A research field within general optical physics concerned with light and its material interaction: where light is modelled by full quantum mechanical description.
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906 views
Rigorous justification for rotating wave approximation
Whenever I have encountered the rotating wave approximation, I have seen "the terms that we are neglecting correspond to rapid oscillations in the interaction Hamiltonian, so they will average to 0 in ...
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5answers
2k views
Does a photon interfere only with itself?
I sometimes hear statements like that:
Quantum-mechanically, interference pattern occurs due to quantum interference of wavefunction of a photon. Wavefunction of a single photon only interferes ...
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2answers
824 views
Quantum memories: What are they?
Searching the literature for the term "quantum memory" seems to bring up results from two different communities.
On the one hand there are quantum opticians, who see a quantum memory as something ...
10
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2answers
525 views
Unambiguous distinguishing of quantum states by local measurement
Let's have two orthogonal n-particle quantum states: $|\psi \rangle$ and $|\phi \rangle$. In theory it is always possible to make an unambiguous measurement.
However, things get complicated when one ...
10
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2answers
1k views
Virtual photon description of B and E fields
I continue to find it amazing that something as “bulky” and macroscopic as a static magnetic or electric field is actually a manifestation of virtual photons.
So putting on your QFT spectacles, look ...
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6answers
249 views
optical equivalent of a superconductor
Is there some material state that can propagate light indefinitely without dissipation or absorption, like superconductors are able to trasmit current indefinitely?
If not, then the question is, why ...
9
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4answers
550 views
Nonlinear optics as gauge theory
the widely used approach to nonlinear optics is a Taylor expansion of the dielectric displacement field $\mathbf{D} = \epsilon_0\cdot\mathbf{E} + \mathbf{P}$ in a Fourier representation of the ...
8
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3answers
535 views
Informational capacity of qubits and photons
How much information is contained in one qubit?
A qubit is defined in Wikipedia as $a\left|0\right> +b\left|1\right>$, where a and b are complex numbers subject to $a^2 + b^2 = 1$.
One complex ...
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2answers
197 views
What are some ways to (approximately) symbolically diagonalize Hamiltonian operator?
Specifically the Hamiltonian takes the form of
$$\hat H = \frac{\Delta }{2}{\hat \sigma _z} + {\omega _1}\hat a_1^\dagger {\hat a_1} + {\omega _2}\hat a_2^\dagger {\hat a_2} + {g_1}\left( {{{\hat ...
8
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1answer
255 views
Which qubit states are accessible with linear optics operations?
Given a quantum state of $n$ qubits, and being restricted to linear optics (that is, the output annihilation operators are linear combinations of the input annihilation operators):
Which states are ...
8
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2answers
557 views
Quantum shot-noise and the fluctuation dissipation theorem
Classically, shot noise observed in the signal generated by a laser incident on a photodiode is explained as being due to the quantization of light into photons, giving rise to a Poisson process. In ...
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3answers
627 views
Can we transport energy over infinite distances through vacuum using light?
I know that light (or electromagnetic radiation in general) attenuates in intensity as the square of the distance it travels.
Why does it attenuate?
Are the photons being scattered by the medium ...
7
votes
2answers
182 views
Finding the spectrum of a polynomial of the creation and annihilation operators
Is there a general algorithm to find the spectrum of $S S^\dagger$, where $S$ is a homogenous polynomial (of degree $n$) of the annihilation operators (of $d$ variables)?
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2answers
827 views
How to count photons
How are photons counted?
What is the experimental setup used to count photons from a laser or even a lamp? Of course, in the case of the lamp, I would be able to count only the photons that pass ...
6
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3answers
448 views
How is squeezed light produced?
Ordinary laser light has equal uncertainty in phase and amplitude. When an otherwise perfect laser beam is incident onto a photodetector, the uncertainty in photon number will produce shot noise with ...
6
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1answer
183 views
Can a photon exhibit multiple frequencies?
Can a photon be a superposition of multiple frequency states? Kind of similar to how an electron can be a superposition of multiple spin states.
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3answers
423 views
Computer game with quantum optics / quantum information
Is there a computer game using principles of quantum optics or quantum information?
By game I mean not just a simulation or an interactive course, but something than can be played in an enjoyable ...
