We study localization of atomic position when a three-level atom interacts with a quantized standing-wave field in the Ramsey interferometer setup. Both the field quadrature amplitude and the atomic internal state are measured to obtain the atomic position information. It is found that this dual measurement scheme produces an interference pattern superimposed on a diffraction-like pattern in the atomic position distribution, where the former pattern originates from the state-selective measurement and the latter from the field measurement. The present scheme results in a better resolution in the position localization than the field-alone measurement schemes. We also discuss the measurement-correlated mechanical action of the standing-wave field on the atom in the light of Popper's test.
The quantum optical response of high density ultracold atomic systems is critical to a wide range of fundamentally and technically important physical processes. These include quantum image storage, optically based quantum repeaters and ultracold molecule formation. We present here a microscopic analysis of the light scattering on such a system, and we compare it with a corresponding description based on macroscopic Maxwell theory. Results are discussed in the context of the spectral resonance structure, time-dependent response, and the light localization problem.
The sub-wavelength localization of an ensemble of atoms concentrated to a small volume in space is investigated. The localization relies on the interaction of the ensemble with a standing wave laser field. The light scattered in the interaction of standing wave field and atom ensemble depends on the position of the ensemble relative to the standing wave nodes. This relation can be described by a fluorescence intensity profile, which depends on the standing wave field parameters, the ensemble properties, and which is modified due to collective effects in the ensemble of nearby particles. We dem…
We demonstrate an atom localization scheme based on monitoring of the atomic coherences. We consider atomic transitions in a Lambda configuration where the control field is a standing wave field. The probe field and the control field produce coherence between the two ground states. We show that this coherence has the same fringe pattern as produced by a Fabry-Perot interferometer and thus measurement of the atomic coherence would localize the atom. Interestingly enough the role of the cavity finesse is played by the ratio of the intensities of the pump and probe. This is in fact the reason for…
Dimension 2 is expected to be the lower critical dimension for Anderson localization in a time reversal-invariant disordered quantum system. Using an atomic quasiperiodic kicked rotor -- equivalent to a two-dimensional Anderson-like model -- we experimentally study Anderson localization in dimension 2 and we observe localized wavefunction dynamics. We also show that the localization length depends exponentially on the disorder strength and anisotropy and is in quantitative agreement with the predictions of the self-consistent theory for the 2D Anderson localization.
We theoretically explore the possibility to detect weak localization of light in a hot atomic vapor, where one usually expects the fast thermal motion of the atoms to destroy any interference in multiple scattering. To this end, we compute the coherent backscattering peak, assuming high temperature and taking into account the quantum level structure of the atomic scatterers. It is found that the decoherence due to thermal motion can be partially counterbalanced by working at large laser detuning and using small atomic cells with an elongated geometry. Under these conditions, our estimates sugg…
Architectures based on waveguide quantum electrodynamics have emerged as promising candidates for quantum networks. In this paper, we analyze the propagation of single-photons in disordered many-atom waveguides. We pay special attention to the influence of chirality (directionality of photon transport) on the formation of localized photonic states, considering separately the cases of the disorder in the atomic positions and in the atomic transition frequencies.
