Terms Of Quantum Interference Research Articles

Quantum localization corrections from the Bethe–Salpeter equation

We investigate coherent matter wave transport in isotropic 3D speckle potentials by using the Bethe–Salpeter equation and the self-consistent theory of localization. This model constitutes an efficient tool to properly evaluate corrections to Boltzmann diffusion by taking into consideration quantum interference terms between the multiple-scattering paths. We calculate analytically and numerically the static current density, the density of states, the dipolar contribution and the reduced diffusion coefficient. Our results reveal that quantum corrections to diffusive transport, known as weak localization may not only lead to shift the above quantities but affect also the position of the mobility edge.

Swapping of optical vorticity in a three-level coherent media

In this paper, we have spoken about how the superposition of two upper states and the quantum interference effect affect exchange efficiency in a V-type atomic system. We have demonstrated that the same orbital angular momentum can generate an additional signal field in response to a single optical vortex light acting on one transition of the V-type quantum system. We have also discussed about how the exchange efficiency of optical vorticity is affected by the quantum interference term, the probe’s detuning, and the superposition of the higher states. Our model is ideal for quantum information processing based on the orbital angular momentum of light due to the enhancement in exchange efficiency.

Supported or unsupported three-center two-electron bonds? A criterion based on Interference Energy Analysis.

The classification of three-center two-electron (3c2e) bonds into supported (closed) or unsupported (open) was proposed by Lipscomb in his work on boranes and extended to transition metal complexes by Bau and co-workers. The species in which the interactions of the terminal atoms are negligible are called "unsupported bonds." Examples of chemical species that are said to exhibit such bonds are Li2H+, Na2H+, B2H7 -, Al2(CH3)7 -, and [(μ2-H)Cr2(CO)10]- although the general criterion for distinguishing these types of bonds is somewhat qualitative. Besides providing a unifying view of the nature of the chemical bond, in terms of quantum interference among electronic states, the Generalized Product Function Energy Partitioning method through the Interference Energy Analysis (IEA) is also potentially capable of providing a rigorous ground to the concept of supported bonds by looking at the specific interference energies between the orbital pairs associated with the bond. The IEA was performed in the species Li2H+, Na2H+, B2H7 -, C2H7 -, Al2H7 -, and [(μ2-H)Cr2(CO)10]-, as well as along the reaction path Li2H+ → Li2 + + H. The results shown that in all studied A-B-C bonds, the A-C interactions are as important as the A-B/B-C ones, leading to the conclusion that all studied 3c2e bonds are "supported," in the sense that the A-C interaction is not negligible. The particularity of those species in preferring linear geometry is completely explained by quasi-classical effects, more specifically, by minimization of the electron-electron and nucleus-nucleus repulsions.

Beyond Fermi’s golden rule in free-electron quantum electrodynamics: acceleration/radiation correspondence

In this article, we present a unified reciprocal quantum electrodynamics (QED) formulation of free-electron and quantum–light interaction. For electron–light interactions, we bridge the underlying theories of photon-induced near-field electron microscopy, laser-induced particle accelerators, and radiation sources, such as quantum free electron laser, transition radiation and Smith-Purcell effect. We demonstrate an electron–photon spectral reciprocity relation between the electron energy loss/gain and the radiation spectra. This ‘acceleration/radiation correspondence’ (ARC) conserves the electron energy, and photon number exchanged, that is, ΔE/ℏω + Δν q = 0, and in the representation of a quantum electron wavepacket, displays explicit dependence on the history-dependent phase and shape of the wavepacket configuration. It originates from an interaction-induced quantum interference term that is usually ignored in Fermi’s golden rule analyses, but is kept in our combined quantum free electron–photon state formulation. We apply this formulation to both stimulated interaction and spontaneous emission of classical and quantum light by the quantum-featured electrons. The ‘spontaneous’ emissions of coherent states (‘classical’ light) are remarked and squeezed states of quantum light is shown to be enhanced with squeezing. This reciprocal QED formulation has promise for extensions to other fundamental research issues in quantum light and quantum matter interactions.

