SEARCH · Searcharxiv

Results for “physics.atom-ph”

Search indexed arXiv papers on artificial intelligence, large language models, computer vision and robotics. Read source abstracts and follow links to arXiv.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 631 records · Page 35Linked to original sources

arXiv2014

Controlling magnetic Feshbach resonances in polar open-shell molecules with non-resonant light

Magnetically tunable Feshbach resonances for polar paramagnetic ground-state diatomics are too narrow to allow for magnetoassociation starting from trapped, ultracold atoms. We show that non-resonant light can be used to engineer the Feshbach resonances in their position and width. For non-resonant field strengths of the order of $10^9\,$W/cm$^2$, we find the width to be increased by three orders of magnitude, reaching a few Gauss. This opens the way for producing ultracold molecules with sizeable electric and magnetic dipole moments and thus for many-body quantum simulations with such particles.

physics.atom-ph↗

arXiv2013

Shifts of a resonance line in a dense atomic sample

We study the collective response of a dense atomic sample to light essentially exactly using classical-electrodynamics simulations. In a homogeneously broadened atomic sample there is no overt Lorentz-Lorenz local field shift of the resonance, nor a collective Lamb shift. However, addition of inhomogeneous broadening restores the usual mean-field phenomenology.

physics.atom-ph↗

arXiv2013

Demonstration of fold and cusp catastrophes in an atomic cloud reflected from an optical barrier in the presence of gravity

We experimentally demonstrate first-order (fold) and second-order (cusp) catastrophes in the density of an atomic cloud reflected from an optical barrier in the presence of gravity, and show their corresponding universal asymptotic behavior. The cusp point enables robust, field-free refocusing of an expanding atomic cloud with a wide velocity distribution. Specifically, the density attained at the cusp point in our experiment reached 65% of the peak density of the atoms in the trap prior to their release. We thereby add caustics to the various phenomena with parallels in optics that can be harnessed for manipulation of cold atoms. The structural stability of catastrophes provides inherent robustness against variations in the system's dynamics and initial conditions, making them suitable for manipulation of atoms under imperfect conditions and limited controllability.

physics.atom-ph↗

arXiv2014

Non equilibrium phase transition with gravitational-like interaction in a cloud of cold atoms

We propose to use a cloud of laser cooled atoms in a quasi two dimensional trap to investigate a non equilibrium collapse phase transition in presence of gravitational-like interaction. Using theoretical arguments and numerical simulations, we show that, like in two dimensional gravity, a transition to a collapsed state occurs below a critical temperature. In addition and as a signature of the non equilibrium nature of the system, persistent particles currents, dramatically increasing close to the phase transition, are observed.

physics.atom-ph↗

arXiv2014

Muon Loop Light-by-Light Contribution to Hyperfine Splitting in Muonium

Three-loop corrections to hyperfine splitting in muonium generated by the gauge invariant sets of diagrams with muon and tauon loop light-by-light scattering blocks are calculated. These results complete calculations of all light-by-light scattering contributions to hyperfine splitting in muonium.

hep-ph↗

arXiv2014

Fast quantum gate via Feshbach-Pauli blocking in a nanoplasmonic trap

We propose a simple idea for realizing a quantum gate with two identical fermions in a double well trap via external optical pulses without addressing the atoms individually. The key components of the scheme are Feshbach resonance and Pauli blocking, which decouple unwanted states from the dynamics. As a physical example we study atoms in the presence of a magnetic Feshbach resonance in a nanoplasmonic trap and discuss the constraints on the operation times for realistic parameters, reaching a fidelity above $99.9\%$ within $42μ$s.

quant-ph↗

arXiv2014

High-precision spectroscopy of the forbidden 2 3S1 - 2 1P1 transition in quantum degenerate metastable helium

We have measured the forbidden 2 3S1 - 2 1P1 transition at 887 nm in a quantum degenerate gas of metastable He-4 atoms confined in an optical dipole trap. The determined transition frequency is 338 133 594.4 (0.5) MHz, from which we obtain an ionization energy of the 2 1P1 state of 814 709 148.6 (0.5) MHz. This ionization energy is in disagreement by > 3 sigma with the most accurate quantum electrodynamics (QED) calculations available. Our measurements also provide a new determination of the lifetime of the 2 1P1 state of 0.551 (0.004)stat (+ 0.013,- 0.000)syst ns, which is the most accurate determination to date and in excellent agreement with theory.

