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29 results on '"Sjöqvist, E."'

1. Heat-conserving three-temperature model for ultrafast demagnetization of 3d ferromagnets

Author

Pankratova, M., Miranda, I. P., Thonig, D., Pereiro, M., Sjoqvist, E., Delin, A., Scheid, P., Eriksson, O., and Bergman, A.

Subjects
Condensed Matter - Materials Science
Abstract

We study the ultrafast magnetization dynamics of bcc Fe and fcc Co using the recently suggested heat-conserving three-temperature model (HC3TM), together with atomistic spin- and lattice dynamics simulations. It is shown that this type of Langevin-based simulation is able to reproduce observed trends of the ultrafast magnetization dynamics of fcc Co and bcc Fe, in agreement with previous findings for fcc Ni. The simulations are performed by using parameters that to as large extent as possible are obtained from electronic structure theory. The one parameter that was not calculated in this way, was the damping term used for the lattice dynamics simulations, and here a range of parameters were investigated. It is found that this term has a large influence on the details of the magnetization dynamics. The dynamics of iron and cobalt is compared with previous results for nickel and similarities and differences in the materials' behavior are analysed following the absorption of a femtosecond laser pulse. Importantly, for all elements investigated so far with this model, we obtain a linear relationship between the value of the maximally demagnetized state and the fluence of the laser pulse, which is in agreement with experiments., Comment: 9 pages, 9 figures, Submitted to Physical Review B

Published
2023
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3. Influence of nonlocal damping on magnon properties of ferromagnets

Author

Lu, Z., Miranda, I.P., Streib, S., Pereiro, M., Sjöqvist, E., Eriksson, O., Bergman, A., Thonig, Danny, Delin, A., Lu, Z., Miranda, I.P., Streib, S., Pereiro, M., Sjöqvist, E., Eriksson, O., Bergman, A., Thonig, Danny, and Delin, A.

Abstract

We study the influence of nonlocal damping on the magnon properties of Fe, Co, Ni, and Fe1-xCox (x=30%,50%) alloys. The Gilbert damping parameter is typically considered as a local scalar both in experiment and in theoretical modeling. However, recent works have revealed that Gilbert damping is a nonlocal quantity that allows for energy dissipation between atomic sites. With the Gilbert damping parameters calculated from a state-of-the-art real-space electronic structure method, magnon lifetimes are evaluated from spin dynamics and linear response, where a good agreement is found between these two methods. It is found that nonlocal damping affects the magnon lifetimes in different ways depending on the system. Specifically, we find that in Fe, Co, and Ni, the nonlocal damping decreases the magnon lifetimes, while in Fe70Co30 and Fe50Co50 an opposite, nonlocal damping effect is observed, and our data show that it is much stronger in the former., Financial support from Vetenskapsradet (Grants No. VR 2016-05980, No. VR 2019-05304, and No. VR 2019-03666) , the Knut and Alice Wallenberg foundation (Grant No. 2018.0060) , the Foundation for Strategic Research (SSF) , the Swedish Energy Agency (Energimyndigheten) , the European Research Council (854843-FASTCORR) , the ChinaScholarship Council (CSC) , eSSENCE, and STandUP is acknowledged. The computations/data handling were enabled by resources provided by the Swedish National Infrastructure for Computing (SNIC) at the National Supercomputing Centre (NSC, Tetralith cluster) , partially funded by the Swedish Research Council through Grant Agreement No. 2016-07213.r Scholarship Council (CSC) , eSSENCE, and STandUP is acknowledged. The computations/data handling were enabled by resources provided by the Swedish National Infrastructure for Computing (SNIC) at the National Supercomputing Cen-tre (NSC, Tetralith cluster) , partially funded by the Swedish Research Council through Grant Agreement No. 2016-07213.

Published
2023
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5. Heat-conserving three-temperature model for ultrafast demagnetization in nickel

Author

Pankratova, M., Miranda, I. P., Thonig, Danny, Pereiro, M., Sjöqvist, E., Delin, A., Eriksson, Olle, Bergman, A., Pankratova, M., Miranda, I. P., Thonig, Danny, Pereiro, M., Sjöqvist, E., Delin, A., Eriksson, Olle, and Bergman, A.

