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.

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Cavity Input-Output Formalism: Physical significance and intuitive understanding

I have spent a lot of time trying to understand the input-output formalism for cavities. I sort of understand the idea Fields inside an optical cavity(our system) will have losses because the mirrors ...
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Photon though a single-slit and uncertainty in the $z$- (longitudinal) direction

Heisenberg's uncertainty principle is sometimes invoked in explaining the width of the diffraction pattern as light passes a single slit. In the case of single photons, when a photon is directed ...
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Two-level system with natural frequency $\omega_{21}$ exposed to an EM radiation of frequency $\omega$

Consider a two-level system with energies $E_1$ and $E_2(\gt E_1)$, and an energy gap $$E_2-E_1=\hbar\omega_{21}.$$ If this system is excited by an EM radiation of frequency $\omega(\lll\omega_{21})$, ...
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Husimi $Q$-function of Infinite Square well

Eigen-Wavefunction of infinite square well is $$\psi(x)=\sqrt{2/l}\sin(n\pi x/l).$$ I want to write Husimi $Q$ function for infinite square well. General expression of Q function is $$Q=(1/2)\pi \...
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Measuring the degree of second-order coherence of a quantum optical field

I have been studying quantum optics, mainly from Rodney Loudon's book "The Quantum Theory of Light" third edition. I understand the physical significance and mathematics of the second-order ...
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What is the explicit quantum state describing thermal light?

I know that a (single-mode $\ell$) coherent wavepacket is a light pulse in state $$ |\alpha_{\ell}\rangle = e^{-|\alpha|^{2}/2}\sum_{n=0}^{\infty} \frac{\alpha^{n}}{\sqrt{n!}} |n_{\ell}\rangle $$ for ...
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Is this atomic interaction realizable?

I am thinking about similar trilinear Hamiltonian similiar of the form $a^{\dagger}bc + ab^{\dagger}c^{\dagger}$ of the form given in https://arxiv.org/abs/1805.11193 such as Such that $\omega_{a}=\...
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When do we need to consider Quantum electrodynamic density functional theory?

We know well quantum electrodynamics (QED) and density functional theory (DFT). The former describes the quantum nature of electromagnetic field, and the latter typically concerns the quantum and many-...
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Hong-Ou-Mandel (HOM) effect in Bohm interpretation

Can someone answer how is Hong-Ou-Mandel (HOM) effect treated in Bohm interpretation? I looked on the net but couldnt find anything.
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Where can one find the expression for the origin of the Hamiltonian of the Kerr nonlinear interaction in an optical cavity?

Recently, I was reading some papers about Kerr media in a cavity, and I found that almost all articles give the Hamiltonian as $$H=K\hat{a}^\dagger\hat{a}\hat{a}^\dagger\hat{a}.$$ In order to ...
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Squeezed vacuum state

From: Loudon, Rodney. The quantum theory of light. OUP Oxford, 2000. Consider the single-mode quadrature-squeezed vacuum state defined by $ | \zeta \rangle = \hat{S} (\zeta) | 0 \rangle $ where the ...
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What are the typical values for squeezed states of light?

Which range of values of the squeezing parameter is achievable with today's technology ?
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Projection Postulate of Quantum Mechanics. Where does the Projection occur in the detection process?

This question is about a specific instance of the measurement problem. Let's say we excite a single emitter producing a single photon (described by state $ |\psi_{i}>$), which then "travels&...
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What does $\langle -z|$ mean in this expression $\langle -z|\rho|z\rangle$?

In some formulas of the Wigner function, there is an expression $\langle -z|\rho|z\rangle$ where $|z\rangle$ represents a coherent state. I don't understand what $\langle - z|$ means. Some other ...
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SPDC One Arm vs Very Weak Coherent state

I know that SPDC(Spontaneous Parametric Down Conversion) is a method to generate heralded single photon source. So If we do homodyne tomography of single photon fock state, another arm of SPDC is used ...
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What is the connection between stimulated Raman scattering (SRS) and electromagnetically induced transparency(EIT)?

For a lambda system, SRS and EIT are involved with 3 levels, my question is what will be different for EIT if the energy levels are Raman active/inactive?
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CNOT gate path interference

I have a question on paper "https://doi.org/10.1038/nature02054". In this paper, the CNOT gate is realized using a beam displacer for higher stability. The figure below shows a 1:1 mapping ...
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Why are the $x$ and $y$ components of the Bloch vector for a two-level system called 'coherences'?

