uu.seUppsala University Publications
Change search
Refine search result
12 1 - 50 of 58
Cite
Citation style
• apa
• ieee
• modern-language-association
• vancouver
• Other style
More styles
Language
• de-DE
• en-GB
• en-US
• fi-FI
• nn-NO
• nn-NB
• sv-SE
• Other locale
More languages
Output format
• html
• text
• asciidoc
• rtf
Rows per page
• 5
• 10
• 20
• 50
• 100
• 250
Sort
• Standard (Relevance)
• Author A-Ö
• Author Ö-A
• Title A-Ö
• Title Ö-A
• Publication type A-Ö
• Publication type Ö-A
• Issued (Oldest first)
• Created (Oldest first)
• Last updated (Oldest first)
• Disputation date (earliest first)
• Disputation date (latest first)
• Standard (Relevance)
• Author A-Ö
• Author Ö-A
• Title A-Ö
• Title Ö-A
• Publication type A-Ö
• Publication type Ö-A
• Issued (Oldest first)
• Created (Oldest first)
• Last updated (Oldest first)
• Disputation date (earliest first)
• Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
• 1.
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Quantum Chemical Studies of Protein-Bound Chromophores, UV-Light Induced DNA Damages, and Lignin Formation2004Doctoral thesis, comprehensive summary (Other academic)

Quantum chemical methods have been used to provide a better understanding of the photochemistry of astaxanthin and phytochromobilin; the photoenzymic repair of UV-light induced DNA damages; and the formation of lignin.

The carotenoid astaxanthin (AXT) is responsible for the colouration of lobster shell. In solution, the electronic absorption spectra of AXT peak in the 470-490 nm region, corresponding to an orange-red colouration. Upon binding to the lobster-shell protein-complex α-crustacyanin, the absorption maximum is shifted to 632 nm, yielding a slate-blue colouration. Herein, the structural origin of this bathochromic shift is investigated on the basis of recent experimental work.

The tetrapyrrole phytochromobilin (PΦB) underlies the photoactivation of the plant photoreceptor phytochrome. Upon absorption of 660-nm light, PΦB isomerizes from a C15-Z,syn configuration (in the inactive form of the protein) to C15-E,anti (in the active form). In this work, a reaction mechanism for this isomerization is proposed.

DNA photolyases are enzymes that repair DNA damages resulting from far-UV-light induced [2+2] cycloaddition reactions involving pyrimidine nucleobases. The catalytic activity of these enzymes is initiated by near-UV and visible light, and is governed by electron transfer processes between a catalytic cofactor of the enzyme and the DNA lesions. Herein, an explanation for the experimental observation that the repair of cyclobutane pyrimidine dimers (CPD) – the major type of lesion – proceeds by electron transfer from the enzyme to the dimer is presented. Furthermore, the formation of CPD is studied.

Lignin is formed by dehydrogenative polymerization of hydroxycinnamyl alcohols. A detailed understanding of the polymerization mechanism and the factors controlling the outcome of the polymerization is, however, largely missing. Quantum chemical calculations on the initial dimerization step have been performed in order to gain some insight into these issues.

1. On the bathochromic shift of the absorption by astaxanthin in crustacyanin: a quantum chemical study
Open this publication in new window or tab >>On the bathochromic shift of the absorption by astaxanthin in crustacyanin: a quantum chemical study
2003 In: Chemical Physics Letters, ISSN 0009-2614, Vol. 375, no 1-2, p. 30-38Article in journal (Refereed) Published
##### Identifiers
urn:nbn:se:uu:diva-92091 (URN)
Available from: 2004-09-03 Created: 2004-09-03Bibliographically approved
2. Conformational dependence of the electronic absorption by astaxanthin and its implications for the bathochromic shift in crustacyanin
Open this publication in new window or tab >>Conformational dependence of the electronic absorption by astaxanthin and its implications for the bathochromic shift in crustacyanin
2004 In: Physical Chemistry Chemical Physics, ISSN 1463-9076, Vol. 6, p. 4190-4198Article in journal (Refereed) Published
##### Identifiers
urn:nbn:se:uu:diva-92092 (URN)
Available from: 2004-09-03 Created: 2004-09-03Bibliographically approved
3. Phytochromobilin C15-Z,syn to C15-E,anti isomerization - concerted or stepwise?
Open this publication in new window or tab >>Phytochromobilin C15-Z,syn to C15-E,anti isomerization - concerted or stepwise?
Article in journal (Refereed) Submitted
##### Identifiers
urn:nbn:se:uu:diva-92093 (URN)
Available from: 2004-09-03 Created: 2004-09-03Bibliographically approved
4. Thermodynamics of the photoenzymic repair mechanism studied by density functional theory
Open this publication in new window or tab >>Thermodynamics of the photoenzymic repair mechanism studied by density functional theory
2000 In: Journal of the American Chemical Society, ISSN 0002-7863, Vol. 122, no 41, p. 10126-10132Article in journal (Refereed) Published
##### Identifiers
urn:nbn:se:uu:diva-92094 (URN)
Available from: 2004-09-03 Created: 2004-09-03Bibliographically approved
5. On the formation of cyclobutane pyrimidine dimers in UV-irradiated DNA: why are thymines more reactive?
Open this publication in new window or tab >>On the formation of cyclobutane pyrimidine dimers in UV-irradiated DNA: why are thymines more reactive?
2003 In: Photochemistry and Photobiology, ISSN 0031-8655, Vol. 78, no 2, p. 159-167Article in journal (Refereed) Published
##### Identifiers
urn:nbn:se:uu:diva-92095 (URN)
Available from: 2004-09-03 Created: 2004-09-03Bibliographically approved
6. Electron-transfer induced repair of 6-4 photoproducts in DNA: A computational study
Open this publication in new window or tab >>Electron-transfer induced repair of 6-4 photoproducts in DNA: A computational study
2007 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 111, no 12, p. 2351-2361Article in journal (Refereed) Published
##### Abstract [en]

