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QMCPACK : an open source ab initio quantum Monte Carlo package for the electronic structure of atoms, molecules and solids

Journal of Physics. Condensed Matter

Kim, Jeongnim; Baczewski, Andrew D.; Beaudet, Todd D.; Benali, Anouar; Bennett, Michael; Berrill, Mark A.; Blunt, Nick S.; Casula, Michele; Ceperley, David M.; Chiesa, Simone; Clark, Bryan K.; Clay III, Raymond C.; Delaney, Kris T.; Dewing, Mark; Esler, Kenneth P.; Hao, Hongxia; Hein, Olle; Kent, Paul R.C.; Krogel, Jaron T.; Kylanpaa, Ilkka; Li, Ying W.; Lopez, M.G.; Luo, Ye; Martin, Richard M.; Mathuriya, Amrita; Mcminis, Jeremy; Melton, Cody A.; Mitas, Lubos; Neuscamman, Eric; Parker, William D.; Pineda Flores, Sergio D.; Romero, Nichols A.; Rubenstein, Brenda M.; Shea, Jacqueline A.R.; Shin, Hyeondeok; Shulenburger, Luke N.; Tillack, Andreas F.; Townsend, Joshua P.; Tubman, Norm M.; Van Der Goetz, Brett; Vincent, Jordan E.; Yang, Yubo; Zhang, Shuai; Morales, Miguel A.; Zhao, Luning

QMCPACK is an open source quantum Monte Carlo package for ab-initio electronic structure calculations. It supports calculations of metallic and insulating solids, molecules, atoms, and some model Hamiltonians. Implemented real space quantum Monte Carlo algorithms include variational, diffusion, and reptation Monte Carlo. QMCPACK uses Slater-Jastrow type trial wave functions in conjunction with a sophisticated optimizer capable of optimizing tens of thousands of parameters. The orbital space auxiliary field quantum Monte Carlo method is also implemented, enabling cross validation between different highly accurate methods. The code is specifically optimized for calculations with large numbers of electrons on the latest high performance computing architectures, including multicore central processing unit (CPU) and graphical processing unit (GPU) systems. We detail the program’s capabilities, outline its structure, and give examples of its use in current research calculations. The package is available at http://www.qmcpack.org.

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TYPE Journal Article YEAR 2018
DOIOSTI

Advanced Electronic Structure Calculations For Nanoelectronics Using Finite Element Bases and Effective Mass Theory

Springer Series in Materials Science series Computational Materials, Chemistry, and Biochemistry: From Bold Initiatives to the Last Mile

Foulk, James W.; Nielsen, Erik N.; Baczewski, Andrew D.; Moussa, J.E.; Gao, Xujiao; Salinger, Andrew G.; Muller, Richard P.

This paper describes our work over the past few years to use tools from quantum chemistry to describe electronic structure of nanoelectronic devices. These devices, dubbed "artificial atoms", comprise a few electrons, con ned by semiconductor heterostructures, impurities, and patterned electrodes, and are of intense interest due to potential applications in quantum information processing, quantum sensing, and extreme-scale classical logic. We detail two approaches we have employed: nite-element and Gaussian basis sets, exploring the interesting complications that arise when techniques that were intended to apply to atomic systems are instead used for artificial, solid-state devices.

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TYPE Journal Article YEAR 2017
OSTI

Probing low noise at the MOS interface with a spin-orbit qubit

arXiv.org

Jock, Ryan M.; Jacobson, Noah T.; Harvey-Collard, Patrick; Mounce, Andrew M.; Srinivasa, Vanita; Ward, Daniel R.; Anderson, John M.; Manginell, Ronald; Wendt, Joel R.; Rudolph, Martin; Pluym, Tammy; Foulk, James W.; Baczewski, Andrew D.; Witzel, Wayne M.; Carroll, M.S.

The silicon metal-oxide-semiconductor (MOS) material system is technologically important for the implementation of electron spin-based quantum information technologies. Researchers predict the need for an integrated platform in order to implement useful computation, and decades of advancements in silicon microelectronics fabrication lends itself to this challenge. However, fundamental concerns have been raised about the MOS interface (e.g. trap noise, variations in electron g-factor and practical implementation of multi-QDs). Furthermore, two-axis control of silicon qubits has, to date, required the integration of non-ideal components (e.g. microwave strip-lines, micro-magnets, triple quantum dots, or introduction of donor atoms). In this paper, we introduce a spin-orbit (SO) driven singlet- triplet (ST) qubit in silicon, demonstrating all-electrical two-axis control that requires no additional integrated elements and exhibits charge noise properties equivalent to other more model, but less commercially mature, semiconductor systems. We demonstrate the ability to tune an intrinsic spin-orbit interface effect, which is consistent with Rashba and Dresselhaus contributions that are remarkably strong for a low spin-orbit material such as silicon. The qubit maintains the advantages of using isotopically enriched silicon for producing a quiet magnetic environment, measuring spin dephasing times of 1.6 μs using 99.95% 28Si epitaxy for the qubit, comparable to results from other isotopically enhanced silicon ST qubit systems. This work, therefore, demonstrates that the interface inherently provides properties for two-axis control, and the technologically important MOS interface does not add additional detrimental qubit noise. isotopically enhanced silicon ST qubit systems

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TYPE Journal Article YEAR 2017
OSTI

Valley splitting of single-electron Si MOS quantum dots

Applied Physics Letters

Foulk, James W.; Harvey-Collard, Patrick; Jacobson, Noah T.; Baczewski, Andrew D.; Nielsen, Erik N.; Maurer, Leon; Montano, Ines; Rudolph, Martin; Carroll, M.S.; Yang, C.H.; Rossi, A.; Dzurak, A.S.; Muller, Richard P.

Silicon-based metal-oxide-semiconductor quantum dots are prominent candidates for high-fidelity, manufacturable qubits. Due to silicon's band structure, additional low-energy states persist in these devices, presenting both challenges and opportunities. Although the physics governing these valley states has been the subject of intense study, quantitative agreement between experiment and theory remains elusive. Here, we present data from an experiment probing the valley states of quantum dot devices and develop a theory that is in quantitative agreement with both this and a recently reported experiment. Through sampling millions of realistic cases of interface roughness, our method provides evidence that the valley physics between the two samples is essentially the same.

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TYPE Journal Article YEAR 2016
DOIOSTIScopus
Results 151–200 of 243
Results 151–200 of 243