What is Quantum optics: Definition and 101 Discussions

Quantum optics is a branch of atomic, molecular, and optical physics dealing with how individual quanta of light, known as photons, interact with atoms and molecules. It includes the study of the particle-like properties of photons. Photons have been used to test many of the counter-intuitive predictions of quantum mechanics, such as entanglement and teleportation, and are a useful resource for quantum information processing.

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  1. H

    A Anyone knows the slow light in EIT?

    I built a EIT system in rubidium gas cell and measured the pulse delay between the reference and probe light. Here, I used a zero-order diffracted light of an AOM as my probe light, but there is just several nanoseconds between these two pulse. I read some papers, like adjusting the Rabi...
  2. Q

    A Feynman rules for Entangled photons

    Should we add to the usual amplitude (sum over all extremal paths of this photon) also the amplitude of the other photon of the pair?
  3. Daniel Petka

    I Can a single photon of a single frequency pass through a FP cavity?

    I was watching this amazing video about FP cavities and the creator mentioned that a single photon shouldn't pass through that cavity. Only multiple photons can. This doesn't make sense to me. The cavity works thanks to interference and single photons still interfere with themselves, so...
  4. Sciencemaster

    I How does one time-evolve a quantum state with its kernel function?

    I'd like to model the evolution of a squeezed state and its properties (such as phase at different spatiotemporal coordinates). I know one can represent them using kernel functions (and I have found a paper that gives a kernel function for a squeezed state: https://arxiv.org/pdf/2105.05990.pdf)...
  5. H

    A How to measure the two-photon detuning in 3-level system?

    hi,everyone! if i have a 3-level system,like this: now,i want know how to measure the two-photon detuning in this system,and i‘ve known that,Δ2 and Δ3 are the two- and on-photon detunings,like this paper said: my questions are below: 1.how other researchers measure these two parameters? they...
  6. H

    A What’s the meaning of decay rate in optical Bloch equations?

    i have some questions about decay rate. 1:why do we need decay rate in these equations? 2:is it a constant for a specific medium? 3:it can be changed with respect to some conditions like temprature or pressure? 4:how can i know the decay rate of some energy levels in 85Rubidium
  7. richard_andy

    A Relation between the density matrix and the annihilation operator

    This question is related to equation (1),(3), and (4) in the [paper][1] [1]: https://arxiv.org/abs/2002.12252
  8. yucheng

    A Jaynes-Cummings Hamiltonian: Where did the time dependence go?

    Consider the interaction of a two level atom and an electric field (semiclassically, we treat the field as 'external' i.e. not influenced by the atom; the full quantum treats the change in the field as well) Electric field in semiclassical Hamiltonian: plane wave ##H_{int,~semiclassical}=-\mu...
  9. LittleSchwinger

    Quantum What are some good modern Quantum Optics textbooks?

    What would people here say are good modern Quantum Optics textbooks?
  10. yucheng

    A How are quantum optical experiments designed? ;)

    inspiration: How does one predict the effects of small modifications (ordering of optical devices etc)? https://www.physicsforums.com/threads/the-experiment-of-kim-et-al-1999-with-small-modification.1047803/ In chapter 5 and 6 of A Guide to Experiments in Quantum Optics, the authors deal with...
  11. LCSphysicist

    Courses Quantum optics for graduate students

    I have just finished my course on electromagnetism. Due to my performance, the professor has contact me for congratulations and asking, if i want, to join his quantum optics course for graduate students. Even so i think it is interesting to follow the advice, i am a little afraid if this...
  12. H

    A Exploring Electromagnetic Induced Transparency in 85Rb Gas

    Hello,everyone! Recently i am doing an experiments about electromagnetic induced transparency in 85rubidum gas. I have two light source,which use the polarization spectrom frequncy stablizaiton technology to make them stable.One is used for probing light,and the other one is used for coupling...
  13. H

    A Calculate the group velocity in EIT (famous paper: light speed 17m/s)

    hello 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 some calculation about the velocity of slow light.here are below: i try to use the...
  14. A

