Observation of a quantum Cheshire Cat in a matter-wave interferometer experiment

Denkmayr, Tobias; Geppert, Hermann; Sponar, Stephan; Lemmel, Hartmut; Matzkin, A.; Tollaksen, Jeff; Hasegawa, Yuji

doi:10.1038/ncomms5492

Cited by 177 publications

(246 citation statements)

References 39 publications

(79 reference statements)

Supporting

Mentioning

234

Contrasting

Order By: Relevance

“…Aside from possible practical applications (see [3] and references therein), it has been suggested that such values have foundational significance. For example, both their theoretical prediction and experimental observation are said to shed light on "quantum paradoxes" [4][5][6][7][8][9] and even the nature of time [10].…”

mentioning

confidence: 99%

Anomalous Weak Values Are Proofs of Contextuality

2014

View full text Add to dashboard Cite

The average result of a weak measurement of some observable A can, under post-selection of the measured quantum system, exceed the largest eigenvalue of A. The nature of weak measurements, as well as the presence of post-selection and hence possible contribution of measurement-disturbance, has led to a long-running debate about whether or not this is surprising. Here, it is shown that such "anomalous weak values" are non-classical in a precise sense: a sufficiently weak measurement of one constitutes a proof of contextuality. This clarifies, for example, which features must be present (and in an experiment, verified) to demonstrate an effect with no satisfying classical explanation.In 1988 Aharonov, Albert and Vaidman explained "How the result of a measurement of a component of the spin of a spin-1 2 particle can turn out to be 100." [1] Defining the weak value of an observable A for a quantum system prepared in state |ψ and post-selected on giving the first outcome of {|φ φ| , I − |φ φ|},they exhibited a |ψ and |φ on a qubit for which Z w = 100. The motivation for weak values starts by considering a von Neumann model [2] of the measurement of A. The strength of the interaction between the system and "pointer" is then drastically reduced, such that the pointer reading is correlated only slightly with A. The weak value then arises as an approximation of the average pointer reading to first order in the interaction strength. Weak values outside the eigenvalue range of A are termed anomalous. Aside from possible practical applications (see [3] and references therein), it has been suggested that such values have foundational significance. For example, both their theoretical prediction and experimental observation are said to shed light on "quantum paradoxes" [4][5][6][7][8][9] and even the nature of time [10].However, there is still no consensus on the most basic question about anomalous weak values: to what extent do they represent a genuinely non-classical effect? The lesser the extent, the more severe the limitations on their practical and foundational significance.The arguments that anomalous weak values are nonclassical have often been somewhat heuristic, appearing to depend on issues such as the extent to which weak measurements should be called measurements at all [11,12]. Perhaps the most rigorous evidence provided so far is a connection between anomalous weak values and the failure of a notion of classicality called "macroscopic realism" [13][14][15]. On the other hand, classical models have been given that reproduce various aspects of the phenomena [16][17][18].The question can be made precise by asking if anomalous weak values constitute proofs of the incompatibility of quantum theory with non-contextual ontological models [19], or equivalently [20] if anomalous weak values require negativity in all quasi-probability representations. This was conjectured to be the case in [21]. Here I will prove it. Interestingly, the proof hinges on two issues already identified in the literature: what do weak measureme...

show abstract

mentioning

confidence: 99%

Anomalous Weak Values Are Proofs of Contextuality

2014

View full text Add to dashboard Cite

show abstract

“…This behavior can be quantified by calculating the weak values using the recorded intensities. Details of this calculation are presented in detail in the Methods of [66]. The final results for the weak values of the populations and magnetic moment are summarized in Table 1.…”

Section: Methodsmentioning

confidence: 99%

Fundamental Features of Quantum Dynamics Studied in Matter-Wave Interferometry—Spin Weak Values and the Quantum Cheshire-Cat

Sponar

Denkmayr

Geppert

et al. 2016

Atoms

Self Cite

View full text Add to dashboard Cite

Abstract:The validity of quantum-mechanical predictions has been confirmed with a high degree of accuracy in a wide range of experiments. Although the statistics of the outcomes of a measuring apparatus have been studied intensively, little has been explored and is known regarding the accessibility of quantum dynamics. For these sorts of fundamental studies of quantum mechanics, interferometry using neutron matter-waves in particular, provides almost ideal experimental circumstances. In this device quantum interference between spatially separated beams occurs on a macroscopic scale. Recently, the full determination of weak-values of neutrons 1 /2 -spin adds a new aspect to the study of quantum dynamics. Moreover, a new counter-intuitive phenomenon, called quantum Cheshire Cat, is observed in an interference experiment. In this article, we present an overview of these experiments.

show abstract

“…When researchers separated a beam of neutrons from their magnetic moment (Denkmayr et al 2014;Morgan 2014), they found "the Cat in one place, and its grin in another" (Aharonov et al 2013: 1).…”

Section: Ii) Characters From Carroll's Books On Alice Transmitted Intmentioning

confidence: 99%

Alice’s Adventures in Scienceland

Bilban¹

2016

L&L

View full text Add to dashboard Cite

Lewis Carroll based much of his nonsense humour and curious themes in Alice's Adventures in Wonderland and Through the Looking-Glass on his expertise in logic and mathematics. Years after the books were written, Alice, under the guidance of new authors, is experiencing new adventures in different regions of Scienceland, from Quantumland to Computerland. Situations, characters and concepts from Carroll's books on Alice are often reused in different scientific fields to illustrate scientific phenomena. Alice has become an archetype placeholder name for experimentalists in physics and cryptology. Carroll's books on Alice have been adopted by the scientific community and it seems that, although it is characteristic for science to keep changing, Alice's adventures in Scienceland are here to stay.

show abstract

Observation of a quantum Cheshire Cat in a matter-wave interferometer experiment

Cited by 177 publications

References 39 publications

Anomalous Weak Values Are Proofs of Contextuality

Anomalous Weak Values Are Proofs of Contextuality

Fundamental Features of Quantum Dynamics Studied in Matter-Wave Interferometry—Spin Weak Values and the Quantum Cheshire-Cat

Alice’s Adventures in Scienceland

Contact Info

Product

Resources

About