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Comment on "Franson Interference Generated by a Two-Level System"
Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.ORCID iD: 0000-0002-8032-1466
Departamento de Física Aplicada II, Universidad de Sevilla, Sevilla, Spain.
Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.ORCID iD: 0000-0002-1082-8325
2017 (English)Other (Other academic)
Abstract [en]

In a recent Letter [Phys. Rev. Lett. 118, 030501 (2017)], Peiris, Konthasinghe, and Muller report a Franson interferometry experiment using pairs of photons generated from a two-level semiconductor quantum dot. The authors report a visibility of 66% and claim that this visibility “goes beyond the classical limit of 50% and approaches the limit of violation of Bell’s inequalities (70.7%).” We explain why we do not agree with this last statement and how to fix the problem.

Place, publisher, year, pages
Ithaca, New York, USA: Cornell University Press, 2017. , p. 1
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:liu:diva-142073OAI: oai:DiVA.org:liu-142073DiVA, id: diva2:1150938
Available from: 2017-10-20 Created: 2017-10-20 Last updated: 2017-10-20
In thesis
1. Breaking the Unbreakable: Exploiting Loopholes in Bell’s Theorem to Hack Quantum Cryptography
Open this publication in new window or tab >>Breaking the Unbreakable: Exploiting Loopholes in Bell’s Theorem to Hack Quantum Cryptography
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis we study device-independent quantum key distribution based on energy-time entanglement. This is a method for cryptography that promises not only perfect secrecy, but also to be a practical method for quantum key distribution thanks to the reduced complexity when compared to other quantum key distribution protocols. However, there still exist a number of loopholes that must be understood and eliminated in order to rule out eavesdroppers. We study several relevant loopholes and show how they can be used to break the security of energy-time entangled systems. Attack strategies are reviewed as well as their countermeasures, and we show how full security can be re-established.

Quantum key distribution is in part based on the profound no-cloning theorem, which prevents physical states to be copied at a microscopic level. This important property of quantum mechanics can be seen as Nature's own copy-protection, and can also be used to create a currency based on quantummechanics, i.e., quantum money. Here, the traditional copy-protection mechanisms of traditional coins and banknotes can be abandoned in favor of the laws of quantum physics. Previously, quantum money assumes a traditional hierarchy where a central, trusted bank controls the economy. We show how quantum money together with a blockchain allows for Quantum Bitcoin, a novel hybrid currency that promises fast transactions, extensive scalability, and full anonymity.

Abstract [sv]

En viktig konsekvens av kvantmekaniken är att okända kvanttillstånd inte kan klonas. Denna insikt har gett upphov till kvantkryptering, en metod för två parter att med perfekt säkerhet kommunicera hemligheter. Ett komplett bevis för denna säkerhet har dock låtit vänta på sig eftersom en attackerare i hemlighet kan manipulera utrustningen så att den läcker information. Som ett svar på detta utvecklades apparatsoberoende kvantkryptering som i teorin är immun mot sådana attacker.

Apparatsoberoende kvantkryptering har en mycket högre grad av säkerhet än vanlig kvantkryptering, men det finns fortfarande ett par luckor som en attackerare kan utnyttja. Dessa kryphål har tidigare inte tagits på allvar, men denna avhandling visar hur även små svagheter i säkerhetsmodellen läcker information till en attackerare. Vi demonstrerar en praktisk attack där attackeraren aldrig upptäcks trots att denne helt kontrollerar systemet. Vi visar också hur kryphålen kan förhindras med starkare säkerhetsbevis.

En annan tillämpning av kvantmekanikens förbud mot kloning är pengar som använder detta naturens egna kopieringsskydd. Dessa kvantpengar har helt andra egenskaper än vanliga mynt, sedlar eller digitala banköverföringar. Vi visar hur man kan kombinera kvantpengar med en blockkedja, och man får då man en slags "kvant-Bitcoin". Detta nya betalningsmedel har fördelar över alla andra betalsystem, men nackdelen är att det krävs en kvantdator.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2017. p. 239
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1875
National Category
Atom and Molecular Physics and Optics Communication Systems
Identifiers
urn:nbn:se:liu:diva-140912 (URN)10.3384/diss.diva-140912 (DOI)9789176854600 (ISBN)
Public defence
2017-11-17, Ada Lovelace, B House, Campus Valla, Linköping, 13:00 (English)
Opponent
Supervisors
Available from: 2017-10-23 Created: 2017-10-20 Last updated: 2017-10-23Bibliographically approved

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