    I Understanding the diagonal elements of the transition dipole moment

    Hey guys, I just numerically calculated the matrix elements for a superconducting qubit and I'm having some trouble to interpret the result. I will include a plot of the matrix I got below: I basically have "large" non zero elements on the main diagonal of this matrix. In previous courses I...
  15. PhysPaig

    Admissions Chances with a Low/mid GPA but high PGRE and research experience

    Hello, and thanks so much in advance for any advice. I’m currently a third year physics undergraduate student who’s looking for what programs I should apply to for my PhD. I’m not sure I should bother applying for anything top 20 but wanted to get a second opinion on my applications...
  16. C

    A Understand Polaron Transformation in Quantum Optics: Wilson-Rae, Imamoğlu

    I'm trying to understand the so-called polaron transformation as frequently encountered in quantum optics. Take the following paper as example: "Quantum dot cavity-QED in the presence of strong electron-phonon interactions" by I. Wilson-Rae and A. Imamoğlu. We have the spin-phonon model with...
  17. C

    A Physical explanation of time-correlation function and spectrum

    From my reading of several quantum optics textbooks and spectroscopy texbooks, the emission and absorption spectrum of an atom or molecule are always given in terms of the time-correlation function, for example the emission spectrum of a two level atom is given by: $$...
  18. C

    A Absorption and emission spectrum in quantum optics

    The emission spectrum or resonance fluorescence for a quantum dot, atom or defect center are discussed in many quantum optics textbook, for example see "Quantum Optics" by Marlan O. Scully and M. Suhail Zubairy Chapter 10 , "Quantum Optics" by D. F. Walls and Gerard J. Milburn Chapter 10 and...
  19. S

    I Interference of signal photons entangled with idlers

    Consider the following experiment: A photon hits a beam splitter, then a non-linear crystal (nichtlinearer Kristall - sorry, prepared the image in German) on each path that does parametric down conversion, splitting the photon into a signal and an idler. The idlers proceed to two detectors (D1...
  20. D

    I Commutation of Beam splitter operator with Displacement operator

    I have a beam splitter operator (a†)b +(b†)a. Does it commute with exp(αâ†-α*â). Here a and ↠are creation and lowering operator
  21. D

    A Cat state acting on given Hamiltonian

    For example if I consider H = (a^†)b+a(b^†), how will it act on even coherent state i.e. |α⟩+|-α⟩?. I know that |α⟩ don't act on (a^†) because |α⟩ is a eigenstate of lowering operator.
  22. stephen8686

    A Jaynes-Cummings Density Operator Evolution

    I am studying two level atoms interacting with fields in order to study Dicke Superradiance. From Loudon's book, the Optical Bloch Equations for a two level atom interacting with a field say (with rotating wave approx): $$\frac{d\rho_{22}}{dt}=- \frac{d\rho_{11}}{dt} = -\frac{1}{2}...
  23. stephen8686

    Courses Quantum Optics, Feeling Overwhelmed and Underprepared

    I am an undergraduate at a fairly well known research university. I have taken undergraduate QM 1, QM 2, and the graduate course on Quantum Optics. I got As in all of them and found them not very difficult. Now I am in a research group researching superradiance. I do not feel like any of my...
  24. CptXray

    I Coherent state evolution - nonlinear Hamiltonian

    Given the hamiltonian: \hat{H} = \hbar \omega_{0} \hat{a}^{+}\hat{a} + \chi (\hat{a}^{+}\hat{a})^2, where ##\hat{a}^{+}##, ##\hat{a}## are creation and annihilation operators. Find evolution of the state ##|\psi(t) \rangle##, knowing that initial state ##|\psi(0)\rangle = |\alpha\rangle##...
  25. C

    Courses The right Curriculum for a Physics Master's Degree (Quantum Optics & Info)?

