2023 New's Items

Demonstration of a quantum-classical coprocessing protocol for simulating nuclear reactions

Turro F
Siddiqi I
2023

Quantum computers hold great promise for exact simulations of nuclear dynamical processes (e.g., scattering and reactions), which are paramount to the study of nuclear matter at the limit of stability and in the formation of chemical elements in stars. However, quantum simulations of the unitary (real) time dynamics of fermionic many-body systems require a currently prohibitive number of reliable and long-lived qubits. We propose a co-processing algorithm for the simulation of real-time dynamics in which the time evolution of the spatial coordinates is carried out on a classical...

Time-Dependent Hamiltonian Reconstruction Using Continuous Weak Measurements

Siva K
Jordan AN
Siddiqi I
2023

Reconstructing the Hamiltonian of a quantum system is an essential task for characterizing and certifying quantum processors and simulators. Existing techniques either rely on projective measurements of the system before and after coherent time evolution and do not explicitly reconstruct the full time-dependent Hamiltonian or interrupt evolution for tomography. Here, we experimentally demonstrate that an a priori unknown, time-dependent Hamiltonian can be reconstructed from continuous weak measurements concurrent with coherent time evolution in a system of two...

Demonstrating Scalable Randomized Benchmarking of Universal Gate Sets

Hines J
Proctor T
Siddiqi I
2023

Randomized benchmarking (RB) protocols are the most widely used methods for assessing the performance of quantum gates. However, the existing RB methods either do not scale to many qubits or cannot benchmark a universal gate set. Here, we introduce and demonstrate a technique for scalable RB of many universal and continuously parametrized gate sets, using a class of circuits called randomized mirror circuits. Our technique can be applied to a gate set containing an entangling Clifford gate and the set of arbitrary single-qubit gates, as well as gate sets containing controlled...

Benchmarking quantum logic operations relative to thresholds for fault tolerance

Hashim A
Siddiqi
2023

Contemporary methods for benchmarking noisy quantum processors typically measure average error rates or process infidelities. However, thresholds for fault-tolerant quantum error correction are given in terms of worst-case error rates—defined via the diamond norm—which can differ from average error rates by orders of magnitude. One method for resolving this discrepancy is to randomize the physical implementation of quantum gates, using techniques like randomized compiling (RC). In this work, we use gate set tomography to perform precision characterization of a set of two-qubit logic...

Predictive stochastic analysis of massive filter-based electrochemical reaction networks

Barter D
Redkar NS
Persson KA
2024

Chemical reaction networks (CRNs) are powerful tools for obtaining insight into complex reactive processes. However, they are difficult to employ in domains such as electrochemistry where reaction mechanisms and outcomes are not well understood. To overcome these limitations, we report new methods to assist in CRN construction and analysis. Beginning with a known set of potentially relevant species, we enumerate and then filter all stoichiometrically valid reactions, constructing CRNs without reaction templates. By applying efficient stochastic algorithms, we can then interrogate...

Continuum-level modeling of Li-ion battery SEI by upscaling atomistically informed reaction mechanisms

Weddle PJ
Colclasure AM
Persson KA
2023

Understanding and controlling solid-electrolyte interphase (SEI) formation to stabilize cell performance is a significant challenge for next-generation Li-ion battery technologies. In recent years, computational modeling has become an essential tool in providing fundamental insights into SEI properties and dynamics. However, neither atomistic nor continuum-level approaches alone can capture the complexities of SEI ...

Enabling automated high-throughput Density Functional Theory studies of amorphous material surface reactions

Siron M
Persson KA
2023

Amorphous materials are increasingly considered for electronic and energy applications. However, modeling site-specific processes on amorphous materials is prohibitively expensive due to the large...

Rational Design of Fluorinated Electrolytes for Low Temperature Lithium-Ion Batteries

Yoo DJ
Zhang Z
Persson KA
2023

Nonaqueous carbonate electrolytes are commonly used in commercial lithium-ion battery (LIB). However, the sluggish Li+ diffusivity and high interfacial charge transfer resistance at low temperature (LT) limit their wide adoption among geographical areas with high latitudes and altitudes. Herein, a rational design of new electrolytes is demonstrated, which can significantly improve the low temperature performance below −20 °C. This electrolyte is achieved by tailoring the chemical structure, i.e., altering the fluorination position and the degree of...

Tin Metal Improves the Lithiation Kinetics of High-Capacity Silicon Anodes

Yao K
Tong W
Persson KA
2023

Si-based anodes present a great promise for high energy density lithium-ion batteries. However, its commercialization is largely hindered by a grand challenge of a rapid capacity fade. Here, we demonstrate excellent cycling stability on a Si–Sn thin film electrode that outperforms pure Si or Sn counterpart under the similar conditions. Combined with the first-principles calculations, in situ transmission electron microscopy studies reveal a reduced volume expansion, increased conductivity, as well as dynamic rearrangement upon lithiation of the Si–Sn film. We attribute the improved...

Spatially resolved structural order in low-temperature liquid electrolyte

Xie Y
Zheng H
Persson KA
2023

Determining the degree and the spatial extent of structural order in liquids is a grand challenge. Here, we are able to resolve the structural order in a model organic electrolyte of 1 M lithium hexafluorophosphate (LiPF6) dissolved in 1:1 (v/v) ethylene carbonate:diethylcarbonate by developing an integrated method of liquid-phase transmission electron microscopy (TEM), cryo-TEM operated at −30°C, four-dimensional scanning TEM, and data analysis based on deep learning. This study reveals the presence of short-range order (SRO) in the high–salt concentration...