Records |
Author |
Bru, L.A.; de Valcarcel, G.J.; Di Molfetta, G.; Perez, A.; Roldan, E.; Silva, F. |
Title |
Quantum walk on a cylinder |
Type |
Journal Article |
Year |
2016 |
Publication |
Physical Review A |
Abbreviated Journal |
Phys. Rev. A |
Volume |
94 |
Issue |
3 |
Pages |
032328 - 7pp |
Keywords |
|
Abstract |
We consider the two-dimensional alternate quantum walk on a cylinder. We concentrate on the study of the motion along the open dimension, in the spirit of looking at the closed coordinate as a small or “hidden” extra dimension. If one starts from localized initial conditions on the lattice, the dynamics of the quantum walk that is obtained after tracing out the small dimension shows the contribution of several components which can be understood from the study of the dispersion relations for this problem. In fact, these components originate from the contribution of the possible values of the quasimomentum in the closed dimension. In the continuous space-time limit, the different components manifest as a set of Dirac equations, with each quasimomentum providing the value of the corresponding mass. We briefly discuss the possible link of these ideas to the simulation of high-energy physical theories that include extra dimensions. Finally, entanglement between the coin and spatial degrees of freedom is studied, showing that the entanglement entropy clearly overcomes the value reached with only one spatial dimension. |
Address |
[Bru, Luis A.] Univ Politecn Valencia, ITEAM Res Inst, Opt & Quantum Commun Grp, Camino Vera S-N, E-46022 Valencia, Spain |
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Thesis |
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Publisher |
Amer Physical Soc |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
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Original Title |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2469-9926 |
ISBN |
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Medium |
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Area |
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Expedition |
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Conference |
|
Notes |
WOS:000384060700005 |
Approved |
no |
Is ISI |
yes |
International Collaboration |
yes |
Call Number |
IFIC @ pastor @ |
Serial |
2823 |
Permanent link to this record |
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Author |
Degiovanni, A.; Wuensch, W.; Giner Navarro, J. |
Title |
Comparison of the conditioning of high gradient accelerating structures |
Type |
Journal Article |
Year |
2016 |
Publication |
Physical Review Accelerators and Beams |
Abbreviated Journal |
Phys. Rev. Accel. Beams |
Volume |
19 |
Issue |
3 |
Pages |
032001 - 6pp |
Keywords |
|
Abstract |
Accelerating gradients in excess of 100 MV/m, at very low breakdown rates, have been successfully achieved in numerous prototype CLIC accelerating structures. The conditioning and operational histories of several structures, tested at KEK and CERN, have been compared and there is clear evidence that the conditioning progresses with the number of rf pulses and not with the number of breakdowns. This observation opens the possibility that the optimum conditioning strategy, which minimizes the total number of breakdowns the structure is subject to without increasing conditioning time, may be to never exceed the breakdown rate target for operation. The result is also likely to have a strong impact on efforts to understand the physical mechanism underlying conditioning and may lead to preparation procedures which reduce conditioning time. |
Address |
[Degiovanni, Alberto; Wuensch, Walter] CERN, European Org Nucl Res, CH-1211 Geneva, Switzerland, Email: walter.wuensch@cern.ch |
Corporate Author |
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Thesis |
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Publisher |
Amer Physical Soc |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2469-9888 |
ISBN |
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Medium |
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Area |
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Expedition |
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Conference |
|
Notes |
WOS:000400274700001 |
Approved |
no |
Is ISI |
yes |
International Collaboration |
yes |
Call Number |
IFIC @ pastor @ |
Serial |
3090 |
Permanent link to this record |
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Author |
Marquez-Martin, I.; Arnault, P.; Di Molfetta, G.; Perez, A. |
Title |
Electromagnetic lattice gauge invariance in two-dimensional discrete-time quantum walks |
Type |
Journal Article |
Year |
2018 |
Publication |
Physical Review A |
Abbreviated Journal |
Phys. Rev. A |
Volume |
98 |
Issue |
3 |
Pages |
032333 - 8pp |
Keywords |
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Abstract |
Gauge invariance is one of the more important concepts in physics. We discuss this concept in connection with the unitary evolution of discrete-time quantum walks in one and two spatial dimensions, when they include the interaction with synthetic, external electromagnetic fields. One introduces this interaction as additional phases that play the role of gauge fields. Here, we present a way to incorporate those phases, which differs from previous works. Our proposal allows the discrete derivatives, that appear under a gauge transformation, to treat time and space on the same footing, in a way which is similar to standard lattice gauge theories. By considering two steps of the evolution, we define a density current which is gauge invariant and conserved. In the continuum limit, the dynamics of the particle, under a suitable choice of the parameters, becomes the Dirac equation and the conserved current satisfies the corresponding conservation equation. |
Address |
