Matthew D. Frye

Bio: Matthew D. Frye is an academic researcher from Durham University. The author has contributed to research in topics: Physics & Scattering. The author has an hindex of 12, co-authored 34 publications receiving 432 citations.

Sticky collisions of ultracold RbCs molecules.

Abstract: Understanding and controlling collisions is crucial to the burgeoning field of ultracold molecules. All experiments so far have observed fast loss of molecules from the trap. However, the dominant mechanism for collisional loss is not well understood when there are no allowed 2-body loss processes. Here we experimentally investigate collisional losses of nonreactive ultracold 87Rb133Cs molecules, and compare our findings with the sticky collision hypothesis that pairs of molecules form long-lived collision complexes. We demonstrate that loss of molecules occupying their rotational and hyperfine ground state is best described by second-order rate equations, consistent with the expectation for complex-mediated collisions, but that the rate is lower than the limit of universal loss. The loss is insensitive to magnetic field but increases for excited rotational states. We demonstrate that dipolar effects lead to significantly faster loss for an incoherent mixture of rotational states.

Modeling sympathetic cooling of molecules by ultracold atoms.

Abstract: We model sympathetic cooling of ground-state CaF molecules by ultracold Li and Rb atoms. The molecules are moving in a microwave trap, while the atoms are trapped magnetically. We calculate the differential elastic cross sections for CaF-Li and CaF-Rb collisions, using model Lennard-Jones potentials adjusted to give typical values for the s-wave scattering length. Together with trajectory calculations, these differential cross sections are used to simulate the cooling of the molecules, the heating of the atoms, and the loss of atoms from the trap. We show that a hard-sphere collision model based on an energy-dependent momentum transport cross section accurately predicts the molecule cooling rate but underestimates the rates of atom heating and loss. Our simulations suggest that Rb is a more effective coolant than Li for ground-state molecules, and that the cooling dynamics is less sensitive to the exact value of the s-wave scattering length when Rb is used. Using realistic experimental parameters, we find that molecules can be sympathetically cooled to 100μK in about 10 s. By applying evaporative cooling to the atoms, the cooling rate can be increased and the final temperature of the molecules can be reduced to 1 μK within 30 s.

Robust entangling gate for polar molecules using magnetic and microwave fields.

Abstract: Polar molecules are an emerging platform for quantum technologies based on their long-range electric dipole–dipole interactions, which open new possibilities for quantum information processing and the quantum simulation of strongly correlated systems. Here, we use magnetic and microwave fields to design a fast entangling gate with >0.999 fidelity and which is robust with respect to fluctuations in the trapping and control fields and to small thermal excitations. These results establish the feasibility to build a scalable quantum processor with a broad range of molecular species in optical-lattice and optical-tweezers setups.

Two-photon photoassociation spectroscopy of CsYb: Ground-state interaction potential and interspecies scattering lengths

Abstract: We perform two-photon photoassociation spectroscopy of the heteronuclear CsYb molecule to measure the binding energies of near-threshold vibrational levels of the $X{\phantom{\rule{3.33333pt}{0ex}}}^{2}{\mathrm{\ensuremath{\Sigma}}}_{1/2}^{+}$ molecular ground state. We report results for $^{133}\mathrm{Cs}^{170}\mathrm{Yb}$, $^{133}\mathrm{Cs}^{173}\mathrm{Yb}$, and $^{133}\mathrm{Cs}^{174}\mathrm{Yb}$, in each case determining the energy of several vibrational levels including the least-bound state. We fit an interaction potential based on electronic structure calculations to the binding energies for all three isotopologs and find that the ground-state potential supports 77 vibrational levels. We use the fitted potential to predict the interspecies $s$-wave scattering lengths for all seven Cs+Yb isotopic mixtures.

