Long-lived BLOCH oscillations with bosonic sr atoms and application to gravity measurement at the micrometer scale

Hexagonal warping effects on Bloch oscillations in proximitized Rashba systems

Bloch oscillations (BOs) in Rashba systems, taking into account the effects of hexagonal warping and proximity-induced band gap, are reported. We find that in addition to real-space trajectories, the group and Berry velocities of Bloch electrons exhibit novel BOs which strongly depend on the crystal momentum. This oscillatory motion is affected significantly by variations in the strength of hexagonal warping and the proximity-induced band gap, originating from the substantial changes in the energy spectrum induced by these factors. In addition, it is shown that the Bloch oscillations are modified considerably under the influence of applied uniform in-plane electric and transverse magnetic fields, which allow for a geometric visualization of the Bloch dynamics. Interestingly, when the system is subjected to these fields simultaneously, it undergoes a dynamic phase transition between confined and de-confined states. This phase transition is tuned by the relative strength of the applied fields and is further influenced by variations in the strength of hexagonal warping and proximity-induced band gap. The appearance of such a transition is attributed to the interplay between the external fields and the intrinsic properties of the crystal lattice. Moreover, we find that the direct-current drift velocity shows negative differential conductivity, which is a characteristic feature of the BO regime.

Photonic Crystal Surface Modes for Trapping and Waveguiding of Ultracold Atoms

The design of a photonic system for the trapping and waveguiding of ultracold atoms far above a dielectric surface is proposed and analyzed. The system consists of an optical rib waveguide deposited on a planar one-dimensional photonic crystal, which sustains two wavelengths of photonic crystal surface modes tuned in the red and blue sides relative to the atomic transition of the neutral atom. The addition of a third blue-tuned wavelength to the system allows the neutral atoms to be stabilized in the lateral dimension above the rib waveguide. Trapping atoms at relatively large distances, more than 600 nm above the dielectric surface, allows to reduce the influence of Casimir-Polder forces in this system. The detailed design methodology and specifications of the photonic system are provided. The presented design can be employed in atomic chips and quantum sensors.

Nonlinear Landau-Zener-Stückelberg-Majorana tunneling and interferometry of extended Bose-Hubbard flux ladders

The nonlinear Landau-Zener-Stückelberg-Majorana (LZSM) tunneling dynamics and interferometry of an extended Bose-Hubbard flux ladder are studied. Based on the mean-field theory, the dispersion relation of the system is given, and it is found that loop structures periodically appear in the band structure and the nonlinear LZSM interference occurs naturally without Floquet engineering, which can be effectively modulated by atomic interactions. The nonlinear energy bands and the unique chirality feature of the flux ladder system can be identified through the dynamics of nonlinear Landau-Zener tunneling. Remarkably, the critical position of the noise in the interference pattern can be employed to identify the loop structure in the energy band, establishing an effective link between the nonlinear loop structure and LZSM interferometry. The position, intensity, symmetry, and width of interference patterns strongly depend on the magnetic field, atomic interactions, rung-to-leg coupling ratio, and energy bias, which provides an effective way to measure these parameters using the nonlinear LZSM interferometry. This paper further expands the dynamics of flux ladder systems to complex interaction regions and has potential applications in the precise measurement of related nonlinear systems.

Polarization-dependent Bloch oscillations in optical waveguides

Optical systems provide a new and practical platform for studying Bloch oscillations. This study investigates the fundamental-mode propagation of polarization-dependent Bloch oscillations. By using the three-dimensional properties of femtosecond laser direct writing, we fabricate a polymer-based gradient waveguide array and determine the Bloch oscillations under different polarization inputs by using the birefringence gradient and the equivalent refractive index, thus exhibiting a polarization-dependent Bloch period. Our results provide a new, to the best of our knowledge, paradigm for two-dimensional optical Bloch modes and highlight the influence of optical polarization in the same system, which provides a possibility to observe richer physics related to Bloch oscillations in one structure.

