| 1. |
- Aolita, Leandro, et al.
(författare)
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Fully nonlocal quantum correlations
- 2012
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 85:3, s. 032107-
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Tidskriftsartikel (refereegranskat)abstract
- Quantum mechanics is a nonlocal theory, but not as nonlocal as the no-signalling principle allows. However, there exist quantum correlations that exhibit maximal nonlocality: they are as nonlocal as any nonsignalling correlation and thus have a local content, quantified by the fraction p(L) of events admitting a local description, equal to zero. We exploit the known link between the Kochen-Specker and Bell theorems to derive a maximal violation of a Bell inequality from every Kochen-Specker proof. We then show that these Bell inequalities lead to experimental bounds on the local content of quantum correlations that are significantly better than those based on other constructions. We perform the experimental demonstration of a Bell test originating from the Peres-Mermin Kochen-Specker proof, providing an upper bound on the local content pL less than or similar to 0.22.
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| 2. |
- Santagiustina, Francesco B. L., et al.
(författare)
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Experimental post-selection loophole-free time-bin and energy-time nonlocality with integrated photonics
- 2024
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Ingår i: Optica. - : Optica Publishing Group. - 2334-2536. ; 11:4, s. 498-511
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Tidskriftsartikel (refereegranskat)abstract
- Time-bin (TB) and energy-time (ET) entanglements are crucial resources for long-distance quantum information processing. However, their standard implementations suffer from the so-called post-selection loophole that allows for classical simulation and thus prevents quantum advantage. The post-selection loophole has been addressed in proof-of-principle experiments. An open problem though is to close it in real-life applications based on integrated technologies. This is especially important since, so far, all integrated sources of TB and ET entanglements suffer from the post-selection loophole. Here, we report post-selection loophole-free certification of TB or ET entanglement in integrated technologies, by implementing in a silicon nitride chip the "hug" scheme [Phys. Rev. Lett. 102, 040401 (2009)] and certifying genuine TB entanglement through the violation of a Bell inequality.
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| 3. |
- Tomasin, Marco, et al.
(författare)
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High-visibility time-bin entanglement for testing chained Bell inequalities
- 2017
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Ingår i: Physical Review A. - : AMER PHYSICAL SOC. - 2469-9926. ; 95:3
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Tidskriftsartikel (refereegranskat)abstract
- The violation of Bells inequality requires a well-designed experiment to validate the result. In experiments using energy-time and time-bin entanglement, initially proposed by Franson in 1989, there is an intrinsic loophole due to the high postselection. To obtain a violation in this type of experiment, a chained Bell inequality must be used. However, the local realism bound requires a high visibility in excess of 94.63% in the time-bin entangled state. In this work, we show how such a high visibility can be reached in order to violate a chained Bell inequality with six, eight, and ten terms.
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| 4. |
- Vallone, Giuseppe, et al.
(författare)
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Bell scenarios in which nonlocality and entanglement are inversely related
- 2014
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 89:1, s. 012102-
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Tidskriftsartikel (refereegranskat)abstract
- We show that for two-qubit chained Bell inequalities with an arbitrary number of measurement settings, nonlocality and entanglement are not only different properties but are inversely related. Specifically, we analytically prove that in absence of noise, robustness of nonlocality, defined as the maximum fraction of detection events that can be lost such that the remaining ones still do not admit a local model, and concurrence are inversely related for any chained Bell inequality with an arbitrary number of settings. The closer quantum states are to product states, the harder it is to reproduce quantum correlations with local models. We also show that, in presence of noise, nonlocality and entanglement are simultaneously maximized only when the noise level is equal to the maximum level tolerated by the inequality; in any other case, a more nonlocal state is always obtained by reducing the entanglement. In addition, we observed that robustness of nonlocality and concurrence are also inversely related for the Bell scenarios defined by the tight two-qubit three-setting I-3322 inequality, and the tight two-qutrit inequality I-3.
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| 5. |
- Vedovato, Francesco, et al.
(författare)
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Postselection-Loophole-Free Bell Violation with Genuine Time-Bin Entanglement
- 2018
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Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 121:19
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Tidskriftsartikel (refereegranskat)abstract
- Entanglement is an invaluable resource for fundamental tests of physics and the implementation of quantum information protocols such as device-independent secure communications. In particular, time-bin entanglement is widely exploited to reach these purposes both in free space and optical fiber propagation, due to the robustness and simplicity of its implementation. However, all existing realizations of time-bin entanglement suffer from an intrinsic postselection loophole, which undermines their usefulness. Here, we report the first experimental violation of Bells inequality with "genuine" time-bin entanglement, free of the postselection loophole. We introduced a novel function of the interferometers at the two measurement stations, that operate as fast synchronized optical switches. This scheme allowed us to obtain a postselection-loophole-free Bell violation of more than 9 standard deviations. Since our scheme is fully implementable using standard fiber-based components and is compatible with modem integrated photonics, our results pave the way for the distribution of genuine time-bin entanglement over long distances.
