A5028440699- Physics of Superconductivity and Magnetism
- Quantum many-body systems
- Quantum and electron transport phenomena
- Cold Atom Physics and Bose-Einstein Condensates
- Theoretical and Computational Physics
- Quantum Computing Algorithms and Architecture
- Quantum, superfluid, helium dynamics
- Advanced Condensed Matter Physics
- Quantum Information and Cryptography
- Topological Materials and Phenomena
- Advanced Chemical Physics Studies
- Quantum Mechanics and Applications
- Atomic and Subatomic Physics Research
- Distributed and Parallel Computing Systems
- Magnetic and transport properties of perovskites and related materials
- Machine Learning in Materials Science
- Spectroscopy and Quantum Chemical Studies
- Scientific Computing and Data Management
- Graphene research and applications
- Advanced Thermodynamics and Statistical Mechanics
- Quantum Chromodynamics and Particle Interactions
- Parallel Computing and Optimization Techniques
- Complex Network Analysis Techniques
- Electronic and Structural Properties of Oxides
- Strong Light-Matter Interactions
Microsoft (United States)
2016-2024
ETH Zurich
2013-2023
Pacific Northwest National Laboratory
2023
Microsoft (Switzerland)
2016-2023
Microsoft (Norway)
2021-2023
Technical University of Munich
2023
Quantum Group (United States)
2020
University of Oxford
2017
Microsoft Research (United Kingdom)
2016-2017
Board of the Swiss Federal Institutes of Technology
2005-2016
The challenge posed by the many-body problem in quantum physics originates from difficulty of describing non-trivial correlations encoded exponential complexity wave function. Here we demonstrate that systematic machine learning function can reduce this to a tractable computational form, for some notable cases physical interest. We introduce variational representation states based on artificial neural networks with variable number hidden neurons. A reinforcement-learning scheme is then...
Quantum impurity models describe an atom or molecule embedded in a host material with which it can exchange electrons. They are basic to nanoscience as representations of quantum dots and molecular conductors play increasingly important role the theory ``correlated electron'' materials auxiliary problems whose solution gives ``dynamical mean-field'' approximation self-energy local correlation functions. These applications require method provides access both high low energy scales is...
Quantum Monte Carlo simulations, while being efficient for bosons, suffer from the "negative sign problem'' when applied to fermions - causing an exponential increase of computing time with number particles. A polynomial solution problem is highly desired since it would provide unbiased and numerically exact method simulate correlated quantum systems. Here we show, that such a almost certainly unattainable by proving NP-hard, implying generic also solve all problems in complexity class NP...
We present a new continuous-time solver for quantum impurity models such as those relevant to dynamical mean field theory. It is based on stochastic sampling of perturbation expansion in the impurity-bath hybridization parameter. Comparisons with Monte Carlo and exact diagonalization calculations confirm accuracy approach, which allows very efficient simulations even at low temperatures strong interactions. As examples power method we results temperature dependence kinetic energy free...
We show how a quantum computer can be employed to elucidate reaction mechanisms in complex chemical systems, using the open problem of biological nitrogen fixation nitrogenase as an example. discuss computers augment classical-computer simulations for such problems, significantly increase their accuracy and enable hitherto intractable simulations. Detailed resource estimates that, even when taking into account substantial overhead error correction, need compile discrete gate sets, necessary...
The preparation of quantum states using short circuits is one the most promising near-term applications small computers, especially if circuit enough and fidelity gates high that it can be executed without error correction. Such state used in variational approaches, optimizing parameters to minimize energy constructed for a given problem Hamiltonian. For this purpose we propose simple-to-implement class motivated by adiabatic preparation. We test its accuracy determine required depth Hubbard...
The development of small-scale digital and analog quantum devices raises the question how to fairly assess compare computational power classical devices, detect speedup. Here we show define measure speedup in various scenarios, avoid pitfalls that might mask or fake We illustrate our discussion with data from a randomized benchmark test on D-Wave Two device up 503 qubits. Comparing performance random spin glass instances limited precision simulated annealers, find no evidence when entire set...