Resonance and antiresonance in Raman scattering in GaSe and InSe crystals

The temperature effect on the Raman scattering efficiency is investigated in varepsilon-GaSe and gamma-InSe crystals. We found that varying the temperature over a broad range from 5 to 350 K permits to achieve both the resonant conditions and the antiresonance behaviour in Raman scattering of the studied materials. The resonant conditions of Raman scattering are observed at about 270 K under the 1.96 eV excitation for GaSe due to the energy proximity of the optical band gap. In the case of InSe, the resonant Raman spectra are apparent at about 50 and 270 K under correspondingly the 2.41 eV and 2.54 eV excitations as a result of the energy proximity of the so-called B transition. Interestingly, the observed resonances for both materials are followed by an antiresonance behaviour noticeable at higher temperatures than the detected resonances. The significant variations of phonon-modes intensities can be explained in terms of electron-phonon coupling and quantum interference of contributions from different points of the Brillouin zone.

Identifying orbital angular momentum of light in quantum wells

Recently, the generation and detection of structured light have been the subject of intense studies, aiming to realize high-capacity optical storage and continuous-variable quantum technologies. In this Letter, we present a scheme to extract the orbital angular momentum content of vortex beams, possessing integer and fractional azimuthal index, in GaAs/AlGaAs multiple quantum wells with a double- type configuration. Arising from a quantum interference term, the absorption of a non-vortex probe field depends upon the azimuthal phase of vortex fields so that both the magnitude and sign of azimuthal index/indices can be mapped into the absorption profile.

Shot noise on chaotic chiral devices

We investigate both the conductance and the shot-noise power of a confined chiral device that engenders subtle embedded backscattering mechanisms. We present analytical results and the correspondent numerical confirmation of the chiral electronic sublattice signal. Examples of quantum dots generating chiral symmetries include graphene sheets and topological insulators. The analytical results are universal and exhibit a robust and peculiar signal for an arbitrary number of open scattering channels. We also demonstrate a tunable mechanism of the valleytronics shot-noise power signal through perpendicular magnetic fields and/or the device symmetry edges. The results also indicate a ``Fano factor'' associated with the main quantum interference term with a universal value of $1/4$ for a quantum dot with symmetric contacts, regardless of external fields and the number of open channels.

Unconventional photon blockade

We review the unconventional photon blockade mechanism. This quantum effect remarkably enables a strongly sub-Poissonian light statistics, even from a system characterized by a weak single photon nonlinearity. We revisit the past results, which can be interpreted in terms of quantum interferences or optimal squeezing, and show how recent developments on input-output field mixing can overcome the limitations of the original schemes towards passive and integrable single photon sources. We finally present some valuable alternative schemes for which the unconventional blockade can be directly adapted.

Contextuality and truth-value assignment

In the paper, the question whether truth values can be assigned to the propositions before their verification is discussed. To answer this question, a notion of a propositionally noncontextual theory is introduced that to explain the verification outcomes provides a map linking each element of a complete lattice identified with a proposition to a truth value. The paper demonstrates that no model obeying such a theory and at the same time the principle of bivalence can be consistent with the occurrence of a non-vanishing “two-path” quantum interference term and the quantum collapse postulate.

Roadmap to Majorana surface codes

Surface codes offer a very promising avenue towards fault-tolerant quantum computation. We argue that two-dimensional interacting networks of Majorana bound states in topological superconductor/semiconductor heterostructures hold several distinct advantages in that direction, both concerning the hardware realization and the actual operation of the code. We here discuss how topologically protected logical qubits in this Majorana surface code architecture can be defined, initialized, manipulated, and read out. All physical ingredients needed to implement these operations are routinely used in topologically trivial quantum devices. In particular, we show that by means of quantum interference terms in linear conductance measurements, composite single-electron pumping protocols, and gate-tunable tunnel barriers, the full set of quantum gates required for universal quantum computation can be implemented.

The effect of entanglement in gravitational photon-photon scattering

The differential cross-section for gravitational photon-photon scattering calculated in perturbative quantum gravity is shown to depend on the degree of polarization entanglement of the two photons. The interaction between photons in the symmetric Bell state is stronger than between not entangled photons. In contrast, the interaction between photons in the anti-symmetric Bell state is weaker than between not entangled photons. The results are interpreted in terms of quantum interference, and it is shown how they fit into the idea of distance-dependent forces.