The mechanism employed by DNA photolyase to repair 6-4 photoproducts in UV-damaged DNA is explored by means of quantum chemical calculations. Considering the repair of both oxetane and azetidine lesions, it is demonstrated that reduction as well as oxidation enables a reversion reaction by creating anionic or cationic radicals that readily fragment into monomeric pyrimidines. However, on the basis of calculated reaction energies indicating that electron transfer from the enzyme to the lesion is a much more favorable process than electron transfer in the opposite direction, it is suggested that the photoenzymic repair can only occur by way of an anionic mechanism. Furthermore, it is shown that reduction of the oxetane facilitates a mechanism involving cleavage of the C−O bond followed by cleavage of the C−C bond, whereas reductive fragmentation of the azetidine may proceed with either of the intermonomeric C−N and C−C bonds cleaved as the first step. From calculations on neutral azetidine radicals, a significant increase in the free-energy barrier for the initial fragmentation step upon protonation of the carbonylic oxygens is predicted. This effect can be attributed to protonation serving to stabilize reactant complexes more than transition structures.

##### National Category
Chemical Sciences
##### Identifiers
urn:nbn:se:uu:diva-92096 (URN)10.1021/jp0676383 (DOI)000245083600013 ()17388321 (PubMedID)
Available from: 2004-09-03 Created: 2004-09-03 Last updated: 2017-12-14Bibliographically approved
7. A density functional theory study of coniferyl alcohol intermonomeric linkages in lignin - three-dimensional structures, stabilities and the thermodynamic control hypothesis
Open this publication in new window or tab >>A density functional theory study of coniferyl alcohol intermonomeric linkages in lignin - three-dimensional structures, stabilities and the thermodynamic control hypothesis
2003 In: Holzforschung, ISSN 0018-3830, Vol. 57, no 2, p. 150-164Article in journal (Refereed) Published
##### Identifiers
urn:nbn:se:uu:diva-92097 (URN)
Available from: 2004-09-03 Created: 2004-09-03Bibliographically approved
8. Spin distribution in dehydrogenated coniferyl alcohol and associated dilignol radicals
Open this publication in new window or tab >>Spin distribution in dehydrogenated coniferyl alcohol and associated dilignol radicals
2003 In: Holzforschung, ISSN 0018-3830, Vol. 57, no 1, p. 59-61Article in journal (Refereed) Published
##### Identifiers
urn:nbn:se:uu:diva-92098 (URN)
Available from: 2004-09-03 Created: 2004-09-03Bibliographically approved
9. Formation of β-O-4 lignin models - a theoretical study
Open this publication in new window or tab >>Formation of β-O-4 lignin models - a theoretical study
2003 In: Holzforschung, ISSN 0018-3830, Vol. 57, no 5, p. 466-478Article in journal (Refereed) Published
##### Identifiers
urn:nbn:se:uu:diva-92099 (URN)
Available from: 2004-09-03 Created: 2004-09-03Bibliographically approved
• 2.
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Phytochromobilin C15-Z,syn to C15-E,anti isomerization - concerted or stepwise?Article in journal (Refereed)
• 3.
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
A density functional theory study of coniferyl alcohol intermonomeric linkages in lignin - three-dimensional structures, stabilities and the thermodynamic control hypothesis2003In: Holzforschung, ISSN 0018-3830, Vol. 57, no 2, p. 150-164Article in journal (Refereed)
• 4.
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Conformational dependence of the electronic absorption by astaxanthin and its implications for the bathochromic shift in crustacyanin2004In: Physical Chemistry Chemical Physics, ISSN 1463-9076, Vol. 6, p. 4190-4198Article in journal (Refereed)
• 5.
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Formation of β-O-4 lignin models - a theoretical study2003In: Holzforschung, ISSN 0018-3830, Vol. 57, no 5, p. 466-478Article in journal (Refereed)
• 6.
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
On the bathochromic shift of the absorption by astaxanthin in crustacyanin: a quantum chemical study2003In: Chemical Physics Letters, ISSN 0009-2614, Vol. 375, no 1-2, p. 30-38Article in journal (Refereed)
• 7.
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
On the formation of cyclobutane pyrimidine dimers in UV-irradiated DNA: why are thymines more reactive?2003In: Photochemistry and Photobiology, ISSN 0031-8655, Vol. 78, no 2, p. 159-167Article in journal (Refereed)
• 8.
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Spin distribution in dehydrogenated coniferyl alcohol and associated dilignol radicals2003In: Holzforschung, ISSN 0018-3830, Vol. 57, no 1, p. 59-61Article in journal (Refereed)
• 9.
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Thermodynamics of the photoenzymic repair mechanism studied by density functional theory2000In: Journal of the American Chemical Society, ISSN 0002-7863, Vol. 122, no 41, p. 10126-10132Article in journal (Refereed)
• 10.
Centre for Quantum Computation, DAMTP, University of Cambridge, UK.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry. Centre for Quantum Computation, DAMTP, Cambridge, UK.
Nodal free geometric phases: concept and application to geometric quantum computation2008In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 372, no 5, p. 596-599Article in journal (Refereed)