[Marquez-Martin, Ivan; Arnault, Pablo; Di Molfetta, Giuseppe; Perez, Armando] Univ Valencia, Dept Fis Teor, Dr Moliner 50, E-46100 Burjassot, Spain, Email: ivan.marquez@uv.es; |
Corporate Author |
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Thesis |
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Publisher |
Amer Physical Soc |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2469-9926 |
ISBN |
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Medium |
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Area |
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Expedition |
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Conference |
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Notes |
WOS:000446163200006 |
Approved |
no |
Is ISI |
yes |
International Collaboration |
yes |
Call Number |
IFIC @ pastor @ |
Serial |
3750 |
Permanent link to this record |
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Author |
Arnault, P.; Perez, A.; Arrighi, P.; Farrelly, T. |
Title |
Discrete-time quantum walks as fermions of lattice gauge theory |
Type |
Journal Article |
Year |
2019 |
Publication |
Physical Review A |
Abbreviated Journal |
Phys. Rev. A |
Volume |
99 |
Issue |
3 |
Pages |
032110 - 16pp |
Keywords |
|
Abstract |
It is shown that discrete-time quantum walks can be used to digitize, i.e., to time discretize fermionic models of continuous-time lattice gauge theory. The resulting discrete-time dynamics is thus not only manifestly unitary, but also ultralocal, i.e., the particle's speed is upper bounded, as in standard relativistic quantum field theories. The lattice chiral symmetry of staggered fermions, which corresponds to a translational invariance, is lost after the requirement of ultralocality of the evolution; this fact is an instance of Meyer's 1996 no-go results stating that no nontrivial scalar quantum cellular automaton can be translationally invariant [D. A. Meyer, J. Stat. Phys. 85, 551 (1996); Phys. Lett. A 223, 337 (1996)]. All results are presented in a single-particle framework and for a (1+1)-dimensional space-time. |
Address |
[Arnault, Pablo; Perez, Armando] Univ Valencia, Dept Fis Teor, Dr Moliner 50, E-46100 Burjassot, Spain, Email: pablo.arnault@ific.uv.es |
Corporate Author |
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Thesis |
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Publisher |
Amer Physical Soc |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2469-9926 |
ISBN |
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Medium |
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Area |
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Expedition |
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Conference |
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Notes |
WOS:000461896700002 |
Approved |
no |
Is ISI |
yes |
International Collaboration |
yes |
Call Number |
IFIC @ pastor @ |
Serial |
3950 |
Permanent link to this record |
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Author |
Woolley, B.; Burt, G.; Dexter, A.C.; Peacock, R.; Millar, W.L.; Catalan Lasheras, N.; Degiovanni, A.; Grudiev, A.; Mcmonagle, G.; Syratchev, I.; Wuensch, W.; Rodriguez Castro, E.; Giner Navarro, J. |
Title |
High-gradient behavior of a dipole-mode rf structure |
Type |
Journal Article |
Year |
2020 |
Publication |
Physical Review Accelerators and Beams |
Abbreviated Journal |
Phys. Rev. Accel. Beams |
Volume |
23 |
Issue |
12 |
Pages |
122002 - 11pp |
Keywords |
|
Abstract |
A normal-conducting, X-band traveling wave structure operating in the dipole mode has been systematically high-gradient tested to gain insight into the maximum possible gradients in these types of structure. Measured structure conditioning, breakdown behavior, and achieved surface fields are reported as well as a postmortem analysis of the breakdown position and a scanning electron microscope analysis of the high-field surfaces. The results of these measurements are then compared to high-gradient results from monopole-mode cavities. Scaled to a breakdown rate of 10(-6), the cavities were found to operate at a peak electric field of 154 MV/m and a peak modified Poynting vector S-c of 5.48 MW/mm(2). The study provides important input for the further development of dipole-mode cavities for use in the Compact Linear Collider as a crab cavity and dipole-mode cavities for use in x-ray free-electron lasers as well as for studies of the fundamental processes in vacuum arcs. Of particular relevance are the unique field patterns in dipole cavities compared to monopole cavities, where the electric and magnetic fields peak in orthogonal planes, which allow the separation of the role of electric and magnetic fields in breakdown via postmortem damage observation. The azimuthal variation of breakdown crater density is measured and is fitted to sinusoidal functions. The best fit is a power law fit of exponent 6. This is significant, as it shows how breakdown probability varies over a surface area with a varying electric field after conditioning to a given peak field. |
Address |
[Woolley, B.; Burt, G.; Dexter, A. C.; Peacock, R.; Millar, W. L.] Univ Lancaster, Lancaster LA1 4YW, England |
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Thesis |
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Publisher |
Amer Physical Soc |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2469-9888 |
ISBN |
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Medium |
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Area |
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Expedition |
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Conference |
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Notes |
WOS:000614886300002 |
Approved |
no |
Is ISI |
yes |
International Collaboration |
yes |
Call Number |
IFIC @ pastor @ |
Serial |
4696 |
Permanent link to this record |