Production of ultracold Cs∗Yb molecules by photoassociation

Abstract: We report the production of ultracold heteronuclear ${\mathrm{Cs}}^{*}\mathrm{Yb}$ molecules through one-photon photoassociation applied to an ultracold atomic mixture of Cs and Yb confined in an optical dipole trap. We use trap-loss spectroscopy to detect molecular states below the $\mathrm{Cs}\phantom{\rule{0.16em}{0ex}}(^{2}P_{1/2})+\mathrm{Yb}(^{1}S_{0})$ asymptote. For $^{133}\mathrm{Cs}\phantom{\rule{0.16em}{0ex}}^{174}\mathrm{Yb}$, we observe 13 rovibrational states with binding energies up to $\ensuremath{\sim}500\phantom{\rule{0.28em}{0ex}}\mathrm{GHz}$. For each rovibrational state we observe two resonances associated with the Cs hyperfine structure and show that the hyperfine splitting in the diatomic molecule decreases for more deeply bound states. In addition, we produce ultracold fermionic $^{133}\mathrm{Cs}\phantom{\rule{0.16em}{0ex}}^{173}\mathrm{Yb}$ and bosonic $^{133}\mathrm{Cs}\phantom{\rule{0.16em}{0ex}}^{172}\mathrm{Yb}$ and $^{133}\mathrm{Cs}\phantom{\rule{0.16em}{0ex}}^{170}\mathrm{Yb}$ molecules. From mass scaling, we determine the number of vibrational levels supported by the 2(1/2) excited-state potential to be 154 or 155.

Condensation of Pairs of Fermionic Atoms Near a Feshbach Resonance

Abstract: We have observed Bose-Einstein condensation of pairs of fermionic atoms in an ultracold 6Li gas at magnetic fields above a Feshbach resonance, where no stable 6Li2 molecules would exist in vacuum. We accurately determined the position of the resonance to be 822+/-3 G. Molecular Bose-Einstein condensates were detected after a fast magnetic field ramp, which transferred pairs of atoms at close distances into bound molecules. Condensate fractions as high as 80% were obtained. The large condensate fractions are interpreted in terms of preexisting molecules which are quasistable even above the two-body Feshbach resonance due to the presence of the degenerate Fermi gas.

Collective excitation of two individual atoms in the Rydberg blockade regime

Abstract: When two single Rydberg atoms—those with electrons in highly excited states—interact, one can be used to control the quantum state of the other. Two independent experiments demonstrate such ‘Rydberg blockade’, an effect that might make long-range quantum gates between neutral atoms possible.

Molecules cooled below the Doppler limit

Abstract: Magneto-optical trapping and sub-Doppler cooling of atoms has been instrumental for research in ultracold atomic physics. This regime has now been reached for a molecular species, CaF. Magneto-optical trapping and sub-Doppler cooling have been essential to most experiments with quantum degenerate gases, optical lattices, atomic fountains and many other applications. A broad set of new applications await ultracold molecules1, and the extension of laser cooling to molecules has begun2,3,4,5,6. A magneto-optical trap (MOT) has been demonstrated for a single molecular species, SrF7,8,9, but the sub-Doppler temperatures required for many applications have not yet been reached. Here we demonstrate a MOT of a second species, CaF, and we show how to cool these molecules to 50 μK, well below the Doppler limit, using a three-dimensional optical molasses. These ultracold molecules could be loaded into optical tweezers to trap arbitrary arrays10 for quantum simulation11, launched into a molecular fountain12,13 for testing fundamental physics14,15,16,17,18, and used to study collisions and chemistry19 between atoms and molecules at ultracold temperatures.

Advances in Atomic, Molecular, and Optical Physics

Abstract: This book contains information on atomic, molecular and optical physics. Topics covered include: muon-catalyzed fusion and cooperative effects in atomic physics.

Observation of an Efimov spectrum in an atomic system

Abstract: In 1970, Vitaly Efimov predicted that three interacting particles can form an infinite series of bound trimer states, even when none of the two-particle subsystems is stable. Experimental evidence for such an exotic state was obtained in 2006, but now an Efimov spectrum, containing two such states with the predicted scaling between them, has been observed.