Nodal free geometric phases are the eigenvalues of the final member of a parallel transporting family of unitary operators. These phases are gauge invariant, always well defined, and can be measured interferometrically. Nodal free geometric phases can be used to construct various types of quantum phase gates.

• 11.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Dlaczego kot Schrödingera laduje na czterech lapach2001In: Delta, ISSN 0137-3005, no 11, p. 1-Article in journal (Other (popular science, discussion, etc.))
• 12.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Quantum computation using the Aharonov-Casher set up2002In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 303, no 1, p. 7-10Article in journal (Refereed)

It is argued that the Aharonov-Casher set up could be used as the basic building block for quantum computation. We demonstrate explicitly in this scenario one- and two-qubit phase shift gates that are fault tolerant to deformations of the path when encircling two sites of the computational system around each other.

• 13.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Towards a quantum Hall effect for atoms using electric fields2002In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 65, no 1, p. 013607-Article in journal (Refereed)

An atomic analogue of Landau quantization based on the Aharonov-Casher (AC) interaction is developed. The effect provides a first step towards an atomic quantum Hall system using electric fields, which may be realized in a Bose-Einstein condensate.

• 14.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Degree of electron-nuclear entanglement in the E x e Jahn-Teller system1999In: Proceedings of the XIV International Symposium on Electron-Phonon Dynamics and Jahn-Teller Effect: Erice, Italy, 7-13 July 1998 / [ed] G. Bevilacqua, L. Martinelli, N. Terzi, Singapore: World Scientific Publishing , 1999, p. 20-Conference paper (Other academic)

Jahn-Teller systems exhibit strong coupling between the electronic and nuclear degrees of freedom. We analyse how linear and quadratic coupling affect the electron-nuclear entanglement in the $E\otimes \epsilon$ system. A measure of quantum entanglement, recently developed by Shimony [Ann. New York Acad. Sci. 755, 675 (1995)], is used. States in the adiabatic regime with quadratic coupling are analysed. The electron-nuclear entanglement in vibronic states of the linear Exe model is calculated numerically. The physical significance of electron-nuclear entanglement is discussed in terms of reduction factors and magnetic vibrational circular dichroism.

• 15.
Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Numerical Analysis.
Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Numerical Analysis. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Time-marching methods for the time-dependent Schrödinger equation2004In: Proc. Int. Conference on Computational and Mathematical Methods in Science and Engineering: CMMSE-2004, Uppsala, Sweden: Uppsala University , 2004, p. 53-56Conference paper (Other academic)
• 16.
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Nematic Liquid Crystal Spatial Light Modulators for Laser Beam Steering2004Doctoral thesis, comprehensive summary (Other academic)

Laser beam control is important in many applications. Phase modulating spatial light modulators (SLMs) can be used to electronically alter the phase distribution of an optical wave-front and thus change the direction and shape of a laser beam. Physical constraints set limitations to the SLM and an ideal phase distribution can usually not be realised. In order to understand how such components can be used for non-mechanical beam control three nematic liquid crystal (NLC) SLMs have been thoroughly characterised and modelled.

The pixel structure and phase quantisation give a discrepancy between ideal and realised phase distributions. The impact on beam steering capability was examined by measurements and simulations of the intensity distribution in the far-field.

