Controlling the ac Stark effect of RbCs with dc electric and magnetic fields

Abstract

We investigate the effects of static electric and magnetic fields on the differential ac Stark shifts for microwave transitions in ultracold bosonic 87 Rb 133 Cs molecules, for light of wavelength λ = 1064 nm. Near this wavelength we observe unexpected two-photon transitions that may cause trap loss. We measure the ac Stark effect in external magnetic and electric fields, using microwave spectroscopy of the first rotational transition. We quantify the isotropic and anisotropic parts of the molecular polarizability at this wavelength. We demonstrate that a modest electric field can decouple the nuclear spins from the rotational angular momentum, greatly simplifying the ac Stark effect. We use this simplification to control the ac Stark shift using the polarization angle of the trapping laser.

Coherent manipulation of the internal state of ultracold 87Rb133Cs molecules with multiple microwave fields

“…For a quantum memory to be effective, long-lived coherence is required. These states are well suited for this, as molecules stored in these states experience the same polarisability, leading to the possibility of long coherence times in optical traps [60,79,80]. In contrast, for qubits constructed from two different rotational states, differential ac Stark shifts arising from the anisotropy of the polarisability are typically the primary cause of decoherence for optically trapped molecules [81][82][83].…”

“…This sequence of microwave transfer and trap recapture is then repeated until the molecules occupy the desired rotational state. For each recapture, we tune the intensity of the trap to maintain the same trap parameters, compensating for the difference in polarisability between the different rotational states [79,80]. For a typical transfer, the dipole trap is switched off for < 500 µs, which is short enough that we do not observe significant molecule losses associated with the switching; the trap frequencies in the trap are (ω x , ω y , ω z )/(2π) = (28,113,111) Hz.…”

Anisotropic Polarizability of Ultracold Ground-state $^{23}$Na$^{87}$Rb Molecules

“…Applying a moderate electric field or a stronger magnetic field will help to decouple the hyperfine levels and suppress the hyperpolarizability effect. In future studies, these improvements should lead to an even longer coherence time [35,36].…”

“…By setting the angle between the trap laser polarization and the quantization axis defined by the magnetic field to the "magic" angle [32], the ac polarizabilities between the excited and ground rotational state can be tuned to be the same. In several UPM species, this method has been proven to be able to extend the rotational coherence time significantly [33][34][35].…”