The magic in molecules

Eunmi Chae

Diatomic polar molecules are one of the most promising platforms of quantum computing due to their rich internal states and large electric dipole moments. Here, we propose entangling rotational states of MgF molecules in an optical tweezer array via strong electric dipole-dipole interactions. We employ two rotational states with the projection quantum number of the total angular momentum MF = 0 to maximize the dipole-dipole interaction with a given separation distance. The splitting of 1.27 kHz between two entangled states is predicted for MgF molecules separated by 1 μm. The resolution of the entangled states can be achieved in a magic optical potential where the rotational states have the same trap frequencies. The magic potential can be formed by tuning the angle between the molecules' quantization axis and the linear polarization of trapping light to a "magic angle". We calculate the magic angle for MgF molecules under reasonable experimental conditions and obtain that the trap frequencies of the two involved states can be matched within a few 10s of Hz. By establishing an entanglement scheme for the molecules, our results provide a first step towards quantum computing using MgF molecules.

Jeffrey Huw Williams

Masatoshi Kajita

The laser cooling and trapping of molecules have recently been achieved. In this paper, the possibility of precisely measuring the vibrational transition frequencies of optically trapped 40Ca19F molecules is discussed. The quadratic Stark shift induced by the trap laser is eliminated using the trap laser frequencies where the Stark energy shifts at upper and lower states are equal (magic frequencies). At one value of the magic frequency, molecules are trapped at the positions where the power density is minimum, therefore, the measurement is not sensitive to the detuning of the trap laser frequency from the magic frequency. Measurement with an uncertainty of 10−17 appears to be possible using the \((v,N,J,F,M) = (0,0,1/2,1, \pm 1) \to (1,0,1/2,1, \pm 1)\) transition frequency.

Jeffrey Huw Williams

Alexander Prehn, Martin Ibrügger, Gerhard Rempe +1 more

Rapid progress in cooling and trapping of molecules has enabled first experiments on high-resolution spectroscopy of trapped diatomic molecules, promising unprecedented precision. Extending this work to polyatomic molecules provides unique opportunities due to more complex geometries and additional internal degrees of freedom. Here, this is achieved by combining a homogeneous-field microstructured electric trap, rotational transitions with minimal Stark broadening at a"magic" offset electric field, and optoelectrical Sisyphus cooling of molecules to the low millikelvin temperature regime. We thereby reduce Stark broadening on the J=5←4 (K=3) transition of formaldehyde at 364 GHz to well below 1 kHz, observe Doppler-limited linewidths down to 3.8 kHz, and determine the magic-field line position with an uncertainty below 100 Hz. Our approach opens a multitude of possibilities for investigating diverse polyatomic molecule species.