For questions related to contextuality, as relevant to quantum computing and/or quantum information. Contextuality means that in any theory that attempts to explain quantum mechanics deterministically, the measurement result of a quantum observable depends on the specific experimental setup being used to measure that observable.
Questions tagged [contextuality]
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Is it true to say that one qubit in an entangled state can instantaneously affect all others?
When a qubit is measured, there is a ‘collapse of the wave-function’ as a result is randomly chosen.
If the qubit is entangled with others, this collapse will also effect them. And the way it affects them depends on the way we chose to measure our…
James Wootton
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How can one define contextuality within the circuit model?
It is in general believed that contextuality is one of the quantum resource that provides the quantum advantage. A context is usually defined in terms of a set of commuting observables. The quantum algorithms are usually describe employing the…
madeel
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Are there any experimental groups currently measuring quantum contextuality?
I work as a theorist with my current research interests in "quantum contextuality". For those perusing the question, this is essentially a generalization of non-locality where we can show a quantum system does not admit a hidden-variable model. So…
Emily Tyhurst
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What does negative probability represent?
"Negative energies and probabilities should not be considered as nonsense. They are well-defined concepts mathematically, like a negative of money." -Paul Dirac
The abstract from Photon-phonon-photon transfer in optomechanics states:
the Wigner…
user820789
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What type of "local hidden variable" is ruled out when discussing (non)contextuality?
While reading about noncontextuality and the Peres-Mermin square, I encountered the statement that noncontextuality is tightly related to nonlocality à la Bell. For example, (Kleinmann et al. 2011) mention (Eq. (2) in the arxiv version) that any…
glS
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Problems in understanding the solution for "Mermin–Peres Magic Square Game"
I am referring to the article Advanced Topics in Quantum Information Theory exercise 4 and to the MS Quantum Kata MS-Quantum-Kata which describes a solution for the Mermin–Peres Magic Square Game.
I could follow the article and do all the maths for…
mbuchberger1967
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Why doesn't the contextual QRAC contradict Nayak's bound?
A QRAC encodes $n$ bits in $m$ qubits so that one of the bits can be retrieved. Let $p>0.5$ be the success probability of the receiver correctly obtaining any one of the $n$ bits of their choice by performing the appropriate measurement.
Nayak's…
shashvat
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What is the quantum strategy required to win the Magic Squares game
This question is about the Magic Squares game. Links here, here and link here in which two players try to win a game. It's a cooperative game - either the team wins or the team loses. It is claimed that without a shared quantum state, they lose at…
Anna Naden
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How does quantum contextuality relate to mutually commuting observables?
I am trying to get a better understanding of what is the idea behind quantum contextuality. Quoting from the wikipedia page (emphasis mine):
Quantum contextuality is a foundational concept in quantum mechanics stating that the outcome one observes…
glS
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What does the probability distribution $\mu_P(\lambda)$ represent in Spekken's contextuality?
In (Spekkens 2005), the author defined an "ontological model" as a model that assumes (page 3, above Eq. 4):
That every preparation procedure $P$ is associated with a normalised probability density over the ontic state space $\Omega$, that is, some…
glS
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What is a simple example of Spekken's measurement contextuality?
Kochen-Specker theoreom (1967) established the notion of contextuality which is usually termed as KS-contextuality. Spekken (2005) generalizes the definition of contextuality. Spekken introduces three components of contextuality: preparation,…
madeel
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How can one show that Alice's and Bob's answers agree at the intersection cells of Mermin-Peres' "magic square"?
This question is along the lines of Problems in understanding the solution for "Mermin–Peres Magic Square Game"
How can one show that Alice's and Bob's answers agree at the intersection cells of Magic Square?
Is it reasonable to expect the following…
KCS
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Can the Peres-Mermin square be reframed as a statement on the associated conditional outcome probabilities?
As mentioned in this answer, and links therein (assuming I'm understanding correctly), (non)contextuality can be defined as a property of a given set of conditional probability distributions, that is, as a property of a behaviour…
glS
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How can a "state" in a contextuality scenario be contextual?
As also discussed in the answers to What do noncontextual scenarios with no quantum model represent? and Can the Peres-Mermin square be reframed as a statement on the associated conditional outcome probabilities?, a contextuality scenario, as…
glS
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What do noncontextual scenarios with no quantum model represent?
I've been reading the info about contextual scenarios given in this answer, as well as the outline of the main ideas as presented in section II of (Leifer and Duarte 2020). Following the notation of said paper, I understand a contextuality scenario…
glS
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