Abstract

Multireservoir models are widely used for modeling and interpreting ultrafast magnetization dynamics. Here we introduce an alternative formulation to existing three-temperature models for the treatment of spin, electron, and lattice temperatures in magnetization dynamics simulations. In contrast to most existing models of calculations of energy transfer between reservoirs in these types of simulations, the heat distribution of the spin and lattice subsystems is evaluated during the simulation instead of being calculated a priori. The model is applied to investigate the demagnetization and remagnetization of fcc Ni, when subjected to a strong laser pulse. In particular, our model results in a fast interplay between the electron and spin subsystems which reproduces the main features of experimental data for fcc Ni significantly better than most reported three-temperature models. We also show that the way in which the electron, spin, and lattice heat capacities are described can have a significant impact on the simulated ultrafast dynamics. By introducing spin-lattice couplings in the simulation, it is shown that these explicit interactions only have a marginal impact on the magnetization dynamics of fcc Ni, albeit it is more pronounced for higher laser pulse powers.

Published
2022
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6. How strict is galactose restriction in adults with galactosaemia? International practice

Author

Adam, Siddig Momin, Akroyd, R., Bernabei, S., Bollhalder, S., Boocock, S., Burlina, A., Coote, T., Corthouts, K., Dalmau, Judith, Dawson, S., Defourny, S., Meyer, A., Desloovere, A., Devlin, Y., Diels, M., Dokoupil, K., Donald, S., Evans, S., Fasan, I., Ferguson, C., Ford, S., Forga, M., Gallo, G., Grünert, S.C., Heddrich-Ellerbrok, M., Heidenborg, C., Jonkers, C.F., Lefebure, K., Luyten, K., MacDonald, A., Meyer, U., Micciche, A., Müller, E., Portnoi, P., Ripley, S., Robert, C.M., Robertson, L.V., Rosenbaum-Fabian, S., Sahm, K., Schultz, Erica S, Singleton, K., Sjöqvist, E., Stoelen, L., Terry, A., Thompson, S., Timmer, C., Vande Kerckhove, K., van den Ploeg, L., Van Driessche, M., van Rijn, M., van Teeffelen-Heithoff, A., Vitoria, I., Voillot, C., Wenz, J., Westbrook, M., Wildgoose, J., Zweers, H., Adam, Siddig Momin, Akroyd, R., Bernabei, S., Bollhalder, S., Boocock, S., Burlina, A., Coote, T., Corthouts, K., Dalmau, Judith, Dawson, S., Defourny, S., Meyer, A., Desloovere, A., Devlin, Y., Diels, M., Dokoupil, K., Donald, S., Evans, S., Fasan, I., Ferguson, C., Ford, S., Forga, M., Gallo, G., Grünert, S.C., Heddrich-Ellerbrok, M., Heidenborg, C., Jonkers, C.F., Lefebure, K., Luyten, K., MacDonald, A., Meyer, U., Micciche, A., Müller, E., Portnoi, P., Ripley, S., Robert, C.M., Robertson, L.V., Rosenbaum-Fabian, S., Sahm, K., Schultz, Erica S, Singleton, K., Sjöqvist, E., Stoelen, L., Terry, A., Thompson, S., Timmer, C., Vande Kerckhove, K., van den Ploeg, L., Van Driessche, M., van Rijn, M., van Teeffelen-Heithoff, A., Vitoria, I., Voillot, C., Wenz, J., Westbrook, M., Wildgoose, J., and Zweers, H.

