Engineering topics

Sun, Yue

Publications and source records attributed to Sun, Yue.

8 records

DOE OSTI2024

Evidence of scaling advantage for the quantum approximate optimization algorithm on a classically intractable problem

The quantum approximate optimization algorithm (QAOA) is a leading candidate algorithm for solving optimization problems on quantum computers. However, the potential of QAOA to tackle classically intractable problems remains unclear. Here, we perform an extensive numerical investigation of QAOA on the low autocorrelation binary sequences (LABS) problem, which is classically intractable even for moderately sized instances. We perform noiseless simulations with up to 40 qubits and observe that the runtime of QAOA with fixed parameters scales better than branch-and-bound solvers, which are the state-of-the-art exact solvers for LABS. The combination of QAOA with quantum minimum finding gives the best empirical scaling of any algorithm for the LABS problem. We demonstrate experimental progress in executing QAOA for the LABS problem using an algorithm-specific error detection scheme on Quantinuum trapped-ion processors. Our results provide evidence for the utility of QAOA as an algorithmic component that enables quantum speedups.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2024

Dipolar spin wave packet transport in a van der Waals antiferromagnet

Antiferromagnets are promising platforms for transduction and transmission of quantum information via magnons—the quanta of spin waves—and they offer advantages over ferromagnets in regard to dissipation, speed of response and robustness to external fields. Recently, transduction was shown in a van der Waals antiferromagnet, where strong spin-exciton coupling enables readout of the amplitude and phase of coherent magnons by photons of visible light. This discovery shifts the focus of research to transmission, specifically to exploring the non-local interactions that enable magnon wave packets to propagate. Here we demonstrate that magnon propagation is mediated by long-range dipole–dipole interaction. This coupling is an inevitable consequence of fundamental electrodynamics and, as such, will likely mediate the propagation of spin at long wavelengths in the entire class of van der Waals magnets currently under investigation. In conclusion, successfully identifying the mechanism of spin propagation provides a set of optimization rules, as well as caveats, that are essential for any future applications of these promising systems.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2023

Coupling of Adhesion and Anti-Freezing Properties in Hydrogel Electrolytes for Low-Temperature Aqueous-Based Hybrid Capacitors

Solid-state zinc-ion capacitors are emerging as promising candidates for large-scale energy storage owing to improved safety, mechanical and thermal stability and easy-to-direct stacking. Hydrogel electrolytes are appealing solid-state electrolytes because of eco-friendliness, high conductivity and intrinsic flexibility. However, the electrolyte/electrode interfacial contact and anti-freezing properties of current hydrogel electrolytes are still challenging for practical applications of zinc-ion capacitors. Here, we report a class of hydrogel electrolytes that couple high interfacial adhesion and anti-freezing performance. The synergy of tough hydrogel matrix and chemical anchorage enables a well-adhered interface between hydrogel electrolyte and electrode. Meanwhile, the cooperative solvation of ZnCl 2 and LiCl hybrid salts renders the hydrogel electrolyte high ionic conductivity and mechanical elasticity simultaneously at low temperatures. More significantly, the Zn||carbon nanotubes hybrid capacitor based on this hydrogel electrolyte exhibits low-temperature capacitive performance, delivering high-energy density of 39 Wh kg –1 at –60 °C with capacity retention of 98.7% over 10,000 cycles. With the benefits of the well-adhered electrolyte/electrode interface and the anti-freezing hydrogel electrolyte, the Zn/Li hybrid capacitor is able to accommodate dynamic deformations and function well under 1000 tension cycles even at –60 °C. This work provides a powerful strategy for enabling stable operation of low-temperature zinc-ion capacitors.

25 ENERGY STORAGE↗

DOE OSTI2023

Elastocaloric signatures of symmetric and antisymmetric strain-tuning of quadrupolar and magnetic phases in DyB 2 C 2

