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See detailFirst law of quantum thermodynamics in a driven open two-level system
Juan-Delgado, Adrian; Chenu, Aurélia UL

in Physical Review. A (2021)

Assigning the variations of internal energy into heat or work contributions is a challenging task due to the fact that these properties are trajectory dependent. A number of proposals have been put ... [more ▼]

Assigning the variations of internal energy into heat or work contributions is a challenging task due to the fact that these properties are trajectory dependent. A number of proposals have been put forward for open quantum systems following an arbitrary dynamics. We here focus on nonequilibrium thermodynamics of a two-level system and explore in addition to the conventional approach, two definitions motivated by either classical work or heat in which the driving Hamiltonian or the trajectory itself, respectively, are used to set up a reference basis. We first give the thermodynamic properties for an arbitrary dynamics and illustrate the results on the Bloch sphere. Then, we solve the particular example of a periodically driven qubit interacting with a dissipative and decoherence bath. Our results illustrate the trajectory-dependent character of heat and work and how contributions originally assigned to dissipation in the Lindblad equation can become a coherent part assigned to work. [less ▲]

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See detailQuantum bath statistics tagging
Farina, Donato; Cavina, Vasco UL; Giovannetti, Vittorio

in Physical Review. A (2019)

The possibility of discriminating the statistics of a thermal bath using indirect measurements performed on quantum probes is presented. The scheme relies on the fact that, when weakly coupled with the ... [more ▼]

The possibility of discriminating the statistics of a thermal bath using indirect measurements performed on quantum probes is presented. The scheme relies on the fact that, when weakly coupled with the environment of interest, the transient evolution of the probe toward its final thermal configuration is strongly affected by the fermionic or bosonic nature of the bath excitations. Using figures of merit taken from quantum metrology such as the Holevo-Helstrom probability of error and the quantum Chernoff bound, we discuss how to achieve the greatest precision in this statistics tagging procedure, analyzing different models of probes and different initial preparations and by optimizing over the time of exposure of the probe. [less ▲]

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See detailRumpling of LiF(001) surface from fast atom diffraction
Schueller, A.; Wethekam, S.; Blauth, D. et al

in Physical Review. A (2010), 82(6), 062902

Quantum diffraction of fast atoms scattered from the topmost layer of surfaces under grazing angles of incidence can be employed for the analysis of detailed structural properties of insulator surfaces ... [more ▼]

Quantum diffraction of fast atoms scattered from the topmost layer of surfaces under grazing angles of incidence can be employed for the analysis of detailed structural properties of insulator surfaces. From comparison of measured and calculated diffraction patterns we deduce the rumpling of the topmost surface layer of LiF(001) (i.e., an inward shift of Li(+) ions with respect to F(-) ions). The effect of thermal vibrations on the measurement of rumpling is accounted for by ab initio calculations of the mean-square vibrational amplitudes of surface ions. At room temperature this leads to a reduction of the apparent rumpling by 0.008 angstrom. We then obtain a rumpling of ( 0.05 +/- 0.04) angstrom, which improves its accuracy achieved in previous work. [less ▲]

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See detailPotential-energy surfaces for charge exchange between singly charged ions and a LiF surface
Wirtz, Ludger UL; Burgdorfer, J.; Dallos, M. et al

in Physical Review. A (2003), 68(3),

We analyze the adiabatic potential-energy surfaces relevant for neutralization of singly charged ions in slow vertical incidence onto a lithium fluoride surface. The surface is represented by a cluster of ... [more ▼]

