arXiv subjects

Ke-Lin Gao

Publications and source records attributed to Ke-Lin Gao.

8 recordsLinked to original sources

arXiv2024

Direct Extraction of Nuclear Structure Information Using Precision Lithium-Ion Spectroscopy

Accurately describing nuclear interactions within atomic nuclei remains a challenge, which hinders our exploration of new physics beyond the Standard Model. However, these nuclear interactions can be characterized by nuclear parameters such as the Zemach radius and the electric quadrupole moment, which are reflected in atomic spectra. Our work has achieved high-precision measurements of lithium ion hyperfine splittings at the level of $10$~kHz, and directly extracted these important nuclear structure parameters. We observed significant discrepancies between our results and both nuclear theory and molecular spectra regarding the electric quadrupole moment. The result for $^7$Li deviated by $2.3\sigma$ from the currently recommended value, whereas the result for $^6$Li deviated by up to $6.2\sigma$ from the recommended value determined by molecular spectroscopy. These discrepancies motivated us to conduct independent calculations based on nuclear structure theory, which provided support for the results obtained from ion spectroscopy. Our results provide valuable information for characterizing nuclear forces, serve as sensitive benchmarks for testing nuclear structure theories, and enable critical comparisons with both electron-nuclear scattering and molecular spectroscopy.

physics.atom-ph↗

arXiv2021

Probing Multiple Electric Dipole Forbidden Optical Transitions in Highly Charged Nickel Ions

Highly charged ions (HCIs) are promising candidates for the next generation of atomic clocks, owing to their tightly bound electron cloud, which significantly suppresses the common environmental disturbances to the quantum oscillator. Here we propose and pursue an experimental strategy that, while focusing on various HCIs of a single atomic element, keeps the number of candidate clock transitions as large as possible. Following this strategy, we identify four adjacent charge states of nickel HCIs that offer as many as six optical transitions. Experimentally, we demonstrated the essential capability of producing these ions in the low-energy compact Shanghai-Wuhan Electron Beam Ion Trap. We measured the wavelengths of four magnetic-dipole ($M$1) and one electric-quadrupole ($E$2) clock transitions with an accuracy of several ppm with a novel calibration method; two of these lines were observed and characterized for the first time in controlled laboratory settings. Compared to the earlier determinations, our measurements improved wavelength accuracy by an order of magnitude. Such measurements are crucial for constraining the range of laser wavelengths for finding the "needle in a haystack" narrow lines. In addition, we calculated frequencies and quality factors, evaluated sensitivity of these six transitions to the hypothetical variation of the electromagnetic fine structure constant $α$ needed for fundamental physics applications. We argue that all the six transitions in nickel HCIs offer intrinsic immunity to all common perturbations of quantum oscillators, and one of them has the projected fractional frequency uncertainty down to the remarkable level of 10$^{-19}$.

physics.atom-ph↗

arXiv2020

Precision calculation of hyperfine structure and the Zemach radii of $^{6,7}$Li$^+$ ions

The hyperfine structures of the $2\,^3\!S_1$ states of the $^6$Li$^+$ and $^7$Li$^+$ ions are investigated theoretically to extract the Zemach radii of the $^6$Li and $^7$Li nuclei by comparing with precision measurements. The obtained Zemach radii are larger than the previous values of Puchalski and Pachucki [\href{https://link.aps.org/doi/10.1103/PhysRevLett.111.243001}{Phys. Rev. Lett. {\bf 111}, 243001 (2013)}] and disagree with them by about 1.5 and 2.2 standard deviations for $^6$Li and $^7$Li, respectively. Furthermore, our Zemach radius of $^6$Li differs significantly from the nuclear physics value, derived from the nuclear charge and magnetic radii [\href{https://link.aps.org/doi/10.1103/PhysRevA.78.012513}{Phys. Rev. A {\bf 78}, 012513 (2008)}], by more than 6 sigma, indicating an anomalous nuclear structure for $^6$Li. The conclusion that the Zemach radius of $^7$Li is about 40\% larger than that of $^6$Li is confirmed. The obtained Zemach radii are used to calculate the hyperfine splittings of the $2\,^3\!P_J$ states of $^{6,7}$Li$^+$, where an order of magnitude improvement over the previous theory has been achieved for $^7$Li$^+$.

physics.atom-ph↗

arXiv2009

Test of Quantum Effects of Spatial Noncommutativity using Modified Electron Momentum Spectroscopy

The possibility of testing spatial noncommutativity by current experiments on normal quantum scales is investigated. For the case of both position-position and momentum-momentum noncommuting spectra of ions in crossed electric and magnetic fields are studied in the formalism of noncommutative quantum mechanics. In a limit of the kinetic energy approaching its lowest eigenvalue this system possesses non-trivial dynamics. Signals of spatial noncommutativity in the angular momentum are revealed. They are within limits of the measurable accuracy of current experiments. An experimental test of the predictions using a modified electron momentum spectrum is suggested. The related experimental sensitivity and subtle points are discussed. The results are the first step on a realizable way towards a conclusive test of spatial noncommutativity.

quant-ph↗

arXiv2004

Coherent manipulation of motional states of trapped ions

The beam splitter and phase shifter, which are the key elements in the experiments of light interference, are realized in the motion of trapped ions. Some applications, such as the creation of quantum motional states and the realization of Mach-Zehnder interferometer, are illustrated. Several detection methods of motional states used in the interferometer are also discussed.

quant-ph↗

arXiv2004

Two-Mode Squeezed States and Their Superposition in the Motion of Two Trapped Ions

We propose a method to create two-mode squeezed states and their superposition in the center-of-mass mode and breathing mode of two-trapped ions. Each ion is illuminated simultaneously by two standing waves. One of the fields is tuned to excite resonantly and simultaneously both upper sidebands of the two normal modes, while the other field tuned to the corresponding lower sidebands.

quant-ph↗

arXiv2001

Jaynes-Cummings Model Dynamics in Two Trapped Ions

We showed that in Lamb-Dicke regime and under rotating wave approximation, the dynamical behavior of two trapped ions interacting with a laser beam resonant to the first red side-band of center-of-mass mode can be described by Jaynes-Cummings Model. An exact analytic solution for this kind of Jaynes-Cummings model is presented. The results showed that quantum collapses and revivals for the occupation of two atoms, and squeezing for vibratic motion of center-of-mass mode existed in both two different types of initial conditions. The maximum momentum squeezing for center-of-mass mode in these two types of conditions are found to be 42.4% and 43.8% respectively. The coherence, in the first type of initial conditions can keeps long times, and in the second type of initial conditions, a concrete form of coherent state is obtained, when the initial average number is very small.

quant-ph↗

arXiv2000

Quantum-State Engineering of Multiple Trapped Ions for Center-of-Mass Mode

We propose a scheme to generate a superposition with arbitrary coefficients on a line in phase space for the center-of-mass vibrational mode of N ions by means of isolating all other spectator vibrational modes from the center-of-mass mode. It can be viewed as the generation of previous methods for preparing motional states of one ion. For large number of ions, we need only one cyclic operatin to generate such a superposition of many coherent states.

quant-ph↗