arXiv subjects

Tanya Zelevinsky

Publications and source records attributed to Tanya Zelevinsky.

At least 19 recordsLinked to original sources

arXiv2026

Creation and precise spectroscopy of $^{86}$Sr$_2$ halo molecules

We report on the creation of $^{86}$Sr$_2$ molecules in the halo state and neighboring weakly bound states. Efficient molecule production via one-photon photoassociation relies on sufficient wavefunction overlap between the target vibrational states in the electronic excited- and ground-state potentials. Using Autler-Townes spectroscopy, transition strengths are measured to identify optimal pathways for production of weakly bound molecules. Vibrational splittings for the three least-bound vibrational states are measured, and dominant systematic uncertainties are evaluated with uncertainties below 100 Hz. From these splittings, absolute binding energies for these weakly bound vibrational states are determined. The results pave the way to a molecular isotope shift measurement with Sr$_2$.

physics.atom-ph↗

arXiv2025

Magneto-Optical Trapping of a Metal Hydride Molecule

We demonstrate a three-dimensional magneto-optical trap (MOT) of a metal hydride molecule, CaH. We are able to scatter $\sim$$10^{4}$ photons with vibrational loss covered up to vibrational quantum number $\nu=2$. This allows us to laser slow the molecular beam near zero velocity with a "white-light" technique and subsequently load it into a radio-frequency MOT. The MOT contains $230(40)$ molecules, limited by beam source characteristics and predissociative loss of CaH. The temperature of the MOT is below one millikelvin. The predissociative loss mechanism could, in turn, facilitate controlled dissociation of the molecule, offering a possible route to optical trapping of hydrogen atoms for precision spectroscopy.

physics.atom-ph↗

arXiv2025

Adiabatic passage of $^{205}$TlF with microwaves in a cryogenic beam

We present a hyperfine-resolved state preparation scheme for thallium fluoride (TlF) molecules based on microwave-driven adiabatic passage (AP) in a spatially varying electric field. This method enables efficient and robust population transfer between selected $\left|J,m_J=0\right\rangle$ hyperfine sublevels of the $X\,^1\Sigma^+_0$ ground state in a cryogenic molecular beam, a key requirement for the CeNTREX search for nuclear time-reversal symmetry violation. Two sequential stages of AP are implemented. The first transfers population from $J=0$ to $J=1$ at a local field of $173~\mathrm{V/cm}$, and the second transfers from $J=1$ to $J=2$ at $110~\mathrm{V/cm}$. Transfer efficiencies are quantified through laser-induced fluorescence, and accounting for residual population in excited rotational levels after a prior stage of rotational cooling. We achieve state transfer efficiencies of $0.92(6)$ and $1.05(5)$ for the first and second states of AP, respectively. This corresponds to a total efficiency of $0.97(8)$ for population transfer from $J=0$ to $J=2$. These results demonstrate robust and high-fidelity preparation of specific rotational/hyperfine states in TlF.

physics.atom-ph↗

arXiv2025

Rotational-hyperfine cooling of $^{205}$TlF in a cryogenic beam

The aim of CeNTREX (Cold Molecule Nuclear Time-Reversal Experiment) is to search for time-reversal symmetry violation in the thallium nucleus, by measuring the Schiff moment of $^{205}$Tl in the polar molecule thallium fluoride (TlF). CeNTREX uses a cryogenic beam of TlF with a rotational temperature of 6.3(2) K. This results in population spread over dozens of rotational and hyperfine sublevels of TlF, while only a single level is useful for the Schiff moment measurement. Here we present a protocol for cooling the rotational and hyperfine degrees of freedom in the CeNTREX beam, transferring the majority of the Boltzmann distribution into a single rotational and hyperfine sublevel by using a single ultraviolet laser and a pair of microwave beams. We achieve a factor of $20.1(4)$ gain in the population of the $J=0$, $F=0$ hyperfine sublevel of the TlF ground state.

physics.atom-ph↗

arXiv2025

Chemistry in a Cryogenic Buffer Gas Cell

Cryogenic buffer gas sources are ubiquitous for producing cold, collimated molecular beams for quantum science, chemistry, and precision measurements. The molecules are typically produced by laser ablating a metal target in the presence of a donor gas. The radical of interest emerges due to a barrier-free reaction or under thermal or optical excitation. High-barrier reactions, such as between Ca and H$_2$, should be precluded. We study chemical reactions between Ca and three hydrogen isotopologues H$_2$, D$_2$, and HD in a cryogenic cell with helium buffer gas. We observe that H$_2$ can serve as both a reactant and a buffer gas, outperforming D$_2$ and HD. We use a reaction network model to describe the chemical dynamics and find that the enhanced molecular yield can be attributed to rapid vibrational excitations of the reactant gas. Our results demonstrate a robust method for generating bright cold beams of alkaline-earth-metal hydrides for laser cooling and trapping.