Published
2015

7. Practices in prescribing protein substitutes for PKU in Europe : No uniformity of approach

Author

Aguiar, A., Ahring, K., Almeida, M.F., Assoun, M., Belanger Quintana, A., Bigot, S., Bihet, G., Blom Malmberg, K., Burlina, A., Bushueva, T., Caris, A., Chan, H., Clark, Rachael A, Clark, Sue, Cochrane, B., Corthouts, K., Dalmau, Judith, Dassy, M., Meyer, A., Didycz, B., Diels, M., Dokupil, K., Dubois, S., Eftring, K., Ekengren, J., Ellerton, C., Evans, S., Faria, A., Fischer, A., Ford, S., Freisinger, P., Gizewska, M., Gokmen-Ozel, H., Gribben, J., Gunden, F., Heddrich-Ellerbrok, M., Heiber, S., Heidenborg, C., Jankowski, C., Janssen-Regelink, R.G., Jones, C.I., Jonkers, C.F., Joerg-Streller, M., Kaalund-Hansen, K., Kiss, E., Lammardo, A.M., Lang, K., Lier, D., Lilje, R., Lowry, S., Luyten, K., MacDonald, A., Meyer, U., de Moor, J., Pal, A., Robert, C.M., Robertson, L., Rocha, J.C., Rohde, C., Ross, K., Saruhan, S., Sjöqvist, E., Skeath, R., Stoelen, L., ter Horst, N.M., Terry, A., Timmer, C., Tuncer, N., Vande Kerckhove, K., van den Ploeg, L., van Rijn, M., van Spronsen, Francjan J., van Teeffelen-Heithoff, A., van Wegberg, A., van Wyk, K., Vasconcelos, C., Vitoria, I., Wildgoose, J., Webster, D., White, F.J., Zweers, H., Aguiar, A., Ahring, K., Almeida, M.F., Assoun, M., Belanger Quintana, A., Bigot, S., Bihet, G., Blom Malmberg, K., Burlina, A., Bushueva, T., Caris, A., Chan, H., Clark, Rachael A, Clark, Sue, Cochrane, B., Corthouts, K., Dalmau, Judith, Dassy, M., Meyer, A., Didycz, B., Diels, M., Dokupil, K., Dubois, S., Eftring, K., Ekengren, J., Ellerton, C., Evans, S., Faria, A., Fischer, A., Ford, S., Freisinger, P., Gizewska, M., Gokmen-Ozel, H., Gribben, J., Gunden, F., Heddrich-Ellerbrok, M., Heiber, S., Heidenborg, C., Jankowski, C., Janssen-Regelink, R.G., Jones, C.I., Jonkers, C.F., Joerg-Streller, M., Kaalund-Hansen, K., Kiss, E., Lammardo, A.M., Lang, K., Lier, D., Lilje, R., Lowry, S., Luyten, K., MacDonald, A., Meyer, U., de Moor, J., Pal, A., Robert, C.M., Robertson, L., Rocha, J.C., Rohde, C., Ross, K., Saruhan, S., Sjöqvist, E., Skeath, R., Stoelen, L., ter Horst, N.M., Terry, A., Timmer, C., Tuncer, N., Vande Kerckhove, K., van den Ploeg, L., van Rijn, M., van Spronsen, Francjan J., van Teeffelen-Heithoff, A., van Wegberg, A., van Wyk, K., Vasconcelos, C., Vitoria, I., Wildgoose, J., Webster, D., White, F.J., and Zweers, H.

