Non-classical properties of the e.m. near field of an atom in spontaneous light emission

We use Glauber's correlation function function as well as the Green functions formalism to investigate, in the case of a dipolar atomic transition, the causal behaviour of the spontaneously emitted electromagnetic field. We also examine the role played by the longitudinal electric field, which is not described in terms of photonic (transverse) degrees of freedom. We predict the existence of a genuinely quantum memory effect at the level of the near field surrounding the atom, which keeps track of the past excitation and emission by the atom

Conditions for anti-Zeno effect observation in free-space atomic radiative decay

Frequent measurements can modify the decay of an unstable quantum state with respect to the free dynamics given by Fermi's golden rule. In a landmark article, Nature 405, 546 (2000), Kofman and Kurizki concluded that in quantum decay processes, acceleration of the decay by frequent measurements, called the quantum anti-Zeno effect (AZE), appears to be ubiquitous, while its counterpart, the quantum Zeno effect, is unattainable. However, up to now there have been no experimental observations of the AZE for atomic radiative decay (spontaneous emission) in free space. In this work, making use of analytical results available for hydrogen-like atoms, we find that in free space, only non-electric-dipolar transitions should present an observable AZE, revealing that this effect is consequently much less ubiquitous than first predicted. We then propose an experimental scheme for AZE observation, involving the electric quadrupole transition between D 5/2 and S 1/2 in the heaviest alkali-earth ions Ca + and Sr +. The proposed protocol is based on the STIRAP technique which acts like a dephasing quasi-measurement

Coherent states and the classical-quantum limit considered from the point of view of entanglement

Three paradigms commonly used in classical, pre-quantum physics to describe particles (that is: the material point, the test-particle and the diluted particle (droplet model)) can be identified as limit-cases of a quantum regime in which pairs of particles interact without getting entangled with each other. This entanglement-free regime also provides a simplified model of what is called in the decoherence approach "islands of classicality", that is, preferred bases that would be selected through evolution by a Darwinist mechanism that aims at optimising information. We show how, under very general conditions, coherent states are natural candidates for classical pointer states. This occurs essentially because, when a (supposedly bosonic) system coherently exchanges only one quantum at a time with the (supposedly bosonic) environment, coherent states of the system do not get entangled with the environment, due to the bosonic symmetry.Comment: This is the definitive version of a paper entitled The classical-quantum limit considered from the point of view of entanglement: a survey (author T. Durt). The older version has been replaced by the definitive on

Radiative and photon-exchange corrections to New Physics contributions to energy levels in few-electron ions

The influence of hypothetical new interactions beyond the Standard Model on atomic spectra has attracted recent interest. In the present work, interelectronic photon-exchange corrections and radiative quantum electrodynamic corrections to the hypothetical contribution to the energy levels of few-electron ions from a new interaction are calculated. The $1s$, $2s$ and $2p_{1/2}$ ground states of H-like, Li-like and B-like ions are considered, as motivated by proposals to use isotope shift spectroscopy of few-electron ions in order to set stringent constraints on hypothetical new interactions. It is shown that, for light Li-like and B-like ions, photon-exchange corrections are comparable to or even larger, by up to several orders of magnitude, than the leading one-electron contribution from the new interaction, when the latter is mediated by heavy bosons

Long-Range Interactions of Hydrogen Atoms in Excited States. I. 2S-1S Interactions and Dirac-δ Perturbations

