Quantum spin Definition and 34 Threads

Starting from this link my understanding of Bell inequality proof goes as follows: Suppose we have a model of local pre-determinate hidden variables for QM. This amounts to say QM objects are in pre-determinate given states even if we do not measure it. Locality just means that spacelike...

Here is my workings out: $$$$ If a particle's spin of magnitude ##\frac {\hbar}{2}## is prepared along direction ##\vec r_1## and subsequently its spin is measured along direction ##\vec r_2 ## at an angle ##\vec \theta ## to ##\vec r_1##, the probability of its being found "spin up" along is...

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...

I read about quantum spin a while ago. If it’s not spinning, what is it doing?

Greetings, I'm new here, I have an interest in the nature of reality, and a question. Does the quantum spin of a particle (its intrinsic angular momentum) have anything to do with its wavelength and frequency? One of the experts on Quora said no, and I cannot find anything about it on the web...

What is the quantum spin of the valence electron in the silver atom in the furnace in the Stern-Gerlach experiment? . Up, down, at random, alternating, in a (quantum) superposition (of both), or none? Does it even have/get one until it's measured/observed /needed? . Does the second electron, in...

Some texts say quantum spin is analogous to the spin of a planet in that it gives a particle angular momentum and a magnetic moment. However, as subatomic particles are tiny, the surfaces of charged particles would have to be moving faster than the speed of light in order to produce the measured...

What kind of research is currently going on in the field of quantum spin liquids and why do we study spin liquids?

Hi all, There is this question; Firstly, I am new to quantum mechanics and there are a lot of terms I am unfamiliar with. So there is this question that asks me to develop a method to reconstruct state and I have no clue how I should start with. Any help or steps to solve this type of...

Hey guy! Can you guy pleas tell me what is quantum spin? I read and watch many stuff but i still don't understand it. Thanks for help!

I have previously read that the spin of a particle is comparable to angular momentum of a system or object on the macroscopic level. However, the quantum world is much different and all I can imagine is a minuscule ball rotating on it's axis.

Its very easy to pull a logic gate or transistor circuit of the internet for example and begin to understand how it represents physical bits, by either having 5V across the circuit or below 3.3V. But I was wondering what are some of the methods for representing qubits from a hardware...

The "color force" doesn't actually change the color of quarks because they don't actually have any color. We use the word "color" non-literally here. Now, I'm told that quarks don't "actually" "spin" either, so again, I infer that it's a term used out of convenience, but I'm also told that they...

Homework Statement It was noted that <00|Su11Su22|00> = -ħ2/4 * u1⋅u2. where u1 and us are unit vectors along which the two spin operators are measured and θ is the angle between. |00> is the singlet state that the two electrons are entangled in (corresponding to total spin values ). Prove...

Homework Statement What are S, L and J for the following states: ##^1S_0, ^2D_{5/2} ^5F_1, ^3F_4## Homework Equations The superscript is defined as: 2S + 1 The subscript is defined as: J = L + S The letter denotes the angular momentum number (s, p, d, f...) starting at s = 0. The Attempt at a...

I just read an article stating physicists have discovered a new state of matter. What is a quantum spin liquid?

Hello I am joining as a Project assistant on a project called "Search for spin liquid and other novel ground states arising from an interplay between electronic correlations, spin-orbit coupling and geometric magnetic frustration" what can i read to get onto the topic for it.

Homework Statement Show that for a two spin 1/2 particle system, the expectation value is \langle S_{z1} S_{n2} \rangle = -\frac{\hbar^2}{4}\cos \theta when the system is prepared to be in the singlet state...

This is my attempt at understanding any real world physical effects from quantum spin. I will start with the short version first. A ... When we have a free floating electron in space is the physical orientation of the quantum spin axis locked into a fixed 3D orientation and from there can only...

Homework Statement I am currently working on a seemingly straightforward eigenvalue problem appearing as problem 1.8 in Sakurai's Modern QM. He asks us to find an eigenket \vert\vec S\cdot\hat n;+\rangle with \vec S\cdot\hat n\vert\vec S\cdot\hat n;+\rangle = \frac\hbar 2\vert\vec S\cdot\hat...

Homework Statement [/B] Please redraw this figure by assuming that an electron can have spin quantum number ms = +1/2 (arrow up), ms = 0 (marked as "I"), or ms = -1/2 (arrow down). It is important to clearly state your arguments/reasoning. http://s30.postimg.org/jz7tfeha9/wow.png Homework...

Question about quantum spin: So for the Schrodinger equation, the angular momentum of a wave-packet, whether it is free or confined to a potential well, appears to be calculated in exactly the manner you would expect it to be: L(x) = m*rxv[Psi(x)]. Aside from quantization (decomposing the...

quantum spin vs ...spin I keep hearing people say, "comparing particle spin to a spinning top will lead you in the wrong direction." I'm curious.. what exactly is the difference between the two?

Help please! Where can I start if I want to learn Quantum Spin Hall Effect? I have learned the some fundamental ideas of integer quantum hall effect by myself. Under this background, what more should I read? cause I really can't find any notes or videos that are teaching about QSHE. I am now in...

Can there be EM radiation with spin zero? I don't mean that the sum of all spins is zero, as it usually is. My thinking is that all light spins and usually the left and right component is of equal intensity. Am I correct in thinking that light reflecting off of a suitable horizontal...

There is an external magnetic field along the positive z direction B = (0,0, B) and the initial spin direction at time t0= 0 is specified by the direction cosines Ŝ0= (cos α0, cos β0, cos γ0) where α0, β0, γ0 are the angles between the initial spin and the x, y, z axes, respectively. This...

Please help a poor stupid layman. When a particle has a spin of 1/2, what does that really mean? 1/2 of WHAT?

Hallo! My question relates to the use of basis states to form operator matrices... In the context of quantum spin chains, where the Hamiltonian on a chain of N sites is defined periodically as:H = sumk=0N-1[ S(k) dot S(k+1) ] (apologies for the notation) so there is a sum over k=0 to N-1...

Is there an invariance relation for angular momentum similar to E^2 = p^2 + m^2 ? How about quantum spin ?

I'm reading Hughes book The Structure and Interpretation of Quantum Mechanics. I was wondering if people knew of any good web resources that graphically (maybe with Java applets, etc.) illustrate how the spin observables Sx Sy and Sz are related to each other, either in real space or in their...

what is the quantum spin chain problem? From my research on the net I can see that its solved through exact diagonlization of some sort of matrix, but I can't work out exactly what the problem is...

My understanding is that when you measure an electron's spin on on Axis A, and then on Axis B, the spin on Axis A is "forgotten" and can be something different next time you measure it. Is this correct? If it is, then how does this work across entanglement? If you measure electron A's spin...

What is the relationship between quantum spin and classical spin? I have seen this question asked many times but have never seen an answer that I was happy with. The most common answer I have seen is that there is no connection. The word "spin" has more to do with history than physics and...

What is quantum spin? I've read lots of things about it and describing it, I still don't quite understand it.