Multiparticle Quantum Walks and Fisher Information in One-Dimensional Lattices

Recent experiments on quantum walks (QWs) demonstrated a full control over the statistics-dependent walks of single particles and two particles in one-dimensional lattices. However, little is known about the general characterization of QWs at the many-body level. Here, we rigorously study QWs, Bloch oscillations, and the quantum Fisher information for three indistinguishable bosons and fermions in one-dimensional lattices using a time-evolving block decimation algorithm and many-body perturbation theory. We show that such strongly correlated QWs not only give rise to statistics-and-interaction-dependent ballistic transports of scattering states and of two- and three-body bound states but also allow a quantum enhanced precision measurement of the gravitational force. In contrast to the QWs of the fermions, the QWs of three bosons exhibit strongly correlated Bloch oscillations, which present a surprising time scaling t^{3} of the Fisher information below a characteristic time t_{0} and saturate to the fundamental limit of t^{2} for t>t_{0}.

Many-Body Quantum Dynamics of Initially Trapped Systems due to a Stark Potential: Thermalization versus Bloch Oscillations

We analyze the dynamics of an initially trapped cloud of interacting quantum particles on a lattice under a linear (Stark) potential. We reveal a dichotomy: initially trapped interacting systems possess features typical of both many-body-localized and thermalizing systems. We consider both fermions (t-V model) and bosons (Bose-Hubbard model). For the zero and infinite interaction limits, both systems are integrable: we provide analytic solutions in terms of the moments of the initial cloud shape and clarify how the recurrent dynamics (many-body Bloch oscillations) depends on the initial state. Away from the integrable points, we identify and explain the timescale at which Bloch oscillations decohere.

Double-Gated Nanohelix as a Novel Tunable Binary Superlattice

We theoretically investigate the problem of an electron confined to a nanohelix between two parallel gates modelled as charged wires. The double-gated nanohelix system is a binary superlattice with properties highly sensitive to the gate voltages. In particular, the band structure exhibits energy band crossings for certain combinations of gate voltages, which could lead to quasi-relativistic Dirac-like phenomena. Our analysis for optical transitions induced by linearly and circularly polarized light suggests that a double-gated nanohelix can be used for versatile optoelectronic applications.

Observation and Uses of Position-Space Bloch Oscillations in an Ultracold Gas

We report the observation and characterization of position-space Bloch oscillations using cold atoms in a tilted optical lattice. While momentum-space Bloch oscillations are a common feature of optical lattice experiments, the real-space center-of-mass dynamics are typically unresolvable. In a regime of rapid tunneling and low force, we observe real-space Bloch oscillation amplitudes of hundreds of lattice sites, in both ground and excited bands. We demonstrate two unique capabilities enabled by tracking of Bloch dynamics in position space: measurement of the full position-momentum phase-space evolution during a Bloch cycle, and direct imaging of the lattice band structure. These techniques, along with the ability to exert long-distance coherent control of quantum gases without modulation, may open up new possibilities for quantum control and metrology.

Optical Bloch oscillation and Zener tunneling in the fractional Schrödinger equation

We demonstrate optical Bloch oscillation (OBO) and optical Zener tunneling (OZT) in the fractional Schrödinger equation (FSE) with periodic and linear potentials, numerically and theoretically. We investigate in parallel the regular Schrödinger equation and the FSE, by adjusting the Lévy index, and expound the differences between the two. We find that the spreading of the OBO decreases in the fractional case, due to the diminishing band width. Increasing the transverse force, due to the linear potential, leads to the appearance of OZT, but this process is suppressed in the FSE. Our results indicate that the adjustment of the Lévy index can effectively control the emergence of OBO and OZT, which can inspire new ideas in the design of optical switches and interconnects.

