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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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Check if total angular momentum is well-defined for a particular photon wave function

I have an exotic state, which can be expressed in a way: $$\pmb{A}(\rho, \phi, z; t)= \hat{e}_{\pmb k, \sigma} A_0 e^{i (k_z z - m \phi +\omega t)}$$ where $A_0$ is a scalar amplitude of the EM-...
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What's the difference between twisted light and light of circular polarization?

Circular polarization: https://en.wikipedia.org/wiki/Circular_polarization Orbital angular momentum of light: https://en.wikipedia.org/wiki/Orbital_angular_momentum_of_light From point of view, ...
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35 views

Photon number representation of a position eigenstate

I wanted to calculate the photon number representation of a position eigenstate, so I developed as follows. \begin{align} \vert x\rangle =\sum_{n}\vert n\rangle\langle n\vert x\rangle =\sum_{n}\...
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1answer
29 views

Furry's theorem and spontaneous parametric down-conversion

In spontaneous parametric down-conversion, a single photon interacts with a nonlinear medium to produce a pair of lower energy photons. It is observed that energy, momentum, and orbital-angular-...
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Evolution of the operators in Mach-Zehnder interferometer

I have trouble understanding how the operators that change the initial state, change when adding extra splitters. As an example, I will use an idealized Mach-Zehnder interferometer where the splitters ...
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41 views

Can we always find a Quasi-Probability distribution representation for density operator of any physical system?

For a pure, quantum optical system, the QPD formalism is straightforward and possible because of the existence of coherent states. The question is whether we can find coherent states for any quantum ...
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44 views

What is the principal cause of diffraction?

I have found another question similar to mine here. But I want to know why does diffraction of light happen in the first place. I have found other resources on google which explain the topic partially ...
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Prove Dipole moment of an isolated quantum system in isotropic space is identically equal to zero, unless there exists an accidental degeneracy [closed]

Dipole moment of an isolated quantum system in isotropic space is identically equal to zero, unless there exists an accidental degeneracy. How to prove this?
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45 views

Does it give sense to speak about field distribution of a single photon?

A Point source of light has radial symmetry. If the source gets attenuated so that only a single photon is leaving each hour, can I still argue, that the field of the single photon is radial but the ...
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82 views

Is it possible to prepare thermal state by performing a single mode quantum operation on vacuum states? [on hold]

Let me define thermal state as \begin{equation} \rho=\sum_{n=0}^{n=\infty}\frac{\bar{n}^n}{(\bar{n}+1)^{n+1}}\left|n\right>\left<n\right|. \end{equation} is it possible to prepare this state ...
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1answer
61 views

The role of the harmonic oscillator eigenfunctions in quantum optics

In quantum optics we quantize the electromagnetic field and describe it using the harmonic oscillator model and the formalism of annihilation and creation operators. For the electric field operator we ...
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1answer
36 views

Scalar product of squeezed coherent states

Consider two states of the type $|\alpha,\xi \rangle = \hat{D}(\alpha) \hat{S}(\xi) |0\rangle$, where $D$ and $S$ are the displacement and squeeze operators, respectively, and $|0\rangle$ is a 1D ...
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What is the interpretation of a photon in quantum mechanics? [duplicate]

Without considering the absorption and emission, can we define a wavefunction for a photon? If so, can we ever have monochromatic photon? Or is it equivalent to the free particle? In that case, would ...
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43 views

Delayed choice experiment for misaligned Mach-Zender interferometer

In quantum Mach-Zender interference, a single photon can be prepared to have a 100 percent probability of traveling through a particular path (that classically would be a 50 percent chance). This can ...
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1answer
87 views

How to bound the dimension of infinite dimensional Hilbert space?

Lets say I have a density matrix $\rho$ encoded into a physical system. Lets say I can have access to as many copy of $\rho$ as I want. I perform hmodyne detection on the copies in phase and out of ...
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1answer
78 views

Projective measurement using two mode squeezed state?