We present a scheme for two-dimensional (2D) atom localization in a three-level atomic system. The scheme is based on quantum coherence via classical standing wave fields between the two excited levels. Our results show that conditional position probability is significantly phase dependent of the applied field and frequency detuning of spontaneously emitted photons. We obtain a single localization peak having probability close to unity by manipulating the control parameters. The effect of atomic level coherence on the sub-wavelength localization has also been studied. Our scheme may be helpful…
Schemes for two-dimensional (2D) and three-dimensional (3D) atomic states localization in a five level M-type system using standing-wave laser fields are presented. In the upper two levels of the system we see a `coupled' localization for both 2D and 3D case. Here, the state in which majority of population will be found depends on the sign of the detunings between the upper levels and the intermediate level. The experimental implementation of the scheme using the D2 line of Rb is also proposed. The scheme may be manipulated to achieve subwavelength localization of atoms in one dimension to a s…
Topological defects in low-dimensional non-linear systems feature a sliding-to-pinning transition of relevance for a variety of research fields, ranging from biophysics to nano- and solid-state physics. We find that the dynamics after a local excitation results in a highly-non-trivial energy transport in the presence of a topological soliton, characterized by a strongly enhanced energy localization in the pinning regime. Moreover, we show that the energy flux in ion crystals with a topological defect can be sensitively regulated by experimentally accessible environmental parameters. Whereas, t…
We propose a robust localization of the highly-excited Rydberg atoms, interacting with doughnut-shaped optical vortices. Compared with the earlier standing-wave (SW)-based localization methods, a vortex beam can provide an ultrahigh-precision two-dimensional localization solely in the zero-intensity center, within a confined excitation region down to the nanometer scale. We show that the presence of the Rydberg-Rydberg interaction permits counter-intuitively much stronger confinement towards a high spatial resolution when it is partially compensated by a suitable detuning. In addition, applyin…
The 3D local atomic structures and crystal defects at the interfaces of heterostructures control their electronic, magnetic, optical, catalytic and topological quantum properties, but have thus far eluded any direct experimental determination. Here we determine the 3D local atomic positions at the interface of a MoS2-WSe2 heterojunction with picometer precision and correlate 3D atomic defects with localized vibrational properties at the epitaxial interface. We observe point defects, bond distortion, atomic-scale ripples and measure the full 3D strain tensor at the heterointerface. By using the…
We explore the interplay of disorder and topological phenomena in honeycomb lattices of atoms coupled by the electromagnetic field. On the one hand, disorder can trigger transitions between distinct topological phases and drive the lattice into the topological Anderson insulator state. On the other hand, the nontrivial topology of the photonic band structure suppresses Anderson localization of modes that disorder introduces inside the band gap of the ideal lattice. Furthermore, we discover that disorder can both open a topological pseudogap in the spectrum of an otherwise topologically trivial…
On the basis of our general theoretical results developed previously in JETP 112, 246 (2011), we calculate the spatial distribution of atoms excited in a dense and cold atomic cloud by weak monochromatic light. We also study the atomic distribution over different Zeeman sublevels of the excited state in different parts of the cloud. The dependence of this distribution of atomic excitation on the density of the atomic ensemble and the frequency of external emission is investigated. We show that in the boundary regions of the cloud the orientation and alignment of atomic angular momentum takes p…
Dynamical localization prevents driven atomic systems from fast fragmentation by hampering the excitation process. We present numerical simulations within a collinear model of microwave-driven helium Rydberg atoms and prove that dynamical localization survives the impact of electron-electron interaction, even for doubly excited states in the presence of fast autoionization. We conclude that the effect of electron-electron repulsion on localization can be described by an appropriate rescaling of the atomic level density and of the external field with the strength of the interaction.
As discovered by P. W. Anderson, excitations do not propagate freely in a disordered lattice, but, due to destructive interference, they localise. As a consequence when an atom interacts with a disordered lattice one indeed observes, a non-trivial excitation exchange between atom and lattice. Such non-trivial atomic dynamics will in general be characterised also by a non-trivial quantum information backflow, a clear signature of non-Markovian dynamics. To investigate the above scenario we consider a quantum emitter, or atom, weakly coupled to a uniform coupled-cavity array (CCA). If initially …
We propose and demonstrate an atomic qubit based on a cold $^{85}$Rb-$^{87}$Rb isotopic mixture, entangled with a frequency-encoded optical qubit. The interface of an atomic qubit with a single spatial light mode, and the ability to independently address the two atomic qubit states, should provide the basic element of an interferometrically robust quantum network.
We have investigated the chaotic atomic population oscillations between two coupled Bose-Einstein condensates (BEC) with time-dependent asymmetric trap potential. In the perturbative regime, the population oscillations can be described by the Duffing equation, and the chaotic oscillations near the separatrix solution are analyzed. The sufficient-necessary conditions for stable oscillations depend on the physical parameters and initial conditions sensitively. The first-order necessary condition indicates that the Melnikov function is equal to zero, so the stable oscillations are Melnikov chaoti…
In this letter we investigate the possibility to attain strongly confined atomic localization using interacting Rydberg atoms in a Coherent Population Trapping (CPT) ladder configuration, where a standing-wave (SW) is used as a coupling field in the second leg of the ladder. Depending on the degree of compensation of the Rydberg level energy shift induced by the van der Waals (vdW) interaction, by the coupling field detuning, we distinguish between two antiblockade regimes, i.e. a partial antiblockade (PA) and a full antiblockade (FA). While a periodic pattern of tightly localized regions can …
Atom-waveguide interface mediates significant and long-range light-matter interactions through the guided modes. In this one-dimensional system, we theoretically investigate the excitation localization of multiple atomic excitations under strong position disorders. Deep in the localization side, we obtain the time evolutions of quantum correlations via Kubo cumulant expansions, which arise initially and become finite and leveled afterward, overtaking the ones without disorders. This indicates two distinct regimes in time: before the onset of excitation localization, the disorders engage the di…
We review experimental and theoretical studies of coherent backscattering of near resonant radiation from an ultracold atomic gas in the weak localization regime. Recent accomplishments in high resolution spectroscopy of atomic ensembles based on the coherent backscattering process are discussed. We also propose several new experimental schemes for time-dependent spectroscopy as applied to multiple scattering in the regime of weak localization.
