The Quantum Cheshire Cat effect: Theoretical basis and observational implications

Duprey, Q.; Kanjilal, Som; Sinha, Urbasi; Home, Dipankar; Matzkin, A.

doi:10.1016/j.aop.2018.01.011

Cited by 26 publications

(29 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…(16) was first obtained in [20], where the complex valued fraction in brackets was called "the weak value (WV) of the opera-torQ 2 ". Written in this way, a WV looks like a physical variable of a new kind [21], whose physical significance is still discussed in the literature (see, for example [22], [23]). However the first expression in the r.h.s.…”

Section: H Hertzmentioning

confidence: 99%

A minimalist's view of quantum mechanics

Sokolovski

2020

EPL

View full text Add to dashboard Cite

We analyse a proposition which considers quantum theory as a mere tool for calculating probabilities for sequences of outcomes of observations made by an Observer, who him/herself remains outside the scope of the theory. Predictions are possible, provided a sequence includes at least two such observations. Complex valued probability amplitudes, each defined for an entire sequence of outcomes, are attributed to Observer's reasoning, and the problem of wave function's collapse is dismissed as a purely semantic one. Our examples include quantum "weak values", and a simplified version of the "delayed quantum eraser". PACS numbers:...there must be a certain conformity between nature and our thought. H. HertzUnlike classical mechanics, which has its conceptual issues largely settled by the end of the 19-th century [1], quantum theory appears to need an interpretation, which would go beyond mere statement of its mathematical apparatus. One of the reasons for this is the peculiar use of complex valued wave functions or, more generally, amplitudes, needed whenever one wishes to evaluate frequencies (probabilities) with which the observed events would occur under identical circumstances. Much depends upon how these amplitudes are considered mere computational tools, or essentials attributes of the physical world.. Present suggestions range from the pragmatic Copenhagen interpretation (see [2] and Refs. therein) to the highly subjective QBism (see [3]), and include the Bohmian mechanics (see [4]), Everett's many worlds theory (see [5]), and the consistent histories approach (see [6]), to name but a few. Among the issues at stake is the role and the place of a conscious Observer, famously brought into the discussion as "Wigner's friend" [7]. Another such issue is the "collapse" of the wave function (see [8] and Refs. therein), i.e., a sudden change in the observed system's state, apparently not described by the Schroedinger equation. While many of the mentioned interpretations, [2] -[6], each in its own way, aim at a global description of physical world, our objective is somewhat more modest. The purpose of this paper is to try to formulate a basic approach, consistent with the elementary quantum mechanics, as well as with particular assumptions about the general issues mentioned above. We would like the approach to be as simple as possible, and the assumptions to be few. A certain amount of philosophising is, therefore, unavoidable. We start by asking what could one expect from quantum theory? A possible answer can be found in Feynman's Lectures [9], and we reproduce it here in full: ' So at the present time we must limit ourselves to computing probabilities. We say at the "present time", but we suspect very strongly that it is something that will be with us forever -that it is impossible to beat this puzzle -that it is the way nature really' is.' In the above quote "we" clearly refers to conscious Observers. The probabilities, on the other hand, tend to be mentioned in literature in at lest three different contexts. Obje...

show abstract

Section: H Hertzmentioning

confidence: 99%

A minimalist's view of quantum mechanics

Sokolovski

2020

EPL

View full text Add to dashboard Cite

show abstract

“…In the discussion of the Hardy's paradox [12]-[15] the particle is suspected of simultaneously "being and not being" at the same location [13]. The so called "quantum Cheshire cat" scheme [17]- [21] promises "disembodiment of physical properties from the object they belong to".…”

Section: Pacs Numbersmentioning

confidence: 99%

“…We can also check our calculation by evaluating P(γ) directly. Upon passing a beamsplitter each wave packet is reduced by a factor of 1/ Our last example involves the so called "quantum Cheshire cat" model [17], [18] still discussed in the literature [21]. The authors of [21] suggested that "most of the works criticizing the effect did not introduce a proper framework in order to analyze the issue of spatial separation of a quantum particle from one of its properties", so we take another look at the problem.…”

