| 1. |
- Ahrens, Johan, et al.
(författare)
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Experimental device independent tests of classical and quantum dimensions
- 2012
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Ingår i: Nature Physics. - 1745-2473 .- 1745-2481. ; 8:8, s. 592-595
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Tidskriftsartikel (refereegranskat)abstract
- A fundamental resource in any communication and computation task is the amount of information that can be transmitted and processed. The classical information encoded in a set of states is limited by the number of distinguishable states or classical dimension d(c) of the set. The sets used in quantum communication and information processing contain states that are neither identical nor distinguishable, and the quantum dimension d(q) of the set is the dimension of the Hilbert space spanned by these states. An important challenge is to assess the (classical or quantum) dimension of a set of states in a device-independent way, that is, without referring to the internal working of the device generating the states. Here we experimentally test dimension witnesses designed to efficiently determine the minimum dimension of sets of (three or four) photonic states from the correlations originated from measurements on them, and distinguish between classical and quantum sets of states.
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| 2. |
- Ahrens, Johan, et al.
(författare)
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Two Fundamental Experimental Tests of Nonclassicality with Qutrits
- 2013
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- We report two fundamental experiments on three-level quantum systems (qutrits). The first one tests the simplest task for which quantum mechanics provides an advantage with respect to classical physics. The quantum advantage is certified by the violation of Wright's inequality, the simplest classical inequality violated by quantum mechanics. In the second experiment, we obtain contextual correlations by sequentially measuring pairs of compatible observables on a qutrit, and show the violation of Klyachko et al.'s inequality, the most fundamental noncontextuality inequality violated by qutrits. Our experiment tests exactly Klyachko et al.'s inequality, uses the same measurement procedure for each observable in every context, and implements the sequential measurements in any possible order.
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| 3. |
- Amselem, Elias, et al.
(författare)
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Experimental fully contextual correlations
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Tidskriftsartikel (refereegranskat)abstract
- Quantum correlations are contextual yet, in general, nothing prevents the existence of even morecontextual correlations. We identify and test a simple noncontextual inequality in which the quantumviolation cannot be improved by any hypothetical post-quantum resource, and use it to experimentally obtain correlations in which the maximum noncontextual content, defined as the maximumfraction of noncontextual correlations, is less than 0.06. Our correlations are experimentally generated from the outcomes of sequential compatible measurements on a four-state quantum system encoded in the polarization and path of a single photon.
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| 4. |
- Amselem, Elias, et al.
(författare)
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Experimental fully contextual correlations
- 2012
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 108:20, s. 200405-
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Tidskriftsartikel (refereegranskat)abstract
- Quantum correlations are contextual yet, in general, nothing prevents the existence of even more contextual correlations. We identify and test a noncontextuality inequality in which the quantum violation cannot be improved by any hypothetical postquantum theory, and use it to experimentally obtain correlations in which the fraction of noncontextual correlations is less than 0.06. Our correlations are experimentally generated from the results of sequential compatible tests on a four-state quantum system encoded in the polarization and path of a single photon.
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| 5. |
- Amselem, Elias, et al.
(författare)
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State-Independent Quantum Contextuality with Single Photons
- 2009
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 103:160405
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Tidskriftsartikel (refereegranskat)abstract
- Wepresent an experimental state-independent violation of an inequality for noncontextualtheories on single particles. We show that 20 different single-photonstates violate an inequality which involves correlations between results ofsequential compatible measurements by at least 419 standard deviations. Ourresults show that, for any physical system, even for asingle system, and independent of its state, there is auniversal set of tests whose results do not admit anoncontextual interpretation. This sheds new light on the role ofquantum mechanics in quantum information processing.
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| 6. |
- 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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| 7. |
- Cabello, Adan, et al.
(författare)
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Proposed experiments of qutrit state-independent contextuality and two-qutrit contextuality-based nonlocality
- 2012
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 85:3, s. 032108-
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Tidskriftsartikel (refereegranskat)abstract
- Recent experiments have demonstrated ququart state-independent quantum contextuality and qutrit state-dependent quantum contextuality. So far, the most basic form of quantum contextuality pointed out by Kochen and Specker, and Bell, has eluded experimental confirmation. Here we present an experimentally feasible test to observe qutrit state-independent quantum contextuality using single photons in a three-path setup. In addition, we show that if the same measurements are performed on two entangled qutrits, rather than sequentially on the same qutrit, then the noncontextual inequality becomes a Bell inequality. We show that this connection also applies to other recently introduced noncontextual inequalities.
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| 8. |
- Cabello, Adan, et al.
(författare)
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Simple Hardy-Like Proof of Quantum Contextuality
- 2013
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 111:18, s. 180404-
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Tidskriftsartikel (refereegranskat)abstract
- Contextuality and nonlocality are two fundamental properties of nature. Hardy's proof is considered the simplest proof of nonlocality and can also be seen as a particular violation of the simplest Bell inequality. A fundamental question is: Which is the simplest proof of contextuality? We show that there is a Hardy-like proof of contextuality that can also be seen as a particular violation of the simplest noncontextuality inequality. Interestingly, this new proof connects this inequality with the proof of the Kochen-Specker theorem, providing the missing link between these two fundamental results, and can be extended to an arbitrary odd number n of settings, an extension that can be seen as a particular violation of the n-cycle inequality.
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| 9. |
- D'Ambrosio, Vincenzo, et al.
(författare)
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Experimental Implementation of a Kochen-Specker Set of Quantum Tests
- 2013
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Ingår i: Physical Review X. - 2160-3308. ; 3:1, s. 011012-
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Tidskriftsartikel (refereegranskat)abstract
- The conflict between classical and quantum physics can be identified through a series of yes-no tests on quantum systems, without it being necessary that these systems be in special quantum states. Kochen-Specker (KS) sets of yes-no tests have this property and provide a quantum-versus-classical advantage that is free of the initialization problem that affects some quantum computers. Here, we report the first experimental implementation of a complete KS set that consists of 18 yes-no tests on four-dimensional quantum systems and show how to use the KS set to obtain a state-independent quantum advantage. We first demonstrate the unique power of this KS set for solving a task while avoiding the problem of state initialization. Such a demonstration is done by showing that, for 28 different quantum states encoded in the orbital-angular-momentum and polarization degrees of freedom of single photons, the KS set provides an impossible-to-beat solution. In a second experiment, we generate maximally contextual quantum correlations by performing compatible sequential measurements of the polarization and path of single photons. In this case, state independence is demonstrated for 15 different initial states. Maximum contextuality and state independence follow from the fact that the sequences of measurements project any initial quantum state onto one of the KS set's eigenstates. Our results show that KS sets can be used for quantum-information processing and quantum computation and pave the way for future developments. DOI: 10.1103/PhysRevX.3.011012
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| 10. |
- Gaertner, Sascha, et al.
(författare)
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Experimental demonstration of a quantum protocol for byzantine agreement and liar detection
- 2008
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 100:7, s. 70504-
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Tidskriftsartikel (refereegranskat)abstract
- We introduce a new quantum protocol for solving detectable Byzantine agreement (also called detectable broadcast) between three parties, and also for solving the detectable liar detection problem. The protocol is suggested by the properties of a four-qubit entangled state, and the classical part of the protocol is simpler than that of previous proposals. In addition, we present an experimental implementation of the protocol using four-photon entanglement.
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