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- Balcou, Philippe, et al.
(författare)
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Generalized phase-matching conditions for high harmonics : The role of field-gradient forces
- 1997
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 55:4, s. 3204-3210
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Tidskriftsartikel (refereegranskat)abstract
- We present an approach to describe the phase matching of high harmonics emitted by laser driven atoms in a nonperturbative regime, for which the atomic response displays an intrinsic intensity-dependent phase. We show that the traditional phase-matching conditions involving conservation of wave vectors should be modified by taking into account the gradient of this atomic phase. We investigate various focusing geometries and interpret the numerical results of Sali`eres et al. [Phys. Rev. Lett. 74, 3776 (1995)]. Within the framework of the two-step model, we demonstrate that the gradient of the intensity-dependent phase can be considered as the canonical momentum gained by the electron in the continuum due to acceleration by field-gradient forces, including in particular the ponderomotive force.
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| 2. |
- Krutitsky, Konstantin V., et al.
(författare)
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Dark solitons near the Mott-insulator-superfluid phase transition
- 2010
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 82:3, s. 33618-
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Tidskriftsartikel (refereegranskat)abstract
- Dark solitons of ultracold bosons in the vicinity of the Mott-insulator-superfluid phase transition are studied. Making use of the Gutzwiller ansatz we have found antisymmetric eigenstates corresponding to standing solitons, as well as propagating solitons created by phase imprinting. Near the phase boundary, superfluidity has either a particle or a hole character depending on the system parameters, which greatly affects the characteristics of both types of solitons. Within the insulating Mott regions, soliton solutions are prohibited by lack of phase coherence between the lattice sites. Linear and modulational stability show that the soliton solutions are sensitive to small perturbations and, therefore, unstable. In general, their lifetimes differ for on-site and off-site modes. For the on-site modes, there are small areas between the Mott-insulator regions where the lifetime is very large, and in particular much larger than that for the off-site modes.
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| 3. |
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| 4. |
- Lim, Soon Hoe, et al.
(författare)
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Homogenization for Generalized Langevin Equations with Applications to Anomalous Diffusion
- 2020
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Ingår i: Annales de l'Institute Henri Poincare. Physique theorique. - : Springer Science and Business Media LLC. - 1424-0637 .- 1424-0661. ; 21, s. 1813-1871
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Tidskriftsartikel (refereegranskat)abstract
- We study homogenization for a class of generalized Langevin equations (GLEs) with state-dependent coefficients and exhibiting multiple time scales. In addition to the small mass limit, we focus on homogenization limits, which involve taking to zero the inertial time scale and, possibly, some of the memory time scales and noise correlation time scales. The latter are meaningful limits for a class of GLEs modeling anomalous diffusion. We find that, in general, the limiting stochastic differential equations for the slow degrees of freedom contain non-trivial drift correction terms and are driven by non-Markov noise processes. These results follow from a general homogenization theorem stated and proven here. We illustrate them using stochastic models of particle diffusion.
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| 7. |
- Tuziemski, Jan, et al.
(författare)
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Reexamination of the decoherence of spin registers
- 2019
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 99:2
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Tidskriftsartikel (refereegranskat)abstract
- We revisit the decoherence process of a multiqubit register interacting with a thermal bosonic bath. We generalize the previous studies by considering not only the register's behavior but also a part of its environment. In particular, we are interested in information flow from the register to the environment, which we describe using recently introduced multipartite quantum state structures called spectrum broadcast structures. Working in two specific cases of (i) two-qubit register and (ii) collective decoherence, we identify the regimes where the environment acquires almost complete information about the register state. We also study in more detail the interesting causal aspects related to the finite propagation time of the field disturbances between the qubits. Finally, we describe quantum state structures which appear due to the presence of protected spaces.
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