We analyze the adiabatic potential-energy surfaces relevant for neutralization of singly charged ions in slow vertical incidence onto a lithium fluoride surface. The surface is represented by a cluster of varying size augmented by point charges of alternating sign in order to include the proper Madelung potential of the ionic crystal. Our calculation proceeds on the multiconfiguration self-consistent-field and multireference configuration-interaction levels. Size-consistency corrections based on the Davidson correction and multireference averaged quadratic coupled cluster methods are included as well. We emphasize the importance of a proper treatment of electron correlation signifying the polarization of the surrounding cluster environment in ab initio calculations of charge transfer at surfaces. From the topology of the surfaces, in particular the existence or absence of avoided crossings (or, more generally, conical intersections), qualitative predictions for the neutralization process can be made. The comparative analysis of potential curves for H+, C+, S+, and Ne+ projectiles provides an explanation for the recently observed threshold behavior for potential sputtering. [less ▲]

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See detailLiouville master equation for multielectron dynamics: Neutralization of highly charged ions near a LiF surface
Wirtz, Ludger UL; Reinhold, C. O.; Lemell, C. et al

in Physical Review. A (2003), 67(1),

We present a simulation of the neutralization of highly charged ions in front of a lithium fluoride surface including the close-collision regime above the surface. The present approach employs a Monte ... [more ▼]

We present a simulation of the neutralization of highly charged ions in front of a lithium fluoride surface including the close-collision regime above the surface. The present approach employs a Monte Carlo solution of the Liouville master equation for the joint probability density of the ionic motion and the electronic population of the projectile and the target surface. It includes single as well as double particle-hole (de)excitation processes and incorporates electron correlation effects through the conditional dynamics of population strings. The input in terms of elementary one- and two-electron transfer rates is determined from classical trajectory Monte Carlo calculations as well as quantum-mechanical Auger calculations. For slow projectiles and normal incidence, the ionic motion depends sensitively on the interplay between image acceleration towards the surface and repulsion by an ensemble of positive hole charges in the surface ("trampoline effect"). For Ne10+ we find that image acceleration is dominant and no collective backscattering high above the surface takes place. For grazing incidence, our simulation delineates the pathways to complete neutralization. In accordance with recent experimental observations, most ions are reflected as neutral or even as singly charged negative particles, irrespective of the charge state of the incoming ions. [less ▲]

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See detailHollow-ion formation in microcapillaries
Tokesi, K.; Wirtz, Ludger UL; Lemell, C. et al

in Physical Review. A (2001), 64(4),

Transmission of highly charged ions through microcapillaries is studied theoretically by a classical trajectory simulation. The interaction of highly charged ions with the internal surface of the ... [more ▼]

Transmission of highly charged ions through microcapillaries is studied theoretically by a classical trajectory simulation. The interaction of highly charged ions with the internal surface of the capillary is treated within the framework of dielectric-response theory. The simulation is based on the classical over-the-barrier model modified for open cylindrical surfaces. The multielectron evolution and relaxation is taken into account as a stochastic event sequence. We consider N6+ and Ne10+ with an energy of 2.1 keV/amu passing through a metallic microcapillary of Ni. We analyze the distance of closest approach. the angular distribution, and the distribution of the mean occupation numbers of n shells of highly charged ions. We find the resulting charge state distribution of transmitted projectiles in good agreement with recent measurements. Implications for nanotube targets will be discussed. [less ▲]

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See detailCharge-state evolution of highly charged ions transmitted through microcapillaries
Tokesi, K.; Wirtz, Ludger UL; Lemell, C. et al

in Physical Review. A (2000), 61(2),

The charge-state evolution of highly charged ions transmitted through microcapillaries is studied theoretically by a classical trajectory Monte Carlo simulation.: The interaction of highly charged ions ... [more ▼]

The charge-state evolution of highly charged ions transmitted through microcapillaries is studied theoretically by a classical trajectory Monte Carlo simulation.: The interaction of highly charged ions with the internal surface of the capillary is treated within the framework of dielectric response theory. We analyze the distance of closest approach and the angular distributions of the highly charged ions at the exit of the microcapillary. We find the charge-state fraction of transmitted N6+ projectiles, in: good agreement with first measurements. Moreover, our calculations indicate that grazing collisions with the microcapillary surface hold the promise of direct observation of charge transfer and hollow-atom formation at a large distance from the surface. [less ▲]

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