arXiv subjects

Yuiki Takahashi

Publications and source records attributed to Yuiki Takahashi.

10 recordsLinked to original sources

arXiv2026

Enhanced coherence of rare-earth nuclear spins in a crystal

Rare-earth ions in crystals are useful in precision measurements and quantum information science because of their exceptional optical and spin coherence properties. We show that the nuclear spin coherence time of $^{153}\mathrm{Eu}^{3+}$ ions doped into yttrium orthosilicate can be significantly enhanced by driving the $^{89}\mathrm{Y}$ nuclear spins in the host crystal. This improvement in spin coherence time opens up ways to improve the precision of measurements using rare-earth-doped crystals.

physics.atom-ph↗

arXiv2026

Sensing T-violating nuclear moments of paramagnetic ions in crystals

Precision measurements of time-reversal (T) symmetry violating moments probe physics beyond the Standard Model. We show that precision spectroscopy of paramagnetic lanthanide and actinide ions doped into noncentrosymmetric crystals offers a promising platform for extending the sensitivity of searches for T-violation in nuclear physics. The unpaired valence electron in these ions allows the engineering of highly-coherent hyperfine transitions that are insensitive to magnetic fields, yet highly sensitive to new physics. These systems also provide other advantages for new physics searches, including large numbers of ions that can be measured in doped crystals, strong electric polarization of the ions by the crystal fields, enhancement of T-violating nuclear moments in nonspherical nuclei, and accurate comagnetometers generated by crystal symmetry. We estimate the new physics sensitivity of these proposed systems to be two orders of magnitude better than existing constraints.

physics.atom-ph↗

arXiv2025

Engineered Molecular Clock Transitions for Symmetry Violation Searches

Heavy polar molecules are sensitive probes of physics Beyond the Standard Model. However, uncontrolled external electromagnetic fields pose challenges to achieving precise and accurate measurements. Minimizing susceptibility to these fields is therefore critical and has played an important role in all precision experiments of this type. Here we devise and demonstrate clock transitions engineered to realize robust symmetry violation searches in the polyatomic molecule YbOH. Sensitivities to external fields can be suppressed by orders-of-magnitude while preserving high sensitivity to the electron electric dipole moment (eEDM). We perform Ramsey measurements on these clock transitions and observe suppression of electric and magnetic sensitivities by at least a factor of 700 and 200, respectively, and demonstrate the robustness of their spin coherence against large electromagnetic field fluctuations. We further identify and employ selected quantum states to make sensitive measurements of external magnetic and electric fields, another critical feature for highly accurate measurements. This approach of molecular engineering is broadly applicable to diverse molecular species and states, including those with complex nuclei and those that are compatible with state-of-the-art cooling and trapping techniques, thereby offering the potential to significantly improve experimental sensitivity to a wide range of New Physics while expanding the chemical design space for molecular quantum science.

physics.atom-ph↗

arXiv2023

Measuring the nuclear magnetic quadrupole moment of optically trapped ytterbium atoms in the metastable state

We propose a scheme to measure a nuclear magnetic quadrupole moment (MQM), a CP-violating electromagnetic moment that appears in the nuclear sector, using the long-lived $^3P_2$ metastable state in neutral $^{173}$Yb atoms. Laser-cooling and trapping techniques enable us to prepare ultracold $^{173}$Yb atoms in the $^3P_2$ state trapped in an optical lattice or an optical tweezer array, providing an ideal experimental platform with long spin coherence time. In addition, our relativistic configuration interaction calculation for the $^3P_2$ electronic wavefunction reveals a large magnetic field gradient generated by the atomic electrons in this state, which amplifies the measurable effect of an MQM. Our scheme could lead to an improvement of more than one order of magnitude in MQM sensitivity compared to the best previous measurement [S. A. Murthy et al., Phys. Rev. Lett. 63, 965 (1989)]

physics.atom-ph↗

arXiv2023

Engineering field-insensitive molecular clock transitions for symmetry violation searches

Molecules are a powerful platform to probe fundamental symmetry violations beyond the Standard Model, as they offer both large amplification factors and robustness against systematic errors. As experimental sensitivities improve, it is important to develop new methods to suppress sensitivity to external electromagnetic fields, as limits on the ability to control these fields are a major experimental concern. Here we show that sensitivity to both external magnetic and electric fields can be simultaneously suppressed using engineered radio frequency, microwave, or two-photon transitions that maintain large amplification of CP-violating effects. By performing a clock measurement on these transitions, CP-violating observables including the electron electric dipole moment, nuclear Schiff moment, and magnetic quadrupole moment can be measured with suppression of external field sensitivity of $\gtrsim$100 generically, and even more in many cases. Furthermore, the method is compatible with traditional Ramsey measurements, offers internal co-magnetometry, and is useful for systems with large angular momentum commonly present in molecular searches for nuclear CP-violation.

physics.atom-ph↗

arXiv2023

Characterizing the Fundamental Bending Vibration of a Linear Polyatomic Molecule for Symmetry Violation Searches

