A research field within general optical physics concerned with light and its material interaction: where light is modelled by full quantum mechanical description.

learn more… | top users | synonyms

4
votes
1answer
193 views

Is $\hat{\phi}^{-}\hat{\phi}^{+}$ a well defined observable in the Quantum field theory of a scalar field?

Is the Hermitian operator $\hat{\mathcal{O}}=\hat{\phi}^{-}(x)\hat{\phi}^{+}(x)$, where $\hat{\phi}^{+}(x)$ is positive frequency part of the scalar field operator, a well defined observable in QFT? ...
1
vote
0answers
142 views

How do I write the Hamiltonian for a 3-level system?

I came across following types of three-level systems like V-system, Λ-system and 2-photon absorption It seems that their Hamiltonians can be written intuitively by checking out the coupled levels ...
5
votes
1answer
87 views

Why are “quadratures” called this way?

In quantum optics (and hence also cv quantum information), given the annihilation and creation operators of the electromagnetic fields $a$ and $a^{\dagger}$, the "position" and "momentum" operators ...
2
votes
1answer
80 views

Is boson sampling a problem in 'continuous variable' quantum information?

When people generally speak of quantum information in the context of continuous variables, what is generally meant is that observables, like position/momentum or the field quadratures of quantum ...
3
votes
1answer
141 views

Is there a way to increase the speed of light itself?

When light enters materials it slows down due to its refractive index (due to absorbing and re-emission of photons). But, is there a way to increase the speed of light itself? Can there be some ...
2
votes
0answers
39 views

Determine laser cavity modal content from beating / interference?

I'm trying to better understand the modal content and dynamics of laser cavities. I'm specifically interested in mode-locking, although this question is pretty general and applies to CW lasers too. I ...
2
votes
1answer
133 views

Physical significance of effective wave function

In Yanhua Shih's book on quantum optics, the coherence functions are expressed in terms of effective wave function. Here are the expressions for single photon wave packets. To derive the coherence ...
3
votes
1answer
48 views

Measuring spin direction by means of coherent light?

Let us assume that we have the ferromagnetic surface where all atoms have the same direction of spins. And we can interact with the single atom in such lattice. Is it possible to measure the ...
6
votes
4answers
318 views

Are coherent states of light 'classical' or 'quantum'?

Coherent states of light, defined as $$|\alpha\rangle=e^{-\frac{|\alpha|^2}{2}}\sum_{n=0}^\infty \frac{\alpha^n}{n!}|n\rangle$$ for a given complex number $\alpha$ and where $|n\rangle$ is a Fock ...
3
votes
1answer
299 views

Back-action noise vs shot noise

I have recently come across two key concepts in quantum optics: shot noise and back-action noise. This is very important for me to know: first, are shot noise and back-action noise the same? Please ...
1
vote
3answers
200 views

What limits laser pulse duration to single cycle?

Why pulses shorter than single cycle cannot propagate in free space ? Is there fundamental reason or it is engineering ? Is it possible for a laser pulse to have bandwidth that can support half cycle ...
7
votes
2answers
582 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? ...
0
votes
0answers
53 views

normal ordering from anti normal ordering of creation and anhilation operators

I am working on entanglement of systems in beam splitters. I constantly come across equations of creation and annihilation operator (ladder operators) in anti normal ordering. I want those equations ...
2
votes
3answers
370 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 ...
1
vote
0answers
67 views

Casimir force between plate and sphere

In our quantum optics lecture we derived the formula for the Casimir force between two plates (or at least the force per unit surface, since for two infinite plates we would have an infinite force). ...
4
votes
3answers
437 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
votes
0answers
93 views

How do we show that photons generated by a constant electric current are distributed according to a Poisson distribution?

I saw the answer sometimes ago in a book "Quantum Electronics" or similar title. I don't remember the author since I lost the book. The book sets ( I believe so ) a constant electric current $I$ in a ...
0
votes
2answers
493 views

What is optical confinement?

What is optical confinement? What is it intuitively? How does this 'optical confinement' affect the performance of a laser?
3
votes
1answer
81 views

Quantum Cascade Laser [closed]

I want to learn about quantum cascade laser in a six month time. Can anyone please suggest me any reading materials or video lectures. I have background in calculus and linear algebra. I am learning ...
10
votes
3answers
509 views

What causes atoms to have their specific colors?

I understand that light (color) is part of the electromagnetic spectrum, and that it depends on what wavelengths are reflected/absorbed. Though what property of an individual atom gives it its color? ...
0
votes
1answer
92 views

Time duration for pulse of single electron viewed as a wave

Electron as an example has a de Broglie wavelength and could diffract. If it has a single wavelength the time extent of the particle's pulse duration would be infinite .. If it carries a broadband ...
4
votes
4answers
248 views

Why do lasers require mirror at the ends?

Laser uses mirrors to reflect photons in order to stimulate atoms to emit photons, but why this is so?. I mean, why does a photon stimulate atoms to produce more photons? If a photon made an atom to ...
1
vote
3answers
137 views

Can one build a laser using spontaneous emission?

We use stimulated emission and not spontaneous emission to produce lasers. Why is this? Can't we produce lasers by the spontaneous emission method?
5
votes
1answer
158 views

Are Rabi oscillations a pure quantum process?

