Experimental study of magnetically insensitive transitions in ultracold Fermi gas of $^{40}$K

TL;DR

This study experimentally identifies microwave hyperfine transitions in ultracold $^{40}$K Fermi gases that are insensitive to magnetic field fluctuations, enabling stable quantum coherence for potential quantum information and precision measurement applications.

Contribution

It reports the discovery of specific magnetic-field-insensitive microwave transitions in ultracold $^{40}$K, demonstrating their stability and potential for quantum technologies.

Findings

Two sets of hyperfine transitions are insensitive to low magnetic fields.

Long coherence times are achieved under magnetic field fluctuations.

Transitions show promise for quantum information and precision measurement.

Abstract

This paper presents an experimental study of microwave single-photon transitions that are magnetic-field-insensitive in degenerate Fermi gases of $^{40}$K. This contrasts with microwave single-photon clock transitions for 0-0 magnetic-field-insensitive states and two-photon clock transitions for non 0-0 magnetic-field-insensitive states in bosonic alkali metal atoms. We show that there are two sets of special transitions between two different hyperfine ground states ($|F$=9/2, $m_{F}$=1/2$\rangle$ $\Leftrightarrow$ $|$7/2, -1/2$\rangle$ and $|$9/2, -1/2$\rangle$ $\Leftrightarrow$ $|$7/2, 1/2$\rangle$), whose microwave single-photon transition frequency is insensitive to low magnetic fields, as the first-order Zeeman shift is almost completely canceled. By using the microwave spectrum and Ramsey interference fringes, we demonstrate the long-time stability of the coherent transition under magnetic field fluctuations. These magnetic-field-insensitive microwave hyperfine transitions in ultracold $^{40}$K Fermi gases offer promising applications in quantum information and precision measurements.