The New Concept of Nano-Device Spectroscopy Based on Rabi–Bloch Oscillations for THz-Frequency Range

We considered one-dimensional quantum chains of two-level Fermi particles coupled via the tunneling driven both by ac and dc fields in the regimes of strong and ultrastrong coupling. The frequency of ac field is matched with the frequency of the quantum transition. Based on the fundamental principles of electrodynamics and quantum theory, we developed a general model of quantum dynamics for such interactions. We showed that the joint action of ac and dc fields leads to the strong mutual influence of Rabi- and Bloch oscillations, one to another. We focused on the regime of ultrastrong coupling, for which Bloch- and Rabi-frequencies are significant values of the frequency of interband transition. The Hamiltonian was solved numerically, with account of anti-resonant terms. It manifests by the appearance of a great number of narrow high-amplitude resonant lines in the spectra of tunneling current and dipole moment. We proposed the new concept of terahertz (THz) spectroscopy, which is promising for different applications in future nanoelectronics and nano-photonics.

Bifurcation trees of Stark-Wannier ladders for accelerated Bose-Einstein condensates in an optical lattice

In this paper we show that in the semiclassical regime of periodic potential large enough, the Stark-Wannier ladders become a dense energy spectrum because of a cascade of bifurcations while increasing the ratio between the effective nonlinearity strength and the tilt of the external field; this fact is associated to a transition from regular to quantum chaotic dynamics. The sequence of bifurcation points is explicitly given.

Low phase noise beams for Raman transitions with a phase modulator and a highly birefringent crystal

We present a technique to excite Raman transitions with minimum phase noise. A phase modulator generates the Raman beams and a long calcite crystal rotates the polarization of the sidebands by 90° with respect to the carrier. That polarization converts the destructive interference of the Raman pairs into constructive interference, opening the possibility to drive both co-propagating and counter-propagating transitions at high detuning with the same setup. The technique has low phase noise and a low sensitivity to vibrations or temperature fluctuations. We apply it to drive velocity insensitive Raman transitions. The crystal can be also configured to filter out one of the sidebands.

Coherence Times of Bose-Einstein Condensates beyond the Shot-Noise Limit via Superfluid Shielding

We demonstrate a new way to extend the coherence time of separated Bose-Einstein condensates that involves immersion into a superfluid bath. When both the system and the bath have similar scattering lengths, immersion in a superfluid bath cancels out inhomogeneous potentials either imposed by external fields or inherent in density fluctuations due to atomic shot noise. This effect, which we call superfluid shielding, allows for coherence lifetimes beyond the projection noise limit. We probe the coherence between separated condensates in different sites of an optical lattice by monitoring the contrast and decay of Bloch oscillations. Our technique demonstrates a new way that interactions can improve the performance of quantum devices.

Direct Tunneling Delay Time Measurement in an Optical Lattice

We report on the measurement of the time required for a wave packet to tunnel through the potential barriers of an optical lattice. The experiment is carried out by loading adiabatically a Bose-Einstein condensate into a 1D optical lattice. A sudden displacement of the lattice by a few tens of nanometers excites the micromotion of the dipole mode. We then directly observe in momentum space the splitting of the wave packet at the turning points and measure the delay between the reflected and the tunneled packets for various initial displacements. Using this atomic beam splitter twice, we realize a chain of coherent micron-size Mach-Zehnder interferometers at the exit of which we get essentially a wave packet with a negative momentum, a result opposite to the prediction of classical physics.

Synchronization of Bloch oscillations by a ring cavity

We consider Bloch oscillations of ultracold atoms stored in a one-dimensional vertical optical lattice and simultaneously interacting with a unidirectionally pumped optical ring cavity whose vertical arm is collinear with the optical lattice. We find that the feedback provided by the cavity field on the atomic motion synchronizes Bloch oscillations via a mode-locking mechanism, steering the atoms to the lowest Bloch band. It also stabilizes Bloch oscillations against noise, and even suppresses dephasing due to atom-atom interactions. Furthermore, it generates periodic bursts of light emitted into the counter-propagating cavity mode, providing a non-destructive monitor of the atomic dynamics. All these features may be crucial for future improvements of the design of atomic gravimeters based on recording Bloch oscillations.