Published
2015

8. Practices in prescribing protein substitutes for PKU in Europe: No uniformity of approach

Author

UCL - (SLuc) Service d'endocrinologie et de nutrition, Aguiar, A., Ahring, K., Almeida, M.F., Assoun, M., Belanger Quintana, A., Bigot, S., Bihet, G., Blom Malmberg, K., Burlina, A., Bushueva, T., Caris, A., Chan, H., Clark, A., Clark, S., Cochrane, B., Corthouts, K., Dalmau, J., Dassy, Martine, De Meyer, A., Didycz, B., Diels, M., Dokupil, K., Dubois, S., Eftring, K., Ekengren, J., Ellerton, C., Evans, S., Faria, A., Fischer, A., Ford, S., Freisinger, P., Gizewska, M., Gokmen-Ozel, H., Gribben, J., Gunden, F., Heddrich-Ellerbrok, M., Heiber, S., Heidenborg, C., Jankowski, C., Janssen-Regelink, R., Jones, I., Jonkers, C., Joerg-Streller, M., Kaalund-Hansen, K., Kiss, E., Lammardo, A.M., Lang, K., Lier, D., Lilje, R., Lowry, S., Luyten, K., MacDonald, A., Meyer, U., Moor, D., Pal, A., Robert, M., Robertson, L., Rocha, J.C., Rohde, C., Ross, K., Saruhan, S., Sjöqvist, E., Skeath, R., Stoelen, L., Ter Horst, N.M., Terry, A., Timmer, C., Tuncer, N., Vande Kerckhove, K., van der Ploeg, L., van Rijn, M., van Spronsen, F.J., van Teeffelen-Heithoff, A., van Wegberg, A., van Wyk, K., Vasconcelos, C., Vitoria, I., Wildgoose, J., Webster, D., White, F.J., Zweers, H., UCL - (SLuc) Service d'endocrinologie et de nutrition, Aguiar, A., Ahring, K., Almeida, M.F., Assoun, M., Belanger Quintana, A., Bigot, S., Bihet, G., Blom Malmberg, K., Burlina, A., Bushueva, T., Caris, A., Chan, H., Clark, A., Clark, S., Cochrane, B., Corthouts, K., Dalmau, J., Dassy, Martine, De Meyer, A., Didycz, B., Diels, M., Dokupil, K., Dubois, S., Eftring, K., Ekengren, J., Ellerton, C., Evans, S., Faria, A., Fischer, A., Ford, S., Freisinger, P., Gizewska, M., Gokmen-Ozel, H., Gribben, J., Gunden, F., Heddrich-Ellerbrok, M., Heiber, S., Heidenborg, C., Jankowski, C., Janssen-Regelink, R., Jones, I., Jonkers, C., Joerg-Streller, M., Kaalund-Hansen, K., Kiss, E., Lammardo, A.M., Lang, K., Lier, D., Lilje, R., Lowry, S., Luyten, K., MacDonald, A., Meyer, U., Moor, D., Pal, A., Robert, M., Robertson, L., Rocha, J.C., Rohde, C., Ross, K., Saruhan, S., Sjöqvist, E., Skeath, R., Stoelen, L., Ter Horst, N.M., Terry, A., Timmer, C., Tuncer, N., Vande Kerckhove, K., van der Ploeg, L., van Rijn, M., van Spronsen, F.J., van Teeffelen-Heithoff, A., van Wegberg, A., van Wyk, K., Vasconcelos, C., Vitoria, I., Wildgoose, J., Webster, D., White, F.J., and Zweers, H.

Abstract

Background: There appears little consensus concerning protein requirements in phenylketonuria (PKU). Methods: A questionnaire completed by 63 European and Turkish IMD centres from 18 countries collected data on prescribed total protein intake (natural/intact protein and phenylalanine-free protein substitute [PS]) by age, administration frequency and method, monitoring, and type of protein substitute. Data were analysed by European region using descriptive statistics. Results: The amount of total protein (from PS and natural/intact protein) varied according to the European region. Higher median amounts of total protein were prescribed in infants and children in Northern Europe (n. =. 24 centres) (infants <. 1. year, >. 2-3. g/kg/day; 1-3. years of age, >. 2-3. g/kg/day; 4-10. years of age, >. 1.5-2.5. g/kg/day) and Southern Europe (n. =. 10 centres) (infants <. 1. year, 2.5. g/kg/day, 1-3. years of age, 2. g/kg/day; 4-10. years of age, 1.5-2. g/kg/day), than by Eastern Europe (n. =. 4 centres) (infants <. 1. year, 2.5. g/kg/day, 1-3. years of age, >. 2-2.5. g/kg/day; 4-10. years of age, >. 1.5-2. g/kg/day) and with Western Europe (n. =. 25 centres) giving the least (infants <. 1. year, >. 2-2.5. g/kg/day, 1-3. years of age, 1.5-2. g/kg/day; 4-10. years of age, 1-1.5. g/kg/day). Total protein prescription was similar in patients aged >. 10. years (1-1.5. g/kg/day) and maternal patients (1-1.5. g/kg/day). Conclusions: The amounts of total protein prescribed varied between European countries and appeared to be influenced by geographical region. In PKU, all gave higher than the recommended 2007 WHO/FAO/UNU safe levels of protein intake for the general population.