Let me define two mode squeezed states as $ \left | \xi \right>_n=\exp\left(\xi \hat{a}^\dagger \hat{b}^\dagger-\hat{a} \hat{b} \xi^\star\right)\left | n,0 \right>$ where $\left|n,0\right>$ ...
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Material on Coherent Control

I'm looking into coherent control for a new module, I was hoping to find some material that is beginner friendly be a book, website, video etc. . All books I have found on my own all expect some ...
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3answers
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Shot noise in optics

There are many explanations to be found about shot noise in optics, but the answers I find are incompatible. There are three ways shot noise in optics is explained. (Note that according to ...
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1answer
62 views

Laser power and coherent state amplitude

How it is possible to relate the power $P$ of a laser light with frequency $\omega$, to the amplitude $\alpha$ of its description as a coherent state $\vert \alpha \rangle$ ? For a massive particle in ...
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1answer
40 views

Non deterministic quantum gates

There are situations (e.g. in quantum optics) where local non-unitary operators can be defined. In these cases, people say that the operation is non-deterministic. Could you please clarify how the ...
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1answer
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Eigenstates of the creation operator

We know that coherent states $\vert\alpha\rangle$ are eigenvectors of the annihilation operator $\hat{a}$, i.e. $$ \hat{a} \vert\alpha\rangle = \alpha \vert\alpha\rangle $$ while the creation operator ...
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1answer
86 views

Single Photon though prism

What will happen to a single photon when it goes through a prism? Will it just be deflected in the direction related to its frequency? I made this drawing for better understanding, here if I place a ...
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Calculate variance of number of photon counts in detector with second coherence function

Knowing the second coherence function of the light beam that's normally incident to a detector how do can you find the variance of the number of counts $n$ received in the time interval $T$.
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Blackbody photon variance and number of modes [closed]

In an experiment to measure the photon statistics of thermal light, the radiation from a black- body source is filtered with an interference filter of bandwidth 0.1 nm centered at 500 nm, and allowed ...
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Tutorial for the quantum jump method

Are there any tutorials that you would recommend for self-learning the quantum jump method or quantum Monte-Carlo. I am not exactly into Quantum Optics, so I would really be interested to see how is ...
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Something strange in the quantum Ghost imaging experiment

In his paper, Strekalov, D. V., Sergienko, A. V., Klyshko, D. N., & Shih, Y. H. (1995). Observation of two-photon “ghost” interference and diffraction. Physical review letters, 74(18), 3600., they ...
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What does a photon emitted by an atom “look” like?

Consider the emission of a photon when an atom decays from an excited state to its ground state. In most cases, this emitted photon is depicted as a small wave-packet being expelled by the atom in a ...
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1answer
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Will the frustrated total internal reflection occur if the third medium is a metal?

What would happen if i set up a frustrated total internal reflection experiment with a metal as the material close to the interface? Would radiation energy be transmitted to it and undergo attenuation ...
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1answer
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What is shot noise related to?

I have a question about the shot noise and i encountered that when i was studying about squeezed state of light and beam splitters and homodyne detection and etc. but my question is : Is the shot ...
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Limitations of Optical Bloch equations and the physics?

This might be too general a question. I'm looking at an OBE simulation on simple atomic evolutions while interacting with lasers. The problem is that I often take too much time to understand a result. ...
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1answer
70 views

Is the beam splitter transformation related to Hamiltonian?

Consider a general beam splitter with input 'ports,' 1 and 2. It mathematically described by a unitary transformation $\hat{U} = exp[i\theta(\hat{a}_1^\dagger \hat{a}_2+\hat{a}_2^\dagger \hat{a}_1)]$. ...
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1answer
26 views

Difference between using 2 and 3 polarizer [closed]

Is there a difference in using 2, 3 or more polarizer? Is there anything that 3 polarizer can do but not 2 polarizer cannot?
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88 views

Optical coherence versus quantum coherence

Optical coherence is usually defined to be the measure of statistical correlation (for example if the phase difference is constant) of a pair of waves. Recently I came across the notion of quantum ...
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Bose-Einstein distributions when combining different sources of photons

In a telescope, the photons coming from the object you want to observe will pass through a lens, which emits its own photons from heat. It's possible to calculate a B-E distribution from both these ...
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1answer
27 views

Is the purpose of a distributed Bragg reflector to only allow specific wavelengths in the quantum well?

