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Doppler and Sisyphus cooling of 174YbOH are achieved and studied. This polyatomic molecule has high sensitivity to physics beyond the Standard Model and represents a new class of species for future high-precision probes of new T-violating physics. The transverse temperature of the YbOH beam is reduced by nearly two orders of magnitude to < 600 K and the phase-space density is increased by a factor of > 6 via Sisyphus cooling. We develop a full numerical model of the laser cooling of YbOH and find excellent agreement with the data. We project that laser cooling and magneto-optical trapping of long-lived samples of YbOH molecules are within reach and these will allow a high sensitivity probe of the electric dipole moment of the electron. The approach demonstrated here is easily generalized to other isotopologues of YbOH that have enhanced sensitivity to other symmetry-violating electromagnetic moments.

We propose a new scalable platform for quantum computing (QC)-an array of optically trapped symmetric-top molecules (STMs) of the alkaline earth monomethoxide (MOCH3) 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.

Laser cooling and trapping 1 , 2 , and magneto-optical trapping methods in particular 2 , have enabled groundbreaking advances in science, including Bose–Einstein condensation 3 – 5 , quantum computation with neutral atoms 6 , 7 and high-precision optical clocks 8 . Recently, magneto-optical traps (MOTs) of diatomic molecules have been demonstrated 9 – 12 , providing access to research in quantum simulation 13 and searches for physics beyond the standard model 14 . Compared with diatomic molecules, polyatomic molecules have distinct rotational and vibrational degrees of freedom that promise a variety of transformational possibilities. For example, ultracold polyatomic molecules would be uniquely suited to applications in quantum computation and simulation 15 – 17 , ultracold collisions 18 , quantum chemistry 19 and beyond-the-standard-model searches 20 , 21 . However, the complexity of these molecules has so far precluded the realization of MOTs for polyatomic species. Here we demonstrate magneto-optical trapping of a polyatomic molecule, calcium monohydroxide (CaOH). After trapping, the molecules are laser cooled in a blue-detuned optical molasses to a temperature of 110 μK, which is below the Doppler cooling limit. The temperatures and densities achieved here make CaOH a viable candidate for a wide variety of quantum science applications, including quantum simulation and computation using optical tweezer arrays 15 , 17 , 22 , 23 . This work also suggests that laser cooling and magneto-optical trapping of many other polyatomic species 24 – 27 will be both feasible and practical. The polyatomic molecule calcium monohydroxide is magneto-optically trapped and cooled below the Doppler cooling limit, making it a candidate for applications in quantum simulation and computation.

The emission of light by polyatomic molecules in the spectral region of the second near-infrared (NIR(II)) window is severely hampered by the energy gap law, namely the quenching induced by exciton–vibration coupling. As a result, organic light-emitting diodes (OLEDs) with efficient emission wavelengths of ~1,000 nm and above are rare, despite their potential for phototherapy and bioimaging. In this study we revisit the theory of the energy gap law to quantify the contribution of each coupled vibrational mode to non-radiative transitions. The results lead us to propose two approaches that favour emission: molecular packing to extend exciton delocalization, and deuterium substitution to reduce high-frequency vibrations. We provide an experimental proof of concept by designing and synthesizing a new series of self-assembled Pt(II) complexes that exhibit high-intensity phosphorescence with peak quantum yields of (23 ± 0.3)% at approximately 1,000 nm. The corresponding OLEDs emit at a peak wavelength of 995 nm with a maximum external quantum efficiency of 4.31% and a radiance of 1.55 W sr−1 m−2, marking a substantial contribution to the development of efficient OLEDs in the NIR(II) region.A new series of self-assembled Pt(II) complexes with high emission quantum yields enables OLEDs with a maximum emission wavelength of 995 nm and an external quantum efficiency of 4.3%.

Motion picture of a conical intersectionIn most chemical reactions, electrons move earlier and faster than nuclei. It is therefore common to model reactions by using potential energy surfaces that depict nuclear motion in a particular electronic state. However, in certain cases, two such surfaces connect in a conical intersection that mingles ultrafast electronic and nuclear rearrangements. Yang et al. used electron diffraction to obtain time-resolved images of CF3I molecules traversing a conical intersection in the course of photolytic cleavage of the C–I bond (see the Perspective by Fielding).Science, this issue p. 64; see also p. 30Conical intersections play a critical role in excited-state dynamics of polyatomic molecules because they govern the reaction pathways of many nonadiabatic processes. However, ultrafast probes have lacked sufficient spatial resolution to image wave-packet trajectories through these intersections directly. Here, we present the simultaneous experimental characterization of one-photon and two-photon excitation channels in isolated CF3I molecules using ultrafast gas-phase electron diffraction. In the two-photon channel, we have mapped out the real-space trajectories of a coherent nuclear wave packet, which bifurcates onto two potential energy surfaces when passing through a conical intersection. In the one-photon channel, we have resolved excitation of both the umbrella and the breathing vibrational modes in the CF3 fragment in multiple nuclear dimensions. These findings benchmark and validate ab initio nonadiabatic dynamics calculations.

Polyatomic molecules have rich structural features that make them uniquely suited to applications in quantum information science 1 – 3 , quantum simulation 4 – 6 , ultracold chemistry 7 and searches for physics beyond the standard model 8 – 10 . However, a key challenge is fully controlling both the internal quantum state and the motional degrees of freedom of the molecules. Here we demonstrate the creation of an optical tweezer array of individual polyatomic molecules, CaOH, with quantum control of their internal quantum state. The complex quantum structure of CaOH results in a non-trivial dependence of the molecules’ behaviour on the tweezer light wavelength. We control this interaction and directly and non-destructively image individual molecules in the tweezer array with a fidelity greater than 90%. The molecules are manipulated at the single internal quantum state level, thus demonstrating coherent state control in a tweezer array. The platform demonstrated here will enable a variety of experiments using individual polyatomic molecules with arbitrary spatial arrangement. An optical tweezer array of individual polyatomic molecules is created, revealing the obvious state control in the tweezer array and enabling further research on polyatomic molecules with diverse spatial arrangements.