In two of the studied SLMs the pixel period was shorter than the thickness of the LC layer giving the optical phase shift. This results in a so-called “fringing field”, which was shown to degrade the phase modulation and couple light between polarisation modes. The deformation of the LC was simulated and a finite-difference time-domain (FDTD) algorithm was used to calculate how polarised light propagates through the optically anisotropic SLM.

Non-mechanical beam steering and tracking in an optical free-space communication link were demonstrated. Continual optimisation of the steering angle was achieved by feedback from a video camera.

The optical properties of the SLM in the time period right after a voltage update were studied. It was shown how light is redistributed between orders during the switching from one blazed grating to another. By appropriate choice of the blazed gratings the effects on the diffraction efficiency can be minimised.

The detailed knowledge of the SLM structure and its response to electronic control makes it possible to predict and optimise the device performance in future systems.

1. Intensity variations using a quantized spatial light modulator for non-mechanical beam steering
Open this publication in new window or tab >>Intensity variations using a quantized spatial light modulator for non-mechanical beam steering
2003 In: Optical Engineering, ISSN 0091-3286, Vol. 42, no 3, p. 613-619Article in journal (Refereed) Published
##### Identifiers
urn:nbn:se:uu:diva-92439 (URN)
Available from: 2004-11-24 Created: 2004-11-24Bibliographically approved
2. Fringing fields in a nematic liquid crystal spatial light modulator for beam steering
Open this publication in new window or tab >>Fringing fields in a nematic liquid crystal spatial light modulator for beam steering
2004 In: Journal of Modern Optics, ISSN 00950-0340, Vol. 51, no 8, p. 613-619Article in journal (Refereed) Published
##### Identifiers
urn:nbn:se:uu:diva-92440 (URN)
Available from: 2004-11-24 Created: 2004-11-24Bibliographically approved
3. Polarization properties of a nematic liquid-crystal spatial light modulator for phase modulation
Open this publication in new window or tab >>Polarization properties of a nematic liquid-crystal spatial light modulator for phase modulation
2005 (English)In: Optical Society of America. Journal A: Optics, Image Science, and Vision, ISSN 1084-7529, E-ISSN 1520-8532, Vol. 22, no 1, p. 177-184Article in journal (Refereed) Published
##### Abstract [en]

The polarization properties of a nematic zero-twist liquid-crystal (NLC) spatial light modulator (SLM) were studied. A large ratio between the liquid-crystal (LC) layer thickness and the pixel pitch combined with spatial variations in the applied electric field causes fringing fields between pixels. Depending on the LC alignment, the electric field components within the LC layer can result in a twist deformation. The produced inhomogeneous optical anisotropy affects the polarization of light propagating through the device. We experimentally examined polarization effects in different diffraction orders for both binary and blazed phase gratings. Simulations of the LC deformation together with finite-difference time-domain simulations for the optical propagation were used to calculate the corresponding far-field intensities. It was demonstrated how rigorous simulations of the NLC SLM properties can be used to understand the polarization features of different diffraction orders.

##### National Category
Natural Sciences
##### Identifiers
urn:nbn:se:uu:diva-92441 (URN)10.1364/JOSAA.22.000177 (DOI)15669628 (PubMedID)
Available from: 2004-11-24 Created: 2004-11-24 Last updated: 2017-12-14Bibliographically approved
4. Retrocommunication utilizing electroabsorption modulators and non-mechanical beam steering
Open this publication in new window or tab >>Retrocommunication utilizing electroabsorption modulators and non-mechanical beam steering
2005 (English)In: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 44, no 4, p. 045001-Article in journal (Refereed) Published
##### Abstract [en]

A novel retrocommunication link utilizing reflective multiplequantum well (MQW) optical modulators and nonmechanical beamsteering and tracking is demonstrated. Large aperture reflective MQWmodulators using AlGaAs/GaAs are optimized and manufactured. Themodulators exhibit a contrast ratio larger than 4:1 and a modulationbandwidth of 10 MHz. Nonmechanical beam steering and tracking arestudied using nematic liquid crystal (NLC) spatial light modulators(SLMs). The communication link is comprised of a retromodulating arraywith four MQW modulators and a transceiver using a NLC SLM for beamsteering and tracking. Transfer of audio, real-time image data and pseudorandombit sequences over 100-m range while tracking the movingretromodulator is shown. The link is capable of transferring data at approximately8 Mbps.