Is the actual useful function of the dielectric mirrors in a distributed Bragg reflector the stopband they create, so that only specific frequencies will make into the quantum well in the middle? Or ...
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2answers
108 views

In a camera pixel, why does photon shot noise *not* result in a poisson distribution?

I'm currently working to characterize the noise in a CMOS camera. I understand that on top of the read noise and dark noise inherent to the sensor, the data is also subject to photon shot noise. I've ...
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What is the Bogoliubov transformation matrix for Fermions?

Is there any Bogoliubov transformation matrix for the operator $O=|g\rangle\langle e|$ where $|e\rangle$ and $|g\rangle$ are arbitrary states? I know that, for annihilation and creation operator $a$ ...
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Eiegenstates of Elelectric Field

If we quantize the electromagnetic wave, and we look for eigenstate of electric field (that is in term of annihilation and creation operators), can we say that an electric field eigenstate would be a ...
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Degenerate Two-Level Atom and Light Interaction

Assume that we have a degenerate two-level atom, (our atom has Zeeman sublevels), and then we have a light that has a polarization in specific direction for example x direction, now we have the ...
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Why does classical light (arbitrary mixtures of coherent states) always result in super-Poissonian statistics?

It is a well-known result that classical light (which I take here to mean mixtures of coherent states) cannot produce sub-Poissonian photon-counting statistics, with a single beam of coherent light ...
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what is “cavity mode width”

to my knowledge a cavity mode is a standing wave with nodes at either edge of its cavity. (standing light wave) each has a frequency and a wavelength and the first 1 is just half a wavelength etc... ...
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61 views

Dispersion of cavity photons

I read a paper called "strong coupling phenomena in microcavity structure" in that with regard to photons in a microcavity For small $k$, the dispersion is parabolic, and so it can be described by ...
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understanding effective length of a microcavity

to find the effective length of a microcavity you have to take into account the penetration outside of the cavity (as in quantum tunnelling) Leffective=Lcavity+Lpenetration and mainly what's ...
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1answer
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quantum correlation and Bell inequalities [closed]

when i read about quantum correlation , its written that quantum entanglement violates bell inequalities. But in every book we always take bell states as a example of entanglement. I am cofused that ...
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What is bose enhancement factor?

I am studying about composite bosons ,when we write N state for composite bosons in terms of its constituent particles, we add factor of normalization constant \chi in denominator.This normalization ...
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4answers
206 views

What is the current consensus on a well-behaving 'Quantum Phase Operator' (in Fock-state basis)?

I'm interested in a quantum operator that returns the phase of some quantized light in the Fock state basis. That is, if I perform (in a density matrix picture) the expected value of this 'phase ...
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2answers
83 views

What determines the timescale for fluctuations in the electromagnetic field from a light source?

Let's say you place an electric field meter some distance from a light bulb. As a function of time the output of the meter would be $\mathbf{E}(t)$. I would guess that the electric field will be some ...
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1answer
49 views

Covariance matrix after projection on gaussian state

I cannot understand the proof in Eisert article (https://arxiv.org/abs/quant-ph/0204052) about finding the covariance matrix of a state after projecting some of its modes onto a gaussian state. We ...
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What happens when an electron in a coherent superposition interacts with a coherent laser beam?

Suppose we have an electron which may occupy three electronic states states $|1⟩, |2⟩,|3⟩$ with energies $E_{1}, E_{2}, E_{3}$. It happens to be the case that $E_{3} - E_{2} \ggg E_{2} - E_{1}$, so ...
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Fock states and beam splitters

A classical beam splitter divides incoming light into two parts according to the reflection and transmission coefficients. A quantum beam splitter on the other hand, can be modelled using Fock states,...