| 1. |
- Anwer, Hammad, et al.
(författare)
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Experimental test of maximal tripartite nonlocality using an entangled state and local measurements that are maximally incompatible
- 2019
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 100:2
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Tidskriftsartikel (refereegranskat)abstract
- The only known qubit states that produce maximal quantum violation of a tight Bell inequality with maximally incompatible local measurements are Bell states, Greenberger-Horne-Zeilinger states, and a recently identified three-qubit state called vertical bar S >. Here we report the results of an experiment for preparing vertical bar S > and testing the maximum quantum violation of the corresponding tripartite Bell inequality. Using a heralded source of three entangled photons and three tunable polarization-dependent filters, we experimentally prepare vertical bar S > with 0.924 fidelity. Using maximally incompatible measurements for the three parties, we observe a value of T-26 = 7.30 +/- 0.06, which clearly violates the tight Bell inequality T-26 <= 5. In addition, we show that our setup allows preparing multipartite states that were inaccessible with previous methods and are useful for quantum information and metrology.
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| 2. |
- Jogenfors, Jonathan, 1988-, et al.
(författare)
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Hacking the Bell test using classical light in energy-time entanglement-based quantum key distribution
- 2015
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 1:11
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Tidskriftsartikel (refereegranskat)abstract
- Photonic systems based on energy-time entanglement have been proposed to test local realism using the Bell inequality. A violation of this inequality normally also certifies security of device-independent quantum key distribution (QKD) so that an attacker cannot eavesdrop or control the system. We show how this security test can be circumvented in energy-time entangled systems when using standard avalanche photodetectors, allowing an attacker to compromise the system without leaving a trace. We reach Bell values up to 3.63 at 97.6% faked detector efficiency using tailored pulses of classical light, which exceeds even the quantum prediction. This is the first demonstration of a violation-faking source that gives both tunable violation and high faked detector efficiency. The implications are severe: the standard Clauser-Horne-Shimony-Holt inequality cannot be used to show device-independent security for energy-time entanglement setups based on Franson's configuration. However, device-independent security can be reestablished, and we conclude by listing a number of improved tests and experimental setups that would protect against all current and future attacks of this type.
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| 3. |
- Marques, Breno, et al.
(författare)
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Experimental Observation of Hardy-Like Quantum Contextuality
- 2014
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 113:25
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Tidskriftsartikel (refereegranskat)abstract
- Contextuality is a fundamental property of quantum theory and a critical resource for quantum computation. Here, we experimentally observe the arguably cleanest form of contextuality in quantum theory [A. Cabello et al., Phys. Rev. Lett. 111, 180404 (2013)] by implementing a novel method for performing two sequential measurements on heralded photons. This method opens the door to a variety of fundamental experiments and applications.
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| 4. |
- Mohamed El Hassan, Ashraf, 1976-
(författare)
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Multiparty Quantum Communication and fs-laser Written Integrated Optics Circuits
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Quantum information science, the rapidly developing interdisciplinary field, gives power to the information and communications technologies (ICT) by providing secure communication, precision measurements, ultra-powerful simulation and ultimately computation. It is well known that photons are an ideal candidate for encoding the quantum bit, or "qubit", in quantum information and specially for quantum communication. This thesis consists of two main parts. In the first part, realization of quantum security tasks using optical fibers has been implemented. Bell tests are a cornerstone of quantum key distribution and are necessary for device-independent security. Device-independent Bell inequality test must be performed with care to avoid loopholes. Time-energy entanglement has a distinct advantage over polarization as it is easier transmitted over longer distances, therefore, it may be preferable as a quantum resource to perform reliable key distribution. Novel multi-party communication protocols: secret sharing, detectable Byzantine agreement, clock synchronization, and reduction of communication complexity, all these quantum protocols has been realized without compromising on detection efficiency or generating extremely complex many-particle entangled states. These protocols are realized in an optical fiber setup with sequential phase modulation on single photons. In recent years there has been great interest in fabricating ICT optical setups in low scale in glass chips, which would replace the bulk setups on tables used today. In the second part of the thesis, realization of photonic waveguides in glass has been implemented. Using femtosecond laser inscription of waveguides in glass, photonic quantum technologies and integrated optical circuits are becoming more and more important in miniaturization of optical circuits written in different glass samples for the quantum optics and quantum information processing. These platforms offer stability over the time-scales required for multi-photon coincidence based measurements. The study and optimization the different building blocks for integrated photonic quantum circuits, for instance the directional coupler and Mach-Zehnder interferometer is very important. The principal goal is to develop a method for design, fabrication and characterization of integrated optics circuits for further applications in quantum information. Incorporation of photon sources, detectors, and circuits integrating waveguides technology can be used to produce integrated photonics devices.
