Bell Definition and 223 Threads

Why or why not?

When there are EPR/Bell test inequality violations and no signal faster than light, the terms: Bell Non Locality, Quantum Non Locality, Weak Locality and the Cluster Decomposition Principle: Initial state of space like systems can be factorized. Subsystems remain space like separated. Then final...

Hi. I wonder if following thought experiment (which is most probably impossible to be put into practice) could have any implications concerning interpretations of QM. Consider five parties A, B, C, D and E, lined up in that order and with no relevant relative motion. No pair of them have ever...

Hi. Bell formulated local realism as follows: The probability of a coincidence between separated measurements of particles with correlated (e.g. identical or opposite) orientation properties can be written as $$P(a,b)=\int{d\lambda\cdot \rho(\lambda)\cdot p_A(a,\lambda)\cdot...

Hi. A while ago, I apparently had a wrong idea about the meaning of realism. I stood corrected: I'm still struggling with those subtleties. Would following formulation be more appropriate: "Realism means, that every observable ##x## is attributed a probability distribution ##p_P(x)## that...

Bell scenarios with communication J B Brask and R Chaves Journal of Physics A: Mathematical and Theoretical, Volume 50, Number 9 (https://arxiv.org/abs/1607.08182) Abstract Classical and quantum physics provide fundamentally different predictions about experiments with separate observers that...

Hi .. I have this problem needed to solve I hope can find someone help me.. 1- Is the system of three cubic in pure state <ψABC| each pair cubic in bell state |φ+>? 2- Consider a system of two cubits in state Is the measurement without selecting observable which changes the state of a cubit...

Just wanted to check if my understanding is correct. So, it is not important who makes the measurement first of the entangled pair, Bob and Alice decohere the particle with each other independently, creating a "spectrum" or Alices and Bobs on each side. This is trivial, local and there are no...

Bell inequality in page 171 of https://www.scientificamerican.com/media/pdf/197911_0158.pdf is ##n[A^+B^+] \le n[A^+C^+]+n[B^+C^+]## In page 174 we can see that this causes linear dependency according to angle. How to derive this? Let us suppose that angle between ##A^+## and ##B^+## is 30°...

Please read this Insight here: https://www.physicsforums.com/insights/quantum-amplitudes-probabilities-epr/

You got to love this! A top experimental team was assembled to test the "freedom of choice" loophole (if you can call it that). Usually, when random settings are needed in a Bell test, a computer generated value is obtained (pseudo random), or similar. This is relatively "local", and subject...

Hi, I am a student in the Netherlands, and I'll be attending university next year. However, I am doing some form of research on Quantum Computing with another student for our so-called "profielwerkstuk" but my understanding of Quantum Physics and math is sometimes not at the level that is...

As I understand it most, if not all, experiments carried out to test Bells theorem test the local hidden variables assumption that photons have definite polarisations. What I would like to know is whether experiments on properties other than polarisation have been carried out. If not are there...

Looking at experimental results it seems that measuring Bell's nonlocality in semiconductors, ie very close (see Ansmann) lead to a smaller value than the correlation for more further configuration for example Aspect or Hensen. Is there any study about this tendency that seems highly...

A discussion with some friends: Suppose you have a large wheel, say 10 meters in diameter and a bell jar with a good vacuum inside, the wheel is rotating horizontally to Earth. In the jar is a bob, and it is on a 10 meter string which is connected to the center of the bell jar furthest from...

From drchinese website http://www.drchinese.com/David/Bell_Compact.pdf on page 406 there are 2 equations at the top. How do you get from the top one to the second one? There is a hint about using (1) but I think it cannot be done. You might be able to do it with other assumptions but I think...

I am starting this B thread for people to discuss and learn from. In particular, I am hoping it will help to clarify some of the confusing issues which have come up in the "CFD - Counterfactual Definiteness" thread. "Well wishings to ALL, for a complete and successful understanding!"...

Hello, In the four maximally entangled two-qubit Bell states, what is the difference between the first and the second states, similarly, the difference between the third and the fourth states. What the different in signs mean( +,-)...

Hi all My question: One of the four Bell's state are measuring in the Bell basis. Whether the result of measurement of this one of the four Bell's state will be the same Bell's state (just that Bell's state which are measuring) ? The each of four Bell's state is a quantum superposition of the...

"A unifying principle explaining the numerical bounds of quantum correlations remains elusive, despite the efforts devoted to identifying it. Here, we show that these bounds are indeed not exclusive to quantum theory: for any abstract correlation scenario with compatible measurements, models...

Hi. In most articles on Bell's inequalities, both the reality and locality assumptions are thrown at the reader from the beginning. DrChinese however starts with only the reality assumption and shows that it doesn't comply with QM IF it were possible to measure two non-commuting observables...

I've been trying to find information on how Bell's experiment works on the macroscopic scale. I think that the scale of current measurements is meters, for the most part. I've been curious about how Bell's Inequality is supposed to work, Relativistically. Haven't found quite what I'm looking...

Decades ago a massive neodymium bar was going to be used for measuring GW's. I know noise was a problem. Anyone know what happened to this technology? Sounded cool, a big bell at the resonance frequency of a GW.

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...

I'm having trouble with the mathematics of tensor products as applied to Bell states. Say I have the state \begin{align*} \left|\psi\right> &= \frac{1}{\sqrt{2}} \left(\left|0\right>_A \otimes \left|0\right>_B + \left|1\right>_A \otimes \left|1\right>_B\right) \end{align*} How would the...

What is the difference between quantum mechanics and realism ? quantum mechanics states on statistics while the hardy assumption of EPR is that hidden variables may describe exactly the outcomes of each individual test. Bell refutes the last idea. But, he didn't need to refute the case where...

