Questions tagged [quantum-optics]

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

Filter by
Sorted by
Tagged with
0
votes
0answers
17 views

Quantum noise in quantum optical coherence tomography

I use the field operator to calculate the coincidence count rate of quantum optical coherence tomography, and the result is related to the time the photons arrive at the detectors. The result is ...
0
votes
0answers
23 views

A question on the beam splitter unitary matrix

In my notes on quantum optics I have that a beam splitter's unitary matrix may be written as: $U(z)=\exp(za_1^{\dagger}a_2-z^*a_1a_2^{\dagger})$. So $$U(z)^{\dagger}a_1U(z)=\cos(|z|)a_1-e^{i\arg(z)}\...
0
votes
1answer
19 views

How does one apply multiple beamsplitters to a covariance matrix in the covariance matrix (2nd moments) formalism?

I would like to propagate a two-mode squeezed vacuum state through a collection of beamsplitters. I'd like to represent this in the second moments, that is, the covariance formalism such as used in ...
8
votes
2answers
152 views
+50

Why is laser light described by a coherent state?

This is a follow-up to this recent answer by Wouter to this related question from 2015, and a comment by Emilio Pisanty underneath. I have read the papers by Mølmer, Bartlett et al., Wiseman, and ...
0
votes
0answers
19 views

Derive master equation if one Lindblad term is already given

I have a following question: is it possible to derive master equation with Open Quantum systems approach if one Lindblad term is already given? For example, assume we have Liouville equation given ...
-1
votes
0answers
60 views

Parity of a Displaced Cat State [closed]

I am looking at the parity of a displaced cat state, where even and odd parity cat states are defined as $$ |\pm \rangle = \mathcal{N}_\pm \left(|\alpha\rangle + |-\alpha\rangle \right) $$ where $|\...
0
votes
0answers
37 views

Density matrix after quantum jumps

So, when in the Monte Carlo wavefunction algorithm we have that: New state after the jump (if occurs): $$ |ψ(\tau_1)⟩=JS(\tau_1)|ψ(0⟩ $$ If there is no jump $$ |ψ(t, t\in [0,\tau_1])⟩=S(t)|ψ(0)⟩ $$ ...
1
vote
0answers
22 views

Derivation of Correlation function in Open Quantum Systems and Master Equation

I have a question and I have searched a long time about it without any success. It is about how to include convolution broadening incorrelation functions of bath operators, when using Open Quantum ...
0
votes
0answers
13 views

Steady State Solution atom light interaction

I am trying to solve a problem about a differential equation which describes the population of states in a atom-light interaction system. The differential equations are given by: $$i\hbar\dot{c}_g(t)=\...
0
votes
1answer
60 views

How to distinguish between no state and the state with zero photon?

This question comes from my consideration of the superposition of coherent states such as $(|\alpha\rangle+|0\rangle)/\sqrt{N}$. I know the annihilation operator has $\hat{a}|\alpha\rangle=\alpha|\...
0
votes
2answers
37 views

In cavity quantum electrodynamics why is $\langle \hat{a} \rangle$ called the cavity amplitude?

What is the physical meaning behind $\langle \hat{a} \rangle$ (where $\hat{a}$ is the annhilation operator)? I was thinking that it represents $\sqrt{n}$ (where $n$ is the number of photons in the ...
2
votes
0answers
46 views

Action of quantum channel on the state $|\alpha_x\rangle \langle \alpha_y|$

Suppose we have a coherent state with amplitude $\alpha_x$ and density matrix $\rho_x := |\alpha_x\rangle \langle \alpha_x |$. This state is sent through a quantum channel. We do not have a concrete ...
1
vote
0answers
42 views

Continuous Valued POVMs

I'm thinking about the mathematical details of continuous variable QM, namely the infinite $|x\rangle$ and $|p\rangle$ bases. Is it possible (and should we) think of these bases and their measurements ...
0
votes
1answer
35 views

What software / methods to learn for nanophotonics (a branch of photonics) applications?

I'm new to nanophotonics and been looking for some software and methods (Design, modelling, simulation .etc) used in this scientific field. I'll be grateful to know some.
2
votes
1answer
62 views

Purcell enhancement at an angle: Direction of charge oscillation

It is well-known that a hydrogen atom in free space prepared in an excited state, for example $\left| 2p_y \right\rangle$, will over time decay into the ground state $\left| 1s \right\rangle$. If not ...
0
votes
1answer
37 views

Error associated with bins in a histogram

I have recently performed a laboratory experiment using an Hanbury Brown and Twiss setup to measure the g^(2) correlation function (intensity correlation function) of different sources. The apparatus ...
0
votes
1answer
74 views

Solving linear Lindblad equations in the Heisenberg picture?

I'm interested in solving the explicit time dependence of operators in a simple open system described by a Lindblad equation. The concrete example I'm interested in is a harmonic oscillator with the ...
2
votes
0answers
72 views

How does a broadband dielectric Mirror work?