Scattering resonances are an essential tool for controlling the interactions of ultracold atoms and molecules. However, conventional Feshbach scattering resonances 1 , which have been extensively studied in various platforms 1 – 7 , are not expected to exist in most ultracold polar molecules because of the fast loss that occurs when two molecules approach at a close distance 8 – 10 . Here we demonstrate a new type of scattering resonance that is universal for a wide range of polar molecules. The so-called field-linked resonances 11 – 14 occur in the scattering of microwave-dressed molecules because of stable macroscopic tetramer states in the intermolecular potential. We identify two resonances between ultracold ground-state sodium–potassium molecules and use the microwave frequencies and polarizations to tune the inelastic collision rate by three orders of magnitude, from the unitary limit to well below the universal regime. The field-linked resonance provides a tuning knob to independently control the elastic contact interaction and the dipole–dipole interaction, which we observe as a modification in the thermalization rate. Our result provides a general strategy for resonant scattering between ultracold polar molecules, which paves the way for realizing dipolar superfluids 15 and molecular supersolids 16 , as well as assembling ultracold polyatomic molecules. A type of universal scattering resonance between ultracold microwave-dressed polar molecules associated with field-linked tetramer bound states in the long-range potential well is observed, providing a general strategy for resonant scattering between ultracold polar molecules.

Positron binding to molecules is key to extremely enhanced positron annihilation and positron-based molecular spectroscopy 1 . Although positron binding energies have been measured for about 90 polyatomic molecules 1 – 6 , an accurate ab initio theoretical description of positron–molecule binding has remained elusive. Of the molecules studied experimentally, ab initio calculations exist for only six; these calculations agree with experiments on polar molecules to at best 25 per cent accuracy and fail to predict binding in nonpolar molecules. The theoretical challenge stems from the need to accurately describe the strong many-body correlations including polarization of the electron cloud, screening of the electron–positron Coulomb interaction and the unique process of virtual-positronium formation (in which a molecular electron temporarily tunnels to the positron) 1 . Here we develop a many-body theory of positron–molecule interactions that achieves excellent agreement with experiment (to within 1 per cent in cases) and predicts binding in formamide and nucleobases. Our framework quantitatively captures the role of many-body correlations and shows their crucial effect on enhancing binding in polar molecules, enabling binding in nonpolar molecules, and increasing annihilation rates by 2 to 3 orders of magnitude. Our many-body approach can be extended to positron scattering and annihilation γ-ray spectra in molecules and condensed matter, to provide the fundamental insight and predictive capability required to improve materials science diagnostics 7 , 8 , develop antimatter-based technologies (including positron traps, beams and positron emission tomography) 8 – 10 , and understand positrons in the Galaxy 11 . A many-body theory of binding interactions between positrons and polar and nonpolar molecules is developed, showing agreement with experimental data up to within 1%.

The quest for accurate exchange-correlation functionals has long remained a grand challenge in density functional theory (DFT), as it describes the many-electron quantum mechanical behavior through a computationally tractable quantity—the electron density—without resorting to multi-electron wave functions. The inverse DFT problem of mapping the ground-state density to its exchange-correlation potential is instrumental in aiding functional development in DFT. However, the lack of an accurate and systematically convergent approach has left the problem unresolved, heretofore. This work presents a numerically robust and accurate scheme to evaluate the exact exchange-correlation potentials from correlated ab-initio densities. We cast the inverse DFT problem as a constrained optimization problem and employ a finite-element basis—a systematically convergent and complete basis—to discretize the problem. We demonstrate the accuracy and efficacy of our approach for both weakly and strongly correlated molecular systems, including up to 58 electrons, showing relevance to realistic polyatomic molecules. The inverse DFT problem of mapping the ground-state density to its exchange correlation potential has been numerically challenging so far. Here, the authors propose an approach for an accurate solution to the inverse DFT problem, enabling the evaluation of exact exchange and correlation potential from an ab initio density.

We propose a new class of bosonic dark matter (DM) detectors based on resonant absorption onto a gas of small polyatomic molecules. Bosonic DM acts on the molecules as a narrow-band perturbation, like an intense but weakly coupled laser. The excited molecules emit the absorbed energy into fluorescence photons that are picked up by sensitive photodetectors with low dark count rates. This setup is sensitive to any DM candidate that couples to electrons, photons, and nuclei, and may improve on current searches by several orders of magnitude in coupling for DM masses between 0.2 eV and 20 eV. This type of detector has excellent intrinsic energy resolution, along with several control variables—pressure, temperature, external electromagnetic fields, and molecular species or isotopes—that allow for powerful background rejection methods as well as precision studies of a potential DM signal. The proposed experiment does not require usage of novel exotic materials or futuristic technologies, relying instead on the well-established field of molecular spectroscopy and on recent advances in single-photon detection. Cooperative radiation effects, which arise due to the large spatial coherence of the nonrelativistic DM field in certain detector geometries, can tightly focus the DM-induced radiative emission in a direction that depends on the DM’s velocity, possibly permitting a detailed reconstruction of the full 3D velocity distribution in our Galactic neighborhood, as well as further background rejection.