Published
2015

9. Practices in prescribing protein substitutes for PKU in Europe: No uniformity of approach

Author

Afdeling Dietetiek, Other research (not in main researchprogram), Aguiar, A., Ahring, K., Almeida, M.F., Assoun, M., Belanger Quintana, A., Bigot, S., Bihet, G., Blom Malmberg, K., Burlina, A., Bushueva, T., Caris, A., Chan, H., Clark, Rachael A, Clark, Sue, Cochrane, B., Corthouts, K., Dalmau, Judith, Dassy, M., Meyer, A., Didycz, B., Diels, M., Dokupil, K., Dubois, S., Eftring, K., Ekengren, J., Ellerton, C., Evans, S., Faria, A., Fischer, A., Ford, S., Freisinger, P., Gizewska, M., Gokmen-Ozel, H., Gribben, J., Gunden, F., Heddrich-Ellerbrok, M., Heiber, S., Heidenborg, C., Jankowski, C., Janssen-Regelink, R.G., Jones, C.I., Jonkers, C.F., Joerg-Streller, M., Kaalund-Hansen, K., Kiss, E., Lammardo, A.M., Lang, K., Lier, D., Lilje, R., Lowry, S., Luyten, K., MacDonald, A., Meyer, U., de Moor, J., Pal, A., Robert, C.M., Robertson, L., Rocha, J.C., Rohde, C., Ross, K., Saruhan, S., Sjöqvist, E., Skeath, R., Stoelen, L., ter Horst, N.M., Terry, A., Timmer, C., Tuncer, N., Vande Kerckhove, K., van den Ploeg, L., van Rijn, M., van Spronsen, Francjan J., van Teeffelen-Heithoff, A., van Wegberg, A., van Wyk, K., Vasconcelos, C., Vitoria, I., Wildgoose, J., Webster, D., White, F.J., Zweers, H., Afdeling Dietetiek, Other research (not in main researchprogram), Aguiar, A., Ahring, K., Almeida, M.F., Assoun, M., Belanger Quintana, A., Bigot, S., Bihet, G., Blom Malmberg, K., Burlina, A., Bushueva, T., Caris, A., Chan, H., Clark, Rachael A, Clark, Sue, Cochrane, B., Corthouts, K., Dalmau, Judith, Dassy, M., Meyer, A., Didycz, B., Diels, M., Dokupil, K., Dubois, S., Eftring, K., Ekengren, J., Ellerton, C., Evans, S., Faria, A., Fischer, A., Ford, S., Freisinger, P., Gizewska, M., Gokmen-Ozel, H., Gribben, J., Gunden, F., Heddrich-Ellerbrok, M., Heiber, S., Heidenborg, C., Jankowski, C., Janssen-Regelink, R.G., Jones, C.I., Jonkers, C.F., Joerg-Streller, M., Kaalund-Hansen, K., Kiss, E., Lammardo, A.M., Lang, K., Lier, D., Lilje, R., Lowry, S., Luyten, K., MacDonald, A., Meyer, U., de Moor, J., Pal, A., Robert, C.M., Robertson, L., Rocha, J.C., Rohde, C., Ross, K., Saruhan, S., Sjöqvist, E., Skeath, R., Stoelen, L., ter Horst, N.M., Terry, A., Timmer, C., Tuncer, N., Vande Kerckhove, K., van den Ploeg, L., van Rijn, M., van Spronsen, Francjan J., van Teeffelen-Heithoff, A., van Wegberg, A., van Wyk, K., Vasconcelos, C., Vitoria, I., Wildgoose, J., Webster, D., White, F.J., and Zweers, H.

