Measurement Definition and 1000 Threads

If I'm correct, a series of with respect to some property entangled particles exhibits a correlation between several measurements of that property by means of two measuring devices. My question is: is it possible that between measurements the physical constitutions of the measuring devices...

Ok, This probably seems a silly question, but has there been any 'serious' attempt to measure Pi PHYSICALLY, like in a lab, using say a light fiber in a circle and one down the radius? If so, where can I find the results/paper? Thanks!

I read that in 2014 the gravitational constant was measured by atomic intereferometry. Now I read that they speculate that measurements of G are in correlation with 5,9 years cycle. But, when we can expect new measurements of G? Are they in preparation?

I learned that the moment a wavefunction collapse takes place is a matter of interpretation. So, I suppose the phenomenon 'wavefuntion collapse' is something that has to be witnessed by observation at some point to be able to establish it at all! So my question is: if collapse doesn't actually...

What equipment is needed for illuminated I-V measurements of a solar cell? light source, 2 multimeters light source, 2 multimeters, variable resistor, voltage source light source of variable intensity, 2 multimeters, irradiance meter Light source, 2 multimeters, variable resistor PV analyser...

The ensemble interpretation asserts that QM is only applicable to an ensemble of similarly prepared systems and has nothing to say about an individual system and in this way, it seems, it can prevent the need for introducing the concept of wave-function collapse and so it may seem that there is...

A measurement of an observable that does not commute with energy will generally cause a change in the expectation value of the energy. Is there a clear formalism to describe how energy is conserved overall?

I read that measurement changes things because we have to bounce photons off an object to 'see' it and that changes its position, momentum etc... But on the other hand, Griffiths' QM book seems to suggest we don't know what it is about measurement that changes the state of something. We don't...

Homework Statement [/B] The surface tension (T) is measured by capillary rise formula T = \frac {rh ρg}{2 cos\Theta} . The quantities of ρ, g and θ are taken from the table of constants while the height and diameter are measured as h = (3.00 + 0.01)cm and D = (0.250 ± 0.001)cm Find the...

I am desgning a circuit(network), where i need to show the path traversed by the greater part of the current at each node, consecutively. using an ammeter (or voltmeter) in every branch (around 20) makes it too tedious. Will LEDs do the required work? But they would light up at all locations...

Does measuring a polarized photon after it passed a polarization filter put the measurement apparatus in a superposition of detected/not-deteced (the photon)? Does this depend on whether the photon is part of an entangled pair?

So in quantum mechanics, there are at least three different kinds of measurement operators: the General, the Projective, and the Positive Operator-Valued (POVM). They have different properties and relationships. In a typical QM book, these are not delineated, but in Quantum Computing they are...

If we measure, say, the polarisation of a photon, the polarisation state of the photon collapses along the eigenvector of the observable corresponding to the measurement. This may seem as a loss of information of the original polarisation (for it is now collapsed into another value). However...

In the double slit experiment, when you measure which slit your photon passes through, it will land in the corresponding location on the photosensitive film at the end of the apparatus. If, however, you don't measure which slit it goes through, an interference pattern will appear on the film...

Hi, if I have a block of metal with a quarter circle curve cut out of it, and a metal roller of matching radius that contacts this curved piece, what are some ways I could go about measuring the friction between these two surfaces? The roller is fixed and the block is pushed into it with a...

Most protocols on Quantum Teleportation (using Alice and Bob as performers) include a crucial step where Alice performs a Bell State Measurement. Usually the applicable math is given in the protocol, but many protocols make the following kind of statement with no explanation: "Alice must...

Hi, I'm doing a lot of temperature measurement, and I would like to add a function that could estimate how high the temperature would rise and how long it will take to get there. The calculations would be based on the current temperature relative to the past x measurements. Anyone have any...

I'm wondering if time is just a way we have to "measure" how things change its characteristics in space. Is that correct?

Problem I would like to determine the combined standard measurement uncertainty for a mean mass ##\bar{m}## computed from a mean volume ##\bar{V}## and a constant density ##\rho## with $$\bar{m} = \bar{V} \, \rho.$$ I know the mean volume ##\bar{V}##, volume standard deviation ##\sigma_V##...

Homework Statement This problem is from Zetelli 3.21 http://imgur.com/wYTNVwz http://imgur.com/wYTNVwz Homework Equations Just the standard probability via product between the eigenfunction and the wavefunction The Attempt at a Solution I've found the eigenvectors for the Hamiltonian...

I am currently reading papers discussing the Zeno Effect, which discuss how measuring a system at high frequencies can almost freeze the state of a system, or keep the system in a specific subspace of states. This can be easily seen using the projection postulate. Often the topic of decoherence...

Having a bit of trouble estimating total scale uncertainty. In this experiment, I used four precision weights (error << scale resolution). Each weight has a known mass and is weighted on a scale 20 different times. Therefore, for each weight, I have a mean scale measurement, a standard...

Let's suppose that we have an entangled state of two systems ##A## and ##B##: $$ \frac{1}{2}\left(|\psi_1 \phi_1\rangle+|\psi_2 \phi_2\rangle \right) $$ where ##|\psi \rangle## and ##|\phi \rangle## are energy eigenstates of ##A## and ##B## respectively. However the eigenstates##|\phi_1\rangle##...

What's the unit used to measure α ? if α=(Kd/C)0.5 where Kd is the dissociation constant and C is the total concentration of electrolyte .