##### National Category
Natural Sciences
##### Identifiers
urn:nbn:se:uu:diva-92442 (URN)10.1117/1.1883063 (DOI)
Available from: 2004-11-24 Created: 2004-11-24 Last updated: 2017-12-14Bibliographically approved
5. Temporal properties of a nematic liquid-crystal spatial light modulator used for laser beam steering and tracking
Open this publication in new window or tab >>Temporal properties of a nematic liquid-crystal spatial light modulator used for laser beam steering and tracking
In: Applied Optics, ISSN 0003-6935Article in journal (Refereed) Submitted
##### Identifiers
urn:nbn:se:uu:diva-92443 (URN)
Available from: 2004-11-24 Created: 2004-11-24Bibliographically approved
• 17.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Polarization properties of a nematic liquid-crystal spatial light modulator for phase modulation2005In: Optical Society of America. Journal A: Optics, Image Science, and Vision, ISSN 1084-7529, E-ISSN 1520-8532, Vol. 22, no 1, p. 177-184Article in journal (Refereed)

The polarization properties of a nematic zero-twist liquid-crystal (NLC) spatial light modulator (SLM) were studied. A large ratio between the liquid-crystal (LC) layer thickness and the pixel pitch combined with spatial variations in the applied electric field causes fringing fields between pixels. Depending on the LC alignment, the electric field components within the LC layer can result in a twist deformation. The produced inhomogeneous optical anisotropy affects the polarization of light propagating through the device. We experimentally examined polarization effects in different diffraction orders for both binary and blazed phase gratings. Simulations of the LC deformation together with finite-difference time-domain simulations for the optical propagation were used to calculate the corresponding far-field intensities. It was demonstrated how rigorous simulations of the NLC SLM properties can be used to understand the polarization features of different diffraction orders.

• 18.
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Intensity variations using a quantized spatial light modulator for non-mechanical beam steering2003In: Optical Engineering, ISSN 0091-3286, Vol. 42, no 3, p. 613-619Article in journal (Refereed)
• 19.
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Temporal properties of a nematic liquid-crystal spatial light modulator used for laser beam steering and trackingIn: Applied Optics, ISSN 0003-6935Article in journal (Refereed)
• 20.
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Fringing fields in a nematic liquid crystal spatial light modulator for beam steering2004In: Journal of Modern Optics, ISSN 00950-0340, Vol. 51, no 8, p. 613-619Article in journal (Refereed)
• 21.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Retrocommunication utilizing electroabsorption modulators and non-mechanical beam steering2005In: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 44, no 4, p. 045001-Article in journal (Refereed)

A novel retrocommunication link utilizing reflective multiplequantum well (MQW) optical modulators and nonmechanical beamsteering and tracking is demonstrated. Large aperture reflective MQWmodulators using AlGaAs/GaAs are optimized and manufactured. Themodulators exhibit a contrast ratio larger than 4:1 and a modulationbandwidth of 10 MHz. Nonmechanical beam steering and tracking arestudied using nematic liquid crystal (NLC) spatial light modulators(SLMs). The communication link is comprised of a retromodulating arraywith four MQW modulators and a transceiver using a NLC SLM for beamsteering and tracking. Transfer of audio, real-time image data and pseudorandombit sequences over 100-m range while tracking the movingretromodulator is shown. The link is capable of transferring data at approximately8 Mbps.

• 22.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
Radical Carbonylation with [11C]Carbon Monoxide Promoted by Oxygen-Centered Radicals: Experimental and DFT studies of the mechanism2007In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 129, no 29, p. 9020-9031Article in journal (Refereed)

Photoinitiated carbonylation of alkyl iodides with [11C]carbon monoxide (11C t1/2 = 20.4 min) is enhanced by ketones that have lowest-lying excited triplet state of nπ* character. For example, adding 5 mol % of acetophenone increases radiochemical yields from 3 to 59% in brief 6-min long reactions. Similar or higher yields were achieved by adding di-tert-butyl peroxide. Since radicaloid nπ* exited-state ketones and tert-butoxyl radicals have similar reactivity, the photosensitization proceeds most likely via a H-atom transfer mechanism rather than via energy transfer. We propose a mechanism that can account for the enhancement as well as for the formation of observed byproducts. The energy profile obtained by DFT calculations support the feasibility of the mechanism, and observed experimental differences in reactivity could be well rationalized by the calculated data. NBO calculations were performed to further analyze the obtained energetics. Various [carbonyl-11C]esters and some [carbonyl-11C]amides were synthesized in good radiochemical yields from primary and secondary alkyl iodides illustrating the utility of dialkyl peroxides to accelerate the carbonylations. These findings have potential in elaborating new synthetic protocols for the production of 11C-labeled tracers for positron emission tomography.

• 23. Komaguchi, Kenji
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Direct ESR evidence for SH2 type reaction of methyl radical with methylsilane and methylgermane in a low temperature solid: A deuterium labeling study2005In: Chemical Physics Letters, ISSN 0009-2614, Vol. 410, p. 1-5Article in journal (Refereed)
• 24.
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Quantum Holonomies: Concepts and Applications to Quantum Computing and Interferometry2007Doctoral thesis, comprehensive summary (Other academic)

Quantum holonomies are investigated in different contexts.

