6,283 reputation
1132
bio website www3.imperial.ac.uk/…
location United Kingdom
age
visits member for 2 years, 7 months
seen 10 hours ago

Currently doing a PhD in Controlled Quantum Dynamics at Imperial College and the University of Oxford.


10h
revised Example of closed quantum system and open quantum system?
deleted 1 character in body
10h
answered Example of closed quantum system and open quantum system?
May
25
awarded  Pundit
May
24
comment Independent boson model with an arbitrary finite-dimensional impurity
Excellent answer, thanks Emilio. I guess the unboundedness of the Hamiltonian could be remedied by a sufficiently strong non-linearity in the impurity Hamiltonian. Regarding my reasons for believing the bosonic case fails, they can be summarised succinctly as "laziness".
May
24
accepted Independent boson model with an arbitrary finite-dimensional impurity
May
19
comment Is it possible to write the fermionic quantum harmonic oscillator using $P$ and $X$?
The Majorana fermion operators $x \sim (f+f^\dagger)/\sqrt{2}$ and $p \sim i(f-f^\dagger)/\sqrt{2}$ do not satisfy your requirement $\{x,x\} = 0$ etc. Actually $\{x,x\} = 1$. So it is not the case that linear combinations of fermion operators are always nilpotent.
May
19
comment Is it possible to write the fermionic quantum harmonic oscillator using $P$ and $X$?
You can typeset braces in MathJax using the command \{
May
18
comment Naive quantization of Schrödinger field
In non-relativistic quantum mechanics what you have described is called "second quantisation". (Note this has nothing to do with quantisation, it's an example of disastrously misleading terminology that has stuck for historical reasons.) Here one can write down a "Schroedinger" field operator which has a mode expansion in terms of creation and annihilation operators, each of which creates a single-particle state that solves the 1-particle Schroedinger equation for a given potential. This is a convenient formal technique for computations in non-relativistic many-body physics (i.e. QFT).
May
18
comment Why doesn’t the Sagnac Effect disprove relativity?
If observer B is rotating then they are accelerating, and therefore not in an inertial frame. Thus special relativity does not require them to measure the speed of light tangential to the Sagnac loop to be $c$. This point is explained briefly in the Wiki page.
May
18
comment Measuring electron spin with multiple Stern–Gerlach apparatus at an angle
Presumably here you mean the relative angles of the Stern-Gerlach apparatus? At the moment it seems like you are talking about the directions in which the spins move in space. The position or velocity of the spins has no effect on the correlations.
May
18
reviewed Approve Measuring electron spin with multiple Stern–Gerlach apparatus at an angle
May
16
comment Is molecular vibration just phonon modes for a single molecule?
@EmilioPisanty No idea about literature, but this terminology was frequently bandied about in discussions about electron transport in biomolecules, and I believe also in descriptions of molecular junctions etc. Doubt it's very common in AMO physics.
May
15
comment Is molecular vibration just phonon modes for a single molecule?
I think the simple answer is yes. Indeed such vibrational modes are often called phonons.
May
15
comment Why the underside of an object isn't a different colour after light reflects off a different coloured surface
I think the important point here is that the light reflected from a "green" object is not actually monochromatic. It also contains some blue light, but you perceive it to be green because these wavelengths dominate the blue. This means that effectively the other side of the blue plate would appear to be a darker blue, since much less light within the range of wavelengths that the plate reflects would be incident on it from the green background. This is true assuming there is no white light leaking in from elsewhere.
May
15
comment When can I swap around the order of operators?
@PPG So do you understand now why there is no "swapping of operator order"? $p$ is not an operator.
May
15
comment When can I swap around the order of operators?
Method 1 is incorrect anyway. On the third line, the $\hat{p}$ should just be $p$, i.e. the eigenvalue of the operator $\hat{p}$ corresponding to the eigenvector $\lvert p\rangle$. However Method 2 is doubly incorrect, since you need to integrate over all $p$ to use the resolution of identity $1 = \int\mathrm{d}p\,\lvert p \rangle\langle p \rvert$.
May
15
revised Evolution operator in driven harmonic oscillator
added 2 characters in body
May
15
answered Evolution operator in driven harmonic oscillator
May
15
comment Evolution operator in driven harmonic oscillator
I don't understand the downvote here, this is a good conceptual question which obviously satisfies the homework policy.
May
14
comment Is the dimension “number of particles” a fundamental, or derived dimension (based on mass), or does it depend on the context, or is it dimensionless?
@user89 Recommended reading.