6
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1answer
297 views
How many stabilised qubits have been achieved in Quantum Computing?
The latest I read is 3 but that was in Oct. With Lene Hau of Harvard's "frozen light" and with quantum donuts, newer strategies for stabilization are appearing, but the problem of keeping the qubit in ...
6
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3answers
954 views
Photon wave packets from distant stars
A distant star like the sun, thousands of light years away, could be so faint that only one photon might arrive per square meter every few hundred seconds. How can we think about such an arriving ...
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2answers
109 views
Quantum Mechanical Operators in the argument of an exponential
In Quantum Optics and Quantum Mechanics, the time evolution operator
$$U(t,t_i) = \exp\left[\frac{-i}{\hbar}H(t-t_i)\right]$$
is used quite a lot.
Suppose $t_i =0$ for simplicity, and say the ...
5
votes
2answers
56 views
Heuristics for definitions of open and closed quantum dynamics
I've been reading some of the literature on "open quantum systems" and it looks like the following physical interpretations are made:
Reversible dynamics of a closed quantum system are represented ...
5
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2answers
246 views
Reference request: Susskind-Glogower original paper
I'm trying to find Susskind and Glogower's original paper,
L. Susskind and J. Glogower, Quantum mechanical phase and time operator, Physics 1 (1964) 49-61,
where they propose their exponential ...
5
votes
4answers
364 views
Interpretation of Wigner function in optics
I work in the field of synchrotron radiation sources where radiation (often x-rays) is produced from an electron beam going through magnetic fields. The quality of the resulting x-ray beam is ...
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1answer
179 views
Matlab package: graphical calculus for quantum operations (esp. linear optics)
I need a matlab package that will make my life easier. I have quantum circuits with optical beam splitters, polarizing beam splitters and photodetectors. These circuits are getting very complicated ...
5
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1answer
255 views
Why can't fermions be affected by effective gravity in non-linear quantum electrodynamics?
Quantum electrodynamics based upon Euler-Heisenberg or Born-Infeld Lagrangians predict photons
to move according to an effective metric which is dependent on the background electromagnetic
field. In ...
5
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1answer
177 views
What is the “direction” of the transition dipole moment? (Understanding Eq. 9.29, Charge and Energy Transfer 3rd Ed, May & Kuhn)
For a real vector $\mathbf{r}$, the direction is given by: $\hat{\mathbf{n}}=\mathbf{r}/\left|\mathbf{r}\right|$.
The transition dipole moment is a complex vector. How do you define its direction?
...
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2answers
153 views
Does the Casimir effect allow to change the lifetime of a radiating atom?
Is it true that a spontaneously light-emitting atom changes its lifetime if it is put between two parallel plates that are so near that they attract each other through the Casimir effect?
Thus: does ...
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1answer
98 views
What Cat States of light have been experimentally produced?
I'm specifically looking for Schrödinger's Cat states involving superpositions of two, or if it's been done more, coherent states, i.e. monomodal states of the form ...
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2answers
221 views
In optics, how does the vacuum state compare to thermal radiation?
In quantum optics, a perfect absorber of light is said to emit the "vacuum field". In practice, any beam dump will be at finite temperature, so it will emit blackbody radiation. How do these fields ...
3
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2answers
449 views
Alkali atom - photon interaction in zero magnetic field
An alkali atom has a single outer electron that interacts with incoming photons of the right wavelength (for alkalies it's in the visible & IR range). If there is an external magnetic field, the ...
3
votes
2answers
301 views
The most price-efficient experimental setup involving SPDC, single-photon counting etc
I would like a suggestion on a price-efficient way of experimenting with spontaneous down-conversion and single-photon counting. The simple dual-slit experiment could be one part of an application ...
3
votes
1answer
87 views
Use and understanding of higher-order correlation functions
The correlation function g1 is pretty easy to understand and the relation to young's double slit experiment is also clear to me.
In every quantum optics book I read so far correlation functions ...
3
votes
1answer
241 views
What is Electromagnetic Induced Transparency?
Please can anyone explain the concepts of electromagnetic induced transparency? I am having problem with the technicality of the explanation on wikipedia. Please I am an engineer with a physics ...
