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seen Jul 7 '13 at 22:47

Jul
6
awarded  Yearling
May
19
comment Can we measure “wavefunction” of quantum particles?
The no-cloning theorem prohibits the copying of an unknown quantum state. Making multiple copies of the same state is required for many experimental systems. If I want a spin-up particle, and I build a system that always generates spin-up particles, then I have made multiple copies of the same state.
Mar
16
comment Is energy always proportional to frequency?
I agree that X is much easier to measure than Y because, for instance, it has a lower mass (X=atom, Y=cat). But you should be careful about saying that something "cannot be measured in principle", which means that it is impossible to elucidate the desired quantity from the experiment on theoretical grounds. Such a statement requires a qualitative, not quantitative, difference. It was long thought that atomic and molecular matter-wave interference would be impossible. I agree that we shouldn't expect a cat-ter wave interferometer any time soon.
Mar
10
answered How is a Rydberg Blockade Radius defined?
Mar
5
answered Is energy always proportional to frequency?
Mar
5
comment Is energy always proportional to frequency?
In other words, a cat does have a fantastically large frequency.
Mar
5
answered Do photons actually generate a slight kinetic force?
Feb
11
awarded  Nice Answer
Feb
10
comment What would happen if Large Hadron Collider would collide electrons?
"Electrons (as far as we know) don't break apart (and not at these low energies)": I'm scared to imaging what "high" energies are! E.g.: slac.stanford.edu/cgi-wrap/getdoc/slac-pub-7436.pdf
Feb
10
revised What would happen if Large Hadron Collider would collide electrons?
added 40 characters in body
Feb
10
answered What would happen if Large Hadron Collider would collide electrons?
Feb
10
comment Time-reversal symmery and topological insulators
@annushka, Does this answer your question? If so, please mark it. =)
Feb
10
comment Why Does Light Not Become Polarized In A Magnetic and/or Electric Field?
@John, if we're discussing the Faraday effect, it's completely incorrect to say that there's no interaction. The whole point is that you can use materials to couple DC magnetic fields and optical fields. If you restrict yourself to a vacuum, you miss most of the interesting phenomena in electromagnetism and I'd be out of a job.
Feb
10
comment Is a hard drive heavier when it is full?
@OBrien, I mean "much greater than". The energy (or energy barrier) needs to be much greater than the thermal energy to prevent temperature-induced changes in the bits. Since we're thinking in terms of an exponential process, we can satisfy $E>>kT$ with $6 >>1$.
Feb
5
comment Time-reversal symmery and topological insulators
It is an interesting topic, and one that makes the "feel" of statistical mechanics very different that other areas of physics. I think many physicists would disagree with the following statement, but I think of the difference between microscopic and macroscopic reversibility as an example of an emergent phenomena.
Feb
5
revised Why Does Light Not Become Polarized In A Magnetic and/or Electric Field?
added 701 characters in body
Feb
5
comment Why Does Light Not Become Polarized In A Magnetic and/or Electric Field?
The Faraday effect in particular is an off-resonant excitation, hence it's only dispersive. Dichroism is a related effect in which the light polarization it changed or rotated through absorption -- this is what I mean by "relaxation". Incidentally, dichroism is an excellent example where the light becomes aligned with the magnetic field: one ciruclar polarization is absorbed and the other one remains. "Information" about the original state is lost. To distinguish these effects, I'm referring to the way that light can be dissipitated, absorbed, or incoherently scattered.
Feb
4
answered Why Does Light Not Become Polarized In A Magnetic and/or Electric Field?
Feb
3
answered Superconducting Wavefunction Phase (Feynman Lectures)
Feb
3
answered Time-reversal symmery and topological insulators