Homework Statement Hi! I have lately come across some tricky experimental physics tasks, where no solution is given. Some of them involved parts where the focal length of a convex lens had to be measured with a laser. How do you do this? Homework Equations 1/l + 1/d = 1/f (1) where f is the...

Hello, Are there any anthropologists, archaeologists, or geologists around on this board for help? I am trying to teach myself about radioactive decay via beta emission whereby a neutron spontaneously transmutes into a proton, releasing an electron. But, I do not understand the practical side...

the wave/particle duality is no more seen as the opposite sides of a coin. We now see it as a point in a segment [0 , 1]. It is the same with pure states. The visibility of the fringes varies between 0 and 1. In regards to measurement, We are often in the old yes/no habit: At a some point the...

I have been under the impression that application of a magnetic field will quantise the z component of an electrons spin in that direction. I see this as a physical process, but Is this incorrect as it is often described as a measurement of a random variable/ wavefunction collapse? I am familiar...

Svein submitted a new PF Insights post Administering TCP/IP In Automation or Measurement Networks Continue reading the Original PF Insights Post.

Its been a while that I'm thinking in what sense we can say the SG experiment is a measurement. What I concluded, is that there are two kinds of measurements. 1) Measurements that advocates of the ensemble interpretation (like our own @vanhees71) declare as the only one that QM has anything to...

LIGO reported the announced event with a redshift of 0.6 < z < 1.3. With no em radiation event reported (AFAIK), does anyone know how they have determined the redshift? I understand how they could measure the pre-merger, chirp and ring-down frequencies with good accuracy. In order to determine...

Hi, here is my thinking about the gravity wave measurement. Could we actually measure something relative?

As the length distortion due to a gravitational wave as it passes by Earth is on the order of the dimension of an atom, or << a wavelength of light, can someone describe in a general sort of way what measurement steps are employed to detect such small changes in an interference pattern? It would...

I am taking my first semester of QM so excuse my question if it is way off mark, totally wrong, or very well known. As I understand it, one of the postulates of QM are that states evolve unitarily, a consequence (but not THE defining feature) of unitary transformations is that they are...

Consider a measurement of a photon after it has passed a polarisationfilter. Does the photon jump in a (polarisation-)eigenstate by passing the filter? Does the filter do a measurement? Is the filter part of the entire measurement?

Is there a difference between measurement and preparation? When we have two Young slits we prepare a superposition of position. The apparatus which can measure this state is a copy of these slits near them with detectors outside them. If they never click you have build the correct measurement...

Homework Statement What is a more precise way of finding the total mass? Weighing 5 individual quarters or weighing them all together? 2. Relevant equation individual weights n1+n2+n3+n4+n5 = total weight total weighed together N = total weight The Attempt at a Solution I think weighing...

Hi guys, I'm a newbie in quantum physics and it has blown my mind so far. I feel a bit confused because it seems very unintuitive, but I'm ready to learn more and I need some help on this forum. I have few questions. 1) I red that the wavefunction of an electron is spread all over the universe...

Hello, Could you explain or prompt me to an article or source that mentions the advantages/setbacks from measuring the grain size of materials using X-Ray Diffraction (XRD)?

Hey guys, long time reader first time poster. I'm undertaking a project in partial fulfillment of my Mechanical Engineering degree with regards to the cooling of an intercooler heat exchanger with an exterior water spray. basically i have an intercooler and i am using a hair dryer to supply a...

I have a very basic question about superposition. Suppose two experimenters do a measurement on a particle in superposition. Does de measurement apparatus become in superposition? Do the experimenters become in superposition? What is superposition?

Hello Forum, I am taking a lab and we are learning about measurement and uncertainty. Suppose we have to measure the length L of an object. Once the data has been collected we can calculate the mean (average) and the standard deviation s. The resulting measurement would be expressed as [ mean...

I am taking a course in quantum information theory. In this theory, the state of a system is given by a density matrix, while a measurement is completely positive, trace preserving map of the form: Λ = ∑il i >< i l ⊗ Λi , where Λi is completely positive. Can anyone tell me how this is...

I was wondering about decoherence: Suppose a measuring apparatus measures a single quantum property (say, spin). After the actual measurement of the property has taken place, the result 'decoheres' into the apparatus until the apparatus shows the measurement result, after which it decoheres...

Homework Statement It's been a little while since I did one of these. My question is: We have to use http://phet.colorado.edu/sims/mass-spring-lab/mass-spring-lab_en.html to find the measurement of k, the spring factor using two different methods. For the method I am looking at, is the static...

What is an (the?) empirically demonstrable method used for determining a substance's state of matter? If a new substance was discovered and scientist A said it's solid and scientist B said it's a liquid, how would it be demonstrably proven to be one or the other? The books I have define states...

Whats the significance of Atmospheric pressure being refereed as 100kPa ? Does that really mean 10000 kg/m2 acting upon us ? If we are measuring only collision force on the surface and not the weight of the entire column of air above us, then why figure 100kPa (100000 N force/m2) which is huge...

Hello, Can anybody help me to understand the solved example as attached here. How can I follow that using dirac, bra notations. Regards

Homework Statement A horizontal Pitot tube (with one end open for airflow and another closed) is accidentally installed into an airplane askew, so that the tube is not horizontal. Instead the closed tube end is higher (in the y-direction of a xy-plane) than the inlet end. How does this affect...

I have a 3-axis accelerometer suspended on rubber bands inside a soccer ball and am wondering how to calculate the impact force of the ball with it. I have an intuition that the force will be proportional to the frequency of the oscillations of the sensor after a collision but I am having...