scholarly journals Orbital transformations to reduce the 1-norm of the electronic structure Hamiltonian for quantum computing applications

2021 ◽  
Vol 3 (3) ◽  
Author(s):  
Emiel Koridon ◽  
Saad Yalouz ◽  
Bruno Senjean ◽  
Francesco Buda ◽  
Thomas E. O'Brien ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Quantum Computing

scholarly journals Compilation by stochastic Hamiltonian sparsification

Quantum ◽  
2020 ◽  
Vol 4 ◽  
pp. 235 ◽  
Author(s):  
Yingkai Ouyang ◽  
David R. White ◽  
Earl T. Campbell
Keyword(s):  
Electronic Structure ◽  
Quantum Computing ◽  
Probability Distribution ◽  
Quantum Chemistry ◽  
Error Bounds ◽  
Simulation Methods ◽  
Physical Systems ◽  
First Order ◽  
Convex Optimisation ◽  
Principal Application

Simulation of quantum chemistry is expected to be a principal application of quantum computing. In quantum simulation, a complicated Hamiltonian describing the dynamics of a quantum system is decomposed into its constituent terms, where the effect of each term during time-evolution is individually computed. For many physical systems, the Hamiltonian has a large number of terms, constraining the scalability of established simulation methods. To address this limitation we introduce a new scheme that approximates the actual Hamiltonian with a sparser Hamiltonian containing fewer terms. By stochastically sparsifying weaker Hamiltonian terms, we benefit from a quadratic suppression of errors relative to deterministic approaches. Relying on optimality conditions from convex optimisation theory, we derive an appropriate probability distribution for the weaker Hamiltonian terms, and compare its error bounds with other probability ansatzes for some electronic structure Hamiltonians. Tuning the sparsity of our approximate Hamiltonians allows our scheme to interpolate between two recent random compilers: qDRIFT and randomized first order Trotter. Our scheme is thus an algorithm that combines the strengths of randomised Trotterisation with the efficiency of qDRIFT, and for intermediate gate budgets, outperforms both of these prior methods.

scholarly journals Quantum computing approaches to graph partitioning for electronic structure problems

2020 ◽  
Author(s):  
Susan Mniszewski ◽  
Christian F. A. Negre ◽  
Hayato Ushijima-Mwesigwa
Keyword(s):  
Electronic Structure ◽  
Quantum Computing ◽  
Graph Partitioning

scholarly journals NMR for Single Ion Magnets

2021 ◽  
Vol 7 (7) ◽  
pp. 96
Author(s):  
Lucia Gigli ◽  
Silvia Di Grande ◽  
Enrico Ravera ◽  
Giacomo Parigi ◽  
Claudio Luchinat
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Properties ◽  
Electronic Structure ◽  
Quantum Computing ◽  
Magnetic Resonance ◽  
Structural Information ◽  
Paramagnetic Nmr ◽  
Recent Advances ◽  
Ideal Tool ◽  
Structure Of Matter

Nuclear Magnetic Resonance is particularly sensitive to the electronic structure of matter and is thus a powerful tool to characterize in-depth the magnetic properties of a system. NMR is indeed increasingly recognized as an ideal tool to add precious structural information for the development of Single Ion Magnets, small complexes that are recently gaining much popularity due to their quantum computing and spintronics applications. In this review, we recall the theoretical principles of paramagnetic NMR, with particular attention to lanthanoids, and we give an overview of the recent advances in this field.

scholarly journals Quantum computing approaches to graph partitioning for electronic structure problems

2020 ◽  
Author(s):  
Susan Mniszewski ◽  
Christian F. A. Negre ◽  
Hayato Ushijima-Mwesigwa
Keyword(s):  
Electronic Structure ◽  
Quantum Computing ◽  
Graph Partitioning

scholarly journals Quantum simulation of electronic structure with a transcorrelated Hamiltonian: improved accuracy with a smaller footprint on the quantum computer

2020 ◽  
Vol 22 (42) ◽  
pp. 24270-24281
Author(s):  
Mario Motta ◽  
Tanvi P. Gujarati ◽  
Julia E. Rice ◽  
Ashutosh Kumar ◽  
Conner Masteran ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Quantum Computing ◽  
Quantum Computer ◽  
Quantum Simulation ◽  
Coupled Cluster ◽  
Improved Accuracy

Molecular quantum computing simulations are currently limited by the use of minimal Gaussian bases, a problem we overcome using a canonical transcorrelated Hamiltonian to accelerate basis convergence, with unitary coupled cluster as an example.

EELS Measurement of the Local Electronic Structure of Copper Atoms Segregated to Aluminum Grain Boundaries

1996 ◽  
Vol 54 ◽  
pp. 342-343
Author(s):  
S.J. Splinter ◽  
J. Bruley ◽  
P.E. Batson ◽  
D.A. Smith ◽  
R. Rosenberg
Keyword(s):  
Electronic Structure ◽  
Grain Boundaries ◽  
Boundary Segregation ◽  
Thin Layers ◽  
Nominal Composition ◽  
Spatially Resolved ◽  
Service Lifetime ◽  
Heat Treated ◽  
Probe Size ◽  
Local Electronic Structure

It has long been known that the addition of Cu to Al interconnects improves the resistance to electromigration failure. It is generally accepted that this improvement is the result of Cu segregation to Al grain boundaries. The exact mechanism by which segregated Cu increases service lifetime is not understood, although it has been suggested that the formation of thin layers of θ-CuA12 (or some metastable substoichiometric precursor, θ’ or θ”) at the boundaries may be necessary. This paper reports measurements of the local electronic structure of Cu atoms segregated to Al grain boundaries using spatially resolved EELS in a UHV STEM. It is shown that segregated Cu exists in a chemical environment similar to that of Cu atoms in bulk θ-phase precipitates.Films of 100 nm thickness and nominal composition Al-2.5wt%Cu were deposited by sputtering from alloy targets onto NaCl substrates. The samples were solution heat treated at 748K for 30 min and aged at 523K for 4 h to promote equilibrium grain boundary segregation. EELS measurements were made using a Gatan 666 PEELS spectrometer interfaced to a VG HB501 STEM operating at 100 keV. The probe size was estimated to be 1 nm FWHM. Grain boundaries with the narrowest projected width were chosen for analysis. EDX measurements of Cu segregation were made using a VG HB603 STEM.

Electronic structure studies of conducting polymers by electron energy-loss spectroscopy

1996 ◽  
Vol 54 ◽  
pp. 160-161
Author(s):  
J. Fink
Keyword(s):  
Electronic Structure ◽  
Conducting Polymers ◽  
Conjugated Polymers ◽  
Electron Acceptors ◽  
Electron Donors ◽  
Light Emitting ◽  
One Dimensional ◽  
New Class ◽  
Electrical Conductivities ◽  
Electron Energy Loss

Conducting polymers comprises a new class of materials achieving electrical conductivities which rival those of the best metals. The parent compounds (conjugated polymers) are quasi-one-dimensional semiconductors. These polymers can be doped by electron acceptors or electron donors. The prototype of these materials is polyacetylene (PA). There are various other conjugated polymers such as polyparaphenylene, polyphenylenevinylene, polypoyrrole or polythiophene. The doped systems, i.e. the conducting polymers, have intersting potential technological applications such as replacement of conventional metals in electronic shielding and antistatic equipment, rechargable batteries, and flexible light emitting diodes.Although these systems have been investigated almost 20 years, the electronic structure of the doped metallic systems is not clear and even the reason for the gap in undoped semiconducting systems is under discussion.

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