14 research outputs found
Erosion mechanisms during abrasive waterjet machining: model microstructures and single particle experiments
The erosion mechanisms during abrasive waterjet (AWJ) machining have been examined for a variety of materials. However, no systematic study has considered the effect of the microstructure–property relationship on the erosion mechanisms in metals. In this work, the influence of microstructure and mechanical properties on the erosion mechanisms is investigated using AWJ controlled-depth milling and single particle impact experiments performed on nanocrystalline, microcrystalline and single crystal nickel samples. The resulting footprints and subsurface microstructure evolution were analysed using advanced characterization techniques. The erosion rate of the target metal is found to correlate positively with grain size and negatively with hardness but this correlation is nonlinear. The subsurface microstructure of the single crystal and microcrystalline are altered, while only the texture of the nanocrystalline nickel is modified. The grain refinement mechanism observed in microcrystalline and single crystal microstructure is elucidated by electron backscatter diffraction. It proceeds by the generation of dislocations under severe plastic deformation, which transforms into subgrains before forming new grains under further strain. Therefore, severe plastic deformation induced by AWJ machining leads to surface nanocrystallization and induces substantial subsurface work-hardening, as revealed by nanoindentation tests and confirmed by single particle impacts, with the consequence that the erosion rate decreases with decreasing grain size. This work clarifies the erosion mechanisms in pure metals and highlights the dynamic nature of AWJ machining as a result of the complex interplay between microstructure, mechanical properties and material removal mechanisms, providing new insights into AWJ controlled-depth milling technique
Phase transition in Random Circuit Sampling
Quantum computers hold the promise of executing tasks beyond the capability
of classical computers. Noise competes with coherent evolution and destroys
long-range correlations, making it an outstanding challenge to fully leverage
the computation power of near-term quantum processors. We report Random Circuit
Sampling (RCS) experiments where we identify distinct phases driven by the
interplay between quantum dynamics and noise. Using cross-entropy benchmarking,
we observe phase boundaries which can define the computational complexity of
noisy quantum evolution. We conclude by presenting an RCS experiment with 70
qubits at 24 cycles. We estimate the computational cost against improved
classical methods and demonstrate that our experiment is beyond the
capabilities of existing classical supercomputers
Non-Abelian braiding of graph vertices in a superconducting processor
Indistinguishability of particles is a fundamental principle of quantum
mechanics. For all elementary and quasiparticles observed to date - including
fermions, bosons, and Abelian anyons - this principle guarantees that the
braiding of identical particles leaves the system unchanged. However, in two
spatial dimensions, an intriguing possibility exists: braiding of non-Abelian
anyons causes rotations in a space of topologically degenerate wavefunctions.
Hence, it can change the observables of the system without violating the
principle of indistinguishability. Despite the well developed mathematical
description of non-Abelian anyons and numerous theoretical proposals, the
experimental observation of their exchange statistics has remained elusive for
decades. Controllable many-body quantum states generated on quantum processors
offer another path for exploring these fundamental phenomena. While efforts on
conventional solid-state platforms typically involve Hamiltonian dynamics of
quasi-particles, superconducting quantum processors allow for directly
manipulating the many-body wavefunction via unitary gates. Building on
predictions that stabilizer codes can host projective non-Abelian Ising anyons,
we implement a generalized stabilizer code and unitary protocol to create and
braid them. This allows us to experimentally verify the fusion rules of the
anyons and braid them to realize their statistics. We then study the prospect
of employing the anyons for quantum computation and utilize braiding to create
an entangled state of anyons encoding three logical qubits. Our work provides
new insights about non-Abelian braiding and - through the future inclusion of
error correction to achieve topological protection - could open a path toward
fault-tolerant quantum computing
Measurement-induced entanglement and teleportation on a noisy quantum processor
Measurement has a special role in quantum theory: by collapsing the
wavefunction it can enable phenomena such as teleportation and thereby alter
the "arrow of time" that constrains unitary evolution. When integrated in
many-body dynamics, measurements can lead to emergent patterns of quantum
information in space-time that go beyond established paradigms for
characterizing phases, either in or out of equilibrium. On present-day NISQ
processors, the experimental realization of this physics is challenging due to
noise, hardware limitations, and the stochastic nature of quantum measurement.
Here we address each of these experimental challenges and investigate
measurement-induced quantum information phases on up to 70 superconducting
qubits. By leveraging the interchangeability of space and time, we use a
duality mapping, to avoid mid-circuit measurement and access different
manifestations of the underlying phases -- from entanglement scaling to
measurement-induced teleportation -- in a unified way. We obtain finite-size
signatures of a phase transition with a decoding protocol that correlates the
experimental measurement record with classical simulation data. The phases
display sharply different sensitivity to noise, which we exploit to turn an
inherent hardware limitation into a useful diagnostic. Our work demonstrates an
approach to realize measurement-induced physics at scales that are at the
limits of current NISQ processors
Synthesis of lipopolysaccharide-protein conjugate vaccines with conserved internal oligosaccharide epitopes.: Carbohyd.Res.
NRC publication: Ye
Orientation-dependent mechanical behaviour of electrodeposited copper with nanoscale twins
The mechanical properties of electrodeposited copper with highly-oriented nanoscale twins were investigated by micropillar compression. Uniform nanotwinned copper films with preferred twin orientations, either vertical or horizontal, were obtained by controlling the plating conditions. In addition, an ultrafine grained copper film was synthesized to be used as a reference sample. The mechanical properties were assessed by in situ SEM microcompression of micropillars fabricated with a focused ion beam. Results show that the mechanical properties are highly sensitive to the twin orientation. When compared to the ultrafine grained sample, an increase of 44% and 130% in stress at 5% offset strain was observed in quasistatic tests for vertically and horizontally aligned twins, respectively. Inversely strain rate jump microcompression testing reveals higher strain sensitivity for vertical twins. These observations are attributed to a change in deformation mechanism from dislocation pile-ups at the twin boundary for horizontal twins to dislocations threading inside the twin lamella for vertical twins