@article { WOS:000661896800004,
title = {Efficient Stabilized Two-Qubit Gates on a Trapped-Ion Quantum Computer},
journal = {Phys. Rev. Lett.},
volume = {126},
number = {22},
year = {2021},
month = {JUN 4},
publisher = {AMER PHYSICAL SOC},
type = {Article},
abstract = {In order to scale up quantum processors and achieve a quantum advantage, it is crucial to economize on the power requirement of two-qubit gates, make them robust to drift in experimental parameters, and shorten the gate times. Applicable to all quantum computer architectures whose two-qubit gates rely on phase-space closure, we present here a new gate-optimizing principle according to which negligible amounts of gate fidelity are traded for substantial savings in power, which, in turn, can be traded for substantial increases in gate speed and/or qubit connectivity. As a concrete example, we illustrate the method by constructing optimal pulses for entangling gates on a pair of ions within a trapped-ion chain, one of the leading quantum computing architectures. Our method is direct, noniterative, and linear, and, in some parameter regimes, constructs gate-steering pulses requiring up to an order of magnitude less power than the standard method. Additionally, our method provides increased robustness to mode drift. We verify the new trade-off principle experimentally on our trapped-ion quantum computer.},
issn = {0031-9007},
doi = {10.1103/PhysRevLett.126.220503},
author = {Blumel, Reinhold and Grzesiak, Nikodem and Nguyen, Nhung H. and Green, Alaina M. and Li, Ming and Maksymov, Andrii and Linke, Norbert M. and Nam, Yunseong}
}
@article { WOS:000687394800001,
title = {Relativistic aspects of orbital and magnetic anisotropies in the chemical bonding and structure of lanthanide molecules},
journal = {New J. Phys.},
volume = {23},
number = {8},
year = {2021},
month = {AUG},
publisher = {IOP PUBLISHING LTD},
type = {Article},
abstract = {The electronic structure of magnetic lanthanide atoms is fascinating from a fundamental perspective. They have electrons in a submerged open 4f shell lying beneath a filled 6s shell with strong relativistic correlations leading to a large magnetic moment and large electronic orbital angular momentum. This large angular momentum leads to strong anisotropies, i. e. orientation dependencies, in their mutual interactions. The long-ranged molecular anisotropies are crucial for proposals to use ultracold lanthanide atoms in spin-based quantum computers, the realization of exotic states in correlated matter, and the simulation of orbitronics found in magnetic technologies. Short-ranged interactions and bond formation among these atomic species have thus far not been well characterized. Efficient relativistic computations are required. Here, for the first time we theoretically determine the electronic and ro-vibrational states of heavy homonuclear lanthanide Er-2 and Tm-2 molecules by applying state-of-the-art relativistic methods. In spite of the complexity of their internal structure, we were able to obtain reliable spin-orbit and correlation-induced splittings between the 91 Er-2 and 36 Tm-2 electronic potentials dissociating to two ground-state atoms. A tensor analysis allows us to expand the potentials between the atoms in terms of a sum of seven spin-spin tensor operators simplifying future research. The strengths of the tensor operators as functions of atom separation are presented and relationships among the strengths, derived from the dispersive long-range interactions, are explained. Finally, low-lying spectroscopically relevant ro-vibrational energy levels are computed with coupled-channels calculations and analyzed.},
keywords = {lanthanide molecules, relativistic electronic structure, spin tensor decomposition, ultracold lanthanide atoms},
issn = {1367-2630},
doi = {10.1088/1367-2630/ac1a9a},
author = {Tiesinga, Eite and Klos, Jacek and Li, Ming and Petrov, Alexander and Kotochigova, Svetlana}
}
@article { WOS:000677582200001,
title = {Resource-Optimized Fermionic Local-Hamiltonian Simulation on a Quantum Computer for Quantum Chemistry},
journal = {Quantum},
volume = {5},
year = {2021},
month = {JUL 26},
pages = {1-36},
publisher = {VEREIN FORDERUNG OPEN ACCESS PUBLIZIERENS QUANTENWISSENSCHAF},
type = {Article},