Quasi-periodic Wannier–Stark ladders from driven atomic Bloch oscillations

Periodic Wannier–Stark ladder structures of the energy resonances associated with Bloch oscillations can be readily modified into quasi-periodic ones that exhibit peculiar self-similar effects. A compact theoretical description of the dynamics of driven Bloch oscillations is developed here within the quasi-momentum representation. We identify a rather viable scheme based on ultracold atomic wavepackets subject to gravity in a driven optical lattice potential where a self-similar scaling could be observed. Its feasibility in terms of realistic experimental parameters is also discussed.

Multimode Kapitza-Dirac interferometry with trapped cold atoms

We design a multimode interferometer with cold atoms confined in a harmonic trap. A first Kapitza-Dirac pulse creates several spatially addressable modes which are coherently recombined by the harmonic potential and mixed again by a second Kapitza-Dirac pulse. A phase shift among the mode is estimated by fitting the density profile or by measuring the number of atoms in each output mode. The expected sensitivity is rigorously calculated with the Fisher information and the Cramér-Rao lower bound. For the measurement of the gravitational acceleration g we predict, with typical parameters of a compact setup, a temperature independent sensitivity which can exceed, by several orders of magnitude, the sensitivity of current atomic interferometers.

Graphene supported plasmonic photocatalyst for hydrogen evolution in photocatalytic water splitting

It is well known that the noble metal nanoparticles show active absorption in the visible region because of the existence of the unique feature known as surface plasmon resonance (SPR). Here we report the effect of plasmonic Au nanoparticles on the enhancement of the renewable hydrogen (H2) evolution through photocatalytic water splitting. The plasmonic Au/graphene/TiO2 photocatalyst was synthesized in two steps: first the graphene/TiO2 nanocomposites were developed by the hydrothermal decomposition process; then the Au was loaded by photodeposition. The plasmonic Au and the graphene as co-catalyst effectively prolong the recombination of the photogenerated charges. This plasmonic photocatalyst displayed enhanced photocatalytic H2 evolution for water splitting in the presence of methanol as a sacrificial reagent. The H2 evolution rate from the Au/graphene co-catalyst was about 9 times higher than that of a pure graphene catalyst. The optimal graphene content was found to be 1.0 wt %, giving a H2 evolution of 1.34 mmol (i.e., 26 μmolh(-1)), which exceeded the value of 0.56 mmol (i.e., 112 μmolh(-1)) observed in pure TiO2. This high photocatalytic H2 evolution activity results from the deposition of TiO2 on graphene sheets, which act as an electron acceptors to efficiently separate the photogenerated charge carriers. However, the Au loading enhanced the H2 evolution dramatically and achieved a maximum value of 12 mmol (i.e., 2.4 mmolh(-1)) with optimal loading of 2.0 wt% Au on graphene/TiO2 composites. The enhancement of H2 evolution in the presence of Au results from the SPR effect induced by visible light irradiation, which boosts the energy intensity of the trapped electron as well as active sites for photocatalytic activity.

Low-voltage graphene field-effect transistors based on octadecylphosphonic acid modified solution-processed high-k dielectrics

In this study, a solution-processed bilayer high-k dielectric (Al2O(y)/TiO(x), abbrev. as ATO) was used to realize the low-voltage operation of graphene field-effect transistors (GFETs), in which the graphene was grown by atmospheric pressure chemical vapor deposition (APCVD). Upon modifying the interface between graphene and the dielectric by octadecylphosphonic acid (ODPA), outstanding room-temperature hole mobility up to 5805 cm(2) V(-1) s(-1) and electron mobility of 3232 cm(2) V(-1) s(-1) were obtained in a small gate voltage range from -3.0 V to 3.0 V under a vacuum. Meanwhile, an excellent on/off current ratio of about 8 was achieved. Our studies demonstrate an effective route in which utilizing the low-temperature solution-processed dielectrics can achieve low-voltage and high performance GFETs.