Section: Composite Systems the Hardy's "Paradox"mentioning

confidence: 99%

“…Upon passing a beamsplitter each wave packet is reduced by a factor of 1/ Our last example involves the so called "quantum Cheshire cat" model [17], [18] still discussed in the literature [21]. The authors of [21] suggested that "most of the works criticizing the effect did not introduce a proper framework in order to analyze the issue of spatial separation of a quantum particle from one of its properties", so we take another look at the problem. Our more detailed analysis can be found in [19], [20], and here we will discuss a minimalist version of the model, which captures its essential properties.…”

Section: Composite Systems the Hardy's "Paradox"mentioning

confidence: 99%

See 1 more Smart Citation

Path probabilities for consecutive measurements, and certain “quantum paradoxes”

Sokolovski

2018

Annals of Physics

View full text Add to dashboard Cite

We consider a finite-dimensional quantum system, making a transition between known initial and final states. The outcomes of several accurate measurements, which could be made in the interim, define virtual paths, each endowed with a probability amplitude. If the measurements are actually made, the paths, which may now be called "real", acquire also the probabilities, related to the frequencies, with which a path is seen to be travelled in a series of identical trials. Different sets of measurements, made on the same system, can produce different, or incompatible, statistical ensembles, whose conflicting attributes may, although by no means should, appear "paradoxical". We describe in detail the ensembles, resulting from intermediate measurements of mutually commuting, or non-commuting, operators, in terms of the real paths produced. In the same manner, we analyse the Hardy's and the "three box" paradoxes, the photon's past in an interferometer, the "quantum Cheshire cat" experiment, as well as the closely related subject of "interaction-free measurements". It is shown that, in all these cases, inaccurate "weak measurements" produce no real paths, and yield only limited information about the virtual paths' probability amplitudes. PACS numbers:Recently, there has been significant interest in the properties of a pre-and post-selected quantum systems, and, in particular, in the description of such systems during the time between the preparation, and the arrival in the pre-determined final state (see, for example [1] and the Refs. therein). Intermediate state of the system can be probed by performing, one after another, measurements of various physical quantities. Although produced from the same quantum system, statistical ensembles, resulting from different sets of measurements, are known to have conflicting and seemingly incompatible qualities. These conflicts have, in turn, led to the discussion of certain "quantum paradoxes", allegedly specific to a system, subjected to post-selection. Such is, for example, the "three box paradox" [2]-[5], claiming that a particle can be, at the same time, at two different locations "with certainty". A similarly "paradoxical" suggestion that a photon could, on its way to detection, have visited the places it had "never entered, nor left, was made in [6]- [7], and further discussed in [8]- [11]. In the discussion of the Hardy's paradox [12]-[15] the particle is suspected of simultaneously "being and not being" at the same location [13]. The so called "quantum Cheshire cat" scheme [17]- [21] promises "disembodiment of physical properties from the object they belong to".One can easily dismiss a "paradox" of this type simply by noting that the conflicting features are never observed in the same experimental setup, and therefore, never occur "simultaneously" [5],[15], [22], [23], [24], [25] . (We agree: one can use a piece of plasticine to make a ball, or a cube, but should not claim that an object can be a ball and a cube at the same time.) There have been attempts to ascertain "simu...

show abstract

“…Quantum Chesire Cat has opened up new understanding of quantum systems and attracted a lot of debates and discussions [3,7,8,14]. It pertains not only to photons and their polarizations but can, in principle, be observed with any quantum system and its property, such as neutron and its magnetic moment, electron and its charge and so on.…”

Section: Introductionmentioning

confidence: 99%

Can two quantum Cheshire cats exchange grins?

Das

Pati

2020

New J. Phys.

View full text Add to dashboard Cite

A common-sense perception of a physical system is that it is inseparable from its physical properties. The notion of Quantum Chesire Cat challenges this, as far as quantum systems are concerned. It shows that a quantum system can be decoupled from its physical property under suitable pre and postselections. However, in the Quantum Cheisre Cat setup, the decoupling is not permanent. The photon, for example, and its polarization is separated and then recombined. In this paper, we present a thought experiment where we decouple two photons from their respective polarizations and then interchange them during recombination. Thus, our proposal shows that that the belongingness of a property for a physical system is very volatile in the world of quantum mechanics.

show abstract

The Quantum Cheshire Cat effect: Theoretical basis and observational implications

Cited by 26 publications

References 32 publications

A minimalist's view of quantum mechanics

A minimalist's view of quantum mechanics

Path probabilities for consecutive measurements, and certain “quantum paradoxes”

Can two quantum Cheshire cats exchange grins?

Contact Info

Product

Resources

About