Quantum state Definition and 95 Threads

In Griffith books of introduction to QM, it say that Quantum State, mathematically represented as a vector. My problem is with understanding what are the components of such a vector. Do I understand it correctly, that, say, in case of a particle in a box, Quantum State, as a vector is a...

Our hard drives are reaching the limit of memory capacity and they are studying about the idea of using the molecules and atoms to store memories. Can information or memories be stored in the quantum state? When we heard of quantum state applications in computer, we mostly think about quantum...

"Let’s begin by labeling the possible spin states along the three coordinate axes. If A is oriented along the z axis, the two possible states that can be prepared correspond to σz= ±1. Let’s call them up and down and denote them by ket-vectors |u> and |d> . Thus, when the apparatus is oriented...

I have a question concerning the paper "Quantum imaging with undetected photons". http://arxiv.org/abs/1401.4318 In the schematic (Fig. 1) a photon (idler) is created at NL1 and passing the object at O to be reflected further to NL2. It is then stated in the paper "By reflection at dichroic...

Several recent arxiv articles like http://arxiv.org/abs/1409.6290/ reviewing the pbr theorem http://arxiv.org/abs/1111.3328/ got me thinking about this again with respect to straightforward two-slit interference, which I'd thought simply and unambiguously resolved the issue in favor of "it's...

I've started few days ago to study quantum physics, and there's a thing which isn't clear to me. I know that a quantum state is represented by a ray in a Hilbert space (so that ##k \left| X \right\rangle## is the same state of ##\left| X \right\rangle##). Suppose now to have these three states...

Another theorem ruling out ψ-epistemic models: http://arxiv.org/pdf/1412.0669.pdf

Question: "Write the quantum state for the following system of particles distributed over evenly spaced energy levels" The diagram (couldn't upload so hope its not too rough): 5 ---------------------- 4 ---------------------- 3 --------------X------- 2 ------X---X------X---- 1...

There is an old controversy in quantum mechanics, with arguments on the borderline between science and philosophy, on the question whether the quantum state describes an objective reality associated with a single system, or mere probability describing properties of a large ensemble of equally...

For part a I have (H0-ω\hbarm)|nlm>, which I think the (H0-ω\hbarm) part is the eigenvalue of the Hamiltonian, also is the energies? And mainly, I am not sure how to approach part b, the time variable is not in any of the states. I saw this in our lecture notes: ψ(r,t)=∑Cnψn(r) e-iEnt/\hbar...

Consider the vacuum state that is hypothesised to precede the moment of inflation in classical inflationary theory. The theory assumes that quantum fluctuations in this vacuum are magnified because of the process of inflation and have gone on to form the real energy structures that we witness...

I've been reading about Bose-Einstein condensates, in which multiple bosons can occupy the same quantum state. I thought I understood how that could work until I learned that some atoms, such as Helium-4, are bosons. It seemed to me that if two He-4 atoms H1 and H2 occupy the same quantum...

hi what is a pure quantum state and a mixed quantum state? I looked up the internet but I did not quite understand. For pure quantum state I have read that they can't be written down as a mixture of other states? are entangled states pure states?

Hello, I have been reading many things on Quantum state but unable to understand what actually it is. Can anybody explain me? Thanks

Hi everyone Homework Statement I have a quantum state \mid \Psi \rangle= a_1 \mid \Psi_1 \rangle + a_2 \mid \Psi_2 \rangle wheres as psi1 and psi are normalized orthognal states. Not I want to express the psi with the following two states \mid \Psi_3 \rangle = \frac...

Hi everyone, I'm new to quantum mechanics, so bear with me o:) Homework Statement I'm not sure if scaling is the right word here, but my problem is about the absolut value of a quantum mechanics state to be one. I have the state | \phi> which is a linear combination of the states |+>...

Question about the "reality of the quantum state" paper by Pusey, Barrettm and Rudolp In the paper I mentioned in the title (on arXiv and supposedly subsequently published in a journal), the authors claim to show that "if a quantum state merely represents information about a system, then...

Is a stokes four-vector like (1 1 0 0) being horizontal polarized vector can be treated as a quantum state? If the answer is yes, this state can be used to construct density matrix?

Would anyone be able to explain s,p,d,f in detail without using complex math? Also quantum states such a m,l etc. or link me to a site/paper that does? thanks

Is Gravity a quantum state like light is? I am sorry if I have not used the proper terms to ask my question.

Any comments on the Pusey, Barret, Rudolph paper of Nov 11th? I didn't find any references to it via search here in the forum yet. http://lanl.arxiv.org/abs/1111.3328" ABSTRACT: Quantum states are the key mathematical objects in quantum theory. It is therefore surprising that physicists...

Homework Statement I need to show that < n l m | z | n l m > = 0 for all states | n l m> [b]2. Relevent Equations: L^2 = Lx^2 + Ly^2 + Lz ^2 Lx = yp(z) - zp(y) Ly = zp(x) - xp(z) Lz = xp(y) - yp(x) L+/- = Lx +/- iLy The Attempt at a Solution I really don't know where to begin...

Can anyone explain to me why we use the periodic boundary condition Ψ(x)=Ψ(x+L), in order to normalize the free particle's quantum state?? I've made 2 threads already on this some time ago, but haven't got an answer still.. I hope this time i`ll have because I am really curious about the...

