Contextuality, coherences, and quantum Cheshire cats

Hance, Jonte R; Ji, Ming; Hofmann, Holger F

doi:10.1088/1367-2630/ad0bd4

Cited by 12 publications

(4 citation statements)

References 47 publications

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“…This shows the protocol is different to counterfactual communication, which does not require any field to travel from Bob (the sender) to Alice (the receiver) for information to be transferred. Further work may try to link this phenomenon instead to contextuality, as has recently been done for the (standard) quantum Cheshire cat protocol [36].…”

Section: Discussionmentioning

confidence: 99%

Is the dynamical quantum Cheshire cat detectable?

Hance,

Ladyman,

Rarity

2024

New J. Phys.

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We explore how one might detect the dynamical quantum Cheshire cat proposed by Aharonov et al. We show that, in practice, we need to bias the initial state by adding/subtracting a small probability amplitude (‘ﬁeld’) of the orthogonal state, which travels with the disembodied property, to make the eﬀect detectable (i.e. if our initial state is |↑z〉, we need to bias this with some small amount δ of state |↓z〉). This biasing, which can be done either directly or via weakly entangling the state with a pointer, eﬀectively provides a phase reference with which we can measure the evolution of the state. The outcome can then be measured as a small probability diﬀerence in detections in a mutually unbiased basis, proportional to this biasing δ. We show this is diﬀerent from counterfactual communication, which provably does not require any probe ﬁeld to travel between sender Bob and receiver Alice for communication. We further suggest an optical polarisation experiment where these phenomena might be demonstrated in a laboratory.

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Section: Discussionmentioning

confidence: 99%

Is the dynamical quantum Cheshire cat detectable?

Hance,

Ladyman,

Rarity

2024

New J. Phys.

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“…We can express this noncontextual requirement as an inequality of the measurement probabilities for these outcomes, P (f NL ) ⩽ P (a, 0) + P (0, a). (7) Note that this is a typical noncontextual inequality, of the same form as given in [19,[35][36][37][38][39][40][41][42][43][44][45][46][47]. This inequality quantifies the limit of the 'either/or' interpretation associated with the detection of single particles.…”

Section: Relation Between Local and Collective Measurement Outcomesmentioning

confidence: 96%

Tracing quantum correlations back to collective interferences

Ji,

Hance,

Hofmann

2024

New J. Phys.

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In this paper, we investigate the possibility of explaining nonclassical correlations between two quantum systems in terms of quantum interferences between collective states of the two systems. We achieve this by mapping the relations between different measurement contexts in the product Hilbert space of a pair of two-level systems onto an analogous sequence of interferences between paths in a single-particle interferometer. The relations between different measurement outcomes are then traced to the distribution of probability currents in the interferometer, where paradoxical relations between the outcomes are identified with currents connecting two states that are orthogonal and should therefore exclude each other. We show that the relation between probability currents and correlations can be represented by continuous conditional (quasi)probability currents through the interferometer, given by weak values; the violation of the noncontextual assumption is expressed by negative conditional currents in some of the paths. Since negative conditional currents correspond to the assignment of negative conditional probabilities to measurements results in different measurement contexts, the necessity of such negative probability currents represents a failure of noncontextual local realism. Our results help to explain the meaning of nonlocal correlations in quantum mechanics, and support Feynman’s claim that interference is the origin of all quantum phenomena.

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“…Projective measurements are not commutative; they in turn yield (new) classical results and constraints, their order matters. Surplus weirdness can be avoided when carefully keeping to the respectively applicable contexts [10,20,21].…”

Section: Timeless Quantum Worldmentioning

confidence: 99%

A Heuristic Sketch How It Could Fit All Together With Time

Thomsen

2024

Preprint

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In the light of almost a century of struggle to make (common) sense of Quantum Mechanics and to reconcile it with General Relativity, it is proposed to (for some time) forget about quantizing gravity or striving for one Theory of Everything or “Weltformel”, which would describe the whole of reality without any joints or suture marks. Instead of one single monolithic formalism, a three-legged compound approach is argued for. Quantum Mechanics, Relativity and Thermodynamics are proposed as the main pillars of reality, each with its well-defined realm, specific features, and clearly marked interfaces between the three of them. Not only classical reality, which is rather directly accessible to us, is then comprehensively modelled by their encompassing combination. Quantum phenomena are understood as undoubtedly lying at the bottom of classical physics and at the same time, they become “fully real” only when embedded in classical frames between preparation and measurement in time. It is then where thermodynamics steps in and provides the mediating glue. The aim of this short contribution is not to deliver novel quantitative results but rather to propose a comprehensive research program and to coarsely lay out a very roughly coherent self-referential sketch starting from the beginning of the one universe, which we inhabit.

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Contextuality, coherences, and quantum Cheshire cats

Cited by 12 publications

References 47 publications

Is the dynamical quantum Cheshire cat detectable?

Is the dynamical quantum Cheshire cat detectable?

Tracing quantum correlations back to collective interferences

A Heuristic Sketch How It Could Fit All Together With Time

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