Questions tagged [bloch-sphere]
A geometrical representation of the pure state space of a two-level quantum mechanical system (qubit), used in quantum mechanics and computing.
114 questions
-1 votes
2 answers
74 views
Quantum Computing Bloch Sphere Convention [closed]
Could somebody please explain why the convention for the Bloch sphere of a qubit has the $|0>$ state pointing up and the $|1>$ pointing down? I understand that the Bloch sphere representation ...
0 votes
1 answer
126 views
Reflecting spin state relative to planes
As we know state of $\frac{1}{2}$spin could be considered on a unit sphere (Bloch sphere). There are famous operators to rotate the state around each axis. What are operators to reflect states ...
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0 votes
1 answer
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Preparing a 2-level system along the $x$-axis of the Bloch sphere
I have a 2-level system (in my case 2 hyperfine levels) which starts in the ground state, $|{g}\rangle$. If I apply a $\pi/2$ pulse, which by definition has $\phi = 0$ as everything else is defined ...
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2 votes
0 answers
97 views
Blue/Red Detuning - AMO Physics
When detuning doesn't equal 0, meaning frequency of light doesn't equal the frequency of the atom oscillating (when dealing with 2 level systems), we see there are light shifts as a result. In the ...
3 votes
1 answer
259 views
What does the nontriviality of the Hopf fibration tell us about the global phases of qubit states on the Bloch sphere?
In this paper, discussing the Hopf fibration, the autors state: Its non trivial character implies that $S_3 \neq S_2 \times S_1$. This non trivial character translates here into the known failure in ...
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5 votes
4 answers
501 views
Is is possible to generate circularly polarized light using a rotating half-wave plate?
Let's assume that I have a laser beam with a frequency $\omega$ that is linearly polarized (say coming out of a laser diode). If I pass it through a half-wave plate (HWP), the light that is ...
- 306
5 votes
1 answer
302 views
Lindblad operators seemingly not working as jump operators
I am currently trying to understand the Lindblad superoperator $$\mathcal{L}[d]\rho = d \rho d^\dagger - (d^\dagger d \rho + \rho d^\dagger d)/2$$ for a simple 2 level system. In the literature i ...
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0 votes
2 answers
162 views
How can the Bloch sphere, built from one complex dimension, specify 2-complex dimensional Pauli spinors?
Two-component spinors can be identified with points on the surface of the Bloch Sphere. The Bloch sphere is constructed from the 1-complex-dimensional complex plane plus the point at infinity. How ...
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1 vote
1 answer
323 views
How is the inner product of two quantum states related to their associated Bloch vectors?
I have a doubt about how two equivalent ways of calculating the inner product between two states seem to not be actually equivalent, as they should. In particular, I'm interested in the case where the ...
8 votes
1 answer
456 views
Can we make a Bloch sphere for Weyl spinors?
If spinors are the "square root" of 3-vectors [$\mathrm{SU}(2)$ double cover of $\mathrm{SO}(3)$], Weyl spinors can be thought of as the "square root" of 4-vectors [$\mathrm{SL}(2,\...
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0 votes
1 answer
392 views
Rotations on the Bloch sphere
I am curious about how different rotations on the Bloch sphere are done in practice. For example, assuming we start in the lower energy state of the $z$-axis (call it $|0\rangle$), a resonant rotation ...
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0 votes
3 answers
494 views
Physical meaning behind the double rotation of spin 1/2 particles [duplicate]
From the Bloch sphere, it is mathematically clear that a $720°$ rotation is necessary to bring a spin $1/2$ particle back to its initial state, as a full rotation changes the sign of the state. ...
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3 votes
5 answers
2k views
How can you determine direction of spin-1/2 states?
How do you determine the direction of the state of a spin-1/2 particle? For instance, given the quantum state $|\psi\rangle=(1,0)$, where does this vector point in space? I would say that it points in ...
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2 votes
1 answer
354 views
Comparison between Jones vectors and spin state vectors
I'm trying to learn about spinors by myself: I've found what it seems to me a very good series of videos on youtube which explains them starting from basic concepts and examples. Now, in this video, ...
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0 votes
1 answer
324 views
Bloch's Theorem and its solutions
I was reading Ali Omar text on solid state course and it said about the fact that electrons in a lattice or in a periodic lattice never scatters or make collisions with the positive ion cores, as the ...
