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1d
comment Limits on the information obtained through optical measurements
$S1$ and $S2$ are as such different lasers so in practice, they can of course be distinguished, e.g., their central wavelengths may differ by a few kHz. I am trying to ask if the information obtained through measuring them could prove sufficient enough to render them indistinguishable with the proposed gedankenexpt. And if so, is this indistinguishability just classical in nature? Or does it exist on the quantum level too?
1d
revised Limits on the information obtained through optical measurements
revised the central question
1d
comment What can change a photon's frequency?
@ConstantineBlack: All implementations of QFC that I am aware of have been realized as nonlinear processes which require special materials and intense optical pulses. Light-matter interactions of these kind can almost never occur in nature by themselves, so yes, it's pretty much a lab phenomenon.
2d
comment What can change a photon's frequency?
The process of quantum frequency conversion can, at least in principle, simply change the frequency of a single photon while preserving its quantum properties.
2d
asked Limits on the information obtained through optical measurements
Apr
22
answered Polarized Filtering Frequency Shift?
Feb
22
asked Question about electron-hole pair generation in depletion layer for a p-n junction photodiode
Feb
11
comment How would a quantum computer receive input from a classical computer?
Insert a grad student between the classical computer and the quantum computer.
Feb
10
comment How are the field operator and quantum state after a beam splitter and a polarizing beam splitter individually?
For a non-ideal PBS, the situation would of course be more complicated. Nonetheless, my feeling is: if you can properly model the action on a single photon with arbitrary polarization, then the action on an arbitrary state could also be evaluated (should be a few lines of code).
Feb
10
comment How are the field operator and quantum state after a beam splitter and a polarizing beam splitter individually?
It shouldn't be a problem for an ideal PBS. The basic transformation would be as follows: $|m^a_H, n^a_V ; p^b_H, q^b_V \rangle \rightarrow |p^c_H, n^c_V ; m^d_H, q^d_V \rangle$, with $m, n, p, q$ denoting arbitrary photon numbers, the superscripts [subscripts] denoting the spatial [polarization] modes. Since you can represent any state in the Fock basis, the above transformation for some multiphoton state containing both polarizations can also be accordingly evaluated.
Feb
8
revised How are the field operator and quantum state after a beam splitter and a polarizing beam splitter individually?
Added figure and reference.
Feb
8
comment How are the field operator and quantum state after a beam splitter and a polarizing beam splitter individually?
@LuZhang : I've updated the answer with a figure and a reference. Hope that helps!
Feb
8
revised How are the field operator and quantum state after a beam splitter and a polarizing beam splitter individually?
Added figure and reference.
Feb
5
comment How are the field operator and quantum state after a beam splitter and a polarizing beam splitter individually?
@LuZhang: I wrote an answer. Let me know if that clarifies your doubts.
Feb
5
answered How are the field operator and quantum state after a beam splitter and a polarizing beam splitter individually?
Feb
5
comment How are the field operator and quantum state after a beam splitter and a polarizing beam splitter individually?
You don't need any prefactors for a polarizing beam splitter (PBS), i.e. $\hat{a}_{\rm out1} = \hat{a}_{\rm H}$ and $\hat{a}_{\rm out2} = \hat{a}_{\rm V}$. An ideal PBS will always transmit [reflect] all the horizontally [vertically] polarized photons.
Feb
4
comment Query about the proof why non-orthogonal states cannot be reliably distinguished
Let $A$ be a positive operator s.t. $\sqrt{A} |\psi \rangle = 0$. If the eigenvalues of $A$ are $\lambda_0$ and $\lambda_1$ and $|\psi \rangle = \alpha |0 \rangle + \beta |1 \rangle$ for arbitrary $\alpha$ and $\beta$, then the equation $\sqrt{\lambda_0} \alpha + \sqrt{\lambda_1} \beta = 0$ need not imply $\lambda_0 \alpha + \lambda_1 \beta = 0$, right?
Feb
4
comment Query about the proof why non-orthogonal states cannot be reliably distinguished
@Phoenix87 : I am not so sure if $\sqrt{E_2} |\psi_1 \rangle = 0$ also necessarily implies $E_2 |\psi_1 \rangle = 0$.
Feb
4
comment Query about the proof why non-orthogonal states cannot be reliably distinguished
@NorbertSchuch And this works only because $E_1$ and $E_2$ have a spectral decomposition because otherwise the $\sqrt{ }$ operation cannot be defined, right?
Feb
4
comment Why breakdown voltage decreases with increasing FWHM of an asperity?
FWHM (which presumably is full width at half maximum) of what exactly?