    Hello everyone. I'm starting my M.Sc. in Physics in the summer term. I'm studying in Germany and completed a standard programm in the bachelor programm which consisted of the obligatory courses like Quantum Mechanics, Electrodynamics, Statistical Mechanics and Mechanics. I have to mention...
  26. Muthumanimaran

    B How trapped ions can be used to make Atomic clocks?

    Can someone explain me conceptually how one can use trapped ions to make atomic clocks? My basic understanding of trapped ions is, we can think of an ionized atom which is controlled by electric and magnetic fields. But i am wondering how can one build an atomic clock using trapped ions.
  27. Supantho Raxit

    A What is a good basis for coupled modes in a resonator?

    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^^ (see the attached image). Here we sum over all modes m and 𝜙0 is a parameter. What will be a good set of basis for the...
  28. matteo137

    I Exponential of momenta to entangle harmonic oscillators

    Consider two harmonic oscillators, described by annihilation operators a and b, both initially in the vacuum state. Let us imagine that there is a coupling mechanism governed by the Hamiltonian H=P_A P_B, where P_i is the momentum operator for the oscillator i. For example P_A =...
  29. JD_PM

    Quantum Optics Question Involving Coherent States

    I've tried to square and compare ##\Delta X## and ##\Delta P## but they are not equal I have to say I am pretty lost here and a hint would be appreciated. I have studied coherent states and I know how to proof some properties related to it. For instance, I see how to proof that the state is...
  30. Haorong Wu

    Courses I am a graduate student in quantum optics. Should I learn QFT?

    I am particularly interesting in QFT, and I am going to be a graduate student in quantum optics and quantum information this autumn. Strangely, I find that there is no courses for QFT. After all, I though QFT are about quantum and field, and quantum optics are about quantum and field, too...
  31. P

    Quadrature distribution for an optical mode in the coherent state

    Hey there, the task I'm working on is written below. Find the quadrature distribution ρ(q), for an optical mode being in the coherent state |α>. Hint: use ∑Hn(x)*(t^n)/(n!) I really am struggling with this type of tasks :D I tried to follow a solved example that I found in my workbook, but...
  32. microsansfil

    A [Quantum Optics] "quantumness"

    Hi, In this presentation slide 17 it is mentionned : Is there any confusion with the fact that coherent states are said to be semi-classical ? /Patrick
  33. E

    Expectation value of operators and squeezing in the even cat state

    I started and successfully showed that the expectation of X_1 and X_2 are zero. However the expectation value of X1^2 and X2^2 which I am getting is <X1^2> = 0.25 + \alpha^2 and <X2^2> = 0.25. How do I derive the given equations?
  34. W

    A Quantum Optics statistics

    Hi everyone, I am following along with the MIT OCW quantum optical communication course. I have a question about this chapter, concerning the linear attenuators and amplifiers. Specifically, the chapter mentions that they are not going to get ##\rho_{out}##, but I am interested in this. More...
  35. C

    How can I derive Eq 9.5.11 in Scully's Quantum Optics

    Firstly, I don't know in which Picture this equation holds (if I hadn't missed some words in the previous text...). I think it may be the Heisenberg Picture. But if it is, the rest target is to prove $$\frac{i}{\hbar}[H_R+H_{FR},(a^\dagger) ^ma^nO_A]=\langle\frac{d}{dt}((a^\dagger)...
  36. Vajhe

    A Oscillator Model with Eigenfunctions

    Hi, I have been reading the Milonni and Eberly book "Laser": in one of the chapters they discuss the Oscillator Model. The treatment is quite straightforward, the Hamiltonian of the process is H=H0+HI where the first term is the "undisturbed" hamiltonian, and the second one is the interaction...
  37. microsansfil

    I Does quantum entanglement depend on the chosen basis?

    Hi, In this presentation about quantum optics it is mentioned that the same quantum state |Ψ> has different expressions in different mode bases : factorized state or entangled state. This presentation is related to this video : In some way entanglement isn't intrinsic. It depend on the...
  38. B

    I What happens to entanglement inside a polarizer?

