| 11. |
- Andersson, Pontus, 1971, et al.
(author)
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Radiative lifetimes of metastable states of negative ions
- 2006
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In: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622 .- 2469-9926 .- 2469-9934. ; 73, s. 032705-
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Journal article (peer-reviewed)abstract
- We present a technique for measuring the radiative lifetimes of metastable states of negative ions that involves the use of a heavy-ion storage ring. The method has been applied to investigate the radiative decay of the np(3) P-2(1/2) levels of Te-(n=5) and Se-(n=4) and the 3p(3) D-2 state of Si- for which the J=3/2 and 5/2 levels were unresolved. All of these states are metastable and decay primarily by emission of E2 and M1 radiation. Multi Configuration Dirac-Hartree-Fock calculations of rates for the transitions in Te- and Se- yielded lifetimes of 0.45 s and 4.7 s, respectively. The measured values agree well with these predicted values. In the case of the D-2 state of Si-, however, our measurement was only able to set a lower limit on the lifetime. The upper limit of the lifetime that can be measured with our apparatus is set by how long the ions can be stored in the ring, a limit determined by the rate of collisional detachment. Our lower limit of 1 min for the lifetime of the D-2 state is consistent with both the calculated lifetimes of 162 s for the D-2(3/2) level and 27.3 h for the D-2(5/2) level reported by O'Malley and Beck and 14.5 h and 12.5 h, respectively, from our Breit-Pauli calculations.
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| 12. |
- Andersson, Åke, et al.
(author)
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Single-photon hot-electron ionization of C70
- 2023
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In: Physical Review A. - 2469-9926 .- 2469-9934. ; 107:1
-
Journal article (peer-reviewed)abstract
- Gas phase C70 molecules have been ionized with single photons of energies between 16 and 70 eV, and the electron spectra measured with velocity map imaging in coincidence with the ions. The doubly ionized and unfragmented species was present at photon energies of 22 eV and up, and triply charged ions were present from 55 eV. The low-kinetic-energy parts of the spectra are explained with thermal emission of transient hot electrons. We propose a generally applicable mechanism, named resonance ionization shadowing, for the creation of hot electrons by absorption of above-threshold energy photons.
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| 13. |
- Angioi, A., et al.
(author)
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Nonlinear single Compton scattering of an electron wave packet
- 2016
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In: Physical Review A - Atomic, Molecular, and Optical Physics. - 2469-9926 .- 2469-9934. ; 93:5
-
Journal article (peer-reviewed)abstract
- Nonlinear single Compton scattering has been thoroughly investigated in the literature under the assumption that the electron initially has a definite momentum. Here, we study a more general initial state and consider the electron as a wave packet. In particular, we investigate the energy spectrum of the emitted radiation and show that, in typical experimental situations, some features of the spectra shown in previous works are almost completely washed out. Moreover, we show that, at comparable relative uncertainties, the one in the momentum of the incoming electron has a larger impact on the photon spectra at a fixed observation direction than the one on the laser frequency.
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| 14. |
- Anwer, Hammad, et al.
(author)
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Experimental test of maximal tripartite nonlocality using an entangled state and local measurements that are maximally incompatible
- 2019
-
In: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 100:2
-
Journal article (peer-reviewed)abstract
- The only known qubit states that produce maximal quantum violation of a tight Bell inequality with maximally incompatible local measurements are Bell states, Greenberger-Horne-Zeilinger states, and a recently identified three-qubit state called vertical bar S >. Here we report the results of an experiment for preparing vertical bar S > and testing the maximum quantum violation of the corresponding tripartite Bell inequality. Using a heralded source of three entangled photons and three tunable polarization-dependent filters, we experimentally prepare vertical bar S > with 0.924 fidelity. Using maximally incompatible measurements for the three parties, we observe a value of T-26 = 7.30 +/- 0.06, which clearly violates the tight Bell inequality T-26 <= 5. In addition, we show that our setup allows preparing multipartite states that were inaccessible with previous methods and are useful for quantum information and metrology.
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| 15. |
- Aourir, Nouria, et al.
