Quantum Definition and 999 Threads

Summary:: The problem solutions contain a lot of unjustified steps, making them pointless. I am trying to use Griffiths Introduction to Quantum Mechanics. He states that the wave function ##\psi## approaches 0 as x approaches infinity to make normalization work. I can accept that. But then I...

Hello, I am a high school student doing a project on pulsars and I would love to get into the deeper workings of a quantum electromagnetic field, but I am a bit lost. Since pulsars are neutron stars, who send out a beam of electromagnetic waves, I was quite curious about it's workings. So...

Trying to understand what the math methods are exist to determine quantum phase transition and how I can calculate it, by what methods.

I was working on plotting fidelity with time for two quantum states. First I used discrete time( t= 0,1,2,3...etc) to plot my fidelity. I got constant fidelity as 1 with continuous value of time. Next I used discrete set of values ( t=0 °,30 °,60 °,90 °). Here I saw my fidelity decreases and...

I had two questions in the field of physics: We know that in quantum mechanics there is an electron in a certain distance from the distance to the nucleus as a cloud or a cover. But is motion for the cloud defined by the electron moving around the nucleus? And the main question is, can the...

In the other thread of a similar name it was stated, and probably rightly so, that I wasn't using rigorous terminology or that I wasn't using them in a rigorous way. While I was making certain assumptions about the ability to interpret the 'jargon' I was using, it seemed to be a serious...

Hey, I found these interesting articles about a proposed way of vaccinating people while also applying a biomarker on them which would help remember one's vaccination status. https://news.rice.edu/2019/12/18/quantum-dot-tattoos-hold-vaccination-record/...

I have a fidelity between the initial state and final state is 1 at t=0,1,2...etc. What does it mean physically? Does it mean that the quantum state is not evolved here. But In quantum dynamics every physical system evolves with time.

Greetings, I'm new here, I have an interest in the nature of reality, and a question. Does the quantum spin of a particle (its intrinsic angular momentum) have anything to do with its wavelength and frequency? One of the experts on Quora said no, and I cannot find anything about it on the web...

In this 1965 paper by Weinberg, https://journals.aps.org/pr/abstract/10.1103/PhysRev.138.B988, he describes a quantum field theory of the graviton in a Coulomb-like fixed gauge, where the free graviton has only space-space components and is traceless. This of course makes the field dynamics...

Is advanced quantum computing the key to achieving the world's first true artificial general intelligence? The astronomical amount of computing power required for an AGI is currently not possible with classical computing.

Continuing the discussion in the 'Assumptions of Bell's Theorem' thread, I'm hoping to explore the question of the location/position of the QM system prior to measurement. I may have some bias or underlying assumption that is affecting the conclusion that I am drawing and, by exploring this...

fidelity for pure state with respect to t=0 is 1. My teacher told me this. But I am not getting this. This is my detailed question the initial state(t=0)##|\psi\rangle=|\alpha\rangle|0\rangle## the final state (t) ##|\chi\rangle= |i\alpha\sin(t)\rangle|cos(t)\alpha\rangle## Fidelity between the...

I was teaching the basics of quantum states and was showing the students that an arbitrary state in a quantum two-level system could be written as ##|\psi\rangle = C_1 |+\rangle + C_2 |-\rangle = R_1 |+\rangle + R_2 e^{i \alpha} |-\rangle##, with {##C_i##} complex and {##R_i##} real. Then...

https://arxiv.org/abs/2010.10345 My question is, Has the Feynman Diagram IIc been published or not? Did Kroll & Karplus lie or not? https://vixra.org/abs/2002.0011 Are these critics valid?

Please note: I am really a beginner in this field. If I write nonsense just let me know, I just gather information. As far as I understood Quantum Computing is super fast but (this is basically my question) not suited to all kinds of engineering questions. As far as I know it should work best...

Hello! If I place a particle with more energy levels (of the order of kT) in a well defined state, in a thermal bath at temperature T, how will the blackbody radiation affect the internal state of the particle i.e. will the distribution be classical or QM? Basically, if I prepare that particle...

How we should understand the randomness of quantum events in the context of the significant role that they apparently play in our macroscopic world. Using processes as superconductivity, super-fluidity, and in Bose-Einstein Condensates researchers have been able to produce macroscopic quantum...

In a textbook, which is not in Englisch language unfortunately, I found a passage saying that intrinsic curvature of spacetime is just a specific definition. The alternative definition is that spacetime is flat, whereas clocks and rods have variable lengths - which is just Feynman’s bug...

How does putting it potentially inbetween 2 basis states, which U will measure only later, on, do it!? That seems like magic, to me. And yet I accept that it does. Somehow.

What is the quantum spin of the valence electron in the silver atom in the furnace in the Stern-Gerlach experiment? . Up, down, at random, alternating, in a (quantum) superposition (of both), or none? Does it even have/get one until it's measured/observed /needed? . Does the second electron, in...

This is how I explain it, away, now: Upon entering the magnetic field the silver atom's valence electron's electric field aligns itself at right angle/s to the magnetic field, the quickest/shortest way it can, as they are wont, to do, somehow, and the rest follows, naturally. And if U are...

Hi there, I would like some help developing a QUBO expression where a Quantum Annealing approach would find the two ways of summing the 5 numbers {1 2 3 4 5) to 8 by selecting 3 of the numbers. I am basing this off of a dwave.sys video example I found on their site. My initial kick at the can...