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Author |
Senes, E.; Argyropoulos, T.; Tecker, F.; Wuensch, W. |
Title |
Beam-loading effect on breakdown rate in high-gradient accelerating cavities: An experiment at the Compact Linear Collider Test Facility at CERN |
Type |
Journal Article |
Year |
2018 |
Publication |
Physical Review Accelerators and Beams |
Abbreviated Journal |
Phys. Rev. Accel. Beams |
Volume |
21 |
Issue |
10 |
Pages |
102001 - 8pp |
Keywords |
|
Abstract |
Radio frequency breakdown rate is a crucial performance parameter that ensures that the design luminosity is achieved in the CLIC linear collider. The required low breakdown rate for CLIC, of the order of 10(-7) breakdown pulse(-1) m(-1), has been demonstrated in a number of 12 GHz CLIC prototype structures at gradients in excess of the design 100 MV/m accelerating gradient, however without the presence of the accelerated beam and associated beam loading. The beam loading induced by the approximately 1 A CLIC main beam significantly modifies the field distribution inside the structures, and the effect on breakdown rate is potentially significant so needs to be determined. A dedicated experiment has been carried out in the CLIC Test Facility CTF3 to measure this effect, and the results are presented. |
Address |
[Senes, Eugenio] John Adams Inst, Denys Wilkinson Bldg,Keble Rd, Oxford OX1 3RH, England, Email: eugenio.senes@cern.ch |
Corporate Author |
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Thesis |
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Publisher |
Amer Physical Soc |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2469-9888 |
ISBN |
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Medium |
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Area |
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Expedition |
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Conference |
|
Notes |
WOS:000447731900003 |
Approved |
no |
Is ISI |
yes |
International Collaboration |
yes |
Call Number |
IFIC @ pastor @ |
Serial |
3768 |
Permanent link to this record |
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Author |
Fuster-Martinez, N.; Bruce, R.; Hofer, M.; Persson, T.; Redaelli, S.; Tomas, R. |
Title |
Aperture measurements with ac dipoles and movable collimators in the Large Hadron Collider |
Type |
Journal Article |
Year |
2022 |
Publication |
Physical Review Accelerators and Beams |
Abbreviated Journal |
Phys. Rev. Accel. Beams |
Volume |
25 |
Issue |
10 |
Pages |
101002 - 13pp |
Keywords |
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Abstract |
This paper presents a first experimental demonstration of a new nondestructive method for aperture measurements based on ac dipoles. In high intensity particle colliders, such as the CERN Large Hadron Collider (LHC), aperture measurements are crucial for a safe operation while optimizing the optics in order to reduce the size of the colliding beams and hence increase the luminosity. In the LHC, this type of measurements became mandatory during beam commissioning and the current method used is based on the destructive blowup of bunches using a transverse damper. The new method presented in this paper uses the ac-dipole excitation to generate adiabatic forced oscillations of the beam in order to create losses to identify the smallest aperture in the machine without blowing up the beam emittance. A precise and tuneable control of the oscillation amplitude enables the beams to be reused for several aperture measurements, as well as for other subsequent commissioning activities. Measurements performed with the new method are presented and compared with the current LHC transverse damper method for two different beam energies and two different operational optics. |
Address |
[Fuster-Martinez, N.] CSIC UV, Inst Fis Corpuscular, Valencia 46908, Spain, Email: nuria.fuster@ific.uv.es |
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Thesis |
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Publisher |
Amer Physical Soc |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
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ISBN |
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Medium |
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Area |
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Expedition |
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Conference |
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Notes |
WOS:000875736400001 |
Approved |
no |
Is ISI |
yes |
International Collaboration |
yes |
Call Number |
IFIC @ pastor @ |
Serial |
5397 |
Permanent link to this record |
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Author |
Perez, A. |
Title |
Asymptotic properties of the Dirac quantum cellular automaton |
Type |
Journal Article |
Year |
2016 |
Publication |
Physical Review A |
Abbreviated Journal |
Phys. Rev. A |
Volume |
93 |
Issue |
1 |
Pages |
012328 - 10pp |
Keywords |
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Abstract |
We show that the Dirac quantum cellular automaton [A. Bisio, G. M. D'Ariano, and A. Tosini, Ann. Phys. (N. Y.) 354, 244 (2015)] shares many properties in common with the discrete-time quantum walk. These similarities can be exploited to study the automaton as a unitary process that takes place at regular time steps on a one-dimensional lattice, in the spirit of general quantum cellular automata. In this way, it becomes an alternative to the quantum walk, with a dispersion relation that can be controlled by a parameter that plays a similar role to the coin angle in the quantum walk. The Dirac Hamiltonian is recovered under a suitable limit. We provide two independent analytical approximations to the long-term probability distribution. It is shown that, starting from localized conditions, the asymptotic value of the entropy of entanglement between internal and motional degrees of freedom overcomes the known limit that is approached by the quantum walk for the same initial conditions and is similar to the ones achieved by highly localized states of the Dirac equation. |