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| 6. |
- Zhao, Haiyu, et al.
(författare)
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Modulation of DNA Repair Systems in Blind Cavefish during Evolution in Constant Darkness
- 2018
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Ingår i: Current Biology. - : Cell Press. - 0960-9822 .- 1879-0445. ; 28:20, s. 3229-3243
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Tidskriftsartikel (refereegranskat)abstract
- How the environment shapes the function and evolution of DNA repair systems is poorly understood. In a comparative study using zebrafish and the Somalian blind cavefish, Phreatichthys andruzzii, we reveal that during evolution for millions of years in continuous darkness, photoreactivation DNA repair function has been lost in P. andruzzii. We demonstrate that this loss results in part from loss-of-function mutations in pivotal DNA-repair genes. Specifically, C-terminal truncations in P. andruzzii DASH and 6-4 photolyase render these proteins predominantly cytoplasmic, with consequent loss in their functionality. In addition, we reveal a general absence of light-, UV-, and ROS-induced expression of P. andruzzii DNA-repair genes. This results from a loss of function of the D-box enhancer element, which coordinates and enhances DNA repair in response to sunlight. Our results point to P. andruzzii being the only species described, apart from placental mammals, that lacks the highly evolutionary conserved photoreactivation function. We predict that in the DNA repair systems of P. andruzzii, we may be witnessing the first stages in a process that previously occurred in the ancestors of placental mammals during the Mesozoic era.
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| 7. |
- Zhao, Haiyu, et al.
(författare)
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Regulation of ddb2 expression in blind cavefish and zebrafish reveals plasticity in the control of sunlight-induced DNA damage repair
- 2021
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Ingår i: PLOS Genetics. - : Public Library of Science (PLoS). - 1553-7390 .- 1553-7404. ; 17:2
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Tidskriftsartikel (refereegranskat)abstract
- We have gained considerable insight into the mechanisms which recognize and repair DNA damage, but how they adapt to extreme environmental challenges remains poorly understood. Cavefish have proven to be fascinating models for exploring the evolution of DNA repair in the complete absence of UV-induced DNA damage and light. We have previously revealed that the Somalian cavefish Phreatichthys andruzzii, lacks photoreactivation repair via the loss of light, UV and ROS-induced photolyase gene transcription mediated by D-box enhancer elements. Here, we explore whether other systems repairing UV-induced DNA damage have been similarly affected in this cavefish model. By performing a comparative study using P. andruzzii and the surface-dwelling zebrafish, we provide evidence for a conservation of sunlight-regulated Nucleotide Excision Repair (NER). Specifically, the expression of the ddb2 gene which encodes a key NER recognition factor is robustly induced following exposure to light, UV and oxidative stress in both species. As in the case of the photolyase genes, D-boxes in the ddb2 promoter are sufficient to induce transcription in zebrafish. Interestingly, despite the loss of D-box-regulated photolyase gene expression in P. andruzzii, the D-box is required for ddb2 induction by visible light and oxidative stress in cavefish. However, in the cavefish ddb2 gene this D-box-mediated induction requires cooperation with an adjacent, highly conserved E2F element. Furthermore, while in zebrafish UV-induced ddb2 expression results from transcriptional activation accompanied by stabilization of the ddb2 mRNA, in P. andruzzii UV induces ddb2 expression exclusively via an increase in mRNA stability. Thus, we reveal plasticity in the transcriptional and post transcriptional mechanisms regulating the repair of sunlight-induced DNA damage under long-term environmental challenges.Author summaryThe integrity of genetic information is frequently challenged by environmental factors such as sunlight which induce mutations in DNA. Therefore, DNA damage repair mechanisms are ubiquitous and highly conserved. While significant progress has been made in understanding how these mechanisms recognize and repair DNA damage, how they adapt to long-term environmental challenges remains poorly understood. Cavefish have proven to be fascinating models for exploring the function of DNA repair systems in extreme photic environments. We have previously shown that during evolution for millions of years in complete isolation from sunlight, the Somalian cavefish, Phreatichthys andruzzii has lost photoreactivation, a ubiquitous, light-dependent DNA repair system. This results in part from a loss of light, UV and ROS-induced gene transcription. Have other repair systems targeting UV-induced DNA damage been affected in cavefish? Here, we provide evidence that Nucleotide Excision Repair (NER) function is retained in cavefish and is upregulated upon sunlight exposure. Furthermore, we reveal complexity in the transcriptional and posttranscriptional mechanisms regulating the repair of UV-induced DNA damage.
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