The magnetic susceptibility ${\ensuremath{\chi}}^{*}(t)$ and specific heat $C(t)$ versus temperature t of the spin $S=1/2$ antiferromagnetic (AF) alternating-exchange ${(J}_{1}$ ${J}_{2})$ Heisenberg chain are studied for entire range $0<~\ensuremath{\alpha}<~1$ alternation parameter $\ensuremath{\alpha}\ensuremath{\equiv}{J}_{2}{/J}_{1}{(J}_{1},$ ${J}_{2}>~0,$ ${J}_{2}<~{J}_{1},$ ${t=k}_{\mathrm{B}}{T/J}_{1},$...
Variational studies of the t-J model on square lattice based infinite projected-entangled pair states (iPEPS) confirm an extremely close competition between a uniform d-wave superconducting state and different stripe states. The site-centered with in-phase order has equal or only slightly lower energy than anti-phase order. optimal filling is not constant but increases J/t. A nematic anisotropy reduces pairing amplitude energies phases are lowered relative to increasing nematicity.
Based on the ab initio calculations, we show that MoTe_{2}, in its low-temperature orthorhombic structure characterized by an x-ray diffraction study at 100 K, realizes 4 type-II Weyl points between Nth and (N+1)th bands, where N is total number of valence electrons per unit cell. Other WPs nodal lines different other bands also appear close to Fermi level due a complex topological band structure. We predict series strain-driven phase transitions this compound, opening wide range possible...
The intense theoretical and experimental interest in topological insulators semimetals has established band structure topology as a fundamental material property. Consequently, identifying topologies become an important, but often challenging problem, with no exhaustive solution at the present time. In this work we compile series of techniques, some previously known, that allow for to problem large set possible topologies. method is based on tracking hybrid Wannier charge centers computed...
We present release 2.0 of the ALPS (Algorithms and Libraries for Physics Simulations) project, an open source software project to develop libraries application programs simulation strongly correlated quantum lattice models such as magnets, bosons, fermion systems. The code development is centered on common XML HDF5 data formats, simplify speed up development, evaluation plotting tools, programs. enable non-experts start carrying out serial or parallel numerical simulations by providing basic...
We discuss generalizations of quantum spin Hamiltonians using anyonic degrees freedom. The simplest model for interacting anyons energetically favors neighboring to fuse into the trivial ("identity") channel, similar Heisenberg favoring spins form singlets. Numerical simulations a chain Fibonacci show that is critical with dynamical exponent z=1, and described by two-dimensional (2D) conformal field theory central charge c=7/10. An exact mapping onto 2D tricritical Ising given...
We determine the phase diagram of hard-core bosons on a triangular lattice with nearest-neighbor repulsion, paying special attention to stability supersolid phase. Similar same model square we find that for densities rho<1/3 or rho>2/3 is unstable and transition between commensurate solid superfluid first order. At intermediate fillings 1/3<rho<2/3 an extended even at half filling rho=1/2. The emergence reflects novel interesting way quantum system avoid classical frustration, similar...
In this work we investigate methods to improve the efficiency and scalability of quantum algorithms for chemistry applications. We propose a transformation electronic structure Hamiltonian in second quantization framework into particle-hole (p/h) picture, which offers better starting point expansion trial wavefunction. The state molecular system at study is parametrized way efficiently explore sector Fock space that contains desired solution. To end, several wavefunctions identify most...
A key challenge in fabrication of superconductor (S)-semiconductor (Sm) hybrid devices is forming highly transparent contacts between the active electrons semiconductor and superconducting metal. In this work, we show that a near perfect interface contact can be achieved using epitaxial growth aluminum on an InAs two-dimensional electron system. We demonstrate material system, Al-InAs, satisfies all requirements necessary to reach into topological regime by individual characterization...
As quantum computing technology improves and computers with a small but nontrivial number of N≥100 qubits appear feasible in the near future question possible applications gains importance. One frequently mentioned application is Feynman's original proposal simulating systems and, particular, electronic structure molecules materials. In this paper, we analyze computational requirements for one standard algorithms to perform chemistry on computer. We focus resources required find ground state...