physics.atom-ph↗

arXiv2014

Two-pulse field-free orientation reveals anisotropy of molecular shape resonance

We report the observation of macroscopic field-free orientation, i.e. more than 73 % of CO molecules pointing in the same direction. This is achieved through an all-optical scheme operating at high particle densities ($>10^{17}$cm$^{-3}$) that combines a one-color ($ω$) and a two-color ($ω+ 2ω$) non-resonant femtosecond laser pulses. We show that the achieved orientation solely relies on the hyperpolarizability interaction as opposed to an ionization-depletion mechanism thus opening a wide range of applications. The achieved strong orientation enables us to reveal the molecular-frame anisotropies of the photorecombination amplitudes and phases caused by a shape resonance. The resonance appears as a local maximum in the even-harmonic emission around 28~eV. In contrast, the odd-harmonic emission is suppressed in this spectral region through the combined effects of an asymmetric photorecombination phase and a sub-cycle Stark effect, generic for polar molecules, that we experimentally identify.

physics.chem-ph↗

arXiv2014

Test of Einstein Equivalence Principle for 0-spin and half-integer-spin atoms: Search for spin-gravity coupling effects

We report on a conceptually new test of the equivalence principle performed by measuring the acceleration in Earth's gravity field of two isotopes of strontium atoms, namely, the bosonic $^{88}$Sr isotope which has no spin vs the fermionic $^{87}$Sr isotope which has a half-integer spin. The effect of gravity upon the two atomic species has been probed by means of a precision differential measurement of the Bloch frequency for the two atomic matter waves in a vertical optical lattice. We obtain the values $η= (0.2\pm 1.6)\times10^{-7}$ for the Eötvös parameter and $k=(0.5\pm1.1)\times10^{-7}$ for the coupling between nuclear spin and gravity. This is the first reported experimental test of the equivalence principle for bosonic and fermionic particles and opens a new way to the search for the predicted spin-gravity coupling effects.

physics.atom-ph↗

arXiv2017

Fast State Transfer and Entanglement Renormalization Using Long-Range Interactions

In short-range interacting systems, the speed at which entanglement can be established between two separated points is limited by a constant Lieb-Robinson velocity. Long-range interacting systems are capable of faster entanglement generation, but the degree of the speed-up possible is an open question. In this paper, we present a protocol capable of transferring a quantum state across a distance $L$ in $d$ dimensions using long-range interactions with strength bounded by $1/r^α$. If $α< d$, the state transfer time is asymptotically independent of $L$; if $α= d$, the time is logarithmic in distance $L$; if $d < α< d+1$, transfer occurs in time proportional to $L^{α- d}$; and if $α\geq d + 1$, it occurs in time proportional to $L$. We then use this protocol to upper bound the time required to create a state specified by a MERA (multiscale entanglement renormalization ansatz) tensor network, and show that, if the linear size of the MERA state is $L$, then it can be created in time that scales with $L$ identically to state transfer up to multiplicative logarithmic corrections.

quant-ph↗

arXiv2017

Possibility to probe negative values of a Wigner function in scattering of a coherent superposition of electronic wave packets by atoms

Within a plane-wave approximation in scattering, an incoming wave packet's Wigner function stays everywhere positive, which obscures such purely quantum phenomena as non-locality and entanglement. With the advent of the electron microscopes with subnanometer-sized beams one can enter a genuinely quantum regime where the latter effects become only moderately attenuated. Here we show how to probe negative values of the Wigner function in scattering of a coherent superposition of two Gaussian packets with a non-vanishing impact-parameter between them (a Schrödinger's cat state) by atomic targets. For hydrogen in the ground $1s$ state, a small parameter of the problem, a ratio $a/σ_{\perp}$ of the Bohr radius $a$ to the beam width $σ_{\perp}$, is no longer vanishing. We predict an azimuthal asymmetry of the scattered electrons, which is found to be up to $10 \%$ and argue that it can be reliably detected. Production of beams with the not-everywhere positive Wigner functions and probing such quantum effects can open new perspectives for non-invasive electron microscopy, quantum tomography, particle physics, etc.

quant-ph↗

arXiv2018

The Collective Lamb Shift of a Nanoscale Atomic Vapour Layer within a Sapphire Cavity

We measure the near-resonant transmission of light through a dense medium of potassium vapor confined in a cell with nanometer thickness in order to investigate the origin and validity of the collective Lamb-shift. A complete model including the multiple reflections in the nano-cell accurately reproduces the observed strong asymmetry of the line shape and allows extraction of a density dependent shift of the atomic resonance. We observe an additional, unexpected dependence of this shift with the thickness of the medium. This extra dependence demands further experimental and theoretical investigations.

physics.atom-ph↗

arXiv2018

Long-term monitoring of the internal energy distribution of isolated cluster systems

A method is presented to monitor the internal energy distribution of cluster anions via delayed electron detachment by pulsed photoexcitation and demonstrated on Co$_4{}^-$ in an electrostatic ion beam trap. In cryogenic operation, we calibrate the detachment delay to internal energy. By laser frequency scans, at room temperature, we reconstruct the time-dependent internal energy distribution of the clusters. The mean energies of ensembles from a cold and a hot ion source both approach thermal equilibrium. Our data yield a radiative emission law and the absorptivity of the cluster for thermal radiation.