Freeze-drying-induced changes in the properties of graphene oxides

We have characterized and evaluated changes in graphene oxide (GO) induced by means of freeze-drying. In order to evaluate these changes, we investigated the effects of freeze-drying and chemical reduction processes on the structure, morphology, chemical composition, and Raman properties of GO and reduced GO. The freeze-dried GO had a pore structure, maintaining a pored morphology even after thermal annealing. The freeze-dried samples were composed of a single folded nanosheet or a few nanosheets stacked and folded. The oxygen-containing functional groups were removed not only during the freeze-drying but also during the reduction processes, with an accompanying decrease in the average size of the sp(2) carbon domain (i.e. an increase in the ID/IG value).

Swallowtail band structure of the superfluid Fermi gas in an optical lattice

We investigate the energy band structure of the superfluid flow of ultracold dilute Fermi gases in a one-dimensional optical lattice along the BCS to Bose-Einstein condensate (BEC) crossover within a mean-field approach. In each side of the crossover region, a loop structure (swallowtail) appears in the Bloch energy band of the superfluid above a critical value of the interaction strength. The width of the swallowtail is largest near unitarity. Across the critical value of the interaction strength, the profiles of density and pairing field change more drastically in the BCS side than in the BEC side. It is found that along with the appearance of the swallowtail, there exists a narrow band in the quasiparticle energy spectrum close to the chemical potential, and the incompressibility of the Fermi gas consequently experiences a profound dip in the BCS side, unlike in the BEC side.

Precision measurement of gravity with cold atoms in an optical lattice and comparison with a classical gravimeter

We report on a precision measurement of gravitational acceleration using ultracold strontium atoms confined in an amplitude-modulated vertical optical lattice. An uncertainty Δg/g ≈ 10(-7) is reached by measuring at the 5th harmonic of the Bloch frequency. The value obtained with this microscopic quantum system is consistent with the one measured with a classical gravimeter. Using lattice modulation to prepare the atomic sample, we also achieve high visibility of Bloch oscillations for ∼ 20 s. These results can be of relevance for testing gravitational redshift and Newtonian law at micrometer scale.

Measuring energy differences by BEC interferometry on a chip

We investigate the use of a Bose-Einstein condensate trapped on an atom chip for making interferometric measurements of small energy differences. We measure and explain the noise in the energy difference of the split condensates, which derives from statistical noise in the number difference. We also consider systematic errors. A leading effect is the variation of the rf magnetic field in the trap with distance from the wires on the chip surface. This can produce energy differences that are comparable with those due to gravity.

Atomic Bloch-Zener oscillations and Stückelberg interferometry in optical lattices

We report on experiments investigating quantum transport and band interferometry of an atomic Bose-Einstein condensate in an optical lattice with a two-band miniband structure, realized with a Fourier-synthesized optical lattice potential. Bloch-Zener oscillations, the coherent superposition of Bloch oscillations and Landau-Zener tunneling between the two bands, are observed. When the relative phase between paths in different bands is varied, an interference signal is observed, demonstrating the coherence of the dynamics in the miniband system. Measured fringe patterns of this Stückelberg interferometer allow us to interferometrically map out the band structure of the optical lattice over the full Brillouin zone.

Inducing transport in a dissipation-free lattice with super Bloch oscillations

Particles in a perfect lattice potential perform Bloch oscillations when subject to a constant force, leading to localization and preventing conductivity. For a weakly interacting Bose-Einstein condensate of Cs atoms, we observe giant center-of-mass oscillations in position space with a displacement across hundreds of lattice sites when we add a periodic modulation to the force near the Bloch frequency. We study the dependence of these "super" Bloch oscillations on lattice depth, modulation amplitude, and modulation frequency and show that they provide a means to induce linear transport in a dissipation-free lattice.