abstract = {The ability to simulate a fermionic system on a quantum computer is expected to revolutionize chemical engineering, materials design, nuclear physics, to name a few. Thus, optimizing the simulation circuits is of significance in harnessing the power of quantum computers. Here, we address this problem in two aspects. In the fault-tolerant regime, we optimize the R-z and T gate counts along with the ancilla qubit counts required, assuming the use of a product-formula algorithm for implementation. We obtain a savings ratio of two in the gate counts and a savings ratio of eleven in the number of ancilla qubits required over the state of the art. In the pre-fault tolerant regime, we optimize the two-qubit gate counts, assuming the use of the variational quantum eigensolver (VQE) approach. Specific to the latter, we present a framework that enables bootstrapping the VQE progression towards the convergence of the ground-state energy of the fermionic system. This framework, based on perturbation theory, is capable of improving the energy estimate at each cycle of the VQE progression, by about a factor of three closer to the known ground-state energy compared to the standard VQE approach in the test-bed, classically-accessible system of the water molecule. The improved energy estimate in turn results in a commensurate level of savings of quantum resources, such as the number of qubits and quantum gates, required to be within a pre-specified tolerance from the known ground-state energy. We also explore a suite of generalized transformations of fermion to qubit operators and show that resource-requirement savings of up to more than 20\%, in small instances, is possible.},
issn = {2521-327X},
author = {Wang, Qingfeng and Li, Ming and Monroe, Christopher and Nam, Yunseong}
}
@article { WOS:000658822200035,
title = {Roaming pathways and survival probability in real-time collisional dynamics of cold and controlled bialkali molecules},
journal = {Sci Rep},
volume = {11},
number = {1},
year = {2021},
month = {MAY 19},
publisher = {NATURE RESEARCH},
type = {Article},
abstract = {Perfectly controlled molecules are at the forefront of the quest to explore chemical reactivity at ultra low temperatures. Here, we investigate for the first time the formation of the long-lived intermediates in the time-dependent scattering of cold bialkali 23Na87Rb molecules with and without the presence of infrared trapping light. During the nearly 50 nanoseconds mean collision time of the intermediate complex, we observe unconventional roaming when for a few tens of picoseconds either NaRb or Na2 and Rb2 molecules with large relative separation are formed before returning to the four-atom complex. We also determine the likelihood of molecular loss when the trapping laser is present during the collision. We find that at a wavelength of 1064 nm the Na2Rb2 complex is quickly destroyed and thus that the 23Na87Rb molecules are rapidly lost.},
issn = {2045-2322},
doi = {10.1038/s41598-021-90004-0},
author = {Klos, Jacek and Guan, Qingze and Li, Hui and Li, Ming and Tiesinga, Eite and Kotochigova, Svetlana}
}
@article { ISI:000568842200012,
title = {Effects of conical intersections on hyperfine quenching of hydroxyl OH in collision with an ultracold Sr atom},
journal = {Sci Rep},
volume = {10},
number = {1},
year = {2020},
month = {AUG 24},
pages = {14130},
publisher = {NATURE PUBLISHING GROUP},
type = {Article},
abstract = {The effect of conical intersections (CIs) on electronic relaxation, transitions from excited states to ground states, is well studied, but their influence on hyperfine quenching in a reactant molecule is not known. Here, we report on ultracold collision dynamics of the hydroxyl free-radical OH with Sr atoms leading to quenching of OH hyperfine states. Our quantum-mechanical calculations of this process reveal that quenching is efficient due to anomalous molecular dynamics in the vicinity of the conical intersection at collinear geometry. We observe wide scattering resonance features in both elastic and inelastic rate coefficients at collision energies below k(B) x 10mK. They are identified as either p- or d-wave shape resonances. We also describe the electronic potentials relevant for these non-reactive collisions, their diabatization procedure, as well as the non-adiabatic coupling between the diabatic potentials near the CIs.},
issn = {2045-2322},
