Quantum Definition and 999 Threads

I’ve never worked with a quantum system with more that two states 1, -1, and I’ve just gotten this homework problem. I'm not sure what it means. Does this mean it has five states? Why are there two 0’s and two 1’s?

I'm learning some QFT from QFT for the Gifted Amateur. Chapter 11 develops the massive scalar quantum field but they don't seem subsequently to do anything with it. I've looked ahead at the next few chapters, which move on to other stuff, which leaves me wondering what we we actually do with...

I tried plugging Psi into the right of the Schrodinger equation but can't get anything close to the solution or anything that is usable. How should I solve this?

Hello, I am struggling with what each piece of these equations are. I generally know the two rules that need to hold for an operator to be linear, but I am struggling with what each piece of each equation is/means. Lets look at one of the three operators in question. A(f(x))=(∂f/∂x)+3f(x) I...

I know we can't use classical mechanics to describe or measure the quantum. That is not what I'm asking. I am asking whether particles still follow the same rules like action/reaction if there is a force involved. If electron A interacts with electron B, is Newton's 3rd law still being applied...

In Abner Shimony's paper "The Reality of the Quantum World", the choice between particle detector and wave interference detector is said to be made "after the photon had interacted with the beam splitter". A: Isn't it true that, at light speed, time is not passing for the photon? And so, with...

Coherent Quantum Physics: A Reinterpretation of the Tradition by @A. Neumaier https://www.amazon.com/dp/3110667290/?tag=pfamazon01-20

I'm looking for a book about the theory of measurement in quantum mechanics. A book that goes deep into understanding different kinds and ways. thank you

As I understand it there have been different attempts to use LQG to make a theory of cosmology. The first one being done by Martin Bojowald and then later one being performed by Ashtekar, Pawloski and Singh. there is a description of what they did that was different but as a non cosmologist I...

Hi all, I'm right now confused about this. As far as I know, when changing from a level to another, the change in l (subshell) can only be a difference of 1, and ##m_{l}## can be the same or a difference of 1. In this case, since the question wants me to state possible quantum states of...

https://www.nature.com/articles/d41586-020-00120-6

Something Deeply Hidden: Quantum Worlds and the Emergence of Spacetime Sean Carroll https://www.amazon.com/dp/1524743011/?tag=pfamazon01-20 Review of the book by Matt Leifer Does the many-worlds interpretation hold the key to spacetime? https://physicstoday.scitation.org/doi/10.1063/PT.3.4366

Hi I hope that you will humour me as I try, in layman’s terms to explain a question I have. I recently watched BBC4’s excellent program about quantum entanglement and it got me thinking. I am aware that there are currently experiments ongoing to prove that quantum entanglement is real and...

A new mathematical result seems to have very important implications for quantum mechanics. https://www.nature.com/articles/d41586-020-00120-6?fbclid=IwAR0DxBdyEW10Te3C1Vfyn17TZshyCRrO8nX6D5Iq4CGahZ_DXgfeQ_Ii0Z8 The original paper is a very hard read: https://arxiv.org/abs/2001.04383

Nobel laureate Hans Bethe was a friend of mathematician-physicist John von Neumann, and he once said: "I have sometimes wondered whether a brain like von Neumann's does not indicate a species superior to that of man" and "[von Neumann's] brain indicated a new species, an evolution beyond man"...

Hi there, popping by here to check my answer because another online platform has already answered it but my answer appears to be wrong. I can't seem to understand why though :/ Since I can find the energy at a state to be ##E_{n}=\dfrac {-13.6z^{2}}{n^{2}}eV## At ground state where n=1...

We say that principal quantum number tells us the average distance from the nucleus, so the sub shells of some principal quantum number say 3 has 3 sub Shells 0,1,2 and in 3p sub shell their will probability of finding the electron near the nucleus which doesn't mean electron will find in region...

I'm self studying so I just want to ensure my answers are correct so I know I truly understand the material as it's easy to trick yourself in thinking you do! A particle of mass m is in a 1-D infinite potential well of width a given by the potential: V= 0 for 0##\leq## x ##\leq## a =...

According to Nobel laureate Frank Wilczek, the universe emerges from a Grid. This was proposed in his book "The Lightness of Being: Mass, Ether, and the Unification of Forces". He also likes the idea that the universe emerged from a state of "nothingness" (or rather, a quantum vacuum) where...

Trying to better understand quantum field theory, I've read that particles are created when it becomes an exitation of its quantum field. Would it then be right to think of a particle as the manifested kinetic energy of its field?

Optical quantum computer goes big in new quest for “quantum supremacy” https://arstechnica.com/science/2019/12/optical-quantum-computer-goes-big-in-new-quest-for-quantum-supremacy/

...researchers at the University of Bristol's Quantum Engineering Technology Labs (QET Labs) demonstrate the quantum teleportation of information between two programmable chip for the first time, which they remark is a cornerstone of quantum communications and quantum computing. Seems they did...

Hello! I'll be entering my second semester of my junior year of my Physics Degree. My uni doesn't have a bad physics program, but it's really small so I have to take my upper level classes as soon as they're offered or I won't take them for another 2 years or so. They are on a cycle so I will be...

Well, I don't understand the integral part of ##1/(VD) = \int_0^{\hbar \omega_D}\frac{\tanh(\beta E/2}{E}dE## and ##\tanh(\beta E/2) \approx 1-2\exp(-\beta E)##, then he writes the following (which I don't understand how did he get it): $$\frac{1}{VD} = \sinh^{-1} (\hbar \omega/\Delta(0)) =...