Published
2015

10. How strict is galactose restriction in adults with galactosaemia? International practice

Author

Afdeling Dietetiek, Other research (not in main researchprogram), Adam, Siddig Momin, Akroyd, R., Bernabei, S., Bollhalder, S., Boocock, S., Burlina, A., Coote, T., Corthouts, K., Dalmau, Judith, Dawson, S., Defourny, S., Meyer, A., Desloovere, A., Devlin, Y., Diels, M., Dokoupil, K., Donald, S., Evans, S., Fasan, I., Ferguson, C., Ford, S., Forga, M., Gallo, G., Grünert, S.C., Heddrich-Ellerbrok, M., Heidenborg, C., Jonkers, C.F., Lefebure, K., Luyten, K., MacDonald, A., Meyer, U., Micciche, A., Müller, E., Portnoi, P., Ripley, S., Robert, C.M., Robertson, L.V., Rosenbaum-Fabian, S., Sahm, K., Schultz, Erica S, Singleton, K., Sjöqvist, E., Stoelen, L., Terry, A., Thompson, S., Timmer, C., Vande Kerckhove, K., van den Ploeg, L., Van Driessche, M., van Rijn, M., van Teeffelen-Heithoff, A., Vitoria, I., Voillot, C., Wenz, J., Westbrook, M., Wildgoose, J., Zweers, H., Afdeling Dietetiek, Other research (not in main researchprogram), Adam, Siddig Momin, Akroyd, R., Bernabei, S., Bollhalder, S., Boocock, S., Burlina, A., Coote, T., Corthouts, K., Dalmau, Judith, Dawson, S., Defourny, S., Meyer, A., Desloovere, A., Devlin, Y., Diels, M., Dokoupil, K., Donald, S., Evans, S., Fasan, I., Ferguson, C., Ford, S., Forga, M., Gallo, G., Grünert, S.C., Heddrich-Ellerbrok, M., Heidenborg, C., Jonkers, C.F., Lefebure, K., Luyten, K., MacDonald, A., Meyer, U., Micciche, A., Müller, E., Portnoi, P., Ripley, S., Robert, C.M., Robertson, L.V., Rosenbaum-Fabian, S., Sahm, K., Schultz, Erica S, Singleton, K., Sjöqvist, E., Stoelen, L., Terry, A., Thompson, S., Timmer, C., Vande Kerckhove, K., van den Ploeg, L., Van Driessche, M., van Rijn, M., van Teeffelen-Heithoff, A., Vitoria, I., Voillot, C., Wenz, J., Westbrook, M., Wildgoose, J., and Zweers, H.

Published
2015

11. Practices in prescribing protein substitutes for PKU in Europe: No uniformity of approach

Author

Aguiar, A., primary, Ahring, K., additional, Almeida, M.F., additional, Assoun, M., additional, Belanger Quintana, A., additional, Bigot, S., additional, Bihet, G., additional, Blom Malmberg, K., additional, Burlina, A., additional, Bushueva, T., additional, Caris, A., additional, Chan, H., additional, Clark, A., additional, Clark, S., additional, Cochrane, B., additional, Corthouts, K., additional, Dalmau, J., additional, Dassy, M., additional, De Meyer, A., additional, Didycz, B., additional, Diels, M., additional, Dokupil, K., additional, Dubois, S., additional, Eftring, K., additional, Ekengren, J., additional, Ellerton, C., additional, Evans, S., additional, Faria, A., additional, Fischer, A., additional, Ford, S., additional, Freisinger, P., additional, Giżewska, M., additional, Gokmen-Ozel, H., additional, Gribben, J., additional, Gunden, F., additional, Heddrich-Ellerbrok, M., additional, Heiber, S., additional, Heidenborg, C., additional, Jankowski, C., additional, Janssen-Regelink, R., additional, Jones, I., additional, Jonkers, C., additional, Joerg-Streller, M., additional, Kaalund-Hansen, K., additional, Kiss, E., additional, Lammardo, A.M., additional, Lang, K., additional, Lier, D., additional, Lilje, R., additional, Lowry, S., additional, Luyten, K., additional, MacDonald, A., additional, Meyer, U., additional, Moor, D., additional, Pal, A., additional, Robert, M., additional, Robertson, L., additional, Rocha, J.C., additional, Rohde, C., additional, Ross, K., additional, Saruhan, S., additional, Sjöqvist, E., additional, Skeath, R., additional, Stoelen, L., additional, Ter Horst, N.M., additional, Terry, A., additional, Timmer, C., additional, Tuncer, N., additional, Vande Kerckhove, K., additional, van der Ploeg, L., additional, van Rijn, M., additional, van Spronsen, F.J., additional, van Teeffelen-Heithoff, A., additional, van Wegberg, A., additional, van Wyk, K., additional, Vasconcelos, C., additional, Vitoria, I., additional, Wildgoose, J., additional, Webster, D., additional, White, F.J., additional, and Zweers, H., additional

Published
2015
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12. How strict is galactose restriction in adults with galactosaemia? International practice