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| 5. |
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| 6. |
- Nawareg, Mohamed, et al.
(författare)
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Experimental Measurement-Device-Independent Entanglement Detection
- 2015
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Entanglement is one of the most puzzling features of quantum theory and of great importance for the new field of quantum information. The determination whether a given state is entangled or not is one of the most challenging open problems of the field. Here we report on the experimental demonstration of measurement-device-independent (MDI) entanglement detection using witness method for general two qubits photon polarization systems. In the MDI settings, there is no requirement to assume perfect implementations or neither to trust the measurement devices. This experimental demonstration can be generalized for the investigation of properties of quantum systems and for the realization of cryptography and communication protocols.
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| 7. |
- Nawareg, Mohamed, et al.
(författare)
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Superadditivity of two quantum information resources
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114.
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Tidskriftsartikel (refereegranskat)abstract
- Entanglement is one of the most puzzling features of quantum theory and a principal resource forquantum information processing. It is well known that in classical information theory, the additionof two classical information resources will not lead to any extra advantages. On the contrary, inquantum information a spectacular phenomenon of the super-additivity of two quantum informationresources emerges. It clearly shows that quantum entanglement, which was completely absent inany of the two resources separately, emerges as a result of combining them together. We presentthe rst experimental demonstration of this quantum phenomenon with photonic three-partite nondistillableentangled states.
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| 8. |
- Nawareg, Mohamed, et al.
(författare)
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Superadditivity of two quantum information resources
- 2017
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 3:9
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Tidskriftsartikel (refereegranskat)abstract
- Entanglement is one of the most puzzling features of quantum theory and a principal resource for quantum information processing. It is well known that in classical information theory, the addition of two classical information resources will not lead to any extra advantages. On the contrary, in quantuminformation, a spectacular phenomenon of the superadditivity of two quantum information resources emerges. It shows that quantum entanglement, which was completely absent in any of the two resources separately, emerges as a result of combining them together. We present the first experimental demonstration of this quantum phenomenon with two photonic three-partite nondistillable entangled states shared between three parties Alice, Bob, and Charlie, where the entanglement was completely absent between Bob and Charlie.
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| 9. |
- Sadiq, Muhammad, 1979-, et al.
(författare)
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Experimental Three-Qubit Bound Entanglement
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114.
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Tidskriftsartikel (refereegranskat)abstract
- Entanglement is one of the most puzzling features of quantum theory and of great importancefor the new eld of quantum information. A peculiar form of entanglement, which emerges inmixed quantum states, is recognized as Bound entanglement since this kind of entanglement is nondistillableby local operations and classical communication. Here we report on the rst experimentaldemonstration of a three qubits bound entangled state and fully characterize its entanglement properties.Remarkably, this is the rst experimental realization of a bound entangled state that can beused for generation of multipartite bound information.
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| 10. |
- Smania, Massimiliano, et al.
(författare)
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Experimental certification of an informationally complete quantum measurement in a device-independent protocol
- 2020
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Ingår i: Optica. - 2334-2536. ; 7:2, s. 123-128
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Tidskriftsartikel (refereegranskat)abstract
- Minimal informationally complete positive operator-valued measures (MIC-POVMs) are special kinds of measurement in quantum theory in which the statistics of their d(2)-outcomes are enough to reconstruct any d-dimensional quantum state. For this reason, MIC-POVMs are referred to as standard measurements for quantum information. Here, we report an experiment with entangled photon pairs that certifies, for what we believe is the first time, a MIC-POVM for qubits following a device-independent protocol (i.e., modeling the state preparation and the measurement devices as black boxes, and using only the statistics of the inputs and outputs). Our certification is achieved under the assumption of freedom of choice, no communication, and fair sampling.
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