Search results for " quantum coherence"
showing 10 items of 20 documents
Validating and controlling quantum enhancement against noise by motion of a qubit
2019
Experimental validation and control of quantum traits for an open quantum system are important for any quantum information purpose. We consider a traveling atom qubit as a quantum memory with adjustable velocity inside a leaky cavity, adopting a quantum witness as a figure of merit for quantumness assessment. We show that this model constitutes an inherent physical instance where the quantum witness does not work properly if not suitably optimized. We then supply the optimal intermediate blind measurements which make the quantum witness a faithful tester of quantum coherence. We thus find that larger velocities protect quantumness against noise, leading to lifetime extension of hybrid qubit…
Cavity-based architecture to preserve quantum coherence and entanglement
2015
Quantum technology relies on the utilization of resources, like quantum coherence and entanglement, which allow quantum information and computation processing. This achievement is however jeopardized by the detrimental effects of the environment surrounding any quantum system, so that finding strategies to protect quantum resources is essential. Non-Markovian and structured environments are useful tools to this aim. Here we show how a simple environmental architecture made of two coupled lossy cavities enables a switch between Markovian and non-Markovian regimes for the dynamics of a qubit embedded in one of the cavity. Furthermore, qubit coherence can be indefinitely preserved if the cavit…
Three New Medicagenic Acid Saponins from Polygala micranthaGuill. & Perr.
2011
Three new medicagenic acid saponins, micranthosides A–C (1–3), were isolated from the roots of Polygala micranthaGuill. & Perr., along with six known presenegenin saponins. Their structures were elucidated on the basis of extensive 1D- and 2D-NMR experiments (1H, 13C, DEPT, COSY, TOCSY, NOESY, HSQC, and HMBC) and mass spectrometry as 3-O-β-D-glucopyranosylmedicagenic acid 28-[O-β-D-galactopyranosyl-(14)-O-β-D-xylopyranosyl-(14)-O-α-L-rhamnopyranosyl-(12)-β-D-fucopyranosyl] ester (1), 3-O-β-D-glucopyranosylmedicagenic acid 28-[O-6-O-acetyl-β-D-galactopyranosyl-(14)-O-β-D-xylopyranosyl-(14)-O-α-L-rhamnopyranosyl-(12)-β-D-fucopyranosyl] ester (2), and 3-O-{O-β-D-glucopyranosyl-(13)-O-[β-D-gluc…
Four new triterpene saponins from Bupleurum rigidum L.
2018
Abstract Four previously undescribed triterpene saponins (1-4) were isolated from the EtOH/H2O extract of the aerial parts of Bupleurum rigidum, together with a known structural analogue. Their structures were elucidated by analysis of 1D-(1H, 13C) and 2D-NMR (1H-1H COSY, TOCSY, ROESY, HSQC, HMBC) spectroscopic data and mass spectrometry (ESI- and HR-ESI-MS) and by comparison with those of related metabolites. An unusual structure was characterized as 3-O-β-D-glucopyranosyl-(1 → 2)-[ β-D-glucopyranosyl-(1 → 3)]- β-D-fucopyranosyl-21-O-β-D-glucoyranosyl-3β,16β,21β,23-tetrahydroxy-13,28-epoxyolean-11-ene (1). The three other compounds shared the same sugar sequence as 1 and differed by the st…
Triterpene saponins from the roots of Bupleurum spinosum Gouan
2020
Abstract Three previously undescribed triterpene saponins, and four known ones, were isolated from the EtOH/H2O extract of the roots of Bupleurum spinosum. Their structures were characterized using spectroscopic techniques including 1D and 2D NMR (1H, 13C, COSY, TOCSY, ROESY, HSQC, and HMBC) experiments and mass spectrometry as 3-O-β-D-glucopyranosyl-(1→6)-[β-D-glucopyranosyl-(1→2)]-[α-L-rhamnopyranosyl-(1→4)]-β-D-glucopyranosyl-3β,16β,23,28-tetrahydroxyolean-12-ene, 3-O-β-D-glucopyranosyl-(1→6)-[β-D-glucopyranosyl-(1→2)]-[α-L-rhamnopyranosyl-(1→4)]-β-D-glucopyranosyl-3β,16β,28-trihydroxy-23-oxoolean-12-ene, 3-O-β-D-glucopyranosyl-(1→6)-[α-L-rhamnopyranosyl(1→4)]-β-D-glucopyranosyl-3β,16β,2…
A new oleanane glycoside from the roots ofAstragalus caprinus
2006
A novel oleanane-type triterpene saponin (1) together with two known molecules, soyasapogenol B and astragaloside VIII were isolated from the roots of Astragalus caprinus. Their structural elucidation was performed mainly by 2D NMR techniques (COSY, TOCSY, NOESY, HSQC, HMBC) and mass spectrometry. Compound 1 was determined as 3-O-[alpha-L-rhamnopyranosyl-(1 --> 2)-beta-D-glucuronopyranosyl]-22-O-beta-D-apiofuranosyl-soyasapogenol B.