Well, I know if both the position and momentum are in a simultaneous eigenstate then, theoretically, we would be able to measure momentum and position without changing the wavefunction. But, is there such an eigenstate out there? Any help is appreciated! (sorry if the wording is awkward)

Homework Statement Suppose we have a spin 1/2 Particle in a prepared state: \left|\Psi\right\rangle = \alpha \left|\uparrow\right\rangle + \beta\left|\downarrow\right\rangle where \left|\uparrow\right\rangle \left|\downarrow\right\rangle are orthonormal staes representing spin up and...

Hi everyone. Can anyone help with this thought. What was the quantum state at t=0 or at the big bang. I thank you very much for your help. TheNaturalist

Homework Statement Homework Equations The Attempt at a Solution OK I have \left| \psi \right> = \alpha \left| 000 \right> + \beta \left| 001 \right> + ... + \theta \left| 111 \right> which I need to normalise. I know that \left| \psi \right>^{*} = \left< \psi \right| and so have...

An experimenter, A, has prepared four photons with known polarization states. In another lab, experimenter B has prepared four photons with random orientation. Is it possible, for the photons prepared by B, to take the polarization states of the photons prepared by A, without B knowing the...

The question is: what is the quantum state of a free particle t time after its detection at the position r0 in t=0? I know I have to use the evolution operator with the hamiltonian of a free particle. My actual problem is more stupid than that: I don't really know how to express the STATE of...

Homework Statement Ok hello, The problem is there is a system in the state characterized by \Psi(x,t) = \int dk e^(ikx)e^(-iwt)f(k), which is the time dependent representation of a wave packet, where individual waves travel with velocity vp = w/k and f(k) =...

Homework Statement To determine whether two wave functions, \psi_{1} and \psi_{1} correspond to the same quantum state of a particle. Homework Equations Calculations (simplified): \psi_{1}(x,y,z)=A \psi_{2}(x,y,z)=e^{z}A The Attempt at a Solution The two wave functions do...

As I'm a new quantum physics learner I confuse energy level,energy state and quantum state, can anyone explain to me with details thank for taking time to explain

Let say we want to prepare a particular superposition state with a specified wavefunction, how can we accomplish that? I tried google but nothing useful showed up. Thanks.

In a following link: http://physicsworld.com/cws/article/news/42019 authors claim to design a 40 micron sized resonator which they were able to set into a superposition of states. Should this be true, I find it fascinating and a new, fruitful way to explore quantum-classical border. Any...

Homework Statement Assume there is a source of some pre-selected atoms. When measuring atoms of that source in a Stern-Gerlach, you find the following probabilities for a spin-up result: x-direction 5/6 y-direction 5/6 z-direction 1/3 Which state would you ascribe to the source...

According to this website, http://www.particleadventure.org/pauli.html "At one time, physicists thought that no two particles in the same quantum state could exist in the same place at the same time. This is called the Pauli Exclusion Principle, and it explains why there is chemistry." 1-What...

Hi all. When a quantum state is said to be degenerate, then it means that two states \psi_1 and \psi_2 result in the same energy and that |\psi_1|2\neq|\psi_2|2, am I correct? Now in my book we have a wavefunction given by: \psi_n =\frac{1}{\sqrt{L}}\exp(2\pi i nx/L), where n is a...

Homework Statement A two-level system is setup so the two eigenvalues are given E_1, E_2, the Hamiltonian is also given as 2x2 matrix (not shown here). The corresponding eigenstates are easy to solved as |1\rangle = \left( \begin{matrix} 1 \\ 0 \end{matrix} \right), \qquad...

A single particle quantum state \Psi is given a by a wave function (vector) representable as a linear superposition of eigenvectors \Upsilon weighted by a number proportional to their probability of occurrence: \Psi=a_1 \Upsilon_1+a_2 \Upsilon_2+... In the case of the observable "spin"...

The other thread was going too off-topic, so I'll repost here. Why is this not possible, without considering FTL signals?

A team of scientists from Princeton University has found that one of the most intriguing phenomena in condensed-matter physics -- known as the quantum Hall effect -- can occur in nature in a way that no one has ever before seen. Writing in the April 24 issue of Nature, the scientists report...

Q: Explain the meanings of the four quantum numbers, n, l, m, σ which label the stationary states of the electron in the hydrogen atom. i know what n and m are i can't find anywhere wat l is but i think its radius of orbit, but what is σ? help would be much appreciated.

Show that the symmetric combination of two single particle wavefunction Gab(r1,r2)=Ga(r1)Gb(r2)+Ga(r2)Gb(r1) where G is psi ( i don't have symbol on my computer) displays the exchange symmetry characteristics of bosons (equation G(r1,r2)=G(r2,r1)) Is it possible for two bosons...

This is my analysis:1)quantum can have two states at one time:0 and 1.So n QBits have the volume 2^n. 2)when it's observed,the quantum state will collapse to a certain one. So the comtradiction is evidence:the information of the 2^n Qbits disappear when I only read n Qbits from it. Ok...if...

Can we (in principle) put a cat into a pure quantum state, without killing the cat?