doi = {10.1038/s41598-020-71068-w},
author = {Li, Ming and Klos, Jacek and Petrov, Alexander and Li, Hui and Kotochigova, Svetlana}
}
@article { ISI:000559739800002,
title = {Feshbach Resonances in p-Wave Three-Body Recombination within Fermi-Fermi Mixtures of Open-Shell Li-6 and Closed-Shell Yb-173 Atoms},
journal = {Phys. Rev. X},
volume = {10},
number = {3},
year = {2020},
month = {AUG 14},
pages = {031037},
publisher = {AMER PHYSICAL SOC},
type = {Article},
abstract = {We report on the observation of magnetic Feshbach resonances in a Fermi-Fermi mixture of ultracold atoms with extreme mass imbalance and on their unique p-wave dominated three-body recombination processes. Our systemconsists of open-shell alkali-metal Li-6 and closed-shell Yb-173 atoms, both spin polarized and held at various temperatures between 1 and 20 mu K. We confirmthat Feshbach resonances in this systemare solely the result of a weak separation-dependent hyperfine coupling between the electronic spin of Li-6 and the nuclear spin of Yb-173. Our analysis also shows that three-body recombination rates are controlled by the identical fermion nature of the mixture, even in the presence of s-wave collisions between the two species and with recombination rate coefficients outside the Wigner threshold regime at our lowest temperature. Specifically, a comparison of experimental and theoretical line shapes of the recombination process indicates that the characteristic asymmetric line shape as a function of applied magnetic field and a maximum recombination rate coefficient that is independent of temperature can only be explained by triatomic collisions with nonzero, p-wave total orbital angular momentum. The resonances can be used to form ultracold doublet ground-state molecules and to simulate quantum superfluidity in mass-imbalanced mixtures.},
issn = {2160-3308},
doi = {10.1103/PhysRevX.10.031037},
author = {Green, Alaina and Li, Hui and Toh, Jun Hui See and Tang, Xinxin and McCormick, Katherine C. and Li, Ming and Tiesinga, Eite and Kotochigova, Svetlana and Gupta, Subhadeep}
}
@article {ISI:000464281100001,
title = {Universal Scattering of Ultracold Atoms and Molecules in Optical Potentials},
journal = {Atoms},
volume = {7},
number = {1},
year = {2019},
month = {MAR 15},
pages = {36},
publisher = {MDPI},
type = {Article},
abstract = {Universal collisions describe the reaction of molecules and atoms as dominated by long-range interparticle interactions. Here, we calculate the universal inelastic rate coefficients for a large group of ultracold polar molecules in their lower ro-vibrational states colliding with one of their constituent atoms. The rate coefficients are solely determined by values of the dispersion coefficient and reduced mass of the collisional system. We use the ab initio coupled-cluster linear response method to compute dynamic molecular polarizabilities and obtain the dispersion coefficients for some of the collisional partners and use values from the literature for others. Our polarizability calculations agree well with available experimental measurements. Comparison of our inelastic rate coefficients with results of numerically exact quantum-mechanical calculations leads us to conjecture that collisions with heavier atoms can be expected to be more universal.},
keywords = {chemical reactions, dispersion interaction, dynamic polorizability, ultracold atom-molecule collisions, universal model, van der Waals coefficients},
issn = {2218-2004},
doi = {10.3390/atoms7010036},
author = {Li, Hui and Li, Ming and Makrides, Constantinos and Petrov, Alexander and Kotochigova, Svetlana}
}
@article { ISI:000426845500044,
title = {Fractal universality in near-threshold magnetic lanthanide dimers},
journal = {SCIENCE ADVANCES},
volume = {4},
number = {2},
year = {2018},
month = {FEB},
pages = {UNSP eaap8308},
issn = {2375-2548},
doi = {10.1126/sciadv.aap8308},
author = {Makrides, Constantinos and Li, Ming and Tiesinga, Eite and Kotochigova, Svetlana}
}
@article { ISI:000433905200011,
title = {Orbital quantum magnetism in spin dynamics of strongly interacting magnetic lanthanide atoms},
journal = {PHYSICAL REVIEW A},
volume = {97},
number = {5},
year = {2018},
month = {MAY 31},
pages = {053627},
issn = {2469-9926},
doi = {10.1103/PhysRevA.97.053627},
author = {Li, Ming and Tiesinga, Eite and Kotochigova, Svetlana}
}