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.…”

Robust storage qubits in ultracold polar molecules

“…To begin, we seek to identify pairs of nuclear spin states with identical magnetic moments that connect to a common excited rotational state, by calculating the rotational and hyperfine structure of the RbCs molecule in externally applied magnetic and optical fields [1,2,6,31]. We construct the Hamiltonian (see Methods) in a fully uncoupled basis set |N, M N |i Rb , m Rb |i Cs , m Cs , where N represents the angular momentum of the molecule with its projection along the quantisation axis M N , and i Rb = 3/2, i Cs = 7/2 denote the nuclear spins of Rb and Cs respectively, with their projections m Rb , m Cs .…”

Rotational Coherence Times of Polar Molecules in Optical Tweezers

“…The environment of the molecule can induce decoherence from sources such as fluctuating electric fields, magnetic fields, and inhomogeneous differential light shifts from the optical tweezer light [31,32]. To date, all previous studies of molecular coherence times have been done in a bulk gas or lat-tices [33][34][35][36][37][38]. In those works, the coherence times were limited below 10 ms by inhomogeneous broadening from the trapping light or density dependent dipolar scattering.…”