All Questions
20 questions with no upvoted or accepted answers
8
votes
0
answers
267
views
Free Will Theorem question
The Kochen-Specker Theorem says, if I understand it correctly, that the results of spin measurements cannot be predetermined independent of measurement. They get to this conclusion by describing 33 ...
- 81
3
votes
0
answers
93
views
Constructing wavefunction for a mixed state
This question is somehow the reverse of another question.
If a quantum system $S$ is in a pure state, then we can find a wavefunction that describes $S$. This wavefunction is unique up to a phase ...
- 1,502
3
votes
0
answers
75
views
Bounding the value of a function for separable spin states
Consider $N$ spin-1/2, for which we can define the collective spin operator $\vec{S}=\sum_i \frac{\vec{\sigma}^{(i)}}{2}$. My question is, what is the upper bound $U$ on
$$
f(\rho) = \text{Var}[ S_z ] ...
- 1,231
3
votes
0
answers
224
views
Spin polarization of decay products
A relativistic moving particle, e.g. muon $\mu^+$, described by its four-momentum vector $p_\mu$, charge $e$ and with a given spin polarization, ${\bf S}=(S_x,S_y,S_z)$, decays into three particles, e....
- 575
2
votes
0
answers
98
views
Entanglement measure for a continuous bipartite system
Consider a cavity-spin system and assume we want to quantify the correlation between them. The cavity system can be described using a bosonic mode whereas the spin system requires 2 bosons to describe ...
- 219
2
votes
1
answer
179
views
Does spin entanglement imply position entanglement?
My question is whether two electrons can be entangled only with respect to their spins but not with respect to some other observable, such as position.
I initially believed that spin-entanglement ...
- 1,073
2
votes
1
answer
299
views
Measurement of the spin of the EPR pair in two orthogonal directions and how did Einstein tackle this?
Let us consider two types of measurement in the EPR experiment. In Bohm's description of this experiment, the state of the electron-positron (called the EPR pair) is given by
$$
|{\rm EPR} \rangle =\...
- 12.3k
1
vote
0
answers
68
views
Spin Correlation Analogy in Three Particle System
I have recently gone through the section on Bell's Inequality in "Modern Quantum Mechanics" by J.J. Sakurai and Jim Napolitano and I am curious as to weather or not there are analogous ...
- 11
1
vote
0
answers
71
views
Measurement of total angular momentum in quantum mechanics
Consider a system composed of two spin-1/2 particles. The total spin operator is defined as
$$
\mathbf{S} = \mathbf{S_1} + \mathbf{S_2}
$$
We can write a common eigenbasis of the operators $\mathbf{S^...
- 324
1
vote
0
answers
52
views
How is entanglement of non-spin variables incompatible with local realism?
It seems to me that spin/polarization entanglement is the only spooky one. That's because the entanglement of other observables would happen even in regular classical physics if we made a "...
- 2,587
1
vote
0
answers
115
views
Hamiltonian basis in multiple particle systems
I have a question about the choosing of basis that compose the Hamiltonian of multiple systems. For example if we have a system of N particles, that depend in our case of Pauli matrixes i will give ...
- 529
1
vote
0
answers
19
views
Do fullerenes have a better quantum yield than carbon quantum dot's of similar dimensions?
As a fullerene and a carbon quantum dot of similar dimensions would have the same surface area but different internal volume, as a Fullerene does not contain carbon within it's interior, but just the ...
- 471
1
vote
0
answers
134
views
Creation of entangled electrons
If one obtains two entangled in polarization photons by parametric down conversion and one of them is accepted by and electron 1 and other by electron 2 - are this electrons now entangled in spin?
- 679
1
vote
0
answers
457
views
Can experiment distinguish the basis in which a singlet state is represented?
Let $\left(|\uparrow\rangle,|\downarrow\rangle\right)$ and $\left(|\nearrow\rangle,|\swarrow\rangle\right)$ be two bases of the $2$-dimensional Hilbert space $H$.
Can an experiment distinguish ...
- 4,246
1
vote
1
answer
570
views
Measuring electron spin with multiple Stern–Gerlach apparatus at an angle
To separate the two spins of electron of a particular direction, we use Stern-Gerlach apparatuses to apply a non-uniform Magnetic field. Suppose we have two identical electrons and we know their spin ...
- 111
0
votes
0
answers
57
views
Total spin of Entangled Electrons
If, say, the z-spins of two electrons are maximally entangled (so that their composite state can be given by $|\Psi\rangle = \frac{1}{\sqrt{2}}(|u\rangle|d\rangle + |d\rangle|u\rangle)$, how do you ...
- 1,073
0
votes
1
answer
99
views
Intuition for Results of a Measurement of Entangled Spins
Suppose I have a source that produces pairs of spin-1/2 spins in the entangled state
$$ \frac{1}{\sqrt{2}} \left( \mid\uparrow_z\uparrow_z\rangle + \mid\downarrow_z\downarrow_z\rangle \right). $$
The ...
- 1,576
0
votes
0
answers
65
views
Why can't we create energy/momentum by selectively measuring the spin of entangled particles?
Suppose we perform a Bell violation type experiment with spin, i.e. we have a stream of entangled, spin-anticorrelated particle pairs and we are to measure their spins along different axes.
Now for ...
0
votes
2
answers
512
views
How to produce a given entangled state of two quantum bits?
I was watching Leonard Susskind's video series on quantum entanglement, where he looks at the spins of two electrons. In particular, there are entangled states of the form $$\alpha\left|\uparrow \...
- 407
-1
votes
1
answer
79
views
Measurements of spin correlations: Alice goes back to Bob and compares results
Take a fully entangled two-photon state, like
$|\Psi>=\frac{1}{\sqrt{2}}\big(|+->-|-+>\big)=\frac{i}{\sqrt{2}}\big( |yx> - |xy> \big)$
where one photon is sent to Bob and the other to ...
- 427