The adiabatic elastocaloric effect measures the temperature change of a given system with strain and provides a thermodynamic probe of the entropic landscape in the temperature-strain space. Here, we demonstrate that the DC bias strain-dependence of AC elastocaloric effect allows decomposition of the latter into symmetric (rotation-symmetry-preserving) and antisymmetric (rotation-symmetry-breaking) strain channels, using a tetragonal f -electron intermetallic DyB 2 C 2 —whose antiferroquadrupolar order breaks local fourfold rotational symmetries while globally remaining tetragonal—as a showcase example. We capture the strain evolution of its quadrupolar and magnetic phase transitions using both singularities in the elastocaloric coefficient and its jumps at the transitions, and the latter we show follows a modified Ehrenfest relation. We find that antisymmetric strain couples to the underlying order parameter in a biquadratic (linear-quadratic) manner in the antiferroquadrupolar (canted antiferromagnetic) phase, which are attributed to a preserved (broken) global tetragonal symmetry, respectively. The broken tetragonal symmetry in the magnetic phase is further evidenced by elastocaloric strain-hysteresis and optical birefringence. Additionally, within the staggered quadrupolar order, the observed elastocaloric response reflects a quadratic increase of entropy with antisymmetric strain, analogous to the role magnetic field plays for Ising antiferromagnetic orders by promoting pseudospin flips. Our results demonstrate AC elastocaloric effect as a compact and incisive thermodynamic probe into the coupling between electronic degrees of freedom and strain in free energy, which holds the potential for investigating and understanding the symmetry of a wide variety of ordered phases in broader classes of quantum materials.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2023

Observing ion diffusion and reciprocating hopping motion in water

When an ionic crystal dissolves in solvent, the positive and negative ions associated with solvent molecules release from the crystal. However, the existing form, interaction, and dynamics of ions in real solution are poorly understood because of the substantial experimental challenge. We observed the diffusion and aggregation of polyoxometalate (POM) ions in water by using liquid phase transmission electron microscopy. Real-time observation reveals an unexpected local reciprocating hopping motion of the ions in water, which may be caused by the short-range polymerized bridge of water molecules. We find that ion oligomers, existing as highly active clusters, undergo frequent splitting, aggregation, and rearrangement in dilute solution. The formation and dissociation of ion oligomers indicate a weak counterion-mediated interaction. Furthermore, POM ions with tetrahedral geometry show directional interaction compared with spherical ions, which presents structure-dependent dynamics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

Quantum computing for finance

Quantum computers are expected to surpass the computational capabilities of classical computers and have a transformative impact on numerous industry sectors. Here, we present a comprehensive summary of the state of the art of quantum computing for financial applications, with particular emphasis on stochastic modelling, optimization and machine learning. This Review is aimed at physicists, so it outlines the classical techniques used by the financial industry and discusses the potential advantages and limitations of quantum techniques. Finally, we look at the challenges that physicists could help tackle. Quantum computers are expected to surpass classical computers and transform industries. This Review focuses on quantum computing for financial applications and provides a summary for physicists on potential advantages and limitations of quantum techniques, as well as challenges that physicists could help tackle.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2023

Advances in Regioselective Functionalization of Endohedral Metallofullerenes †

Comprehensive Summary Endohedral metallofullerenes (EMFs) are a family of molecules with metal clusters or ions encapsulated inside a fullerene cage. Their unique structures provide a powerful interface for organic chemists to manipulate metal elements. Over a decade ago, many reactions on empty fullerenes were adopted for EMFs, resulting in a series of reactions that are well‐established and reviewed in the literature. In recent years, new topics have emerged in EMF chemistry. First, new addition reactions were developed, notably some that are not based on known empty‐fullerene reactions. Second, considerable progress has been made on regioselective multi‐additions on EMFs. Finally, EMFs have been covalently conjugated with fullerene C 60 to form functional materials. This Recent Advances article will focus on these new developments and discuss their implication for future directions of EMFs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

Spin wavepackets in the Kagome ferromagnet Fe 3 Sn 2 : Propagation and precursors

The propagation of spin waves in magnetically ordered systems has emerged as a potential means to shuttle quantum information over large distances. Conventionally, the arrival time of a spin wavepacket at a distance, d , is assumed to be determined by its group velocity, v g . Here, we report time-resolved optical measurements of wavepacket propagation in the Kagome ferromagnet Fe 3 Sn 2 that demonstrate the arrival of spin information at times significantly less than d / v g . We show that this spin wave “precursor” originates from the interaction of light with the unusual spectrum of magnetostatic modes in Fe 3 Sn 2 . Related effects may have far-reaching consequences toward realizing long-range, ultrafast spin wave transport in both ferromagnetic and antiferromagnetic systems.

36 MATERIALS SCIENCE↗