    Suppose you prepare two polarization-entangled horizontally polarized photons. Scenario 1: After the first photon passes through a linear polarizer oriented at 45 degrees, it will have later a 50% probability of being measured as horizontally polarized and 50% as vertically polarized. The...
  39. Korak Biswas

    A Quantum Optics: Squeezed light generation

    Theoretically, squeezed state can be generated using a process called 'parametric down conversion'. I was going through the literature and found that people performed 'second harmonic generation' before doing 'parametric down conversion'. Can anyone tell me why simple harmonic generation is...
  40. Tspirit

    How Does One Derive Equation (8.27) from (8.26) in Gerry's Quantum Optics Text?

    Homework Statement In Gerry's book "Introductory quantum optics", Chapter 8.5 Decoherence, Page 207, there is a calculation which doesn't give the detail derivation, who can give me the calculation from (8.26) to (8.27)? Homework Equations The coherent state is defined by...
  41. Pattarasak

    I Measurement of the mean value of the number of photons?

    Hi everyone, I do experiment in field of quantum optics and I want to calculate the mean of the number of photons (MNP). In the most of papers, MNP can be calculated by using average power which is measured by power meter. But my power meter is defective. For now, I have only the avalanche...
  42. Pattarasak

    I How to create the operator of unknown beamsplitter

    Hello everyone, I'm undergraduate and my project is an experiment in the field of quantum optics. For now, I have an Unknown beamsplitter in my lab and I want to calculate the operator of this beamsplitter in matrix form (this BS is not perfected equipment because the reflected beam is not...
  43. Pattarasak

    I How to calculate the photons/pulse of Laser diode?

    Hello everyone, I'm an Undergrad and I'm trying to set the Quantum key distribution experiment by using weak laser pulses(the laser diode with attenuated filter). but I don't know how to calculate the photon number per pulse. Can anyone tell me how to calculate the photon number per pulse...
  44. Pattarasak

    A Qubit error rate of QKD BB84 protocol

    Hello everyone, I don't know how to measure the QBER of BB84 protocol in a realistic experiment.In the most paper show the data which is only the number but do not show the unit of data, what is the unit of these data?
  45. K

    A Correlation properties of quasi-thermal light

    Hello! I'm measuring the second order correlation function g(2) of quasi-thermal light, generated by focusing a 633 nm laser onto a rotating sandpaper-like surface at 45 deg. Part of the dispersed light is collected into a fiber and split with a fiber beam splitter. A simple HBT setup. g(2) is...
  46. SchroedingersLion

    A Quantum Optics - transition from pure to mixed state

    Hello guys, I am trying to understand the following experiment: 1. Prepare a 2 level atom in state |0> 2. Shine in a Pi/2 pulse --> atom goes to 1/√2 (|0>+|1>) 3. Wait time T 4. Shine in second Pi/2 pulse a) if the state is pure: atom will go to state |1>, p1=1 b) if the state is...
  47. M

    Classical limit of atomic motion

    Hello, I need same help with the following exercise: (1a)Recall Ehrenfest’s theorem and state the conditions for classicality of the trajectory of a quantum particle. (1b) Consider an atom whose state is described by a wavepacket with variance ∆x^2 in position and ∆p^2 in momentum. The atom...
  48. S

    I Does Relativistic Motion Impact Quantum Optical Experiments?

    If we are considering a problem involving generic photon emitters and detectors that are moving at various relativistic velocities with respect to each other, do we need to move outside of non-relativistic quantum optics? I'd like to stress that this question is not about any definite species...
  49. rocdoc

    I Do I have the correct form for the number of states, the |n>?

    I cannot find any explanation of the mathematical form of the single-mode photon number states, i.e. the |n>. I take them to be functions with domain {0,1,2,3, …} and appropriate associated outputs. So |3> I take to have outputs {0,0,0,1, 0, …} , |0> to have outputs {1,0,0,0, 0, …} and...