Breaking the Unbreakable: Exploiting Loopholes in Bell’s Theorem to Hack Quantum Cryptography

Abstract

Akademisk avhandlingsom för avläggande av doktorsexamen vid Linköpings Universitet kommer att offentligt försvaras i sal Ada Lovelace, hus B, universitetsområde Valla, fredagen den 17 november 2017 kl. 13:00. Fakultetsopponent är Professor Marek Zukowski, Instytut Fizyki Teoretycznej i Astrofizyki, Uniwersytet Gdański. AbstractIn 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 quantum mechanics, 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. Cover imageLayout of the Franson interferometer, a scheme used for testing the Bell inequality using energy-time entanglement. AbstractIn 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 quantum mechanics, i.e., quantum money. Here, the traditional copy-protection mechanisms of traditional coins and banknotes can be abandoned in favor of the laws of...

How post-selection affects device-independent claims under the fair sampling assumption

“…Consequently, a separable quantum state cannot violate any Bell inequality when using lossy detectors and post-selection, if fair sampling holds. Similarly, under fair sampling it is impossible to violate the quantum bound of a Bell operator with post-selected statistics: in fact, the models and experiments showing that postselection can lead to incorrect conclusions [5,6,7,8,9,10,11,12] do not satisfy fair sampling. 4 The strong and homogeneous fair sampling assumptions Now we consider two special cases of fair sampling, which we call strong and homogeneous fair sampling.…”

“…erroneously deducing the non-locality of a local model [5,6,7]. Such canny local models are not abstract theoretical constructions, but have been produced experimentally with simple optical elements and detectors that are commonly used [8,9,10,11,12].…”

Energy-Efficient Mining on a Quantum-Enabled Blockchain Using Light

“…non-quantum) platforms. 48,49,50 By presenting an alternative blockchain architecture, we hope to promote further investigation into issues and advantages of novel quantum-enabled blockchain protocols, 51,52,53,54,55,56 and more generally, offer insight into the process of mapping traditional scientific computing technologies onto newly emerging quantum technologies. 57,58,59,60,61,62…”