Polyatomic molecules have been identified as sensitive probes of charge-parity violating and parity-violating physics beyond the Standard Model (BSM). For example, many linear triatomic molecules are both laser-coolable and have parity doublets in the ground electronic $\tilde{X} {}^2Σ^+ (010)$ state arising from the bending vibration, both features that can greatly aid BSM searches. Understanding the $\tilde{X} {}^2Σ^+ (010)$ state is a crucial prerequisite to precision measurements with linear polyatomic molecules. Here, we characterize fundamental bending vibration of ${}^{174}$YbOH using high-resolution optical spectroscopy on the nominally forbidden $\tilde{X} {}^2Σ^+ (010) \rightarrow \tilde{A} {}^2Π_{1/2} (000)$ transition at 588 nm. We assign 39 transitions originating from the lowest rotational levels of the $\tilde{X} {}^2Σ^+ (010)$ state, and accurately model the state's structure with an effective Hamiltonian using best-fit parameters. Additionally, we perform Stark and Zeeman spectroscopy on the $\tilde{X} {}^2Σ^+ (010)$ state and fit the molecule-frame dipole moment to $D_\mathrm{mol}=2.16(1)$ D and the effective electron $g$-factor to $g_S=2.07(2)$. Further, we use an empirical model to explain observed anomalous line intensities in terms of interference from spin-orbit and vibronic perturbations in the excited $\tilde{A} {}^2Π_{1/2} (000)$ state. Our work is an essential step toward searches for BSM physics in YbOH and other linear polyatomic molecules.

physics.atom-ph↗

arXiv2022

High-resolution spectroscopy of buffer-gas-cooled phthalocyanine

For over five decades, studies in the field of chemical physics and physical chemistry have primarily aimed to understand the quantum properties of molecules. However, high-resolution rovibronic spectroscopy has been limited to relatively small and simple systems because translationally and rotationally cold samples have not been prepared in sufficiently large quantities for large and complex systems. In this study, we present high-resolution rovibronic spectroscopy results for large gas-phase molecules, namely, free-base phthalocyanine (FBPc). The findings suggest that buffer-gas cooling may be effective for large molecules introduced via laser ablation. High-resolution electronic spectroscopy, combined with other experimental and theoretical studies, will be useful in understanding the quantum properties of molecules. These findings also serve as a guide for quantum chemical calculations of large molecules.

physics.chem-ph↗

arXiv2022

Measurement of Doppler effects in cryogenic buffer-gas cell

Buffer-gas cooling is a universal cooling technique for molecules and used for various purposes. One of its applications is using molecules inside a buffer-gas cell for low-temperature spectroscopy. Although a high-intensity signal is expected in the cell, complex molecular dynamics is a drawback for precise spectroscopy. In this study, we performed high-resolution absorption spectroscopy of low-J transitions in the $\tilde{A}^2Π(0,0,0)-\tilde{X}^2Σ^+(0,0,0)$ band of calcium monohydroxide (CaOH). CaOH molecules were produced by laser ablation in a copper cell and cooled to $\sim$5\,K using helium buffer gas. We probed the Doppler effects in a buffer-gas cell by injecting counter-propagating lasers inside the cell. The time evolutions of the Doppler width and shift were simulated using a dedicated Monte Carlo simulation and compared with data.

physics.chem-ph↗

arXiv2022

Low-$J$ transitions in $\tilde{A}^2Π(0,0,0)-\tilde{X}^2Σ^+(0,0,0)$ band of buffer-gas-cooled CaOH

Calcium monohydroxide radical (CaOH) is receiving an increasing amount of attention from the astrophysics community as it is expected to be present in the atmospheres of hot rocky super-Earth exoplanets as well as interstellar and circumstellar environments. Here, we report the high-resolution laboratory absorption spectroscopy on low-$J$ transitions in $\tilde{A}^2Π(0,0,0)-\tilde{X}^2Σ^+(0,0,0)$ band of buffer-gas-cooled CaOH. In total, 40 transitions out of the low-$J$ states were assigned, including 27 transitions which have not been reported in previous literature. The determined rotational constants for both ground and excited states are in excellent agreement with previous literature, and the measurement uncertainty for the absolute transition frequencies was improved by more than a factor of three. This will aid future interstellar, circumstellar, and atmospheric identifications of CaOH. The buffer-gas-cooling method employed here is a particularly powerful method to probe low-$J$ transitions and is easily applicable to other astrophysical molecules.

astro-ph.IM↗

arXiv2020

Simulation of Cryogenic Buffer Gas Beams

The cryogenic buffer gas beam (CBGB) is an important tool in the study of cold and ultracold molecules. While there are known techniques to enhance desired beam properties, such as high flux, low velocity, or reduced divergence, they have generally not undergone detailed numerical optimization. Numerical simulation of buffer gas beams is challenging, as the relevant dynamics occur in regions where the density varies by orders of magnitude, rendering standard numerical methods unreliable or intractable. Here, we present a hybrid approach to simulating CBGBs that combines gas dynamics methods with particle tracing. The simulations capture important properties such as velocities and divergence across an assortment of designs, including two-stage slowing cells and de Laval nozzles. This approach should therefore be a useful tool for optimizing CBGB designs across a wide range of applications.

physics.atom-ph↗