| 1. |
- Abascal, Isabel Sainz, et al.
(författare)
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Bipartite entanglement measure based on covariance
- 2007
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 75:6
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Tidskriftsartikel (refereegranskat)abstract
- We propose an entanglement measure for two quNits based on the covariances of a set of generators of the su(N) algebra. In particular, we represent this measure in terms of the mutually unbiased projectors for N prime. For pure states this measure quantifies entanglement, we obtain an explicit expression which relates it to the concurrence hierarchy, specifically the I-concurrence and the three-concurrence. For mixed states we propose a separability criterion.
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| 2. |
- Abdullaev, Fatkhulla, et al.
(författare)
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Collective dynamics of Fermi-Bose mixtures with an oscillating scattering length
- 2019
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 99:3
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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.
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| 3. |
- Abdullaev, Fatkhulla, et al.
(författare)
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Faraday waves in quasi-one-dimensional superfluid Fermi-Bose mixtures
- 2013
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 87:2
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Tidskriftsartikel (refereegranskat)abstract
- The generation of Faraday waves in superfluid Fermi-Bose mixtures in elongated traps is investigated. The generation of waves is achieved by periodically changing a parameter of the system in time. Two types of modulations of parameters are considered: a variation of the fermion-boson scattering length and the boson-boson scattering length. We predict the properties of the generated Faraday patterns and study the parameter regions where they can be excited.
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| 4. |
- Acín, Antonio, et al.
(författare)
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Optimal randomness certification from one entangled bit
- 2016
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 93:4
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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.
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| 5. |
- Adesso, Gerardo, et al.
(författare)
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Coexistence of unlimited bipartite and genuine multipartite entanglement : Promiscuous quantum correlations arising from discrete to continuous variable systems
- 2007
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 76:2, s. 022315-
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Tidskriftsartikel (refereegranskat)abstract
- Quantum mechanics imposes 'monogamy' constraints on the sharing of entanglement. We show that, despite these limitations, entanglement can be fully 'promiscuous', i.e. simultaneously present in unlimited two-body and many-body forms in states living in an infinite-dimensional Hilbert space. Monogamy just bounds the divergence rate of the various entanglement contributions. This is demonstrated in simple families of N-mode (N >= 4) Gaussian states of light fields or atomic ensembles, which therefore enable infinitely more freedom in the distribution of information, as opposed to systems of individual qubits. Such a finding is of importance for the quantification, understanding and potential exploitation of shared quantum correlations in continuous variable systems. We discuss how promiscuity gradually arises when considering simple families of discrete variable states, with increasing Hilbert space dimension towards the continuous variable limit. Such models are somehow analogous to Gaussian states with asymptotically diverging, but finite squeezing. In this respect, we find that non-Gaussian states (which in general are more entangled than Gaussian states), exhibit also the interesting feature that their entanglement is more shareable: in the non-Gaussian multipartite arena, unlimited promiscuity can be already achieved among three entangled parties, while this is impossible for Gaussian, even infinitely squeezed states.
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| 6. |
- Adesso, Gerardo, et al.
(författare)
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Continuous variable entanglement sharing in noninertial frames
- 2007
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 76:6, s. 062112-
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Tidskriftsartikel (refereegranskat)abstract
- We study the distribution of entanglement between modes of a free scalar field from the perspective of observers in uniform acceleration. We consider a two-mode squeezed state of the field from an inertial perspective, and analytically study the degradation of entanglement due to the Unruh effect, in the cases of either one or both observers undergoing uniform acceleration. We find that for two observers undergoing finite acceleration, the entanglement vanishes between the lowest frequency modes. The loss of entanglement is precisely explained as a redistribution of the inertial entanglement into multipartite quantum correlations among accessible and unaccessible modes from a non-inertial perspective. We show that classical correlations are also lost from the perspective of two accelerated observers but conserved if one of the observers remains inertial.
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| 7. |
- Adesso, Gerardo, et al.
(författare)
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Entanglement in Gaussian matrix-product states
- 2006
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 74:3, s. 030305(R)-
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Tidskriftsartikel (refereegranskat)abstract
- Gaussian matrix product states are obtained as the outputs of projection operations from an ancillary space of M infinitely entangled bonds connecting neighboring sites, applied at each of N sites of an harmonic chain. Replacing the projections by associated Gaussian states, the 'building blocks', we show that the entanglement range in translationally-invariant Gaussian matrix product states depends on how entangled the building blocks are. In particular, infinite entanglement in the building blocks produces fully symmetric Gaussian states with maximum entanglement range. From their peculiar properties of entanglement sharing, a basic difference with spin chains is revealed: Gaussian matrix product states can possess unlimited, long-range entanglement even with minimum number of ancillary bonds (M=1). Finally we discuss how these states can be experimentally engineered from N copies of a three-mode building block and N two-mode finitely squeezed states.
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| 8. |
- Ahufinger, V., et al.
(författare)
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Disordered ultracold atomic gases in optical lattices : A case study of Fermi-Bose mixtures
- 2005
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 72:6
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Tidskriftsartikel (refereegranskat)abstract
- We present a review of properties of ultracold atomic Fermi-Bose mixtures in inhomogeneous and random optical lattices. In the strong interacting limit and at very low temperatures, fermions form, together with bosons or bosonic holes, composite fermions. Composite fermions behave as a spinless interacting Fermi gas, and in the presence of local disorder they interact via random couplings and feel effective random local potential. This opens a wide variety of possibilities of realizing various kinds of ultracold quantum disordered systems. In this paper we review these possibilities, discuss the accessible quantum disordered phases, and methods for their detection. The discussed quantum phases include Fermi glasses, quantum spin glasses, “dirty†superfluids, disordered metallic phases, and phases involving quantum percolation.
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| 9. |
- Alagia, M., et al.
(författare)
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Probing the potential energy surface by highresolution x-ray absorption spectroscopy : The umbrella motion of the coreexcited CH3 free radical
- 2007
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Ingår i: Physical Review. A. - 1050-2947 .- 1094-1622. ; 76:2, s. 124305-
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Tidskriftsartikel (refereegranskat)abstract
- A detailed study of the umbrellalike vibration in inner-shell spectroscopy is presented. The high-resolution x-ray absorption spectrum for the lowest lying core excitation of the CH3 free radical was recorded. High quality potential energy surfaces (PES) for the initial and final states of the transition were calculated as a function of the symmetrical stretching and the umbrella deformation coordinates. The strong anharmonicity along the umbrella coordinate in the double-well region of the PES of the core excited state has a strong effect on the bending vibrational progressions. The excellent agreement between the experiment and theory allows an accurate spectroscopic characterization of the vibrational structure of the electronic transition, and the estimation of the umbrella inversion time of 149 fs.
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| 10. |
- Allahverdyan, A, et al.
(författare)
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Brownian entanglement
- 2005
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 72, s. 032102-
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Tidskriftsartikel (refereegranskat)
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