(author)
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Theoretical hyperfine structures of F-19 I and O-17 I
- 2018
-
In: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society. - 2469-9926 .- 2469-9934. ; 97:3
-
Journal article (peer-reviewed)abstract
- Multiconfiguration Hartree-Fock (MCHF) and multiconfiguration Dirac-Hartree-Fock (MCDHF) calculations are performed for the 2p(5) P-2 degrees, 2p(4)(P-3)3s P-4, 2p(4)(P-3)3s P-2, and 2p(4)(P-3)3 p S-4 degrees states of F-19 I to determine their hyperfine constants. Several computing strategies are considered to investigate electron correlation and relativistic effects. High-order correlation contributions are included in MCHF calculations based on single and double multireference expansions. The largest components of the single reference MCHF wave functions are selected to define the multireference (MR) sets. In this scheme, relativistic corrections are evaluated in the Breit-Pauli approximation. A similar strategy is used for the calculation of MCDHF relativistic wave functions and hyperfine parameters. While correlation and relativistic corrections are found to be rather small for the ground state, we highlight large relativistic effects on the hyperfine constant A(3/2) of 2p(4)(P-3)3 p(4)S(degrees) and, to a lesser extent, on A(1/2) of 2p(4)(P-3)3s P-4. As expected for such a light system, electron correlation effects dominate over relativity in the calculation of the hyperfine interaction of all other levels considered. We also revisit the hyperfine constants of 2p(3)((4)(S))3s S-5 degrees and 2p(3)(S-4)3 p P-5 in O-17 using similar strategies. The results are found to be in excellent agreement with experiment.
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| 16. |
- Arzani, Francesco, et al.
(author)
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Random coding for sharing bosonic quantum secrets
- 2019
-
In: Physical Review A. - 2469-9934 .- 2469-9926. ; 100:2
-
Journal article (peer-reviewed)abstract
- We consider a protocol for sharing quantum states using continuous variable systems. Specifically we introduce an encoding procedure where bosonic modes in arbitrary secret states are mixed with several ancillary squeezed modes through a passive interferometer. We derive simple conditions on the interferometer for this encoding to define a secret sharing protocol and we prove that they are satisfied by almost any interferometer. This implies that, if the interferometer is chosen uniformly at random, the probability that it may not be used to implement a quantum secret sharing protocol is zero. Furthermore, we show that the decoding operation can be obtained and implemented efficiently with a Gaussian unitary using a number of single-mode squeezers that is at most twice the number of modes of the secret, regardless of the number of players. We benchmark the quality of the reconstructed state by computing the fidelity with the secret state as a function of the input squeezing.
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| 17. |
- Aurbakken, Einar, et al.
(author)
-
Transient spectroscopy from time-dependent electronic-structure theory without multipole expansions
- 2024
-
In: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society. - 2469-9926 .- 2469-9934. ; 109:1
-
Journal article (peer-reviewed)abstract
- Based on the work done by an electromagnetic field on an atomic or molecular electronic system, a general gauge-invariant formulation of transient absorption spectroscopy is presented within the semiclassical approximation. Avoiding multipole expansions, a computationally viable expression for the spectral response function is derived from the minimal-coupling Hamiltonian of an electronic system interacting with one or more laser pulses described by a source-free, enveloped electromagnetic vector potential. With a fixed-basis expansion of the electronic wave function, the computational cost of simulations of laser-driven electron dynamics beyond the dipole approximation is the same as simulations adopting the dipole approximation. We illustrate the theory by time-dependent configuration interaction and coupled-cluster simulations of core-level absorption and circular dichroism spectra.
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| 18. |
- Aurell, Erik, et al.
(author)
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Real-time dynamics in diluted quantum networks
- 2022
-
In: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : AMER PHYSICAL SOC. - 2469-9926 .- 2469-9934. ; 105:2
-
Journal article (peer-reviewed)abstract
- We introduce an approach to characterize the dynamics of disordered quantum networks. Each quantum element (i.e., each node) of the network experiences the other nodes as an effective environment that can be self-consistently represented by a Feynman-Vernon influence functional. For networks having the topology of locally treelike graphs, these Feynman-Vernon (FV) functionals can be determined by a new version of the cavity or belief propagation (BP) method. Here, we find the fixed point solution of this version of BP for a network of uniform quantum harmonic oscillators. Then, we estimate the effects of the disorder in these networks within the replica symmetry ansatz. We show that over a large time interval, at small disorder, the real part of the FV functional induces decoherence and classicality while at sufficiently large disorder the Feynman-Vernon functional tends to zero and the coherence survives, signaling in a time setting, the onset of an Anderson's transition.
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| 19. |
- Azimi Mousolou, Vahid, et al.
(author)
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Entanglement duality in spin-spin interactions
- 2022
-
In: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society (APS). - 2469-9926 .- 2469-9934. ; 106:3
-
Journal article (peer-reviewed)abstract
- We examine entanglement of thermal states for spin-1/2 dimers in external magnetic fields. Entanglement transition in the temperature-magnetic-field plane demonstrates a duality in spin-spin interactions. This identifies a pair of dual categories of symmetric and antisymmetric dimers with each category classified into toric entanglement classes. The entanglement transition line is preserved from each toric entanglement class to its dual toric class. The toric classification is an indication of the topological signature of the entanglement, which bring about topological stability that could be relevant for quantum information processing.
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| 20. |
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