$Λ$ -Enhanced Gray Molasses Cooling of $^{85}$ Rb Atoms in Tweezers Using the D $_2$ Line$Λ$-Enhanced Gray Molasses Cooling of $^{85}$Rb Atoms in Tweezers Using the D$_2$ Line

Deon Janse van Rensburg, Rogier Venderbosch, Yuri van der Werf +5 more

We demonstrate the implementation of $Λ$ -enhanced gray molasses cooling on the D $_2$ line of $^{85}$ Rb atoms in an optical tweezer array. This technique yields lower atomic temperatures of 4.0(2) $μ$ K compared to red-detuned polarization gradient cooling, and consequently extends the $T_2^*$ coherence time of the hyperfine clock qubit by a factor of 1.5. The method is alignment-free and can be readily implemented on laser beams used for magneto-optical trapping, as it only requires frequency and phase modulation control. Our experimental observations are corroborated by a numerical model based on a semi-classical force approach extended to a four-level system, including two hyperfine states of the upper manifold that are 120 MHz apart.We demonstrate the implementation of $Λ$-enhanced gray molasses cooling on the D$_2$ line of $^{85}$Rb atoms in an optical tweezer array. This technique yields lower atomic temperatures of 4.0(2) $μ$K compared to red-detuned polarization gradient cooling, and consequently extends the $T_2^*$ coherence time of the hyperfine clock qubit by a factor of 1.5. The method is alignment-free and can be readily implemented on laser beams used for magneto-optical trapping, as it only requires frequency and phase modulation control. Our experimental observations are corroborated by a numerical model based on a semi-classical force approach extended to a four-level system, including two hyperfine states of the upper manifold that are 120 MHz apart.

physics.atom-phCross-listedarXiv:2512.17653Physical Review ADec 22, 20250 citations

Λ

-Enhanced Gray Molasses Cooling of

^{85}

Rb Atoms in Tweezers Using the D

_2

Line

We demonstrate the implementation of

Λ

-enhanced gray molasses cooling on the D

_2

line of

^{85}

Rb atoms in an optical tweezer array. This technique yields lower atomic temperatures of 4.0(2)

μ

K compared to red-detuned polarization gradient cooling, and consequently extends the

T_2^*

coherence time of the hyperfine clock qubit by a factor of 1.5. The method is alignment-free and can be readily implemented on laser beams used for magneto-optical trapping, as it only requires frequency and phase modulation control. Our experimental observations are corroborated by a numerical model based on a semi-classical force approach extended to a four-level system, including two hyperfine states of the upper manifold that are 120 MHz apart.