It is widely known that dielectric mirrors work with several layers of at least two materials which differ in refractive index that are layered, such that partially reflected waves interfere ...
3
votes
1answer
175 views

How is Electromagnetically-Induced Transparency a result of “destructive quantum interference between two pathways”?

It has been described that Electromagnetically-Induced Transparency (EIT) is a result of "destructive quantum interference between two pathways." To quote from this source: In these simple ...
0
votes
0answers
17 views

Symplectic Matrix for the Polarizing Beamsplitter Gaussian Unitary Transformation

I would like to use the symplectic matrix for the polarizing beamsplitter's gaussian unitary transformation on the covariance matrix of the two-mode squeezed vacuum state. I have the appropriate ...
3
votes
1answer
47 views

What causes the collective emission in Dicke Model?

Dicke model is a collection of two level atoms prepared in the excited state, when the wavelength of the light absorbed or emitted is very large compared to the distance between the atoms, the rate at ...
1
vote
1answer
54 views

Bogoliubov transformation in quantum optics

I was trying to prove that linear optical component are those whose Bogoliubov transformations take the particular form $$a_i^{\dagger}=\sum^{n}_{j=1}U_{ij}a_j^{\dagger}$$ where $a_i^{\dagger}$ is the ...
0
votes
0answers
24 views

Does Hong-Ou-Mandel dip mean anti-correlation?

When entangled photon which is generated by the SPDC process meet together on 50/50 beam-splitter, they are bunching toward either detector D1 or D2. It leads to see the HOM dip which is non-...
0
votes
0answers
41 views

What happens to photons in an Hanbury Brown-Twiss experiment?

I'm new in the filed of quantum optics, so excuse me if I'll say something really stupid. I've worked in laboratory with an HBT apparatus to obtain the behaviour of the ...
0
votes
0answers
21 views

Good basis for coupled modes

Suppose, there is an electro-optical modulator that can couple the neighboring modes in an optical ring resonator. The Hamiltonian for the system looks something like this: $$H=-\frac{J}{2} \sum_{m}b_{...
3
votes
2answers
41 views

Time dependent Pauli matrix notation in quantum optics

I am reading a quantum optics paper on superradiance and subradiance. In building their Hamiltonian, the authors define an operator $ J_\pm(t)=\sum^N_{n=1}\sigma^{(n)}_\pm \exp{\left(\pm i \delta \...
0
votes
1answer
59 views

Feynman Lecture 26 - Summation of Probability Amplitudes

How does Fig. 26-3 (shown below) correspond to the following paragraph from this Feynman lecture? Finally, we give a very crude view of what actually happens, how the whole thing really works, from ...
0
votes
0answers
19 views

Effective Hamiltonian for Transmission Coefficient

Suppose we have a ring resonator. For the m-th resonant mode, its wave vector along the waveguide $\beta_{m}$ satisfies $\left(\beta_{m}-\beta_{0}\right) L=2 \pi m$. where L is the circumference for ...
2
votes
2answers
51 views

Why does “$|E|^2 \propto $ the number of photons” follow from “$\epsilon_{photon} = hf$”?

For my introduction to quantum physics course we are using the book "University Physics volume 3", availabe here, in the linked chapter in the first paragraph of the "Using the wave ...
1
vote
1answer
54 views

Does amplitude modulation change a photon's frequency or the number of photons?

In the following, we assume that the polarization is aligned such that the scalar treatment of the electric field is justified. Furthermore, we limit the discussion to a fixed coordinate $x=0$ to drop ...
0
votes
0answers
47 views

Difference between photogalvanic effect and Photovoltaic effect

What is the difference between the two phenomena, photovoltaic and photogalvanic effect? I can't find any difference between them. Both are generation of current when a material is illuminated with ...
0
votes
0answers
33 views

Is this two-mode squeezed vacuum state for a continuum of modes physical?

In the book 'Methods in theoretical quantum optics' the squeezing operator for a continuum of modes is given by \begin{equation} S \equiv S [\{ \zeta (\omega)\}] = \exp \bigg[ -\frac{1}{2} \int_0^ {2\...
0
votes
1answer
32 views

In which QED limit are Einstein's rate equations for transitions in atoms valid?

I guess one has to assume low intensities? What are notable differences in a full quantum treatment? I'm familiar with the semi-classical theory of atomic transitions (coupling classical field to ...
0
votes
1answer
63 views

Fourier transform of Bessel function

Please help me find the the representation in $k$-space (Fourier transform) of the following function: $$ f(k_t, k_z, m) = J_m(k_t\rho)\exp(ik_zz)\exp(im\phi)/N $$ The properties of $f$ given below ...
1
vote
0answers
30 views

How can energy conservation not be violated in stimulated emission processes?