This is a rather easy question, but I was still wondering it. I am reading a Quantum Optics (light-matter interactions) script and I have seen two definitions of the Bloch vector for a semiclassical ...
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Covariance matrix of the complete system when only one mode is heterodyned

Let's say we have a two mode Gaussian state $A + B$ characterized by the covariance matrix $\sigma$ (in block matrix form:): $$\sigma = \begin{pmatrix} \sigma_A & \sigma_{AB} \\ \sigma_{AB}^T &...
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Informations about non-Markovianity? [closed]

What are the examples of the practical implementations of studying the non-Markovian dynamics of such open quantum system (e.g. quantum dot)?
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Post-measurement state after homodyne measurements of part of the system

Let us have an $N$ mode Gaussian state and B denote the last mode (for simplicity I just consider a two-modes state) It is said in articles (and for example How to find the covariance matrix after a ...
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Physical meaning of the bath correlation function

In quantum dissipative dynamics, it is defined the bath-system Hamiltonian as $$ \hat{\mathcal{H}}_{SB}=\sum_{\mathbf{k},\lambda} \hbar \left(\kappa_{\mathbf{k},\lambda}^*b^{\dagger}_{\mathbf{k},\...
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Explanation for few things in this paper about photonic crystals

In this paper two weakly coupled cavities are excited with light. Their frequencies are modulated by a mechanical pulse. I have the following questions: What is the Hamiltonian of this system ? I don'...
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Applying law of the unconscious statistician (LOTUS) to wavefunction

I have a wavefunction $\psi(x)$ given by the points-spread function of a spatial invariant aperture. I define the wavefunction of an arbitrary photon incident on the aperture as $\psi_s(x) = \psi(x-...
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Partial measurement of a Two-Mode Squeezed Vacuum state

It seems that if you measure a quadrature on the first mode, let's say $\hat{q}$, on a TMSVS, the second mode will collapse into a coherent state $|q+it\rangle$ Is this true ? What is then the value ...
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Integral-Solving

I know this is a very naive question but during my quantum optics study, I often come across the following kind of integrals. Sometimes there is an identity to get it solved but other times there is ...
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Regarding two-particle interferometry and single-detector probabilities, Horne/Zeilinger (1989)

I was reading Horne, Shimony, Zeilinger "Two-Particle Interferometry" from 1989, an article showcasing how momentum-superpositioned particle pairs from a down-conversion crystal can lead to ...
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Fokker-Planck equation for the Wigner function to covariance matrix

I cannot understand the derivation in Louis Garbe article (https://arxiv.org/abs/1910.00604) about how to obtain the covariance matrix equation from Fokker-Planck equation for the Wigner function in ...
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Is there a simple way to obtain the Quantum Fisher Information (QFI) from a Wigner function? (or any other quasiprobability distribution?)

In theory the Wigner function $W(q,p)$ contains all the same information as the density matrix $\rho$ associated with it, so it's definitely possible to write the QFI $\mathcal F_Q$ in terms of the ...
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Frequency dependent Purcell effect for a broadband emitter

How do I model the following system? I have an NV-center in diamond with a broad fluorescence spectrum, centered at roughly 700 nm with a FWHM of 100 nm. (The NV-center is a defect in diamond, it can ...
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Covariance matrix of Fokker-Planck equation [closed]

Rewrite the Lindblad equation above into a Fokker-Planck equation for the Wigner function is: \begin{equation} \frac{\partial W}{\partial t}(x,p)=-\omega_0p\frac{\partial W}{\partial x} - \omega_0(Xg^...
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Can quantum field theory be used for atom-photon interaction? [closed]

My teacher told me to calculate atom-photon interaction with QFT. But all textbooks talk about elementary particles only. Lewenstein et al. studied QFT of atoms and photons, but he started from the ...
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What happen to a pair of entangled photons when they enter a polarizing beam splitter?

$\newcommand{\ket}[1]{\left|#1\right>}$ Suppose we have two entangled photons in the state of $(\ket{HH}+\ket{VV})/\sqrt{2}$ and one of them enters through the mode a of a polarizing beam splitter ...
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How do I solve this normalization constant for Photon-Added-then-Subtracted Squeezed Vacuum States?