Constraining the energy-momentum dispersion relation with Planck-scale sensitivity using cold atoms

We use the results of ultraprecise cold-atom-recoil experiments to constrain the form of the energy-momentum dispersion relation, a structure that is expected to be modified in several quantum-gravity approaches. Our strategy of analysis applies to the nonrelativistic (small speeds) limit of the dispersion relation, and is therefore complementary to an analogous ongoing effort of investigation of the dispersion relation in the ultrarelativistic regime using observations in astrophysics. For the leading correction in the nonrelativistic limit the exceptional sensitivity of cold-atom-recoil experiments remarkably allows us to set a limit within a single order of magnitude of the desired Planck-scale level, thereby providing the first example of Planck-scale sensitivity in the study of the dispersion relation in controlled laboratory experiments.

Delocalization and spreading in a nonlinear Stark ladder

We study the evolution of a wave packet in a nonlinear Stark ladder. In the absence of nonlinearity all normal modes are spatially localized giving rise to an equidistant eigenvalue spectrum and Bloch oscillations. Nonlinearity induces frequency shifts and mode-mode interactions and destroys localization. For large strength of nonlinearity we observe single-site trapping as a transient, with subsequent explosive spreading, followed by subdiffusion. For moderate nonlinearities an immediate subdiffusion takes place. Finally, for small nonlinearities we find linear Stark localization as a transient, with subsequent subdiffusion. For single-mode excitations and weak nonlinearities, stability intervals are predicted and observed upon variation in the dc bias strength, which affects the short- and the long-time dynamics.

Atom interferometers with scalable enclosed area

Bloch oscillations (i.e., coherent acceleration of matter waves by an optical lattice) and Bragg diffraction are integrated into light-pulse atom interferometers with large momentum splitting between the interferometer arms, and hence enhanced sensitivity. Simultaneous acceleration of both arms in the same internal states suppresses systematic effects, and simultaneously running a pair of interferometers suppresses the effect of vibrations. Ramsey-Bordé interferometers using four such Bloch-Bragg-Bloch beam splitters exhibit 15% contrast at 24variant Planck's over 2pik splitting, the largest so far (variant Planck's over 2pik is the photon momentum); single beam splitters achieve 88variant Planck's over 2pik. The prospects for reaching 100 s of variant Planck's over 2pik and applications such as gravitational wave sensors are discussed.

Suspension of atoms using optical pulses, and application to gravimetry

Atoms from a (87)Rb condensate are suspended against gravity using repeated reflections from a pulsed optical standing wave. Up to 100 reflections are observed, yielding suspension times of over 100 ms. The local gravitational acceleration can be determined from the pulse rate required to achieve suspension. Further, a gravitationally sensitive atom interferometer was implemented using the suspended atoms. This technique could potentially provide a precision measurement of gravity without requiring the atoms to fall a large distance.

Combination of BLOCH oscillations with a Ramsey-Bordé interferometer: new determination of the fine structure constant

We report a new experimental scheme which combines atom interferometry with Bloch oscillations to provide a new measurement of the ratio h/mRb. By using Bloch oscillations, we impart to the atoms up to 1600 recoil momenta and thus we improve the accuracy on the recoil velocity measurement. The deduced value of h/mRb leads to a new determination of the fine structure constant alpha(-1) =137.03599945 (62) with a relative uncertainty of 4.6 x 10(-9). The comparison of this result with the value deduced from the measurement of the electron anomaly provides the most stringent test of QED.

Long-living BLOCH oscillations of matter waves in periodic potentials

The dynamics of matter waves in linear and nonlinear optical lattices subject to a spatially uniform linear force is studied both analytically and numerically. It is shown that by properly designing the spatial dependence of the scattering length it is possible to induce long-living Bloch oscillations of gap-soliton matter waves in optical lattices. This occurs when the effective nonlinearity and the effective mass of the soliton have opposite signs for all values of the crystal momentum in the Brillouin zone. The results apply to all systems modeled by the periodic nonlinear Schrödinger equation, including propagation of light in photonic and photorefractive crystals with tilted band structures.