New Triterpene Saponins fromAcanthophyllum pachystegium
2004
Four new triterpenoid saponins, pachystegiosides A (1), B (2), C (3), and D (4), were isolated from the roots of Acanthophyllum pachystegium K. H. Their structures were elucidated by means of a combination of homo- and heteronuclear 2D-NMR techniques (COSY, TOCSY, NOESY, HSQC, and HMBC) and by FAB-MS. The new compounds were characterized as 3-O-{O-β-D-galactopyranosyl-(12)-O-[β-D-xylopyranosyl-(13)]-β-D-glucuronopyranosyl}quillaic acid 28-{O-β-D-xylopyranosyl-(13)-O-β-D-xylopyranosyl-(14)-O-α-L-rhamnopyranosyl-(12)-O-[3,4-di-O-acetyl-β-D-quinovopyranosyl-(14)]-β-D-fucopyranosyl}ester (1), 3-O-{O-β-D-galactopyranosyl-(12)-O-[β-D-xylopyranosyl-(13)]-β-D-glucuronopyranosyl}quillaic acid 28-{O-…
Triterpenoid saponins from Piptadeniastrum africanum (Hook. f.) Brenan
2013
One new triterpenoid saponin, named piptadeniaoside (1), along with two known saponins (2–3) have been isolated from the stem bark of Piptadeniastrum africanum. After previous isolation of flavone derivatives from this plant, new phytochemical investigations were performed for its saponin content. Their structures were established by direct interpretation of their spectral data, mainly HRESIMS, 1D NMR (1H, 13C NMR, DEPT) and 2D NMR (COSY, NOESY, HSQC and HMBC), and by comparison with the literature data.
Foetidissimosides C–F, Novel Glycosides from the Roots ofCucurbita foetidissima
2004
Two novel echinocystic acid (=(3β,16α)-3,16-dihydroxyolean-12-en-28-oic acid) glycosides, foetidissimosides C (1), and D (2), along with new cucurbitane glycosides, i.e., foetidissimosides E/F (3/4) as an 1 : 1 mixture of the (24R)/(24S) epimers, were obtained from the roots of Cucurbita foetidissima. Their structures were elucidated by means of a combination of homo- and heteronuclear 2D-NMR techniques (COSY, TOCSY, NOESY, ROESY, HSQC, and HMBC), and by FAB-MS. The new compounds were characterized as (3β,16α)-28-{[O-β-D-glucopyranosyl-(13)-O-β-D-xylopyranosyl-(14)-O-6-deoxy-α-L-mannopyranosyl-(12)-α-L-arabinopyranosyl]oxy}-16-hydroxy-28-oxoolean -12-en-3-yl β-D-glucopyranosiduronic acid (1…
Foetidissimosides C—F, Novel Glycosides from the Roots of Cucurbita foetidissima.
2004
Two novel echinocystic acid (=(3β,16α)-3,16-dihydroxyolean-12-en-28-oic acid) glycosides, foetidissimosides C (1), and D (2), along with new cucurbitane glycosides, i.e., foetidissimosides E/F (3/4) as an 1 : 1 mixture of the (24R)/(24S) epimers, were obtained from the roots of Cucurbita foetidissima. Their structures were elucidated by means of a combination of homo- and heteronuclear 2D-NMR techniques (COSY, TOCSY, NOESY, ROESY, HSQC, and HMBC), and by FAB-MS. The new compounds were characterized as (3β,16α)-28-{[O-β-D-glucopyranosyl-(13)-O-β-D-xylopyranosyl-(14)-O-6-deoxy-α-L-mannopyranosyl-(12)-α-L-arabinopyranosyl]oxy}-16-hydroxy-28-oxoolean -12-en-3-yl β-D-glucopyranosiduronic acid (1…