A geometric phase is proposed for decomposition dependent evolution, where each component of a given decomposition of a mixed state evolves independently. It is shown that this geometric phase only depends on the path traversed in the space of decompositions.

A holonomy is associated to general paths of subspaces of a Hilbert space, both discrete and continuous. This opens up the possibility of constructing quantum holonomic gates in the open path setting. In the discrete case it is shown that it is possible to associate two distinct holonomies to a given path. Interferometric setups for measuring both holonomies are

provided. It is further shown that there are cases when the holonomy is only partially defined. This has no counterpart in the Abelian setting.

An operational interpretation of amplitudes of density operators is provided. This allows for a direct interferometric realization of Uhlmann's parallelity condition, and the possibility of measuring the Uhlmann holonomy for sequences of density operators.

Off-diagonal geometric phases are generalized to the non-Abelian case. These off-diagonal holonomies are undefined for cyclic evolution, but must contain members of non-zero rank if all standard holonomies are undefined. Experimental setups for measuring the off-diagonal holonomies are proposed.

The concept of nodal free geometric phases is introduced. These are constructed from gauge invariant quantities, but do not share the nodal point structure of geometric phases and off-diagonal geometric phases. An interferometric setup for measuring nodal free geometric phases is provided, and it is shown that these phases could be useful in geometric quantum computation.

A holonomy associated to a sequence of quantum maps is introduced. It is shown that this holonomy is related to the Uhlmann holonomy. Explicit examples are provided to illustrate the general idea.

1. Geometry of decomposition dependent evolutions of mixed states
Open this publication in new window or tab >>Geometry of decomposition dependent evolutions of mixed states
2004 (English)In: International Journal of Quantum Information, ISSN 0219-7499, Vol. 2, no 2, p. 247-256Article in journal (Refereed) Published
##### Abstract [en]

We examine evolutions where each component of a given decomposition of a mixed quantal state evolves independently in a unitary fashion. The geometric phase and parallel transport conditions for this type of decomposition dependent evolution are delineated. We compare this geometric phase with those previously defined for unitarily evolving mixed states, and mixed state evolutions governed by completely positive maps.

##### Keywords
Geometric phase, mixed quantum states, conditional quantum dynamics
##### National Category
Physical Sciences
Physics
##### Identifiers
urn:nbn:se:uu:diva-96146 (URN)10.1142/S0219749904000250 (DOI)000227719600008 ()
Available from: 2007-09-03 Created: 2007-09-03 Last updated: 2011-10-06
2. Noncyclic geometric changes of quantum states
Open this publication in new window or tab >>Noncyclic geometric changes of quantum states
2006 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 74, no 2, p. 022106-Article in journal (Refereed) Published
##### Abstract [en]

Non-Abelian quantum holonomies, i.e., unitary state changes solely induced by geometric properties of a quantum system, have been much under focus in the physics community as generalizations of the Abelian Berry phase. Apart from being a general phenomenon displayed in various subfields of quantum physics, the use of holonomies has lately been suggested as a robust technique to obtain quantum gates; the building blocks of quantum computers. Non-Abelian holonomies are usually associated with cyclic changes of quantum systems, but here we consider a generalization to noncyclic evolutions. We argue that this open-path holonomy can be used to construct quantum gates. We also show that a structure of partially defined holonomies emerges from the open-path holonomy. This structure has no counterpart in the Abelian setting. We illustrate the general ideas using an example that may be accessible to tests in various physical systems.

##### Keywords
Non-Abelian geometric phase, quantum holonomy, quantum computation
##### National Category
Physical Sciences
Physics
##### Identifiers
urn:nbn:se:uu:diva-96147 (URN)10.1103/PhysRevA.74.022106 (DOI)000240238300017 ()
Available from: 2007-09-03 Created: 2007-09-03 Last updated: 2017-12-14
3. Manifestations of quantum holonomy in interferometry
Open this publication in new window or tab >>Manifestations of quantum holonomy in interferometry
2006 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 74, no 6, p. 062101-Article in journal (Refereed) Published
##### Abstract [en]

Abelian and non-Abelian geometric phases, known as quantum holonomies, have attracted considerable attention in the past. Here, we show that it is possible to associate nonequivalent holonomies to discrete sequences of subspaces in a Hilbert space. We consider two such holonomies that arise naturally in interferometer settings. For sequences approximating smooth paths in the base (Grassmann) manifold, these holonomies both approach the standard holonomy. In the one-dimensional case the two types of holonomies are Abelian and coincide with Pancharatnam's geometric phase factor. The theory is illustrated with a model example of projective measurements involving angular momentum coherent states.

