We propose a new scalable platform for quantum computing (QC)-an array of optically trapped symmetric-top molecules (STMs) of the alkaline earth monomethoxide (MOCH 3 ) family. Individual STMs form qubits, and the system is readily scalable to 100-1000 qubits. STM qubits have desirable features for QC compared to atoms and diatomic molecules. The additional rotational degree of freedom about the symmetric-top axis gives rise to closely spaced opposite parity K-doublets that allow full alignment at low electric fields, and the hyperfine structure naturally provides magnetically insensitive states with switchable electric dipole moments. These features lead to much reduced requirements for electric field control, provide minimal sensitivity to environmental perturbations, and allow for 2-qubit interactions that can be switched on at will. We examine in detail the internal structure of STMs relevant to our proposed platform, taking into account the full effective molecular Hamiltonian including hyperfine interactions, and identify useable STM qubit states. We then examine the effects of the electric dipolar interaction in STMs, which not only guide the design of high-fidelity gates, but also elucidate the nature of dipolar exchange in STMs. Under realistic experimental parameters, we estimate that the proposed QC platform could yield gate errors at the 10 −3 level, approaching that required for fault-tolerant QC.

Alkaline earth monoalkoxide free radicals (MORs) have molecular properties conducive to direct laser cooling to sub-millikelvin temperatures. Using dispersed laser induced fluorescence measurements from a pulsed supersonic molecular beam source we determine vibrational branching ratios and Franck-Condon factors for the MORs CaOH and CaOCH 3 . With narrow linewidth continuous-wave dye laser excitation, we precisely measure fluorescence branching for both X Ã -˜and X B -˜electronic systems in each molecule. Weak symmetry-forbidden decays to excited bending states with non-zero vibrational angular momentum are observed. Normal mode theoretical analysis combined with ab initio structural calculations are performed and compared to experimental results. Our measurements and analysis pave the way for direct laser cooling of these (and other) complex nonlinear polyatomic molecules. We also describe a possible approach to laser cooling and trapping of molecules with fewer symmetries like chiral species.

Precision measurements of Schiff moments in heavy, deformed nuclei are sensitive probes of beyond standard model T, P violation in the hadronic sector. While the most stringent limits on Schiff moments to date are set with diamagnetic atoms, polar polyatomic molecules can offer higher sensitivities with unique experimental advantages. In particular, symmetric top molecular ions possess K doublets of opposite parity with especially small splittings, leading to full polarization at low fields, internal comagnetometer states useful for rejection of systematic effects, and the ability to perform sensitive searches for T, P violation using a small number of trapped ions containing heavy exotic nuclei. We consider the symmetric top cation 225RaOCH þ 3 as a prototypical and candidate platform for performing sensitive nuclear Schiff measurements and characterize in detail its internal structure using relativistic ab initio methods. The combination of enhancements from a deformed nucleus, large polarizability, and unique molecular structure make this molecule a promising platform to search for fundamental symmetry violation even with a single trapped ion.

We demonstrate the coherent optical bichromatic force on a molecule, the polar free radical strontium monohydroxide (SrOH). A dual-frequency retro-reflected laser beam addressing theX 2 Σ + ↔Ã 2 Π 1/2 electronic transition coherently imparts momentum onto a cryogenic beam of SrOH. This directional photon exchange creates a bichromatic force that transversely deflects the molecules. By adjusting the relative phase between the forward and counter propagating laser beams we reverse the direction of the applied force. A momentum transfer of 70 k is achieved with minimal loss of molecules to dark states. Modeling of the bichromatic force is performed via direct numerical solution of the time-dependent density matrix and is compared with experimental observations. Our results open the door to further coherent manipulation of molecular motion, including the efficient optical deceleration of diatomic and polyatomic molecules with complex level structures.Laser manipulation of atomic motion has revolutionized atomic, molecular and optical (AMO) physics [1,2]. The widely-used techniques of laser cooling and trapping made possible the creation of ultracold degenerate quantum gases [3], simulation of important condensed matter models [4] and development of new quantum sensors [5,6] and clocks [7]. Laser deceleration and cooling of atomic beams -a necessary part of the trap loading process -typically requires scattering tens of thousands of photons in order to bring room (or oven) temperature atoms to velocities where they can be confined by electromagnetic traps for further studies [8]. While beam deceleration employing the spontaneous radiation pressure force has been a standard for atomic experiments, its application to slowing molecular beams has been limited by the small change in kinetic energy per scattered photon and the myriad of internal molecular states, which inhibits photon cycling. At the same time, there is extreme interest in creating ultracold molecules for new physics applications [9].Neutral diatomic molecules are predicted to play an important role in diverse research areas of modern physics such as quantum simulation [10] and computation [11], as well as searches for new particles and fields beyond the Standard Model [12]. Larger polyatomic molecules will provide additional opportunities in physics and chemistry [13][14][15]. For example, exploring the origin of biomolecular homochirality [16] and understanding primordial chemistry leading to the development of organic life requires the use of large molecules [17]. However, these molecules' complexity presents significant challenges for direct laser slowing and cooling. Yet these are the key ingredients that allow for optical trapping, which, in turn, realizes long moleculelaser coherence times and high levels of quantum state control. Previously, the external motion of gas-phase polyatomic molecules has been manipulated with off-resonant laser fields [18] as well as electric [19], magnetic [20], and mechanical techniques [21]. Inspired by the success of...

We report on the experimental realization of ultracold 174 Yb-7 Li (Boson-Boson) and 173 Yb-7 Li (Fermion-Boson) mixtures. They are loaded into three dimensional (3D) or one dimensional (1D) optical lattices that are species-selectively deep for the heavy Ytterbium (Yb) and shallow for the light bosonic Lithium (Li) component, realizing novel mixed dimensional systems. In the 1D optical lattice the band structure of 173 Yb is reconstructed in the presence of 7 Li. Spectroscopic measurements of the 174 Yb-7 Li mixture in the 3D lattice give access to the 174 Yb Mott-insulator structure. Ground state inter-species scattering lengths are determined to be |a bg ( 174 Yb-7 Li)| = (1.11 ± 0.17) nm and |a bg ( 173 Yb-7 Li)| = (1.16 ± 0.18) nm. The formation and characterization of an ultracold 173 Yb-7 Li mixture is a first step towards a possible realization of a topological px + i py superfluid in this system.

Optical control of polyatomic molecules promises new opportunities in precision metrology, fundamental chemistry, quantum information, and many-body science. Contemporary experimental and theoretical efforts have mostly focused on cycling photons via...

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