physics.atom-ph↗

arXiv2024

Ground-state selection via many-body superradiant decay

For a single particle, relaxation into different ground states is governed by fixed branching ratios determined by the transition matrix element and the environment. Here, we show that in many-body open quantum systems the occupation probability of one ground state can be boosted well beyond what is dictated by single-particle branching ratios. Despite the competition, interactions suppress all but the dominant decay transition, leading to a 'winner takes all' dynamic where the system primarily settles into the dominant ground state. We prove that, in the presence of permutation symmetry, this problem is exactly solvable for any number of competing channels. Additionally, we develop an approximate model for the dynamics by mapping the evolution onto a fluid continuity equation, and analytically demonstrate that the dominant transition ratio converges to unity as a power law with increasing system size, for any branching ratios. This near-deterministic preparation of the dominant ground state has broad applicability. As an example, we discuss a protocol for molecular photoassociation where collective dynamics effectively acts as a catalyst, amplifying the yield in a specific final state. Our results open new avenues for many-body strategies in the preparation and control of quantum systems.

quant-ph↗

arXiv2024

Laser cooling of a fermionic molecule

Only bosonic molecular species have been directly laser cooled to date, primarily due to an abundance of bosonic isotopes in nature and to their simpler hyperfine structure. Fermionic molecules provide new opportunities for ultracold chemistry, quantum simulation, and precision measurements. Here we report direct laser cooling of a fermionic molecular isotopologue, calcium monodeuteride (CaD). With a nuclear spin I = 1, only 5 hyperfine states need to be addressed for rotational closure in optical cycling. These hyperfine states are unresolved for typical experimental linewidths. We present a method for efficiently producing alkaline-earth metal hydrides and deuterides. We demonstrate rotational closure and show magnetically assisted Sisyphus cooling in one dimension for a beam of CaD molecules. Our results indicate that the experimental complexity for laser cooling CaD is similar to that of calcium monohydride (CaH). Laser cooling of CaD is a promising first step for production of ultracold and trapped atomic deuterium.

physics.atom-ph↗

arXiv2023

Collectively enhanced Ramsey readout by cavity sub- to superradiant transition

When an inverted ensemble of atoms is tightly packed on the scale of its emission wavelength or when the atoms are collectively strongly coupled to a single cavity mode, their dipoles will align and decay rapidly via a superradiant burst. However, a spread-out dipole phase distribution theory predicts a required minimum threshold of atomic excitation for superradiance to occur. Here we experimentally confirm this predicted threshold for superradiant emission on a narrow optical transition when exciting the atoms transversely and show how to take advantage of the resulting sub- to superradiant transition. A $\pi/2$-pulse places the atoms in a subradiant state, protected from collective cavity decay, which we exploit during the free evolution period in a corresponding Ramsey pulse sequence. The final excited state population is read out via superradiant emission from the inverted atomic ensemble after a second $\pi/2$-pulse, and with minimal heating this allows for multiple Ramsey sequences within one experimental cycle. Our scheme is a fundamentally new approach to atomic state readout characterized by its speed, simplicity, and high sensitivity. It demonstrates the potential of sensors using collective effects in cavity-coupled quantum emitters.

quant-ph↗

arXiv2023

Probing the limits of optical cycling in a predissociative diatomic molecule

Molecular predissociation is the spontaneous, nonradiative bond breaking process that can occur upon excitation. In the context of laser cooling, predissociation is an unwanted consequence of molecular structure that limits the ability to scatter a large number of photons required to reach the ultracold regime. Unlike rovibrational branching, predissociation is irreversible since the fragments fly apart with high kinetic energy. Of particular interest is the simple diatomic molecule, CaH, for which the two lowest electronically excited states used in laser cooling lie above the dissociation threshold of the ground potential. In this work, we present measurements and calculations that quantify the predissociation probabilities affecting the cooling cycle. The results allow us to design a laser cooling scheme that will enable the creation of an ultracold and optically trapped cloud of CaH molecules. In addition, we use the results to propose a two-photon pathway to controlled dissociation of the molecules, in order to gain access to their ultracold fragments, including hydrogen.