##### Keywords
Quantum holonomy, geometric phase, quantum interferometry, spin-coherent states
##### National Category
Physical Sciences
Physics
##### Identifiers
urn:nbn:se:uu:diva-96148 (URN)10.1103/PhysRevA.74.062101 (DOI)000243166700014 ()
Available from: 2007-09-03 Created: 2007-09-03 Last updated: 2017-12-14
4. Operational approach to the Uhlmann holonomy
Open this publication in new window or tab >>Operational approach to the Uhlmann holonomy
2007 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 75, no 3, p. 032106-Article in journal (Refereed) Published
##### Abstract [en]

We suggest a physical interpretation of the Uhlmann amplitude of a density operator. Given this interpretation we propose an operational approach to obtain the Uhlmann condition for parallelity. This allows us to realize parallel transport along a sequence of density operators by an iterative preparation procedure. At the final step the resulting Uhlmann holonomy can be determined via interferometric measurements.

##### Keywords
Quantum holonomy, density operators, quantum interferometry
##### National Category
Physical Sciences
Physics
##### Identifiers
urn:nbn:se:uu:diva-96149 (URN)10.1103/PhysRevA.75.032106 (DOI)000245326300023 ()
##### Note
Also in Virtual Journal of Quantum Information, March issue 2007.Available from: 2007-09-03 Created: 2007-09-03 Last updated: 2017-12-14
5. Non-Abelian generalization of off-diagonal geometric phases
Open this publication in new window or tab >>Non-Abelian generalization of off-diagonal geometric phases
2007 (English)In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 78, no 6, p. 60004-Article in journal (Refereed) Published
##### Abstract [en]

If a quantum system evolves in a noncyclic fashion the corresponding geometric phase or holonomy may not be fully defined. Off-diagonal geometric phases have been developed to deal with such cases. Here, we generalize these phases to the non-Abelian case, by introducing off-diagonal holonomies that involve evolution of more than one subspace of the underlying Hilbert space. Physical realizations of the off-diagonal holonomies in adiabatic evolution and interferometry are put forward.

##### National Category
Physical Sciences
Physics
##### Identifiers
urn:nbn:se:uu:diva-96150 (URN)10.1209/0295-5075/78/60004 (DOI)000248593700004 ()
Available from: 2007-09-03 Created: 2007-09-03 Last updated: 2017-12-14
6. Nodal free geometric phases: concept and application to geometric quantum computation
Open this publication in new window or tab >>Nodal free geometric phases: concept and application to geometric quantum computation
2008 (English)In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 372, no 5, p. 596-599Article in journal (Refereed) Published
##### Abstract [en]

Nodal free geometric phases are the eigenvalues of the final member of a parallel transporting family of unitary operators. These phases are gauge invariant, always well defined, and can be measured interferometrically. Nodal free geometric phases can be used to construct various types of quantum phase gates.

##### Keywords
Geometric phase, quantum gates, quantum interferometry
##### National Category
Physical Sciences
Physics
##### Identifiers
urn:nbn:se:uu:diva-96151 (URN)10.1016/j.physleta.2007.08.022 (DOI)000252835300011 ()
Available from: 2007-09-03 Created: 2007-09-03 Last updated: 2017-12-14
7. Holonomy for quantum channels
Open this publication in new window or tab >>Holonomy for quantum channels
2008 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 77, no 1, p. 012114-Article in journal (Refereed) Published
##### Abstract [en]

A quantum holonomy reflects the curvature of some underlying structure of quantum-mechanical systems, such as that associated with quantum states. Here, we extend the notion of holonomy to families of quantum channels, i.e., trace-preserving completely positive maps. By the use of the Jamiolkowski isomorphism, we show that the proposed channel holonomy is related to the Uhlmann holonomy. The general theory is illustrated for specific examples. We put forward a physical realization of the channel holonomy in terms of interferometry. This enables us to identify a gauge-invariant physical object that directly relates to the channel holonomy. Parallel transport condition and concomitant gauge structure are delineated in the case of smoothly parametrized families of channels. Finally, we point out that interferometer tests that have been carried out in the past to confirm the 4 pi rotation symmetry of the neutron spin can be viewed as early experimental realizations of the channel holonomy.

##### Keywords
Geometric phase, quantum holonomy, completely positive maps, quantum channels, Uhlmann holonomy, mixed quantum states, quantum interferometry, Jamiolkowski isomorphism
##### National Category
Physical Sciences
Physics
##### Identifiers
urn:nbn:se:uu:diva-96152 (URN)10.1103/PhysRevA.77.012114 (DOI)000252862000029 ()
Available from: 2007-09-03 Created: 2007-09-03 Last updated: 2017-12-14
• 25.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Noncyclic geometric changes of quantum states2006In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 74, no 2, p. 022106-Article in journal (Refereed)

Non-Abelian quantum holonomies, i.e., unitary state changes solely induced by geometric properties of a quantum system, have been much under focus in the physics community as generalizations of the Abelian Berry phase. Apart from being a general phenomenon displayed in various subfields of quantum physics, the use of holonomies has lately been suggested as a robust technique to obtain quantum gates; the building blocks of quantum computers. Non-Abelian holonomies are usually associated with cyclic changes of quantum systems, but here we consider a generalization to noncyclic evolutions. We argue that this open-path holonomy can be used to construct quantum gates. We also show that a structure of partially defined holonomies emerges from the open-path holonomy. This structure has no counterpart in the Abelian setting. We illustrate the general ideas using an example that may be accessible to tests in various physical systems.