Address |
[Perez, A.] Univ Valencia, CSIC, IFIC, Dept Fis Teor, E-46100 Valencia, Spain |
Corporate Author |
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Thesis |
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Publisher |
Amer Physical Soc |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1050-2947 |
ISBN |
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Medium |
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Area |
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Expedition |
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Conference |
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Notes |
WOS:000368291600005 |
Approved |
no |
Is ISI |
yes |
International Collaboration |
no |
Call Number |
IFIC @ pastor @ |
Serial |
2520 |
Permanent link to this record |
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Author |
Gomis, P.; Perez, A. |
Title |
Decoherence effects in the Stern-Gerlach experiment using matrix Wigner functions |
Type |
Journal Article |
Year |
2016 |
Publication |
Physical Review A |
Abbreviated Journal |
Phys. Rev. A |
Volume |
94 |
Issue |
1 |
Pages |
012103 - 11pp |
Keywords |
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Abstract |
We analyze the Stern-Gerlach experiment in phase space with the help of the matrix Wigner function, which includes the spin degree of freedom. Such analysis allows for an intuitive visualization of the quantum dynamics of the device. We include the interaction with the environment, as described by the Caldeira-Leggett model. The diagonal terms of the matrix provide us with information about the two components of the state that arise from interaction with the magnetic field gradient. In particular, from the marginals of these components, we obtain an analytical formula for the position and momentum probability distributions in the presence of decoherence that shows a diffusive behavior for large values of the decoherence parameter. These features limit the dynamics of the present model. We also observe the decay of the nondiagonal terms with time and use this fact to quantify the amount of decoherence from the norm of those terms in phase space. From here, we can define a decoherence time scale, which differs from previous results that make use of the same model. We analyze a typical experiment and show that, for that setup, the decoherence time is much smaller than the characteristic time scale for the separation of the two beams, implying that they can be described as an incoherent mixture of atoms traveling in the up and down directions with opposite values of the spin projection. Therefore, entanglement is quickly destroyed in the setup we analyzed. |
Address |
[Gomis, P.] Univ Valencia, CSIC, Dept Fis Teor, Dr Moliner 50, E-46100 Burjassot, Spain, Email: Pablo.Gomis@uv.es; |
Corporate Author |
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Thesis |
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Publisher |
Amer Physical Soc |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2469-9926 |
ISBN |
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Medium |
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Area |
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Expedition |
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Conference |
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Notes |
WOS:000378909000003 |
Approved |
no |
Is ISI |
yes |
International Collaboration |
no |
Call Number |
IFIC @ pastor @ |
Serial |
2739 |
Permanent link to this record |
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Author |
Arnault, P.; Di Molfetta, G.; Brachet, M.; Debbasch, F. |
Title |
Quantum walks and non-Abelian discrete gauge theory |
Type |
Journal Article |
Year |
2016 |
Publication |
Physical Review A |
Abbreviated Journal |
Phys. Rev. A |
Volume |
94 |
Issue |
1 |
Pages |
012335 - 6pp |
Keywords |
|
Abstract |
A family of discrete-time quantum walks (DTQWs) on the line with an exact discrete U(N) gauge invariance is introduced. It is shown that the continuous limit of these DTQWs, when it exists, coincides with the dynamics of a Dirac fermion coupled to usual U(N) gauge fields in two-dimensional spacetime. A discrete generalization of the usual U(N) curvature is also constructed. An alternate interpretation of these results in terms of superimposed U(1) Maxwell fields and SU(N) gauge fields is discussed in the Appendix. Numerical simulations are also presented, which explore the convergence of the DTQWs towards their continuous limit and which also compare the DTQWs with classical (i.e., nonquantum) motions in classical SU(2) fields. The results presented in this paper constitute a first step towards quantum simulations of generic Yang-Mills gauge theories through DTQWs. |
Address |
[Arnault, Pablo; Debbasch, Fabrice] Univ Paris 06, Univ Paris 04, PSL Res Univ, LERMA,Observ Paris,CNRS,UMR 8112, F-75014 Paris, France, Email: pablo.arnault@upmc.fr; |
Corporate Author |
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Thesis |
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Publisher |
Amer Physical Soc |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2469-9926 |
ISBN |
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Medium |
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Area |
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Expedition |
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Conference |
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Notes |
WOS:000380095000005 |
Approved |
no |
Is ISI |
yes |
International Collaboration |
yes |
Call Number |
IFIC @ pastor @ |
Serial |
2761 |
Permanent link to this record |