physics.atom-ph↗

arXiv2023

Sub-Natural Linewidth Superradiant Lasing with Cold $^{88}$Sr Atoms

Superradiant lasers operate in the bad-cavity regime, where the phase coherence is stored in the spin state of an atomic medium rather than in the intracavity electric field. Such lasers use collective effects to sustain lasing and could potentially reach considerably lower linewidths than a conventional laser. Here, we investigate the properties of superradiant lasing in an ensemble of ultracold $^{88}$Sr atoms inside an optical cavity. We extend the superradiant emission on the 7.5 kHz wide $^3P_1$ $\rightarrow$ $^1S_0$ intercombination line to several milliseconds, and observe steady parameters suitable for emulating the performance of a continuous superradiant laser by fine tuning the repumping rates. We reach a lasing linewidth of 820 Hz for 1.1 ms of lasing, nearly an order of magnitude lower than the natural linewidth

physics.atom-ph↗

arXiv2020

CeNTREX: A new search for time-reversal symmetry violation in the $^{205}$Tl nucleus

The Cold molecule Nuclear Time-Reversal EXperiment (CeNTREX) is a new effort aiming for a significant increase in sensitivity over the best present upper bounds on the strength of hadronic time reversal ($T$) violating fundamental interactions. The experimental signature will be shifts in nuclear magnetic resonance frequencies of $^{205}$Tl in electrically-polarized thallium fluoride (TlF) molecules. Here we describe the motivation for studying these $T$-violating interactions and for using TlF to do so. To achieve higher sensitivity than earlier searches for $T$-violation in TlF, CeNTREX uses a cryogenic molecular beam source, optical state preparation and detection, and modern methods of coherent quantum state manipulation. Details of the measurement scheme and the current state of the apparatus are presented, with quantitative measurements of the TlF beam. Finally, the estimated sensitivity and methods to control systematic errors are discussed.

physics.atom-ph↗

arXiv2020

Optical cycling, radiative deflection and laser cooling of barium monohydride (BaH)

We present the first experimental demonstration of radiation pressure force deflection and direct laser cooling for barium monohydride (BaH) molecules resulting from multiple photon scattering. Despite a small recoil velocity (2.7 mm/s) and a long excited state lifetime (137 ns), we use 1060 nm laser light exciting the $X\rightarrow A$ electronic transition of BaH to deflect a cryogenic buffer-gas beam and reduce its transverse velocity spread. Multiple experimental methods are employed to characterize the optical cycling dynamics and benchmark theoretical estimates based on rate equation models as well as solutions of the Lindblad master equation for the complete multilevel system. Broader implications for laser cooling and magneto-optical trapping of heavy-metal-containing molecules with narrow transition linewidths are presented. Our results pave the way for producing a new class of ultracold molecules -- alkaline earth monohydrides -- via direct laser cooling and trapping, opening the door to realizing a new method for delivering ultracold hydrogen atoms (Lane 2015 \textit{Phys. Rev. A} 92, 022511).

physics.atom-ph↗

arXiv2020

Large molasses-like cooling forces for molecules using polychromatic optical fields: A theoretical description

Recent theoretical investigations have indicated that rapid optical cycling should be feasible in complex polyatomic molecules with diverse constituents, geometries and symmetries. However, as a composite molecular mass grows, so does the required number of photon scattering events necessary to decelerate and confine molecular beams using laser light. Utilizing coherent momentum exchange between light fields and molecules can suppress spontaneous emission and significantly reduce experimental complexity for slowing and trapping. Working with BaH as a test species, we have identified a robust, experimentally viable configuration to achieve large molasses-like cooling forces for molecules using polychromatic optical fields addressing both $X-A$ and $X-B$ electronic transitions, simultaneously. Using numerical solutions of the time-dependent density matrix as well as Monte Carlo simulations, we demonstrate that creation of Suppressed Emission Rate (SupER) molasses with large capture velocities ($\sim 40$ m/s) is generically feasible for polyatomic molecules of increasing complexity that have an optical cycling center. Proposed SupER molasses are anticipated to not only extend quantum control to novel molecular species with abundant vibrational decay channels, but also significantly increase trapped densities for previously laser-cooled diatomic and triatomic species.

physics.atom-ph↗

arXiv2020

Constraining domain wall dark matter with a network of superconducting gravimeters and LIGO