Anomalous entanglement in chaotic Dirac billiards

We present analytical and numerical results that demonstrate the presence of anomalous entanglement behavior on the Dirac Billiards. We investigate the statistical distribution of the characteristic entangled measures, focusing on the mean, on the variance, and on the quantum interference terms. We show a quite distinct behavior of the Dirac billiard compared with the nonrelativist (Schr\"odinger) ones. Particularly, we show a very plausible Bell state and a sharp amplitude of quantum interference term on entangled electrons left from the Dirac billiards. The results have remarkable relevance to the novel quantum dots build of materials like graphene or topological insulators.

Circular dichroism in molecular-frame photoelectron angular distributions in the dissociative photoionization ofH2andD2molecules

The presence of net circular dichroism in the photoionization of nonchiral homonuclear molecules has been put in evidence recently through the measurement of molecular-frame photoelectron angular distributions in dissociative photoionization of ${\text{H}}_{2}$ [Dowek et al., Phys. Rev. Lett. 104, 233003 (2010)]. In this work we present a detailed study of circular dichroism in the photoelectron angular distributions of ${\text{H}}_{2}$ and ${\text{D}}_{2}$ molecules, oriented perpendicularly to the propagation vector of the circularly polarized light, at different photon energies (20, 27, and 32.5 eV). Circular dichroism in the angular distributions at 20 and to a large extent 27 eV exhibits the usual pattern in which inversion symmetry is preserved. In contrast, at 32.5 eV, the inversion symmetry breaks down, which eventually leads to total circular dichroism after integration over the polar emission angle. Time-dependent ab initio calculations support and explain the observed results for ${\text{H}}_{2}$ in terms of quantum interferences between direct photoionization and delayed autoionization from the ${\mathcal{Q}}_{1}$ and ${\mathcal{Q}}_{2}$ doubly excited states into ionic states $(1s{\ensuremath{\sigma}}_{g}$ and $2p{\ensuremath{\sigma}}_{u})$ of different inversion symmetry. Nevertheless, for ${\text{D}}_{2}$ at 32.5 eV, there is a particular case where theory and experiment disagree in the magnitude of the symmetry breaking: when ${\text{D}}^{+}$ ions are produced with an energy of around 5 eV. This reflects the subleties associated to such simple molecules when exposed to this fine scrutiny.

Low-temperature structural and transport anomalies inCu2Se

Through systematic examination of symmetrically nonequivalent configurations, first-principles calculations have identified a new ground state of ${\mathrm{Cu}}_{2}\mathrm{Se}$, which is constructed by repeating sextuple layers of Se-Cu-Cu-Cu-Cu-Se. The layered nature is in accord with electron and x-ray diffraction studies at and below room temperature and also is consistent with transport properties. Magnetoresistance measurements at liquid helium temperatures exhibit cusp-shaped field dependence at low fields and evolve into quasilinear field dependence at intermediate and high fields. These results reveal the existence of weak antilocalization effect, which has been analyzed using a modified Hikami, Larkin, and Nagaoka model, including a quantum interference term and a classical quadratic contribution. Fitting parameters suggest a quantum coherence length $L$ of 175 nm at 1.8 K. With increasing temperature, the classical parabolic behavior becomes more dominant, and $L$ decreases as a power law of ${T}^{\ensuremath{-}0.83}$.

Quantum Interference Effects for the Electronic Fluctuations in Quantum Dots

For the main quantum interference term of coherent electronic transport, we study the effect of temperature, perpendicular and/or parallel magnetic fields, spin-orbit coupling and tunneling rates in both metallic grains and mesoscopic heterostructures. We show that the Zeeman effects determines a crucial way to characterize the quantum interference phenomena of the noise for anisotropic systems (mesoscopic heterostructures), qualitatively distinct from those observed in isotropic structures (metallic grains).