Atom interferometry with a weakly interacting Bose-Einstein condensate

We demonstrate the operation of an atom interferometer based on a weakly interacting Bose-Einstein condensate. We strongly reduce the interaction induced decoherence that usually limits interferometers based on trapped condensates by tuning the s-wave scattering length almost to zero via a magnetic Feshbach resonance. We employ a 39K condensate trapped in an optical lattice, where Bloch oscillations are forced by gravity. The fine-tuning of the scattering length down to 0.1 a_(0) and the micrometric sizes of the atomic sample make our system a very promising candidate for measuring forces with high spatial resolution. Our technique can be in principle extended to other measurement schemes opening new possibilities in the field of trapped atom interferometry.

Control of interaction-induced dephasing of Bloch oscillations

We report on the control of interaction-induced dephasing of Bloch oscillations for an atomic Bose-Einstein condensate in an optical lattice. We quantify the dephasing in terms of the width of the quasimomentum distribution and measure its dependence on time for different interaction strengths which we control by means of a Feshbach resonance. For minimal interaction, the dephasing time is increased from a few to more than 20 thousand Bloch oscillation periods, allowing us to realize a BEC-based atom interferometer in the noninteracting limit.

Highly coherent spectroscopy of ultracold atoms and molecules in optical lattices

Cooling and trapping of neutral atoms using laser techniques has enabled extensive progress in precise, coherent spectroscopy. In particular, trapping ultracold atoms in optical lattices in a tight confinement regime allows us to perform high-resolution spectroscopy unaffected by atomic motion. We report on the recent developments of optical lattice atomic clocks that have led to optical spectroscopy coherent at the one second timescale. The lattice clock techniques also open a promising pathway toward trapped ultracold molecules and the possible precision measurement opportunities such molecules offer.

Determination of the newtonian gravitational constant using atom interferometry

We present a new measurement of the Newtonian gravitational constant G based on cold-atom interferometry. Freely falling samples of laser-cooled rubidium atoms are used in a gravity gradiometer to probe the field generated by nearby source masses. In addition to its potential sensitivity, this method is intriguing as gravity is explored by a quantum system. We report a value of G = 6.667 x 10(-11) m(3) kg(-1) s(-2), estimating a statistical uncertainty of +/-0.011 x 10(-11) m(3) kg(-1) s(-2) and a systematic uncertainty of +/-0.003 x 10(-11) m(3) kg(-1) s(-2). The long-term stability of the instrument and the signal-to-noise ratio demonstrated here open interesting perspectives for pushing the measurement accuracy below the 100 ppm level.

Coherent delocalization of atomic wave packets in driven lattice potentials

Atomic wave packets loaded into a phase-modulated vertical optical-lattice potential exhibit a coherent delocalization dynamics arising from intraband transitions among Wannier-Stark levels. Wannier-Stark intraband transitions are here observed by monitoring the in situ wave-packet extent. By varying the modulation frequency, we find resonances at integer multiples of the Bloch frequency. The resonances show a Fourier-limited width for interrogation times up to 2 s. This can also be used to determine the gravity acceleration with ppm resolution.

Precision test of mass-ratio variations with lattice-confined ultracold molecules

We propose a precision measurement of time variations of the proton-electron mass ratio using ultracold molecules in an optical lattice. Vibrational energy intervals are sensitive to changes of the mass ratio. In contrast to measurements that use hyperfine-interval-based atomic clocks, the scheme discussed here is model independent and does not require separation of time variations of different physical constants. The possibility of applying the zero-differential-Stark-shift optical lattice technique is explored to measure vibrational transitions at high accuracy.

Condensate splitting in an asymmetric double well for atom chip based sensors

We report on the adiabatic splitting of a Bose-Einstein condensate of 87Rb atoms by an asymmetric double-well potential located above the edge of a perpendicularly magnetized TbGdFeCo film atom chip. By controlling the barrier height and double-well asymmetry, the sensitivity of the axial splitting process is investigated through observation of the fractional atom distribution between the left and right wells. This process constitutes a novel sensor for which we infer a single shot sensitivity to gravity fields of deltag/g approximately 2 x 10(-4). From a simple analytic model, we propose improvements to chip-based gravity detectors using this demonstrated methodology.