There is strong astrophysical evidence that dark matter (DM) makes up some 27% of all mass in the universe. Yet, beyond gravitational interactions, little is known about its properties or how it may connect to the Standard Model. Multiple frameworks have been proposed, and precision measurements at low energy have proven useful to help restrict the parameter space for many of these models. One set of models predicts that DM is a scalar field that "clumps" into regions of high local density, rather than being uniformly distributed throughout the galaxy. If this DM field couples to the Standard Model, its interaction with matter can be thought of as changing the effective values of fundamental constants. One generic consequence of time variation of fundamental constants (or their spatial variation as the Earth passes through regions of varying density) is the presence of an anomalous, composition-dependent acceleration. Here we show how this anomalous acceleration can be measured using superconducting accelerometers, and demonstrate that >20 years of archival data from the International Geodynamics and Earth Tide Services (IGETS) network can be utilized to set new bounds on these models. Furthermore, we show how LIGO and other gravitational wave detectors can be used as exquisitely sensitive probes for narrow ranges of the parameter space. While limited to DM models that feature spatial gradients, these two techniques complement the networks of precision measurement devices already in use for direct detection and identification of dark matter.

astro-ph.IM↗

arXiv2020

Molecular Asymmetry and Optical Cycling: Laser Cooling Asymmetric Top Molecules

We present a practical roadmap to achieve optical cycling and laser cooling of asymmetric top molecules (ATMs). Our theoretical analysis describes how reduced molecular symmetry, as compared to diatomic and symmetric non-linear molecules, plays a role in photon scattering. We present methods to circumvent limitations on rapid photon cycling in these systems. We calculate vibrational branching ratios for a diverse set of asymmetric top molecules and find that many species within a broad class of molecules can be effectively cooled with a manageable number of lasers. We also describe methods to achieve rotationally closed optical cycles in ATMs. Despite significant structural complexity, laser cooling can be made effective using extensions of the current techniques used for linear molecules. Potential scientific impacts of laser-cooled ATMs span frontiers in controlled chemistry, quantum simulation, and searches for physics beyond the Standard Model.

physics.atom-ph↗

arXiv2020

Second-Scale Coherence Measured at the Quantum Projection Noise Limit with Hundreds of Molecular Ions

Cold molecules provide an excellent platform for quantum information, cold chemistry, and precision measurement. Certain molecules have enhanced sensitivity to beyond Standard Model physics, such as the electron's electric dipole moment ($e$EDM). Molecular ions are easily trappable and are therefore particularly attractive for precision measurements where sensitivity scales with interrogation time. Here, we demonstrate a spin precession measurement with second-scale coherence at the quantum projection noise (QPN) limit with hundreds of trapped molecular ions, chosen for their sensitivity to the $e$EDM rather than their amenability to state control and readout. Orientation-resolved resonant photodissociation allows us to simultaneously measure two quantum states with opposite $e$EDM sensitivity, reaching the QPN limit and fully exploiting the high count rate and long coherence.

physics.atom-ph↗

arXiv2017

Globally stable microresonator Turing pattern formation for coherent high-power THz radiation on-chip

In nonlinear microresonators driven by continuous-wave (cw) lasers, Turing patterns have been studied in the formalism of Lugiato-Lefever equation with emphasis on its high coherence and exceptional robustness against perturbations. Destabilization of Turing pattern and transition to spatio-temporal chaos, however, limits the available energy carried in the Turing rolls and prevents further harvest of their high coherence and robustness to noise. Here we report a novel scheme to circumvent such destabilization, by incorporating the effect of local mode hybridizations, and attain globally stable Turing pattern formation in chip-scale nonlinear oscillators, achieving a record high power conversion efficiency of 45% and an elevated peak-to-valley contrast of 100. The stationary Turing pattern is discretely tunable across 430 GHz on a THz carrier, with a fractional frequency sideband non-uniformity measured at 7.3x10^-14. We demonstrate the simultaneous microwave and optical coherence of the Turing rolls at different evolution stages through ultrafast optical correlation techniques. The free running Turing roll coherence, 9 kHz in 200 ms and 160 kHz in 20 minutes, is transferred onto a plasmonic photomixer for one of the highest power THz coherent generation at room-temperature, with 1.1% optical-to-THz power conversion. Its long-term stability can be further improved by more than two orders of magnitude, reaching an Allan deviation of 6x10^-10 at 100 s, with a simple computer-aided slow feedback control. The demonstrated on-chip coherent high-power Turing-THz system is promising to find applications in astrophysics, medical imaging, and wireless communications.

physics.optics↗

arXiv2015

Thermometry via Light Shifts in Optical Lattices

For atoms or molecules in optical lattices, conventional thermometry methods are often unsuitable due to low particle numbers or a lack of cycling transitions. However, a differential spectroscopic light shift can map temperature onto the line shape with a low sensitivity to trap anharmonicity. We study narrow molecular transitions to demonstrate precise frequency-based lattice thermometry, as well as carrier cooling. This approach should be applicable down to nanokelvin temperatures. We also discuss how the thermal light shift can affect the accuracy of optical lattice clocks.

physics.atom-ph↗