I am not sure if I am allowed to ask this, but here's my shot: I find all the explanations of Bell's theorem summed up here, very different in interpretation and also (for me) incomprehensible. I have these simple questions: How does the Bell inequality, stated as N(A, not B) + N(B, not C) ≥...

Is it correct to say that Chsh does not need an average but as soon as AB-AB'+A'B+A'B' is 4, 0 or -4 it means it is nonlocal ?

An example of a two-qubit state is one of the Bell states, for example: lB> = 1/√2 (l00> + l11>) In my book it is stated that the Bell states form an orthonormal basis for the set of two qubit states. But what exactly is the general form of a two-qubit state? Is it any vector of the form: lq>...

There are several Bell inequalities involving 4 values (e.g. CHSH where they are sometimes denoted by Q, R, S, T). The original Bell inequality involved 6. All being refuted by QM. Is it known whether there is one with only 3 values? I can prove there isn't one with 2 values.

The following assessment of a Bell experiment is based on N. David Mermin's example and is intended for persons with very little understanding of mathematics and physics (myself included). Assumptions (A1) A source emits a pair of particles with some opposite pieces of information. (A2) The...

There is a recent article (Optics July 2015) claiming violation of Bell inequalities for classical fields: "Shifting the quantum-classical boundary: theory and experiment for statistically classical optical fields" https://www.osapublishing.org/optica/abstract.cfm?URI=optica-2-7-611...

I have used one UM66 IC, one BC547 Transistor and one 100 Ohm resistor. The circuits of door bell are as follows but same result. The loudness is extremely poor against both the circuits. How can I increase the loudness? Would you please help me in this regard?

This just showed up from a team led by Zeilinger, for those interested in loophole-free Bell tests: http://arxiv.org/abs/1511.03190 A significant-loophole-free test of Bell's theorem with entangled photons Marissa Giustina, Marijn A. M. Versteegh, Soeren Wengerowsky, Johannes Handsteiner...

Homework Statement Consider the bipartite observable O_AB = (sigma_A · n) ⊗ (sigma_B · m) Where n and m are three vectors and sigma_i = (sigma_1_i, sigma_2_i, sigma_3_i) with i = [A,B] are the Pauli vectors. Compute using abstract and matrix representation the expectation value of O_AB...

When interpreting the results of the two channel Bell test, I believe there were roughly 40 nanoseconds between when the particles were created and when they hit the polarized lens. It is believed that sometime during this time information passes between the entangled photons so that they match...

Hi. Bell's formulation of local realism is $$P(a,b)=\int\ d\lambda\cdot\rho(\lambda)p_A(a,\lambda)p_B(b,\lambda)\enspace.$$ Let's for simplicity assume there's only a finite number of states, so this becomes $$P(a,b)=\sum_{i} p_i\cdot\ p_A(a,i)p_B(b,i)\enspace.$$ I'm trying to translate this...

A great new experiment is reported closing simultaneously the loopholes of detection (fair sampling assumption) and distance (locality assumption): Experimental loophole-free violation of a Bell inequality using entangled electron spins separated by 1.3 km B. Hensen, H. Bernien, A.E. Dréau, A...

While this is the first Bell test that simultaneously addresses both the detection and the locality loophole, am I mistaken that this would still not be considered a loophole-free test? Experimental loophole-free violation of a Bell inequality using entangled electron spins separated by 1.3 km...

[Mentor's note: This thread is forked from https://www.physicsforums.com/threads/bell-spaceship-paradox-quantitatively.828670/ for discussion of the basic principles behind the spaceship paradox] Suppose the string was replaced by some structure which linked the ships together to make a longer...

Yesterday, I found the time to write a bit further on my SRT FAQ and wanted to give a quantitative analysis of the Bell space-ship paradox on the example of the two rockets accelerating with constant proper acceleration, and I found a problem, I cannot solve. So I took this section out from my...

https://www.osapublishing.org/optica/fulltext.cfm?uri=optica-2-7-611&id=321243 "In our experimental test, we used light whose statistical behavior (field second-order statistics) is indistinguishable from classical, viz., the light from a broadband laser diode operating below threshold. Our...

let A B B' be Bell usual matrices for spin 1/2. Are the results of $$A\otimes B$$ and $$A\otimes B'$$ independent ? I cannot imagine the contrary since on what could they depend all angles are fixed.

bcrowell submitted a new PF Insights post What Is the Bell Spaceship Paradox, and How Is It Resolved? Continue reading the Original PF Insights Post.

What is wrong with my scenario? A traveler is about to embark on a mission to Mars. A technician is responsible for communications with the traveler. An entangled pair of electrons is prepared, one to make the trip to Mars and one to remain on Earth. When the traveler reaches Mars he changes...

Does anyone know of QM notes (or a review article) that covers entanglement, the measurement problem, Bell inequalities, decoherence, or the delayed choice experiment (or the more recent mesoscopic experiments). So to speak the more modern and the exciting aspects of QM. I think closest to that...

I am just a noob, trying to understand. I suspect the use of the Bell theorem is wrong. Ik think there is only one hidden variable and not 3 or more. That variable is time. A particle is in motion and has a position, depending on time. When two particles are entangled they have the same...

I quoted these post from other thread. I don't want to distract discussion in other thread so I'm starting a new one about statements in these posts. Basically the question is if we can violate Bell inequalities by two separated but correlated systems that can be as non-classical as we like (as...

Did they manage to do a loopholes free Bell test ? The best I got from google was an article from february that says no , they only did one where 2 out of 3 loopholes were eliminated in one test.

Hi, In all the discussions about EPR, Bell's inequality and interpretations of QM locality seems to be a property that nobody likes to drop light-heartedly. This is somehow understandable since SR is an extremely successful theory. But SR only says that we cannot transmit information faster...