State selective photo-recombination cross sections in Be-like C and Al ions

We report results from detailed state selective photo-recombination study along with the doubly excited autoionizing resonances in Be-like C2+ and Al9+ ions. In the present investigation, the primary focus is on detailed energy profiles of the individual photo-recombination cross sections. The calculation was carried out for the excited Rydberg states of type 1s22sns(1Se) which interact with the odd-parity continua up to the C3+ and Al10+ 2p threshold limit. The numerical evaluation has been performed at a fine energy mesh across all the autoionizing Rydberg series of resonances 1s22pns(1P0) converging to Li-like ion 2p threshold. The method of calculation keeps the essential ingredients of the Feshbach projection operator approximation. The photo-ionization cross sections have been evaluated with and without relativistic effects included into the R-matrix numerical procedures, while the allowance for both quantum interference between dielectronic and radiative recombination, and overlapping resonances has been done utilizing results from the earlier R-matrix Floquet calculation. We discuss all these results with respect to the effect of quantum interference term on the energy dependence profile of photo-recombination cross section for studied transitions.

Temporal coherent control of superfluorescent pulses

We demonstrate that collective atomic interferences can be investigated by measuring the superfluorescence (SF) time delay. A pair of broadband (≈20 nm), ultrashort (≈80 fs), collinear pulses with a variable delay coherently excites rubidium (Rb) atoms. The generated superfluorescent pulses at 420 nm on the cascade transition are recorded by a picosecond streak camera. Both intensity and SF time delay of the 420 nm pulse are altered as the delay between input pulses varies. In particular, the SF time delay of the normalized 420 nm pulse exhibits oscillations with different periods. This can be understood in terms of atomic and quantum interferences due to two possible two-photon excitation pathways through the intermediate levels (Rb D-lines).

Microscopic approach to the proton asymmetry in the nonmesonic weak decay ofΛhypernuclei

The non--mesonic weak decay of polarized $\Lambda$-hypernuclei is studied with a microscopic diagrammatic formalism in which one- and two-nucleon induced decay mechanisms, $\vec{\Lambda} N \to NN$ and $\vec{\Lambda} NN \to NNN$, are considered together with (and on the same ground of) nucleon final state interactions. We adopt a nuclear matter formalism extended to finite nuclei via the local density approximation. Our approach adopts different one-meson-exchange weak transition potentials, while the strong interaction effects are accounted for by a Bonn nucleon-nucleon interaction. We also consider the two-pion-exchange effect in the weak transition potential. Both the two-nucleon induced decay mechanism and the final state interactions reduce the magnitude of the asymmetry. The quantum interference terms considered in the present microscopic approach give rise to an opposite behavior of the asymmetry with increasing energy cuts to that observed in models describing the nucleon final state interactions semi-classically via the intranuclear cascade code. Our results for the asymmetry parameter in $^{12}_{\Lambda}$C obtained with different potential models are consistent with the asymmetry measured at KEK.

Decoherence and the retrieval of lost information

We found that in contrast with the common premise, a measurement on the environment of an open quantum system can {\em reduce} its decoherence rate. We demonstrate it by studying an example of indirect qubit's measurement, where the information on its state is hidden in the environment. This information is extracted by a distant device, coupled with the environment. We also show that the reduction of decoherence generated by this device, is accompanied with diminution of the environmental noise in a vicinity of the qubit. An interpretation of these results in terms of quantum interference on large scales is presented.

Microscopic approach to nucleon spectra in hypernuclear non-mesonic weak decay

A consistent microscopic diagrammatic approach is applied for the first time to the calculation of the nucleon emission spectra in the non-mesonic weak decay of Λ-hypernuclei. We adopt a nuclear matter formalism extended to finite nuclei via the local density approximation, a one-meson exchange weak transition potential and a Bonn nucleon–nucleon strong potential. Ground state correlations and final state interactions, at second order in the nucleon–nucleon interaction, are introduced on the same footing for all the isospin channels of one- and two-nucleon induced decays. Single and double-coincidence nucleon spectra are predicted for 12ΛC and compared with recent KEK and FINUDA data. The key role played by quantum interference terms allows us to improve the predictions obtained with intranuclear cascade codes. Discrepancies with data remain for proton emission.