The theory of the long-range interaction of metastable excited atomic states with ground-state atoms is analyzed. We show that the long-range interaction is essentially modified when quasidegenerate states are available for virtual transitions. A discrepancy in the literature regarding the van der Waals coefficient C6 (2S ;1 S ) describing the interaction of metastable atomic hydrogen ( 2 S state) with a ground-state hydrogen atom is resolved. In the the van der Waals range a0 ≪ R ≪ a0 / α , where a0 = ℏ / α m c is the Bohr radius and α is the fine-structure constant, one finds the symmetry-dependent result E2S;1S ( R ) ≈ ( - 176.75 ± 27.98 ) Eh( α0 / R )6 (Eh denotes the Hartree energy). In the Casimir-Polder range a0 / α ≪ R ≪ ℏ c / L , where L ≡ E (2S1/2 ) - E (2P1 / 2 ) is the Lamb shift energy, one finds E2S;1S ( R ) ≈ ( - 121.50 ± 46.61 ) Eh ( a0 / R )6 . In the the Lamb shift range R ≫ ℏ c / L , we find an oscillatory tail with a negligible interaction energy below 10-36 Hz . Dirac- δ perturbations to the interaction are also evaluated and results are given for all asymptotic distance ranges; these effects describe the hyperfine modification of the interaction or, expressed differently, the shift of the hydrogen 2 S hyperfine frequency due to interactions with neighboring 1 S atoms. The 2 S hyperfine frequency has recently been measured very accurately in atomic beam experiments

Long-Range Interactions of Hydrogen Atoms in Excited States. I. 2S-1S Interactions and Dirac-δ Perturbations

The theory of the long-range interaction of metastable excited atomic states with ground-state atoms is analyzed. We show that the long-range interaction is essentially modified when quasidegenerate states are available for virtual transitions. A discrepancy in the literature regarding the van der Waals coefficient C6 (2S ;1 S ) describing the interaction of metastable atomic hydrogen ( 2 S state) with a ground-state hydrogen atom is resolved. In the the van der Waals range a0 ≪ R ≪ a0 / α , where a0 = ℏ / α m c is the Bohr radius and α is the fine-structure constant, one finds the symmetry-dependent result E2S;1S ( R ) ≈ ( - 176.75 ± 27.98 ) Eh( α0 / R )6 (Eh denotes the Hartree energy). In the Casimir-Polder range a0 / α ≪ R ≪ ℏ c / L , where L ≡ E (2S1/2 ) - E (2P1 / 2 ) is the Lamb shift energy, one finds E2S;1S ( R ) ≈ ( - 121.50 ± 46.61 ) Eh ( a0 / R )6 . In the the Lamb shift range R ≫ ℏ c / L , we find an oscillatory tail with a negligible interaction energy below 10-36 Hz . Dirac- δ perturbations to the interaction are also evaluated and results are given for all asymptotic distance ranges; these effects describe the hyperfine modification of the interaction or, expressed differently, the shift of the hydrogen 2 S hyperfine frequency due to interactions with neighboring 1 S atoms. The 2 S hyperfine frequency has recently been measured very accurately in atomic beam experiments

Long-Range Interactions of Hydrogen Atoms in Excited States. I. 2S-1S Interactions and Dirac-δ Perturbations

The theory of the long-range interaction of metastable excited atomic states with ground-state atoms is analyzed. We show that the long-range interaction is essentially modified when quasidegenerate states are available for virtual transitions. A discrepancy in the literature regarding the van der Waals coefficient C6 (2S ;1 S ) describing the interaction of metastable atomic hydrogen ( 2 S state) with a ground-state hydrogen atom is resolved. In the the van der Waals range a0 ≪ R ≪ a0 / α , where a0 = ℏ / α m c is the Bohr radius and α is the fine-structure constant, one finds the symmetry-dependent result E2S;1S ( R ) ≈ ( - 176.75 ± 27.98 ) Eh( α0 / R )6 (Eh denotes the Hartree energy). In the Casimir-Polder range a0 / α ≪ R ≪ ℏ c / L , where L ≡ E (2S1/2 ) - E (2P1 / 2 ) is the Lamb shift energy, one finds E2S;1S ( R ) ≈ ( - 121.50 ± 46.61 ) Eh ( a0 / R )6 . In the the Lamb shift range R ≫ ℏ c / L , we find an oscillatory tail with a negligible interaction energy below 10-36 Hz . Dirac- δ perturbations to the interaction are also evaluated and results are given for all asymptotic distance ranges; these effects describe the hyperfine modification of the interaction or, expressed differently, the shift of the hydrogen 2 S hyperfine frequency due to interactions with neighboring 1 S atoms. The 2 S hyperfine frequency has recently been measured very accurately in atomic beam experiments