This question is in regards to Dwave's quantum computer which is tailored to solve QUBO problems (minimize $x^T Q x$ where $Q$ is a symmetric matrix and $x$ is $n$ length vector of $0$s and $1$s) using quantum annealing. I would like to understand how it works. The claim is that it does so by...

Robert Lawrence Kuhn: It seems that special relativity suggests time is like gravity and electromagnetism, not built into the absolute fabric of reality like logic and causation. David J Gross: Yes, time is dynamical. The phenomena are dynamical and are labeled by what we call time. Including...

Hi guys! These days I've been reading Feynman's description of the quantum behaviour of an ammonia molecule. He assumes the N up or down as tuo basis states. He then says there's a little probability that the state UP becomes DOWN and viceversa. But for definition basis states are...

Is it likely that this year's Nobel prize could be awarded to the field of quantum cryptography with Charles H Bennet, Gilles Brassard and Artur Ekert as possible nobel laureate candidates?

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The standard reference for open quantum systems is The Theory of Open Quantum Systems by Breuer and Petruccione, which seems well-written but it lacks exercises, as do all the other textbooks I googled. Does someone have a recommendation for a textbook on open quantum systems with problems to...

But then I learned a photon can be split into two or even three photons (red-shifted, energy is conserved), and also photon can lose energy and still be a photon (Raman effect, inelastic scattering). Now, I am not sure what it means when it is said photons are quanta of light (smallest unit of...

Hi, I'm going through Nielsen and Chuang's Quantum Computation and Quantum Information textbook and I don't really understand this part about quantum parallelism: Shouldn't the resulting state be (1/sqrt(2^4)) * (|0, f(0)> + |0, f(1)> + |1, f(1)> + |1, f(0)>), since the resulting state would...

From: https://en.wikipedia.org/wiki/Axiomatic_quantum_field_theory But, that seems like a fairly abstract place to begin the kind of QFT construction that was asked of us by Witten in 2012: At the bottom of that page on axiomatic QFT are the "Euclidean CFT axioms": Are there any examples of...

If the answer is Yes, then I would ask, if the mirror absorbs a portion of the energy of the photon, so the photon should simply stop existing because we cannot have a smaller package of light than a photon. If the answer is No, then I would ask why a beam of light (which is made of a big...

It's probably more kind of math question. I consider a wave function of a harmonic oscillator, i.e. a particle in a parabolic well of potential. We know that the Hamiltonian is a Hermitian operator, and so its eigenstates constitute a full basis in the Hilbert space of the wave function states...

I have written and rewritten a lot of times but I need some fresh eyes on my sop. It would be great if someone can help me out. I have less than a week to readjust it and send. My motivation to apply for the Masters Degree in quantum engineering at University of Wurzburg is to...

I imagined all possible quantum gravity theories in one set, of which only one is correct, and further divide these theories into testable and non-testable. Question: how do we know if the correct theory is currently testable? If it is testable, then we need to come up with new theories until...

Hi, I will be starting my research in topological QC (based on non abelian anyons following the work of A. Yu. Kitaev). To begin understanding this theory, I need to develop a background in the braiding group used to describe anyons, fault tolerance in quantum computers and probably condensed...

So initially I thought quantum mechanics was deterministic in the equations but was probabilistic in measurement. I’m aware of bell’s inequality which rules out hidden variables unless you assume super determinism. But recently I’ve come across something called decoherence and some people have...

Hello! I would be really thankful if you could recommend me a good book for an introduction to quantum entanglement . Thanks!

One of the paradoxical principles in Quantum Physics is the principle of quantum superposition, since in quantum theory we are not really talking about the superposition of waves or oscillations, but about the superposition of states. A classic example demonstrating the phenomenon of quantum...

Let as consider a system ##H = A\otimes B## I've been said that quantum negativity, i.e. taking the partial transpose w.r.t A or B and summing the magnitude of the negative eigenvalues obtained, is a measure of how entangled are the parties A and B. First question: Why is it that we do not...

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...

So I have heard that IBM and Google have constructed Quantum computers, how does one actually construct a Quantum computer? I would like as much detail as possible on the construction of one of these devices and how it works exactly, I wanted to buy a Spin Q Quantum computer and I understand how...

Hello, I have 1 undergrad year left and was wondering what the most used programming languages in grad school are. I still don't know which grad school will accept me so I haven't bothered to ask them directly as my application will be in November when I get my GRE scores. I am Interested in...

The concept of decoherence seems to be a major progress in quantum mechanics. Has decoherence or any other new finding the potential that a particular interpretation of quantum mechanics will prove correct or incorrect resp. in the foreseeable future?

Just wanted to share a cool proposal paper from the BASE collaboration. I found this article dense and the theoretical aspects are way above my pay grade, so please chime in if you think I get anything wrong. For the record, I have no ties to this group and hadn't heard of them before this...

Hello everyone. I am studying physics as a self-study and would like advice on the next topics to study. So far I have been studying: -calculus, linear algebra and basic physics -classical mechanics (from Goldstein's textbook) -classical electrodynamics and special relativity (from Griffiths...

intermolecular distance means distance between particles. So, I imagine a sphere. $$\frac{4}{3} \pi d^3 = \frac{V}{N}$$ However, Griffitfhs pictures a box instead, where $$d^3 = \frac{V}{N}$$ And the difference between both models is a factor of ##(4\pi/3)^{2/5} \approx 1.8##, which is...

Suppose a blind man builds a machine that paints three apples with three colors, either red, blue or green. Once the machine has done this, are the three apples in the following superposition: or is the wavefunction just one of It feels like because the man is blind, the apples should be in...