I need to solve the following normalization constant. I have solved this for $m=1$ but I am not sure about power 'm' because it becomes really complicated. Here $|\xi\rangle = S(\xi) |0\rangle$ is ...
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Resources to learn about quantum optics lab experiments?

I would like to improve my knowledge of quantum theory by learning indepth about different quantum optics lab experiments. I would like to find textbooks / resources which give an indepth knowledge ...
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In a double-slit experiment, the peak light intensity is 4 times higher than in the single-slit case. How can it be explained using quantum mechanics?

Using classical physics, this can be explained as follows: at the single-slit, the electric field vector has magnitude $E_0$ and the wave has intensity $I_0 \sim E_0^2$ at each slit of the double-...
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Mechanism: Instantaneously vary frequency of photons emitted, or passing, by, over a wide range of frequencies, with reliable consistent precision?

For an optical computing application, I need to set frequency of photons emitted or passing by a small mechanism, instantaneously, and it needs to be able to change this frequency from one instance to ...
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What does it imply when we say that the waves are perfectly correlated?

I am having a hard time understanding difference between correlation and coherence. I got a nice answer for coherence here- Are two waves being in phase is the same as saying that the two waves are ...
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Doubt in B92 quantum cryptography protocol

I am reading an article on B92 protocol which uses heralded SPDC photons. I don't understand a part of the paragraph. This paragraph mentions Bob's experimental setup for receiving the photons. In ...
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How to find the exact spectrum of the squeezed-driven Kerr-nonlinear model?

Model The Hamiltonian considered is$$H=P({a^{\dagger}}^2+a^2)-K{a^{\dagger}}^2a^2,$$where $a$ is the bosonic annihilation operator $[a,a^{\dagger}]=1$. Ground state By rewriting $H$ as $$H=-K({a^{\...
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Does light have light for itself? Is it really a ray or wave? Or more like a cluster of something ? (Only based on visible light) [duplicate]

During the observation of a laser light (not really laser) we kind of see a ray of light does it mean that every point on light itself is reflecting some other light into our eyes so that we are able ...
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Is photon-photon interaction attractive? [closed]

In vacuum, high-energy photons interact via virtual electron-positron pairs: Is this interaction attractive or repulsive? Can we get the answer from calculating the amplitude?
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Confusion with the notation via Schwinger bosonic representation

There is a known $\mathfrak{su}(2)$ bosonic representation, called Schwinger bosonic representation. In this notation, according to the wiki, the angular momentum state $|j, m\rangle$, where $j = 0, 1/...
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Calculation about the velocity of slow light in electromagnetic induced transparency(EIT)

everyone! Recently,i'm reading a paper about slow light,that's really a famous work published in Nature.[Light speed reduction to 17 metrespersecond in an ultracold atomicgas]. But i'm trouble with ...
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Do quadratures in quantum optics have a physical meaning?

Do quadratures in quantum optics have a physical meaning? Or are they just defined as such to satisfy the same commutation relation as the position and momentum operators ?
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An adequate way to rewrite the following unitary superoperator

Let us consider a set of superoperators: $X_1, \dots, X_8$ which acts on the density matrix $\rho$ as follows \begin{equation} \label{eq:algebra} \tag{1} \begin{array}{ll} X_{1} \rho = a \rho a^\...
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The physical meaning of the action of the following operator [closed]

I've been thinking about different realisations of the two-mode bosonic Lie algebras and faced the following misunderstanding. It is possible to consider different unitary operators, such as the ...
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Photon interference and beamforming

In a double-slit experiment with light, the observed peak intensity is 4 times higher than in the single-slit case. Using classical physics, this can be explained as follows: at the single-slit, the ...
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0 answers
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The second-order correlation function

The second order correlation function for a single mode EM is: $$g^{\left(2\right)}\left(\tau = 0\right)=\frac{\left\langle \hat{a}^{\dagger}\hat{a}^{\dagger}\hat{a}\hat{a}\right\rangle }{\left\langle ...
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Confusion about Feynman rules for free photon propagation

In the book (and lecture series) "QED", Feynman gives a recipe for calculating the amplitude that a photon emitted from point A would be detected at point C. The recipe is to sum the ...
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