| 1. |
- Abdullaev, Fatkhulla, et al.
(författare)
-
Collective dynamics of Fermi-Bose mixtures with an oscillating scattering length
- 2019
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 99:3
-
Tidskriftsartikel (refereegranskat)abstract
- Collective oscillations of superfluid mixtures of ultra cold fermionic and bosonic atoms are investigated while varying the fermion-boson scattering length. We study the dynamics with respect to excited center of mass modes and breathing modes in the mixture. Parametric resonances are also analyzed when the scattering length varies periodically in time, by comparing partial differential equation (PDE) models and ordinary differential equation (ODE) models for the dynamics. An application to the recent experiment with fermionic Li-6 and bosonic Li-7 atoms, which approximately have the same masses, is discussed.
|
|
| 2. |
- Acín, Antonio, et al.
(författare)
-
Optimal randomness certification from one entangled bit
- 2016
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 93:4
-
Tidskriftsartikel (refereegranskat)abstract
- By performing local projective measurements on a two-qubit entangled state one can certify in a device-independent way up to one bit of randomness. We show here that general measurements, defined by positive-operator-valued measures, can certify up to two bits of randomness, which is the optimal amount of randomness that can be certified from an entangled bit. General measurements thus provide an advantage over projective ones for device-independent randomness certification.
|
|
| 3. |
- Andersson, Jonas, et al.
(författare)
-
Triple ionization of atomic Cd involving 4p(-1) and 4s(-1) inner-shell holes
- 2015
-
Ingår i: Physical Review A. - 1050-2947 .- 1094-1622. ; 92:2
-
Tidskriftsartikel (refereegranskat)abstract
- The triple ionization spectrum of atomic Cd formed upon the removal of a 4p or a 4s inner-shell electron and subsequent Auger decays has been obtained at 200 eV photon energy. By using a versatile multielectron coincidence detection technique based on a magnetic bottle spectrometer in combination with multiconfiguration Dirac-Fock calculations, Auger cascades leading to tricationic final states have been analyzed and final-state configurations have been identified. The most prominent Auger cascades leading to the ground state of Cd3+ have been identified in good agreement with theory.
|
|
| 4. |
- Andersson, Ole, et al.
(författare)
-
Device-independent certification of two bits of randomness from one entangled bit and Gisin's elegant Bell inequality
- 2018
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 97:1
-
Tidskriftsartikel (refereegranskat)abstract
- We prove that as conjectured by Acín et al. [Phys. Rev. A 93, 040102(R) (2016)], two bits of randomness can be certified in a device-independent way from one bit of entanglement using the maximal quantum violation of Gisin's elegant Bell inequality. This suggests a surprising connection between maximal entanglement, complete sets of mutually unbiased bases, and elements of symmetric informationally complete positive operator-valued measures, on one side, and the optimal way of certifying maximal randomness, on the other.
|
|
| 5. |
- Asboth, Janos K., et al.
(författare)
-
Edge-state-enhanced transport in a two-dimensional quantum walk
- 2015
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 91:2
-
Tidskriftsartikel (refereegranskat)abstract
- Quantum walks on translation-invariant regular graphs spread quadratically faster than their classical counterparts. The same coherence that gives them this quantum speedup inhibits or even stops their spread in the presence of disorder. We ask how to create an efficient transport channel from a fixed source site (A) to fixed target site (B) in a disordered two-dimensional discrete-time quantum walk by cutting some of the links. We show that the somewhat counterintuitive strategy of cutting links along a single line connecting A to B creates such a channel. The efficient transport along the cut is due to topologically protected chiral edge states, which exist even though the bulk Chern number in this system vanishes. We give a realization of the walk as a periodically driven lattice Hamiltonian and identify the bulk topological invariant responsible for the edge states as the quasienergy winding of this Hamiltonian.
|
|
| 6. |
- Bao, Fanglin, et al.