I calculated the total area of phase space and divided it by the area of one cell i.e. h. n = (x_0*m*2*v)/h => n = (0.1 x 10^-10 x 9.1 x 10^-31 x 2 x 10^7)/6.626 x 10^-34 => n = 0.27 This answer doesn't match with any of the options. What did I do wrong? Edit: The question was printed...

Is there any evidence that Panpsychism may hold its own in the quantum world? What quantum physics principals violate the ideology of Panpsychism? This is meant to be fun. I am curious what other people think.

OReilly published a new book, Programming Quantum Computers. From my brief scan of it, the book looks pretty comprehensive. They use circle notation for the Qubit states and have a simulator (QCengine) to go along with the examples on github. The programming language for their algorithm...

What is the principle of operation of a quantum computer on a silicon chip? What are a qubits and how they connected and interacted between themselves? How does CMOS technology work in a quantum computer?

hello! I've been trying to read through Sakurai's Modern quantum mechanics textbook ( My goal is to finish the first 3 chapters and understand the Dirac formulation of QM specifically) but I find myself stumbling at many places. Are there any video lectures on the internet that follows this text...

Title? Thanks. I think it does since these do : - Quasi particles - Collective behaviour of particles - Phase transitions Any others?

I have read some materials about quantum hall effect and know that at the edge of a 2D material , one can linearize the potential V and the linear dispersion relation represents right/left moving fermion. So , Can I say that for a given hamiltonian , if I can linearizae it at edge, then this...

Homework Statement:: Consider an electron trapped in a one-dimensional finite well of width L. What is the minimum possible kinetic energy of the electron? A) 0 B) Between 0 and h^2/8mL^2 C) ≈h^2/8mL^2, but it is not possible to find the exact value because of the uncertainty principle D)...

Homework Statement:: An electron is in state n=2 in an infinite quantum well with width L. What is the probability to find the electron if you measure within the well's central third? Can someone cofirm whether or not my solution is correct Homework Equations:: Y=Asin(n*pi*x/L) I use the wave...

As a simple example, the probability of measuring the position between x and x + dx is |\psi(x)|^{2} dx since |\psi(x)|^{2} is the probability density. So summing |\psi(x)|^{2} dx between any two points within the boundaries yields the required probability. The integral I'm confused about is...

Summary:: What is the structure and how are minibands and minigaps in QC Lasers implemented Hello everybody, I have a question regarding the miniband and minigaps that are displayed widely in diagrams about the functioning of Quantum Cascade Lasers. How are this mini-gaps established...

Because I do have a background in the latter it was originally very difficult for me to understand some aspects of QP (quantum physics) when I initially learned it. More specifically whenever probabilities were involved I couldn’t really make full sense of it while I never had any problems...

I have heard that one of the of the founders of LQC, Martin Bojowald is now rather critical of it. And sample of his criticism can be found here: https://arxiv.org/pdf/1810.00238.pdf I would be really grateful if someone could explain this in more laymen language . Any thoughts on the issues...

With the application of quantum physics to computing, can it be determined that the location of the bits manipulated are within the computer’s physical spatial location or is the energy likely anywhere. The spooky effect at a distance proposition makes me ask.

This is the V(x) diagrams and what I am thinking (really not sure though) is that for the first one you the energy has to reach V2 before it can start transmitting and the graph can take off from T=0, since there is an increase in energy potential that is V2. And as the energy increases, the...

(This question is on the elementary side...) In the Schrödinger picture, the state is dependent on time. If you have a state composed of several particles, generally you can break them up, with each one depending on local time. But in an entangled system, say of two particles, you can no longer...

Hello, I was always wondering how in research centres scientists are able to apply quantum mechanics' equations to predict an outcome. I mean, let's say you do an experiment and then collect the results, how can someone use quantum mechanics to predict the outcome ,if he can? For example,in...

From the point of view of science and physics, is the simulation hypothesis true? What is the scientific refutation of this hypothesis? What do physicists say about this?

In a typical quantum course we learn how to approximate the ground state of a particular Hamiltonian by making an educated guess at an ansatz with a tunable parameter then calculating the expectation energy for the ansatz. The result will depend on the tunable parameter if done correctly. Then...

I'd really appreciate it if someone could tell me where to obtain the solutions manual for Bransden and Joachin QM as I've been having a go at the problems.

Summary: The quantum fields stem from the quantum mechanical wavefunction, which in the standard QM is epistemological (amplitude of probability). How can they be then considered ontological? The quantum fields stem from the quantum mechanical wavefunction, which in the standard QM is...

What I know of this only comes from popular presentations of the subject. So let's say there are two particles, A and B, known to have opposite values of a particular property such as spin. We don't know which particle has which spin until we measure the spin of one of the particles, say A. Then...

I am going to get laughed out of this forum but at least it will put my mind to rest when this happens. I've been thinking about this for a few years now and what better place for an answer than a physics forum? Amongst many other things I have read A Brief History of Time seven or eight times...

Given that operator ##S_M##, which consists entirely of ##Y## and ##Z## Pauli operators, is a stabilizer of some graph state ##G## i.e. the eigenvalue equation is given as ##S_MG = G## (eigenvalue ##1##). In the paper 'Graph States as a Resource for Quantum Metrology' (page 3) it states that...

In quantum electrodynamics, the energy exchange between two charged particles is called a virtual photon, allowing the exchange of quanta of energy between the two charged particles. But these are not the traditional photons of electromagnetic waves. They apparently just arise from the equations...

The arrival of quantum computing reminds me of "the manhattan project" and "the sputnik alert" when physicists are highly demanded. And this makes me wonder if the age of quantum computing means the better future for physicists since the development of quantum computers needs at least...