2,343 research outputs found
Braiding fractional quantum Hall quasiholes on a superconducting quantum processor
Direct experimental detection of anyonic exchange statistics in fractional
quantum Hall systems by braiding the excitations and measuring the
wave-function phase is an enormous challenge. Here, we use a small, noisy
quantum computer to emulate direct braiding within the framework of a
simplified model applicable to a thin cylinder geometry and measure the
topological phase. Our algorithm first prepares the ground state with two
quasiholes. It then applies a unitary operation controlled by an ancilla,
corresponding to a sequence of adiabatic evolutions that takes one quasihole
around the other. We finally extract the phase of the wave function from
measuring the ancilla with a compound error mitigation strategy. Our results
open a new avenue for studying braiding statistics in fractional Hall states.Comment: 9 pages, 8 figure
Isolated Majorana mode in a quantum computer from a duality twist
Experimental investigation of the interplay of dualities, generalized
symmetries, and topological defects is an important challenge in condensed
matter physics and quantum materials. A simple model exhibiting this physics is
the transverse-field Ising model, which can host a noninvertible topological
defect that performs the Kramers-Wannier duality transformation. When acting on
one point in space, this duality defect imposes the duality twisted boundary
condition and binds a single Majorana zero mode. This Majorana zero mode is
unusual as it lacks localized partners and has an infinite lifetime, even in
finite systems. Using Floquet driving of a closed Ising chain with a duality
defect, we generate this Majorana zero mode in a digital quantum computer. We
detect the mode by measuring its associated persistent autocorrelation function
using an efficient sampling protocol and a compound strategy for error
mitigation. We also show that the Majorana zero mode resides at the domain wall
between two regions related by a Kramers-Wannier duality. Finally, we highlight
the robustness of the isolated Majorana zero mode to integrability and
symmetry-breaking perturbations. Our findings offer an experimental approach to
investigating exotic topological defects in Floquet systems.Comment: 6 pages, 5 figures, 2 pages of supplemental materia
Best practices for quantum error mitigation with digital zero-noise extrapolation
Digital zero-noise extrapolation (dZNE) has emerged as a common approach for
quantum error mitigation (QEM) due to its conceptual simplicity, accessibility,
and resource efficiency. In practice, however, properly applying dZNE to extend
the computational reach of noisy quantum processors is rife with subtleties.
Here, based on literature review and original experiments on noisy simulators
and real quantum hardware, we define best practices for QEM with dZNE for each
step of the workflow, including noise amplification, execution on the quantum
device, extrapolation to the zero-noise limit, and composition with other QEM
methods. We anticipate that this effort to establish best practices for dZNE
will be extended to other QEM methods, leading to more reproducible and
rigorous calculations on noisy quantum hardware.Comment: 10 pages, 11 figures, submitted to IEEE Quantum Week 202
Assessing the Ability of Self-Attention Networks to Learn Word Order
Self-attention networks (SAN) have attracted a lot of interests due to their
high parallelization and strong performance on a variety of NLP tasks, e.g.
machine translation. Due to the lack of recurrence structure such as recurrent
neural networks (RNN), SAN is ascribed to be weak at learning positional
information of words for sequence modeling. However, neither this speculation
has been empirically confirmed, nor explanations for their strong performances
on machine translation tasks when "lacking positional information" have been
explored. To this end, we propose a novel word reordering detection task to
quantify how well the word order information learned by SAN and RNN.
Specifically, we randomly move one word to another position, and examine
whether a trained model can detect both the original and inserted positions.
Experimental results reveal that: 1) SAN trained on word reordering detection
indeed has difficulty learning the positional information even with the
position embedding; and 2) SAN trained on machine translation learns better
positional information than its RNN counterpart, in which position embedding
plays a critical role. Although recurrence structure make the model more
universally-effective on learning word order, learning objectives matter more
in the downstream tasks such as machine translation.Comment: ACL 201
Direct Intracellular Delivery of Cell Impermeable Probes of Protein Glycosylation Using Nanostraws
Bioorthogonal chemistry is an effective tool for elucidating metabolic pathways and measuring cellular activity, yet its use is currently limited by the difficulty of getting probes past the cell membrane and into the cytoplasm, especially if more complex probes are desired. Here we present a simple and minimally perturbative technique to deliver functional probes of glycosylation into cells by using a nanostructured “nanostraw” delivery system. Nanostraws provide direct intracellular access to cells through fluid conduits that remain small enough to minimize cell perturbation. First, we demonstrate that our platform can deliver an unmodified azidosugar, N-azidoacetylmannosamine, into cells with similar effectiveness to a chemical modification strategy (peracetylation). We then show that the nanostraw platform enables direct delivery of an azidosugar modified with a charged uridine diphosphate group (UDP) that prevents intracellular penetration, thereby bypassing multiple enzymatic processing steps. By effectively removing the requirement for cell permeability from the probe, the nanostraws expand the toolbox of bioorthogonal probes that can be used to study biological processes on a single, easy-to-use platform
Context-Aware Self-Attention Networks
Self-attention model have shown its flexibility in parallel computation and
the effectiveness on modeling both long- and short-term dependencies. However,
it calculates the dependencies between representations without considering the
contextual information, which have proven useful for modeling dependencies
among neural representations in various natural language tasks. In this work,
we focus on improving self-attention networks through capturing the richness of
context. To maintain the simplicity and flexibility of the self-attention
networks, we propose to contextualize the transformations of the query and key
layers, which are used to calculates the relevance between elements.
Specifically, we leverage the internal representations that embed both global
and deep contexts, thus avoid relying on external resources. Experimental
results on WMT14 English-German and WMT17 Chinese-English translation tasks
demonstrate the effectiveness and universality of the proposed methods.
Furthermore, we conducted extensive analyses to quantity how the context
vectors participate in the self-attention model.Comment: AAAI 201
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