Author

Adam, S., primary, Akroyd, R., additional, Bernabei, S., additional, Bollhalder, S., additional, Boocock, S., additional, Burlina, A., additional, Coote, T., additional, Corthouts, K., additional, Dalmau, J., additional, Dawson, S., additional, Defourny, S., additional, De Meyer, A., additional, Desloovere, A., additional, Devlin, Y., additional, Diels, M., additional, Dokoupil, K., additional, Donald, S., additional, Evans, S., additional, Fasan, I., additional, Ferguson, C., additional, Ford, S., additional, Forga, M., additional, Gallo, G., additional, Grünert, S.C., additional, Heddrich-Ellerbrok, M., additional, Heidenborg, C., additional, Jonkers, C., additional, Lefebure, K., additional, Luyten, K., additional, MacDonald, A., additional, Meyer, U., additional, Micciche, A., additional, Müller, E., additional, Portnoi, P., additional, Ripley, S., additional, Robert, M., additional, Robertson, L.V., additional, Rosenbaum-Fabian, S., additional, Sahm, K., additional, Schultz, S., additional, Singleton, K., additional, Sjöqvist, E., additional, Stoelen, L., additional, Terry, A., additional, Thompson, S., additional, Timmer, C., additional, Vande Kerckhove, K., additional, van der Ploeg, L., additional, Van Driessche, M., additional, van Rijn, M., additional, van Teeffelen-Heithoff, A., additional, Vitoria, I., additional, Voillot, C., additional, Wenz, J., additional, Westbrook, M., additional, Wildgoose, J., additional, and Zweers, H., additional

Published
2015
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13. Reply to 'Singularities of the mixed state phase'

Author

Anandan, J., Sjöqvist, E., Pati, A. K., Ekert, A., Ericsson, M., Oi, D. K. L., and Vedral, V.

Subjects
Quantum Physics, FOS: Physical sciences, Quantum Physics (quant-ph)
Abstract

The only difference between Bhandari's viewpoint [quant-ph/0108058] and ours [Phys. Rev. Lett. 85, 2845 (2000)] is that our phase is defined modulo $2\pi$, whereas Bhandari argues that two phases that differ by $2\pi n$, $n$ integer, may be distinguished experimentally in a history-dependent manner., Comment: 2 pages

Published
2001
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19. Environment-Assisted Holonomic Quantum Maps.

Author

Ramberg N and Sjöqvist E

Abstract

Holonomic quantum computation uses non-Abelian geometric phases to realize error resilient quantum gates. Nonadiabatic holonomic gates are particularly suitable to avoid unwanted decoherence effects, as they can be performed at high speed. By letting the computational system interact with a structured environment, we show that the scope of error resilience of nonadiabatic holonomic gates can be widened to include systematic parameter errors. Our scheme maintains the geometric properties of the evolution and results in an environment-assisted holonomic quantum map that can mimic the effect of a holonomic gate. We demonstrate that the sensitivity to systematic errors can be reduced in a proof-of-concept spin-bath model.

Published
2019
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20. Geometric phases for mixed states of the Kitaev chain.

Author

Andersson O, Bengtsson I, Ericsson M, and Sjöqvist E

Abstract

The Berry phase has found applications in building topological order parameters for certain condensed matter systems. The question whether some geometric phase for mixed states can serve the same purpose has been raised, and proposals are on the table. We analyse the intricate behaviour of Uhlmann's geometric phase in the Kitaev chain at finite temperature, and then argue that it captures quite different physics from that intended. We also analyse the behaviour of a geometric phase introduced in the context of interferometry. For the Kitaev chain, this phase closely mirrors that of the Berry phase, and we argue that it merits further investigation., (© 2016 The Author(s).)

Published
2016
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21. Fast non-Abelian geometric gates via transitionless quantum driving.

