Questions tagged [bell-experiment]
For questions on Bell test experiments or Bell's inequality experiments, including but not limited to the CHSH and CH74.
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How would a Quantum Computer (network) perform loophole-free Bell tests?
In a simple form, Bell's theorem states that:
No physical theory of local hidden variables can ever reproduce all of the predictions of quantum mechanics.
Bell developed a series of inequalities ...
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Are there Bell-like violations that can be observed without collecting statistics?
Observing the violation of Bell inequalities, be it in their original formulation, or in the nowadays more commonly used CHSH formulation, involves computing averages of specific experimentally ...
glS♦
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References examining Bell inequality violations at large distances
Could anyone point to some references examining Bell inequality violations at large distances please?
I see many times, in pop science articles and research literature alike, that the quantum ...
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What is the no-signaling set and how can it be related to other types of correlations?
The paper Bell nonlocality by Brunner et. al includes a striking diagram on page 7:
This is fascinating to me because it suggests a framework of categorizing correlations that encompasses classical, ...
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Difference between Bell's inequality and CHSH
In this section of the Scholarpedia article on Bell's theorem, the first paragraph comments that Bell's original inequality is not ideal for experimental verification because it requires perfect anti-...
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Definition of locality in Bell experiments
Continuing from my previous question on Brunner et al.'s paper; so given a standard Bell experimental setup:
where independent inputs $x,y \in \{0, 1\}$ decide the measurement performed by Alice &...
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What is an example of an entangled state whose correlations are describable with a local hidden variable model?
When talks about CHSH inequality, we always say that the states that violate the inequality are entangled, while some states that do not violate the inequality can also be entangled.
For the latter ...
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Determining whether $P(ab|xy)$ factorizes in Bell experiments
Continuing from my previous (1, 2) questions on Brunner et al.'s paper on Bell nonlocality.
Again, we have the following standard Bell experiment setup:
where independent inputs $x,y \in \{0, 1\}$ ...
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Why is $P(1,2)_{\text{same}} = \frac{1}{4}$ and not $\frac{1}{2}$ in Preskill's Bell experiment?
Context:
Three coins on the table. Each is either heads or tails. You can
uncover any one of the three coins, revealing whether it is heads or
tails but then you choose two the other two coins ...
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Bell State 11 not working for parity curve
I am currently writing a script to automate the creation of parity curves for a 2 qubit bell state and then calculate fidelity and proving entanglement from that (inspired by this paper). It was going ...
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In Bell's inequalities, what is the meaning of assuming that the physical properties $P_Q,P_R,P_S,P_T$ have definite values?
Two assumptions behind Bell inequalities (Page 117 Nielsen Chuang)
(1) The assumption that the physical properties $P_{Q}$, $P_{R}$, $P_{S}$, $P_{T}$ have definite values
$Q$,$R$, $S$, $T$ which exist ...
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Formal proof of Bell's inequality in CHSH form
I have a sketch of the proof of Bell's theorem that goes as follows: Alice measures an observable $A$ along a direction $\vec a$ with possible outcomes $\pm 1$, and Bob does the same for an observable ...
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Simultaneous eigenstate of commuting observables and their tensor product
So this is about something from Preskill's notes on Quantum Computation and Information, Chapter 4, page 3.
Imagine we have a maximally entangled state (Bell state). We can identify the Bell state by ...
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Problem about entanglement swapping
I have been learning about the concept of entanglement swapping and found an equation mentioned in the textbook, Mathematics Of Quantum Computing: An Introduction written by Wolfgang Scherer.
At ...
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What are the two measurements per box being done in the Bell Tests in the IBM Quantum Experience "Entanglement and Bell tests" Section
I am confused as to what is being measured in the boxes in the example drawings shown on the Entanglement and Bell Tests section in the IBM Q Experience:
https://quantum-computing.ibm.com/docs/guide/...
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How can I measure a qubit on a generic axis on Qiskit?
I'm trying to prove Bell's inequality by following the one made by Wigner, that is:
$P(+_a,+_b) \le P(+_a,+_c) + P(+_c,+_b)$
And that this proof is NOT satisfied for angles between the various axes $\...
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How to measure a Bell inequality violation in IBM Q?
Note: Cross-posted on Physics SE.
I made some circuit to prepare a 2 qubit state, but I am having trouble understanding how to measure Bell's inequality. I know the inequality is of the form
$$|E(a,...
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How is Bell’s Inequality converted to the CHSH inequality?
