arXiv subjects

Fritz von Gierke

Publications and source records attributed to Fritz von Gierke.

3 recordsLinked to original sources

arXiv2026

Electric-field control of atom-molecule Feshbach resonances

Ultracold molecules provide opportunities for exploring quantum matter, chemical dynamics and information processing thanks to their rich interactions, which can be controlled by external fields. Magnetic fields tune interactions through Feshbach resonances, enabling the formation of ultracold dimers and triatomic molecules from atom-dimer collisions. Here we demonstrate electric-field control of atom-molecule Feshbach resonances. In mixtures of ground-state sodium-potassium molecules and potassium atoms, electric fields shift resonance positions systematically, revealing specific trimer bound states and their electric-field dependent energies. The response differs markedly from isolated dimers, showing hindered rotation of the molecular constituent near an atom. Electric fields therefore add an independent knob for atom-molecule resonances, open spectroscopic access to triatomic quantum states, and advance controlled polyatomic quantum matter.

physics.atom-ph↗

arXiv2026

Hyperfine-resolved optical spectroscopy of ultracold $^{87}$Rb$^{133}$Cs molecules: the $\mathrm{b}\,^3Π_0$ metastable state

Using an ultracold gas of $^{87}$Rb$^{133}$Cs molecules, we perform hyperfine-resolved spectroscopy of transitions from the vibronic ground state to the lowest rovibrational states of the electronic state $\mathrm{b}\,^3Π_0$, as a function of magnetic field. These transitions are spin forbidden, resulting in narrow linewidths, and feature near-diagonal Franck-Condon factors. We develop a model of the hyperfine and Zeeman structure that includes coupling between the $0^+$ and $0^-$ components of $\mathrm{b}\,^3Π_0$. We fit the spectra to obtain rotational and hyperfine coupling constants. We measure transition dipole moments associated with specific transitions by directly observing Rabi oscillations as a function of a resonant laser pulse duration. Using resonant $π$ pulses, we prepare molecules in the electronically excited state and directly measure the spontaneous emission rate.

physics.atom-ph↗

arXiv2025

Long-lived multilevel coherences and spin-1 dynamics encoded in the rotational states of ultracold molecules

Rotational states of ultracold polar molecules possess long radiative lifetimes, microwave-domain coupling, and tunable dipolar interactions. The availability of numerous rotational states has inspired many proposed applications, including simulations of quantum magnetism, encodings of information in high-dimensional qudits, and synthetic dimensions with many synthetic lattice sites. Many of these applications are yet to be realised, primarily because engineering long-lived coherent superpositions of multiple rotational states is highly challenging. Here, we investigate how multilevel coherences between rotational states can be engineered by using optical tweezer traps operating close to a magic wavelength for a given pair of states. By performing precision Ramsey spectroscopy we find the exact magic wavelengths and sensitivities to detuning errors for multiple rotational state superpositions. We find that, for a trap polarised parallel to the quantisation axis, the magic wavelengths are closely clustered enabling long-lived coherence across multiple rotational states simultaneously. As an example, we demonstrate simultaneous second-scale coherence between three rotational states. Utilising this extended coherence, we perform multiparameter estimation using a generalised Ramsey sequence and demonstrate coherent spin-1 dynamics encoded in the rotational states. With modest experimental improvements, we predict that second-scale coherent dynamics of ten rotational states should be readily achievable.

physics.atom-ph↗