Author

Zhang J, Kyaw TH, Tong DM, Sjöqvist E, and Kwek LC

Abstract

A practical quantum computer must be capable of performing high fidelity quantum gates on a set of quantum bits (qubits). In the presence of noise, the realization of such gates poses daunting challenges. Geometric phases, which possess intrinsic noise-tolerant features, hold the promise for performing robust quantum computation. In particular, quantum holonomies, i.e., non-Abelian geometric phases, naturally lead to universal quantum computation due to their non-commutativity. Although quantum gates based on adiabatic holonomies have already been proposed, the slow evolution eventually compromises qubit coherence and computational power. Here, we propose a general approach to speed up an implementation of adiabatic holonomic gates by using transitionless driving techniques and show how such a universal set of fast geometric quantum gates in a superconducting circuit architecture can be obtained in an all-geometric approach. Compared with standard non-adiabatic holonomic quantum computation, the holonomies obtained in our approach tends asymptotically to those of the adiabatic approach in the long run-time limit and thus might open up a new horizon for realizing a practical quantum computer.

Published
2015
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22. Nonadiabatic holonomic quantum computation in decoherence-free subspaces.

Author

Xu GF, Zhang J, Tong DM, Sjöqvist E, and Kwek LC

Abstract

Quantum computation that combines the coherence stabilization virtues of decoherence-free subspaces and the fault tolerance of geometric holonomic control is of great practical importance. Some schemes of adiabatic holonomic quantum computation in decoherence-free subspaces have been proposed in the past few years. However, nonadiabatic holonomic quantum computation in decoherence-free subspaces, which avoids a long run-time requirement but with all the robust advantages, remains an open problem. Here, we demonstrate how to realize nonadiabatic holonomic quantum computation in decoherence-free subspaces. By using only three neighboring physical qubits undergoing collective dephasing to encode one logical qubit, we realize a universal set of quantum gates.

Published
2012
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23. Optimal topological test for degeneracies of real Hamiltonians.

Author

Johansson N and Sjöqvist E

Abstract

We consider adiabatic transport of eigenstates of real Hamiltonians around loops in parameter space. It is demonstrated that loops that map to nontrivial loops in the space of eigenbases must encircle degeneracies. Examples from Jahn-Teller theory are presented to illustrate the test. We show furthermore that the proposed test is optimal.

Published
2004
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24. Mixed state geometric phases, entangled systems, and local unitary transformations.

Author

Ericsson M, Pati AK, Sjöqvist E, Brännlund J, and Oi DK

Abstract

The geometric phase for a pure quantal state undergoing an arbitrary evolution is a "memory" of the geometry of the path in the projective Hilbert space of the system. We find that Uhlmann's geometric phase for a mixed quantal state undergoing unitary evolution depends not only on the geometry of the path of the system alone but also on a constrained bilocal unitary evolution of the purified entangled state. We analyze this in general, illustrate it for the qubit case, and propose an experiment to test this effect. We also show that the mixed state geometric phase proposed recently in the context of interferometry requires unilocal transformations and is therefore essentially a property of the system alone.

Published
2003
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25. Off-diagonal geometric phase for mixed states.

Author

Filipp S and Sjöqvist E

Abstract

We extend the off-diagonal geometric phase [Phys. Rev. Lett. 85, 3067 (2000)]] to mixed quantal states. The nodal structure of this phase in the qubit (two-level) case is compared with that of the diagonal mixed state geometric phase [Phys. Rev. Lett. 85, 2845 (2000)]]. Extension to higher dimensional Hilbert spaces is delineated. A physical scenario for the off-diagonal mixed state geometric phase in polarization-entangled two-photon interferometry is proposed.

Published
2003
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26. Locality and topology in the molecular Aharonov-Bohm effect.

Author

Sjöqvist E

Abstract

It is shown that the molecular Aharonov-Bohm effect is neither nonlocal nor topological in the sense of the standard magnetic Aharonov-Bohm effect. It is further argued that there is a close relationship between the molecular Aharonov-Bohm effect and the Aharonov-Casher effect for an electrically neutral spin -1 / 2 particle encircling a line of charge.

Published
2002
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28. Geometric phases for mixed states in interferometry.

Author

Sjöqvist E, Pati AK, Ekert A, Anandan JS, Ericsson M, Oi DK, and Vedral V

Abstract

We provide a physical prescription based on interferometry for introducing the total phase of a mixed state undergoing unitary evolution, which has been an elusive concept in the past. We define the parallel transport condition that provides a connection form for obtaining the geometric phase for mixed states. The expression for the geometric phase for mixed state reduces to well known formulas in the pure state case when a system undergoes noncyclic and unitary quantum evolution.

Published
2000
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