Fermis golden rule, derived from time-dependent perturbation theory, give the rate for a quantum system, disturbed by a weak harmonic pertubation with frequency $\omega$, to transition from a state $|...
0
votes
0answers
13 views

How to filter from $N$-fold coincidence to fourfold coincidence

Let's suppose that i have as a result, 8-fold coincidence, something like $[1,0,1,0,0,0,0,1]$ and we are just interested only in the first two and the last two of this output how can i filter it to be ...
0
votes
1answer
68 views

Is the standard Fock state representation of squeezed vacuum not normalized?

It is said in arXiv:1401.4118 that Squeezed vacuum can be represented in the Fock state basis as: $$|\mathrm{SMSV}\rangle=\frac{1}{\sqrt{\cosh r}} \sum_{n=0}^{\infty}\left(-e^{i \phi} \tanh r\right)^{...
1
vote
0answers
11 views

Can the Jaynes-Cummings model serve as photon induced particle hopping?

If you have an electron in a cavity and it has a ground state and an excited state which are somehow localized in either site of the cavity, does this mean that you can describe this situation as ...
1
vote
1answer
54 views

Can Squeezed Vacuum Produce non-zero $\langle E \rangle$?

I believe that squeed vacuum can be represented in the Fock state basis as: $|\mathrm{SMSV}\rangle=\frac{1}{\sqrt{\cosh r}} \sum_{n=0}^{\infty}\left(-e^{i \phi} \tanh r\right)^{n} \frac{\sqrt{(2 n) !}}...
0
votes
1answer
57 views

Why is there a π phase shift in Fig.4 compare to R01 shown in Fig.3?

About Kim 's delayed choice quantum eraser experiment. Is it possible to adjust the phase of interference fringes from $D_1$ and $D_2$ by adjusting the distance of $D_0$ screen?... Shouldn't they ...
0
votes
0answers
18 views

No even-order harmonics in alkali gases? (Intuition for “symmetry in time domain'')

The polarizability can be expanded in the from: In Alkali gases, it is said that $\chi^3$ can be nonzero, and the combination of multiple waves can produce four-wave-mixing. But what about $\chi^2$? ...
0
votes
1answer
23 views

Can you have radiation when you hop from one site to another site with lower energy in a Bose-Hubbard model?

In the Jaynes-Cummings model (JCM) https://www.tandfonline.com/doi/abs/10.1080/09500349314551321, you have a model for a single cavity where you have two bosonic state operators coupled to a photon ...
0
votes
0answers
11 views

How to convert absorption/emission rate of a molecule from cross section units (or molar extinction units) to frequency units?

I try to find relation how absorption/emission rate of molecules is expressed in different types of units? For example, I found that for Rhodamine 6G the peak absorption rate (in terms of molar ...
1
vote
1answer
65 views

Ambiguity of mean field approximation

I have a Condensed Matter Hamiltonian on some lattice (eg. square or triangular) \begin{equation} H = \sum_{i,j} :\hat{a}_j^\dagger \hat{a}_i \hat{a}_i^\dagger \hat{a}_j: = \sum_{i,j} \hat{a}_j^\...
2
votes
1answer
65 views

What is the physical significance of ladder operators?

If i have a quantum harmonic oscillator system, say, a Quantum Optics system or a crystal where i have some $\Psi$ in occupation number respresentation in energy eigenbasis. $$\Psi=|n_1 n_2 n_3...\gt $...
1
vote
2answers
75 views

Show completeness of general Gaussian POVM

In Continuous-Variable quantum information, a general Gaussian measurement is described by the POVM elements (say on a single mode for simplicity) $$ \Pi(\alpha) = \frac{1}{\pi} D(\alpha) \Pi^0 D^{\...
4
votes
4answers
147 views

Changing the relative phase of two photons in an Hong-Ou-Mandel interference produces anti-bunching?

What happens to the output of a beam splitter when you change the relative phase between two photons that enter from the two input ports? In Hong-Ou-Mandel interference for a beamsplitter of the form, ...
0
votes
0answers
18 views

The quantum mechanical orbital angular momentum operator for light

\begin{align} \hat L_j & = -i\hbar \int d^3k \ \hat a_m(\mathbf k)^\dagger (\mathbf k \wedge \tilde{\mathbf \nabla})_j \hat a_m(\mathbf k), \\ \hat S_j & = -i\hbar \int d^3k \ \hat a_m(\mathbf ...
2
votes
1answer
46 views

Quantum linear optics Boson sampling

I am currently taking a course in Quantum Optics and I am trying to understand Boson sampling. We were given a formula for Boson sampling: if the input is given by: $$|{\psi_{in}}\rangle=a_1^\dagger ...
4
votes
2answers
92 views

How photons make us locate the position of objects?

We detect an object with the help of light. When photons hit the retina our eyes find the presence of the source of the light (object), the source being the original source of detected light or ...

1
2 3 4 5
18