physics.atm-clus↗

arXiv2018

Direct frequency-comb-driven Raman transitions in the terahertz range

We demonstrate the use of a femtosecond frequency comb to coherently drive stimulated Raman transitions between terahertz-spaced atomic energy levels. More specifically, we address the $3d~^2D_{3/2}$ and $3d~^2D_{5/2}$ fine structure levels of a single trapped $^{40}$Ca$^+$ ion and spectroscopically resolve the transition frequency to be $ν_D = 1{,}819{,}599{,}021{,}534 \pm 8$ Hz. The achieved accuracy is nearly a factor of five better than the previous best Raman spectroscopy, and is currently limited by the stability of our atomic clock reference. Furthermore, the population dynamics of frequency-comb-driven Raman transitions can be fully predicted from the spectral properties of the frequency comb, and Rabi oscillations with a contrast of 99.3(6)\% and millisecond coherence time has been achieved. Importantly, the technique can be easily generalized to transitions in the sub-kHz to tens of THz range and should be applicable for driving, e.g., spin-resolved rovibrational transitions in molecules and hyperfine transitions in highly charged ions.

quant-ph↗

arXiv2018

Experimental demonstration of shaken lattice interferometry

We experimentally demonstrate a shaken lattice interferometer. Atoms are trapped in the ground Bloch state of a red-detuned optical lattice. Using a closed-loop optimization protocol based on the dCRAB algorithm, we phase-modulate (shake) the lattice to transform the atom momentum state. In this way, we implement an atom beamsplitter and build five interferometers of varying interrogation times $T_I$. The sensitivity of shaken lattice interferometry is shown to scale as $T_I^2$, consistent with simulation [1]. Finally, we show that we can measure the sign of an applied signal and optimize the interferometer in the presence of a bias signal. [1] C. A. Weidner, H. Yu, R. Kosloff, and D. Z. Anderson, Phys. Rev. A 95, 043624 (2017).

quant-ph↗

arXiv2018

Dissociation energy of the hydrogen molecule at 10$^{-9}$ accuracy

The ionization energy of ortho-H$_2$ has been determined to be $E^\mathrm{o}_\mathrm{I}(\mathrm{H}_2)/(hc)=124\,357.238\,062(25)$ cm$^{-1}$ from measurements of the GK(1,1)--X(0,1) interval by Doppler-free two-photon spectroscopy using a narrow band 179-nm laser source and the ionization energy of the GK(1,1) state by continuous-wave near-infrared laser spectroscopy. $E^\mathrm{o}_\mathrm{I}$(H$_2$) was used to derive the dissociation energy of H$_2$, $D^{N=1}_{0}$(H$_2$), at $35\,999.582\,894(25)$ cm$^{-1}$ with a precision that is more than one order of magnitude better than all previous results. The new result challenges calculations of this quantity and represents a benchmark value for future relativistic and QED calculations of molecular energies.

physics.chem-ph↗

arXiv2017

Magnetically-Trapped Molecules Efficiently Loaded from a Molecular MOT

We describe experiments demonstrating efficient transfer of molecules from a magneto-optical trap (MOT) into a conservative magnetic quadrupole trap. Our scheme begins with a blue-detuned optical molasses to cool SrF molecules to $\sim\!50$ $μ$K. Next, we optically pump the molecules into a strongly-trapped sublevel. This two-step process reliably transfers $64\%$ of the molecules initially trapped in the MOT into the magnetic trap, comparable to similar atomic experiments. Once loaded, the magnetic trap is compressed by increasing the magnetic field gradient. Finally, we demonstrate a magnetic trap lifetime of over $1$ s. This opens a promising new path to the study of ultracold molecular collisions, and potentially the production of quantum-degenerate molecular gases.

physics.atom-ph↗

arXiv2018

Nuclear-spin comagnetometer based on a liquid of identical molecules

Atomic comagnetometers are used in searches for anomalous spin-dependent interactions. Magnetic field gradients are one of the major sources of systematic errors in such experiments. Here we describe a comagnetometer based on the nuclear spins within an ensemble of identical molecules. The dependence of the measured spin-precession frequency ratio on the first-order magnetic field gradient is suppressed by over an order of magnitude compared to a comagnetometer based on overlapping ensembles of different molecules. Our single-species comagnetometer is shown to be capable of measuring the hypothetical spin-dependent gravitational energy of nuclei at the $10^{-17}$ eV level, comparable to the most stringent existing constraints. Combined with techniques for enhancing the signal such as parahydrogen-induced polarization, this method of comagnetometry offers the potential to improve constraints on spin-gravity coupling of nucleons by several orders of magnitude.

physics.atom-ph↗