(författare)
-
First-order correction to the Casimir force within an inhomogeneous medium
- 2015
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 91:6
-
Tidskriftsartikel (refereegranskat)abstract
- For the Casimir piston filled with an inhomogeneous medium, we regularized and expressed the Casimir energy with cylinder kernel coefficients by using the first-order perturbation theory. When the refractive index of the medium is smoothly inhomogeneous (i.e., derivatives of all orders exist), a logarithmically cutoff-dependent term and a quadratically cutoff-dependent term in the Casimir energy are found. We show that in the piston model these terms vanish in the force and thus the Casimir force is always cutoff independent, but these terms will remain in the force in the half-space model and must be removed by additional regularizations. We give explicit benchmark solutions to the first-order corrections of both Casimir energy and Casimir force for an exponentially decaying profile. The present method can be extended to other inhomogeneous profiles. Our results should be useful for future relevant calculations and experimental studies.
|
|
| 7. |
- Bao, Fanglin, et al.
(författare)
-
Inhomogeneity-related cutoff dependence of the Casimir energy and stress
- 2016
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 93:1
-
Tidskriftsartikel (refereegranskat)abstract
- The Casimir stress and energy density are widely used to study the Casimir force, but they diverge in inhomogeneous systems, making the force seem to be infinite as well. Here we characterize the asymptotic behavior of the Casimir stress and energy density in inhomogeneous systems. We show an unambiguous map of all cutoff-dependent terms in the asymptotic expansion to the pressure and the surface tension through the insertion of multiple boundary layers. This result reveals an elegant subtraction to retrieve a finite stress that yields a cutoff-independent force.
|
|
| 8. |
- Barillot, T., et al.
(författare)
-
Angular asymmetry and attosecond time delay from the giant plasmon resonance in C60 photoionization
- 2015
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 91
-
Tidskriftsartikel (refereegranskat)abstract
- This combined experimental and theoretical study demonstrates that the surface plasmon resonance in C 60 alters the valence photoemission quantum phase, resulting in strong effects in the photoelectron angular distribution and emission time delay. Electron momentum imaging spectroscopy is used to measure the photoelectron angular distribution asymmetry parameter that agrees well with our calculations from the time-dependent local density approximation (TDLDA). Significant structure in the valence photoemission time delay is simultaneously calculated by TDLDA over the plasmon active energies. Results reveal a unified spatial and temporal asymmetry pattern driven by the plasmon resonance and offer a sensitive probe of electron correlation. A semiclassical approach facilitates further insights into this link that can be generalized and applied to other molecular systems and nanometer-sized metallic materials exhibiting plasmon resonances.
|
|
| 9. |
- Björk, Gunnar, et al.
(författare)
-
Extremal quantum states and their Majorana constellations
- 2015
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 92:3
-
Tidskriftsartikel (refereegranskat)abstract
- The characterization of quantum polarization of light requires knowledge of all the moments of the Stokes variables, which are appropriately encoded in the multipole expansion of the density matrix. We look into the cumulative distribution of those multipoles and work out the corresponding extremal pure states. We find that SU(2) coherent states are maximal to any order whereas the converse case of minimal states (which can be seen as the most quantum ones) is investigated for a diverse range of the number of photons. Taking advantage of the Majorana representation, we recast the problem as that of distributing a number of points uniformly over the surface of the Poincare sphere.
|
|
| 10. |
- Calderaro, Luca, et al.
(författare)
-
Vortex dynamics in coherently coupled Bose-Einstein condensates
- 2017
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 95:2
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In classical hydrodynamics with uniform density, vortices move with the local fluid velocity. This description is rewritten in terms of forces arising from the interaction with other vortices. Two such positive straight vortices experience a repulsive interaction and precess in a positive (anticlockwise) sense around their common centroid. A similar picture applies to vortices in a two-component two-dimensional uniform Bose-Einstein condensate (BEC) coherently coupled through rf Rabi fields. Unlike the classical case, however, the rf Rabi coupling induces an attractive interaction and two such vortices with positive signs now rotate in the negative (clockwise) sense. Pairs of counter-rotating vortices are instead found to translate with uniform velocity perpendicular to the line joining their cores. This picture is extended to a single vortex in a two-component trapped BEC. Although two uniform vortex-free components experience familiar Rabi oscillations of particle-number difference, such behavior is absent for a vortex in one component because of the nonuniform vortex phase. Instead the coherent Rabi coupling induces a periodic vorticity transfer between the two components.
|
|
