1. ### I What does it mean to influence a quantum measurement's outcome?

This just occurred to me and I don't expect to be the first one to address it: It is said that in a specific measurement basis, the outcome of a measurement in this basis is determined by chance. But in how far is this the case, since if the eigenvectors are for example ##\overrightarrow{A}##...
2. ### I Against "Collapse"

One sees "Collapse" language all the time, and yet it seems there's a very simple argument that shows that it's not necessary. Suppose we measure ##\hat A## twice, at an earlier and at a later time, then the joint probability density for the measurement results being ##u## and ##v##...
3. ### I Human eyes can detect single photons?

I'm not sure where this thread belongs; it is essentially a topic at the intersection between quantum optics, human physiology and even psychology, but I will focus more or less on the implications for quantum physics, so I just opted for this subforum. There is a recent article over Scientific...
4. ### B Are Quantum Entities in Macro Sized Objects Entangled?

Hi. This is my first posting on the Physics Forum so please forgive any issues as a result. I am a (reasonably educated) lay person with a strong physics interest with extensive readings -- so please be patient with my questions. :-> My questions and interest in these issues are sincere. I...
5. ### Insights Interview with Mathematician and Physicist Arnold Neumaier - Comments

Greg Bernhardt submitted a new PF Insights post Interview with Mathematician and Physicist Arnold Neumaier Continue reading the Original PF Insights Post. Arnold will welcome science questions and comments only.
6. J

### A Discrete measurement operator definition

Consider the Gaussian position measurement operators $$\hat{A}_y = \int_{-\infty}^{\infty}ae^{\frac{-(x-y)^2}{2c^2}}|x \rangle \langle x|dx$$ where ##|x \rangle## are position eigenstates. I can show that this satisfies the required property of measurement operators...
7. ### I On the Heisenberg uncertainty relation

Are there fundamental limits on the accuracy for measuring both position ##q## at time ##t## and momentum ##p## at time ##t+\Delta t##, with tiny ##\Delta t##? If yes, why? If no, why can't one then measure (in principle) both ##q## and ##p## arbitrarily well at the same time ##p## (which is...
8. ### A Key problems in classical and quantum measurement

Quantum mechanical foundations are usually phrased in terms of measurement. I believe this is the main cause why these foundations remain shaky after almost 100 years of a good mathematical basis. Classical mechanics never had any reference to measurement in its foundations, and hence it was...
9. ### Calculating steel round bar's max capacity to support?

First off, I am new to this forum.. However I wanted To find out if anyone would be able to help me calculate How much a steel bar (2 in. In diameter, 5 ft. Lengthwise) Would be able to hold up without bending?
10. ### Meter Bridge.

Homework Statement Homework Equations How to find error in resistance ? The Attempt at a Solution I found out the resistance without error. But What is the way to figure out an error of an instrument ?
11. ### Measurement problem and many worlds

Hello, sorry if I created new thread that is already open, but I did not find answer. I would like to ask you about measurement problem (double slit experiment) and many worlds. When interference pattern is created, the dot on screen just show us in which branch or world we are. But if we...