Recent content by gre_abandon
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Undergrad Spectroscopy of Rb - crossover peaks more intense?
I know how saturation spectroscopy works but I am not sure which peaks you are referring by crossover peaks.- gre_abandon
- Post #3
- Forum: Atomic and Condensed Matter
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Undergrad Are Quantum Dots Spherical? Identifying Size of Colloidal Solution
Smear the solution onto a glass substrate and take an image under scanning electron microscope.- gre_abandon
- Post #2
- Forum: Atomic and Condensed Matter
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Undergrad Interpret Heisenberg Picture: Operators & States
In Schrödinger's picture the state ket undergoes unitary time evolution dictated by Schrödinger equation. The exepctation value of a operator A is $$ \langle \psi | U A U^\dagger | \psi \rangle $$. In Heissenberg's picture the operator varies with time and is given by $$ A' = U A U^\dagger $$...- gre_abandon
- Post #2
- Forum: Quantum Physics
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High School How is the strength of a magnetic field measured?
You can measure magnetic field through Hall effect. Suppose you have a piece of conductor of square shape with the four edges labeled A,B,C,D. If you apply a voltage across A,C there be a current. Now if you place this piece of material into magnetic field which will cause the charges in the...- gre_abandon
- Post #3
- Forum: Electromagnetism
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Graduate Can spin be modeled as a spinning vector until "measured" ?
Yes but SU(2) is not equivalent with SO(3). In the representation of Bloch vector the global phase is missing,- gre_abandon
- Post #14
- Forum: Quantum Physics
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Graduate Can spin be modeled as a spinning vector until "measured" ?
No, the state of a spin 1/2 particle is a vector in 2d complex vector space rather than a vector in 3d real space.- gre_abandon
- Post #9
- Forum: Quantum Physics
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Graduate Can spin be modeled as a spinning vector until "measured" ?
You know for a spin 1/2 particle its state is represented by a vector in C^2 and measurement is modeled as a projection. I am not sure what you are really asking but I think reading a book on quantum computation will help clarify your question. Generally any book on quantum computation will talk...- gre_abandon
- Post #7
- Forum: Quantum Physics
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Zettili QM Problem on Trace of an Operator
I see your point. I treated the number as a one-by-one matrix because I am not sure whether it is really a scalar times a identity matrix (not clear from the statement of the problem). Except this point, everything is fine.- gre_abandon
- Post #5
- Forum: Advanced Physics Homework Help
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Zettili QM Problem on Trace of an Operator
Simply speaking $$ trace(\langle \Psi | \Phi \rangle) = \langle \Psi | \Phi \rangle = \sum_n \langle \Psi | n\rangle \langle n | \Phi \rangle = trace(|\Psi\rangle\langle\Phi|)$$- gre_abandon
- Post #2
- Forum: Advanced Physics Homework Help
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Graduate Demon algorithm for microcanonical ensemble
On wikipedia and my textbook the only constraint on the demon is that the demon should hold non-negative energy while in my opinion there also should be an upper bound as well for demon energy. And the energy fluctuation of the system is between E_demon_min and E_demon_max. If the energy...- gre_abandon
- Post #3
- Forum: Atomic and Condensed Matter
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Graduate Demon algorithm for microcanonical ensemble
I simulated a microcanonical ensemble of 10 ideal gas particles in one dimension and yielded the expected normal distribution of velocities. However, I still did not get how the algorithm works. The demon has non-negative energy content and the demon together with the system constitutes a closed...- gre_abandon
- Thread
- Algorithm Demon Ensemble Microcanonical ensemble Sampling
- Replies: 3
- Forum: Atomic and Condensed Matter
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Graduate Unitary evolution and environment
Yes, these theorems both only apply to closed system. Speaking of open quantum system, we usually consider the system we are interested in and the surroundings together as a whole. The time evolution of the whole system, which is unitary, can be written as $$ \mathcal{H^{sys}}\otimes...- gre_abandon
- Post #14
- Forum: Quantum Physics
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Graduate Unitary evolution and environment
The system we dealt with in quantum mechanics is usually a closed system. Sometimes we also study open quantum systems but still the system together with the surroundings constitutes a larger CLOSED system. And Schrödinger equation only applies to a closed system. You are correct on this point...- gre_abandon
- Post #3
- Forum: Quantum Physics