We report the operation of a dual Rb/Cs atomic fountain clock. 133Cs and 87Rb atoms are cooled, launched, and detected simultaneously in LNE-SYRTE's FO2 double fountain. The dual clock operation occurs with no degradation of either the stability or the accuracy. We describe the key features for achieving such a simultaneous operation. We also report on the results of the first Rb/Cs frequency measurement campaign performed with FO2 in this dual atom clock configuration, including a new determination of the absolute 87Rb hyperfine frequency.
Since the work of Anderson on localization, interference effects for the propagation of a wave in the presence of disorder have been extensively studied, as exemplified in coherent backscattering (CBS) of light. In the multiple scattering of light by a disordered sample of thermal atoms, interference effects are usually washed out by the fast atomic motion. This is no longer true for cold atoms where CBS has recently been observed. However, the internal structure of the atoms strongly influences the interference properties. In this paper, we consider light scattering by an atomic dipole transi…
We study the counterpart of Anderson localization in driven one-electron Rydberg atoms. By changing the initial Rydberg state at fixed microwave frequency and interaction time, we numerically monitor the crossover from Anderson localization to the photo effect in the atomic ionization signal.
We study the quantum localization phenomena of noninteracting particles in one-dimensional lattices based on tight-binding models with various forms of hopping terms beyond the nearest neighbor, which are generalizations of the famous Aubry-André and noninteracting Anderson model. For the case with deterministic disordered potential induced by a secondary incommensurate lattice (i.e. the Aubry-André model), we identify a class of self dual models, for which the boundary between localized and extended eigenstates are determined analytically by employing a generalized Aubry-André transformation.…
We study the effects of high optical depth and density on the performance of a light-atom quantum interface. An in-situ imaging method, a dual-port polarization contrast technique, is presented. This technique is able to compensate for image distortions due to refraction. We propose our imaging method as a tool to characterize atomic ensembles for high capacity spatial multimode quantum memories. Ultracold dense inhomogeneous Rubidium samples are imaged and we find a resonant optical depth as high as 680 on the D1 line. The measurements are compared with light-atom interaction models based on …
The recent discovery of single-photon emitting defects hosted by the two-dimensional wide band gap semiconductor hexagonal boron nitride (hBN) has inspired a great number of experiments. Key characteristics of these quantum emitters are their capability to operate at room temperature with a high luminosity. In spite of large theoretical and experimental research efforts, the exact nature of the emission remains unresolved. In this work we utilize layer-by-layer etching of multilayer hBN to localize the quantum emitters with atomic precision. Our results suggest the position of the emitters cor…
Time evolution of quantum many-body systems typically leads to a state with maximal entanglement allowed by symmetries. Two distinct routes to impede entanglement growth are inducing localization via spatial disorder, or subjecting the system to non-unitary evolution, e.g., via projective measurements. Here we employ the idea of space-time rotation of a circuit to explore the relation between systems that fall into these two classes. In particular, by space-time rotating unitary Floquet circuits that display a localization transition, we construct non-unitary circuits that display a rich varie…
We consider two particles hopping on a chain with a contact interaction between them. At strong interaction, there is a molecular bound state separated by a direct gap from a continuous band of atomic states. Introducing weak disorder in the interaction, the molecular state becomes Anderson localized. At stronger disorder, part of the molecular band delocalizes and dissociates due to its hybridization to the atomic band. We characterize these different regimes by computing the density of states, the inverse participation ratio, the level-spacing statistics and the survival probability of an in…