Rabi oscillations are commonly known as the oscillations in time of the occupation probability of a quantum two-level system under the action of a coupling interaction between the two-levels. ...
9
votes
2answers
645 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 ...
2
votes
1answer
103 views

Energy conservation in plane wave

In plane wave the H and E are in phase. So the pointing vector disappears regularly every pi. How is energy conservation validated ? Is it through the uncertainty of energy and time ?
6
votes
3answers
305 views

Commutator with a square root

How to find the commutator $[a, \sqrt{a^\dagger a}]$? Here $a$ is a usual bosonic annihilation operator, and $[a, a^\dagger] = 1$. The first thing I tried is $$ [x,A] = [x, \sqrt{A}]\sqrt{A} + ...
1
vote
0answers
125 views

How to calculate the helicity of polarized light?

At first, I used to think that only circular polarized light has non-zero helicity, linear polarized light has zero helicity, because the linear polarization can be seperated as the superposition of ...
1
vote
0answers
71 views

Arbitrarily using Sin and Cos as eigenfunctions of a Hamiltonian? [closed]

In the context of quantum optics, the rotating wave Hamiltonian can be written: $\hbar\begin{pmatrix} -\Delta & \Omega/2\\ \Omega/2 & 0 \end{pmatrix}$ The eigenvalues can then be calculated ...
14
votes
7answers
459 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 transmit current indefinitely? If not, then the question is, why ...
4
votes
2answers
230 views

Polarisation of Light and Atomic Excitation

How does an atomic transition between ground and excited states depend upon the direction of polarisation of incident light?
2
votes
1answer
222 views

Diffraction Gratings

Is it possible to use the sawtooth shape diffraction grating instead of rectangular grating if yes then which parameters will affect at the output ? Secondly, what is special in blaze grating ...
1
vote
2answers
66 views

Ultrafast Lasers

The main idea of femtosecond or Attosecond lasers is to achive the high energy or do we have any other parameters achieved by ultra-fast lasers ?
1
vote
1answer
206 views

Derivation for 7.14 in Atomic Physics by Foot

I was going thru Ch7 of Foot and trying to fill in the gaps. However I got stuck on (7.14). So Foot was working with a two level system with a small perturbation in the Hamiltonian resulted from an ...
2
votes
0answers
63 views

Adiabatic theorem in the regime of quantum optics

I am wondering whether there is a version of adiabatic theorem in the regime of quantum optics. My understanding of quantum optics involves with the interaction between photon and atom. This ...
3
votes
0answers
169 views

Pockels effect/Kerr effect

In Pockels electro-optic effect, change in Electric field produces change in refractive index/ birefringence. Moreover this effect becomes electric field squared in the case of Kerr effect. If we ...
3
votes
1answer
53 views

Silicon Laser and Laser mirrors

If I will place Silicon as the active medium to create a Silicon Laser. Why I cannot achieve Lasing ? secondly, why do we always consider Laser mirrors in an standing position along the optical axis ...
26
votes
6answers
1k views

Are quantum effects significant in lens design?

Over on Photography, a question was asked as to why (camera) lenses are always cylindrical. Paraphrasing slightly, one of the answers and follow-up comments asserted that quantum effects are ...
6
votes
1answer
2k views

Why does the refractive index depend on wavelength? [duplicate]

Why do different wavelength get impeded more or less when in different materials? Moving with the same speed, but a longer physical distance would imply that the fields oscillate less times in the ...
1
vote
1answer
244 views

Formula for Rabi frequency

I have calculated the dipole transition elements of electronic states $\langle a|D_1^m|b \rangle$ following the book of Cohen-Tannoudji (Complement $E_X$) and tried then to calculate from that the ...
4
votes
1answer
188 views

double slit experiment with two opposite quarter waveplates

Consider the usual double slit experiment involving laser and a double slit and a screen. Now place in front of the left slit a quarter waveplate (let's call it QWP1) that changes a certain linear ...
5
votes
1answer
213 views

How do individual photons make up an EM wave?

I'm trying to understand the connection between the wave model and the particle model for light. It's understood that the energy of a photon is given by E=hf, but from my understanding of fourier ...
1
vote
1answer
132 views

Excitation probability for 2 Level Atom

I currently started learning Quantum Optics using the book "Atom Physics" of Christopher Foot. Currently I am working through Chapter 7 and a question occured concerning the intuitively physical ...
6
votes
3answers
1k 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 ...
-1
votes
1answer
192 views

Eigenvalue of Optical waveguide [closed]

Consider you have a slab waveguide having n1=3.5 and n2=1.45. The value of critical angel is 24.5 degree approx. Similarly effective refractive index will be in between 1.45 and 3.5. How can we find ...
2
votes
1answer
127 views

when is coherent state a good approximation?

Consider a Hamiltonian of a system coupled to a bath. Let $H_{sys}=\nu c^{\dagger}c$ ; $H_{env}=\Sigma \omega_r a^{\dagger}a$ ; $H_{int}=\Sigma (g_r ac^{\dagger}+g_r^* ca^{\dagger})$. Then it is ...
12
votes
2answers
2k 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 ...
0
votes
1answer
113 views

How to estimate number of Laue Spot

Why are "Laue Spots" spots instead of rings? Or is there an effective way to estimate the number of Laue spots? I can't find any formulas or theory concerning this issue. Thanks for your attention!
2
votes
1answer
216 views

Types of photon qubit encoding

How many types of qubit encoding on photons exist nowadays? I know only two: Encoding on polarization: $$ \lvert \Psi \rangle = \alpha \lvert H \rangle + \beta \lvert V \rangle $$ $$ \lvert H ...
3
votes
1answer
66 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 ...