3
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1answer
45 views
What is a $TEM_{900}$ cavity radiation mode?
I am reading a paper by Serge Haroche stating the cavity they use sustains a Gaussian mode of the e.m. field called $TEM_{900}$. I understand what Gaussian means. I found this explaining what TEM ...
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2answers
68 views
limits on a gauss box of light
Consider a wall defined by $w(x,y,z) = \Theta(x-L)$ which is nonzero in the infinite semi-space of $x \ge L$, as well as a coherent planar standing EM wave travelling in the $z$ plane given by its ...
3
votes
1answer
131 views
Can spatial coherence be maintained in fiber optic cables over time?
I am doing research with a double slit experiment, using a beam splitter and 2 lengths of fiber optic cable, whose ends brought close together form the effective double slit. I notice that the ...
3
votes
1answer
172 views
Linearizing Quantum Operators
I was reading an article on harmonic generation and came across the following way of decomposing the photon field operator.
$$ \hat{A}={\langle}\hat{A}{\rangle}I+ \Delta\hat{a}$$
The right hand side ...
3
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0answers
70 views
Dyson Series Second Order Term Importance vs. Time
Given a time ordered Dyson series expansion of
$$H_I=e^{-\frac{i}{\hbar}\sigma_3t}V_0\sin(\omega t)\sigma_1e^{\frac{i}{\hbar}\sigma_3t}$$
$${\cal ...
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0answers
49 views
uncertainty deviations for vacuum astronomy
Since i've done this question, i've been trying to improve and make more precise the statements regarding cosmic squeezed states and how different uncertainties affect the vacuum energy, but as it ...
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0answers
185 views
back-action noise
I recently have come across with two key-concepts: shot noise and back-action noise in quantum optics. This is very important for me to know: first, are shot noise and back-action the same? Please let ...
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3answers
230 views
Quantization of arbitrary electromagnetic field
Quantum optics all discuss the quantization of free electromagnetic radiation. The result is well established.
But what about an arbitrary electromagnetic field? For example, the simplest case, ...
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2answers
198 views
Is there a simple approximation to calculate the index of refraction of water?
A very rough approximation from first principles, from the elementary charge and hbar, would suffice. But is there such an approximation at all?
(Alternatively, if water is too difficult: is there ...
2
votes
1answer
432 views
What are the polarization states of the photons in a polarized and unpolarized light?
The photons are completely polarized, i.e their polarization states can be expressed as $a|R\rangle+b|L\rangle$, where $|R\rangle$ and $|L\rangle$ are two helicity eigenstates of the photon. For ...
2
votes
1answer
285 views
What IS reflection?
How does quantum electrodynamics actually explain HOW reflection occurs on a microscopic scale?
Note that Feynman's QED lecture series/book is not sufficient, as he only assumes that light DOES ...
2
votes
2answers
410 views
Scalar product of coherent states
We suppose for semplicity to have a 1D oscillator, but this is a question abaout the general CCR algebra in oscillators, second quantization, quantum field theory etc.
We know coherent states are a ...
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2answers
257 views
Why does optical pumping of Rubidium require presence of magnetic field?
The optical pumping experiment of Rubidium requires the presence of magnetic field, but I don't understand why.
The basic principle of pumping is that the selection rule forbids transition from ...
2
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1answer
38 views
State emitting from an extended thermal source
This calculation is for a double slit experiment setup which is experiencing a far field radiation from an extended monochromatic thermal source. I assume the source is 1-D and it's length is $b$. ...
2
votes
1answer
161 views
Validity of Einstein Coefficient Derivations
Consider a two-level energy gap with electronic energy states $E_1$ & $E_2$ and associated population densities $n_1$ and $n_2$ with $E_2>E_1$.
In the derivation of the Einstein coefficients ...
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0answers
38 views
What is three-photon interference?
Whilst reading this paper on a quantum processor that performs a type of matrix computation, I came across the concept of 'three-photon interference'. A quick Google search shows that this process is ...
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0answers
118 views
Do Bell inequality violations appear instantly when the source is turned on, or do they increase over time?
This experimental Question is a result of reading a particular article on Bell violations. I addressed the e-mail below to the corresponding authors —because who knows, they might reply— but it is not ...