• 26.
NORDITA, Stockholm, Sweden.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Jahn-Teller-induced Berry phase in spin-orbit-coupled Bose-Einstein condensates2009In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 79, p. 043627-Article in journal (Refereed)

We demonstrate that Berry phases may greatly affect the dynamics of spin-orbit coupled Bose-Einstein condensates. The effective model Hamiltonian under consideration is shown to be equivalent to the Exe Jahn-Teller model first introduced in molecular physics. The corresponding conical intersection is identified and the Berry phase acquired for a wave packet encircling the intersection is studied. It is found that this phase manifests itself in the density profile of the condensate, making it a directly measurable quantity via time-of-flight detection. Moreover, the non-Abelian gauge structure of the system is addressed and we verify how it affects the dynamics.

• 27.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology.
First Principles Electrochemical Study of Redox Events in DNA Bases and Chemical Repair in Aqueous Solution2004In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 6, p. 2426-2433Article in journal (Refereed)

Primary and secondary radiation-induced damage to DNA, and chemical repair of the lesions on the nucleobases in solution involve a cascade of proton transfer (PT), electron transfer (ET), and proton-coupled electron transfer (PT-ET) reactions. The rate constants of these reactions depend on the standard Gibbs energy changes that can be derived from experiment. We here apply a first principles approach to calculate standard Gibbs energy changes of proton, electron, and proton-coupled electron transfer reactions in solution, wherein electrons and protons participate as independent ions; data that is fully compatible with that experimentally derived. Hence, the thermodynamic feasibility of ET and PT-ET pathways for these reactions depending on the effective concentration of hydrogen ions can be directly rationalized from first principles. The focus of this study is the primary and secondary ionization events in nucleobases in the presence of hydrogen atoms, solvated electrons and protons in aqueous solution, leading to the formation of nucleobase radical anions B˙, radical cations B˙+ and their major deprotonated radical forms B(–H)˙. We also examine the chemical repair reaction by thiols, B(–H)˙(aq)+RSH(aq)=B(aq)+RS˙(aq), where B=A,G,C,T. Our results for the chemical repair of B(–H)˙ suggest that a PT-ET pathway should be favored for A and C at any pH, whereas for G and T, a PT-ET pathway is preferred at acidic and near neutral pH, but in the pH range 9-11, the ET pathway would dominate.

• 28. Mundim, Maria S. P.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Study of thiophene inner shell photofragmentation2007In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 155, no 1-3, p. 58-63Article in journal (Refereed)

We investigated the inner shell photofragmentation of thiophene by time of flight (TOF) mass spectroscopy using multi-coincidence electron-ion techniques. Our main purpose was to understand aspects of molecular relaxation process after inner shell excitation and to search for bond break selectivity. Analyses of mass and branching ratios are presented and the results suggest different mechanisms and channel of fragmentation when compared with S 2p and C 1s excitations.

• 29.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry, Quantum Chemistry.
Computational Investigation of Dye-Sensitized Solar Cells2007Doctoral thesis, comprehensive summary (Other academic)

Interfaces between semiconductors and adsorbed molecules form a central area of research in surface science, occurring in many different contexts. One such application is the so-called Dye-Sensitized Solar Cell (DSSC) where the nanostructured dye-semiconductor interface is of special interest, as this is where the most important ultrafast electron transfer process takes place. In this thesis, structural and electronic aspects of these interfaces have been studied theoretically using quantum chemical computations applied to realistic dye-semiconductor systems. Periodic boundary conditions and large cluster models have been employed together with hybrid HF-DFT functionals in the modeling of nanostructured titanium dioxide.

A study of the adsorption of a pyridine molecule via phosphonic and carboxylic acid anchor groups to an anatase (101) surface showed that the choice of anchor group affects the strength of the bindings as well as the electronic interaction at the dye-TiO2 interface. The calculated interfacial electronic coupling was found to be stronger for carboxylic acid than for phosphonic acid, while phosphonic acid binds significantly stronger than carboxylic acid to the TiO2 surface.

Atomistic and electronic structure of realistic dye-semiconductor interfaces were reported for RuII-bis-terpyridine dyes on a large anatase TiO2 cluster and perylene dyes on a periodic rutile (110) TiO2<