Bell’s inequality is $$S = P(a,b)-P(a,d)+P(c,b)+P(c,d) \leq 2,$$ which is calculated as $$S = ab – ad + cb + cd \leq 2.$$
The CHSH version is:
$$E = \frac{N_{11} + N_{00} - N_{10} -N_{01}} {N_{11} + ...
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Projecting $\lvert ++ \rangle$ on Bell Basis
I understand that, projecting $\lvert 00\rangle$ on the Bell states would produce $\lvert\Phi^+\rangle$. Because,
$$
CNOT(H\lvert0\rangle \otimes \lvert0\rangle) = \frac{1}{\sqrt{2}}(\lvert00\rangle +...
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How to prepare an arbitrary two-qubit state?
I know that to prepare a Bell state say $|\phi^+\rangle$, we need to initial state $|0\rangle,|0\rangle$ and then perform a Hadamard on the first and then use it as control to do a NOT gate on the ...
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Output of Bell State Measurement
I was trying to see the output of Bell State Measurement in IBM Quantum Experience but in the simulation down the circuit in the histogram, it showed me that the possible qubit will be $|00\rangle$ ...
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Does the CHSH inequality fully characterise the local polytope?
Consider the standard two-party CHSH scenario. Each party can perform one of two measurements (denoted with $x,y\in\{0,1\}$) and observe one of two outcomes (denoted with $a,b\in\{0,1\}$).
Let $P(ab|...
glS♦
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EPR pair and individual operations [closed]
I have created an EPR pair. Let's suppose it's $(|00\rangle + |11\rangle)/\sqrt{2}$. We both of our halves and then we move into our places.
If I ask you how does your half look like (mathematical ...
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What would the CHSH inequality be equal to if the two qubits were separable?
I am writing an Excel spreadsheet to work through the matrix algebra for a simple Bell's game with the following parameters.
$$\newcommand{\bra}[1]{\langle #1|}\newcommand{\ket}[1]{|#1\rangle}A_\pm = ...
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Is this a Bell test?
Inspired by this article which uses a $|+\rangle$ state as a control for a $CSWAP$, I realised you can conditionally measure a qubit by (maybe) swapping it with an empty ancilla, measuring it and (...
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Where does $xy = a + b \pmod 2$ come from in the context of CHSH inequalities?
I have been looking into the great! video lecture of "CSHS Inequality" by Prof. Umesh V. Vazirani.
There are a few things I have to clarify, hope someone will answer me.
Suppose Alice and ...
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Why is the CHSH inequality defined with a minus sign?
CHSH inequality is defined in the following way. Let $Q, R, S, T$ be two outcomes $\{\pm 1\}$ measurements. The measurements are chosen in a certain way, but that is not our concern right now. We know ...
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Bell's experiment: checking the probabilities
I have some doubts on the calculations behind Bell's experiment, which goes as follows: a pair of entangled photons is shared between two scientists, Alice and Bob, who possess a bunch of polarizers ...
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given an EPR pair, how do I calculate expectation value?
given A and B share EPR pairs $ (|00⟩+|11⟩)/√2$
both are free to measure their own qubit with the following measurement settings
A measures with $[ |0⟩, |1⟩ ]$
B measures with $[ sin(3π/8)|0⟩ + cos(...
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Modified CHSH game - Does entanglement help?
I'm thinking about a modified version of the CHSH game and I'm trying to convince myself that in this case, entanglement cannot be used to gain an advantage or else it would imply signalling is ...
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CHSH test using unbounded operators
I want to perform a CHSH inequalities test using operators $A \, \& B$ and their combinations each possessed by Alice and Bob, which obey the following commutator relation.
$$[A, B] = 2C$$
...
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What is the number of local deterministic behaviours in a Bell scenario?
Consider a Bell scenario: Alice and Bob perform measurements on a shared system, and each of them has a "measurement box" with a bunch of inputs (corresponding to different measurement settings) and ...
glS♦
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Find the Bell States of A and B in the following scenario
Let A has quantum memories $M_1$ and $M_2$ and B has quantum memories $M_3$ and $M_4$ capable of holding one qubit.
2 Bell states are shared among A & B in the following way:
First Bell state $|...
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What is the analysis of the Bell Inequality protocol in Cirq's 'examples'?
This question is taken from https://github.com/quantumlib/Cirq/issues/3032.
The "standard" protocol measures Alice's and Bob's qubits in different bases, while the one in Cirq measures in ...
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