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Non-monotonic projection probabilities as a function of distinguishability
KTH, School of Engineering Sciences (SCI), Applied Physics.ORCID iD: 0000-0002-2082-9583
KTH, School of Engineering Sciences (SCI), Applied Physics.
2014 (English)In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 16, no 1, article id 013006Article in journal (Refereed) Published
Abstract [en]

Typically, quantum superpositions, and thus measurement projections of quantum states involving interference, decrease (or increase) monotonically as a function of increased distinguishability. Distinguishability, in turn, can be a consequence of decoherence, for example caused by the (simultaneous) loss of excitation or due to inadequate mode matching (either deliberate or indeliberate). It is known that for some cases of multi-photon interference a non-monotonic decay of projection probabilities occurs, which has so far been attributed to interference between four or more photons. We show that such a non-monotonic behavior of projection probabilities is not unnatural, and can also occur for single-photon and even semiclassical states. Thus, while the effect traces its roots from indistinguishability and thus interference, the states for which this can be observed do not need to have particular quantum features.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2014. Vol. 16, no 1, article id 013006
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
URN: urn:nbn:se:kth:diva-206217DOI: 10.1088/1367-2630/16/1/013006ISI: 000330574800001Scopus ID: 2-s2.0-84892740861OAI: oai:DiVA.org:kth-206217DiVA, id: diva2:1091971
Note

QC 20170502

Available from: 2017-04-28 Created: 2017-04-28 Last updated: 2017-11-29Bibliographically approved
In thesis
1. Majorana Representation in Quantum Optics: SU(2) Interferometry and Uncertainty Relations
Open this publication in new window or tab >>Majorana Representation in Quantum Optics: SU(2) Interferometry and Uncertainty Relations
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The algebra of SU(2) is ubiquitous in physics, applicable both to the atomic spin states and the polarisation states of light. The method developed by Majorana and Schwinger to represent pure, symmetric spin-states of arbitrary value as a product of spin-1/2 states is a powerful tool that allows for a great conceptual and practical simplification. Foremost, it allows the representation of a qudit on the same geometry as a qubit, i.e., the Bloch sphere.

An experimental implementation of the Majorana representation in the realm of quantum optics is presented. The technique allows the projection of arbitrary quantum states from a coherent state input. It is also shown that the method can be used to synthesise arbitrary interference patterns with unit visibility, and without resorting to quantum resources. In this context, it is argued that neither the shape nor the visibility of the interference pattern is a good measure of quantumness. It is only the measurement scheme that allows for the perceived quantum behaviour.

The Majorana representation also proves useful in delineating uncertainty limits of states with a particular spin value. Issues with traditional uncertainty relations involving the SU(2) operators, such as trivial bounds for certain states and non-invariance, are thereby resolved with the presented pictorial solution.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. p. 66
Series
TRITA-FYS, ISSN 0280-316X ; 2017:25
Keywords
Majorana representation, Quantum optics, interferometry, SU(2) group, angular momentum, arbitrary optical gates
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-206222 (URN)978-91-7729-367-5 (ISBN)
Public defence
2017-05-12, FA31, AlbaNova University Center, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20170428

Available from: 2017-04-28 Created: 2017-04-28 Last updated: 2017-04-28Bibliographically approved

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Björk, Gunnar

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