality of the eigenfunctions of the Hamiltonian

Consider the usual Hamiltonian describing the motion of a particle, $$\hat H = \frac {\hat P^2}{2m} + V(r),$$ where for simplicity the problem can be considered in 1D on the semiaxis $[a, \infty)$ , ...
0
votes
1answer
69 views

Can interacting Hamiltonians always be written in second quantized form?

Is it always possible to write interacting Hamiltonian in a second quantized matrix form like we do it for non-interacting form $$H=\sum _{\alpha\beta}C_\alpha^\dagger h_{\alpha\beta} C_\beta$$ ...
2
votes
2answers
67 views

Is light emitted in zitterbewegung? [duplicate]

Recently I heard of Zitterbewegung, a trembling motion of the electrons in atoms that arises from Dirac's equation. I know that, according to Bohr's model, light is emitted when the electron "jumps" ...
0
votes
1answer
26 views

Dipole approximation in solids

I have seen the use of dipole approximation (where the extent of the wave function is assumed to be much smaller than the wavelengths of the transitions or that of the electromagnetic field applied) ...
1
vote
0answers
10 views

Minimum spread of frequency and wavelength in neodymium laser

What is the equation linking the minimum spread in wavelength and frequency of a pulsed laser, in relation to the lasers pulse time and operational wavelength. For example: If a Neodymium laser ...