149 research outputs found
Randomized benchmarking of single and multi-qubit control in liquid-state NMR quantum information processing
Being able to quantify the level of coherent control in a proposed device
implementing a quantum information processor (QIP) is an important task for
both comparing different devices and assessing a device's prospects with
regards to achieving fault-tolerant quantum control. We implement in a
liquid-state nuclear magnetic resonance QIP the randomized benchmarking
protocol presented by Knill et al (PRA 77: 012307 (2008)). We report an error
per randomized pulse of with a
single qubit QIP and show an experimentally relevant error model where the
randomized benchmarking gives a signature fidelity decay which is not possible
to interpret as a single error per gate. We explore and experimentally
investigate multi-qubit extensions of this protocol and report an average error
rate for one and two qubit gates of for a three
qubit QIP. We estimate that these error rates are still not decoherence limited
and thus can be improved with modifications to the control hardware and
software.Comment: 10 pages, 6 figures, submitted versio
Analytic function methods for nonparametric control
This thesis develops and investigates analytic function methods for nonparametric analysis and design of robust control linear systems. Compared to the parametric approaches, nonparametric approaches may enable the designer to directly use the experimental plant data to design the controller. Nonparametric approaches are potentially more accurate than parametric approaches since they do not need to make significant approximations due to parametric fittings. Moreover, since no parametric identification is required, nonparametric approaches are able to cope with time-delayed and differential difference systems. The design procedure process may also require less human judgement and so may be quicker and more readily automated. In this thesis, nonparametric approaches to control based on H-infinity analytic function theory is presented. It is the main purpose of this thesis to investigate the use of analytic function methods in H-infinity control problems. The implementation of the analytic methods and their applications are both addressed in the thesis
Development of advanced control strategies for Adaptive Optics systems
Atmospheric turbulence is a fast disturbance that requires high control frequency. At the same time, celestial objects are faint sources of light and thus WFSs often work in a low photon count regime. These two conditions require a trade-off between high closed-loop control frequency to improve the disturbance rejection performance, and large WFS exposure time to gather enough photons for the integrated signal to increase the Signal-to-Noise ratio (SNR), making the control a delicate yet fundamental aspect for AO systems. The AO plant and atmospheric turbulence were formalized as state-space linear time-invariant systems. The full AO system model is the ground upon which a model-based control can be designed. A Shack-Hartmann wavefront sensor was used to measure the horizontal atmospheric turbulence. The experimental measurements yielded to the Cn2 atmospheric structure parameter, which is key to describe the turbulence statistics, and the Zernike terms time-series. Experimental validation shows that the centroid extraction algorithm implemented on the Jetson GPU outperforms (i.e. is faster) than the CPU implementation on the same hardware. In fact, due to the construction of the Shack-Hartmann wavefront sensor, the intensity image captured from its camera is partitioned into several sub-images, each related to a point of the incoming wavefront. Such sub-images are independent each-other and can be computed concurrently. The AO model is exploited to automatically design an advanced linear-quadratic Gaussian controller with integral action. Experimental evidence shows that the system augmentation approach outperforms the simple integrator and the integrator filtered with the Kalman predictor, and that it requires less parameters to tune
HAPI: Hardware-Aware Progressive Inference
Convolutional neural networks (CNNs) have recently become the
state-of-the-art in a diversity of AI tasks. Despite their popularity, CNN
inference still comes at a high computational cost. A growing body of work aims
to alleviate this by exploiting the difference in the classification difficulty
among samples and early-exiting at different stages of the network.
Nevertheless, existing studies on early exiting have primarily focused on the
training scheme, without considering the use-case requirements or the
deployment platform. This work presents HAPI, a novel methodology for
generating high-performance early-exit networks by co-optimising the placement
of intermediate exits together with the early-exit strategy at inference time.
Furthermore, we propose an efficient design space exploration algorithm which
enables the faster traversal of a large number of alternative architectures and
generates the highest-performing design, tailored to the use-case requirements
and target hardware. Quantitative evaluation shows that our system consistently
outperforms alternative search mechanisms and state-of-the-art early-exit
schemes across various latency budgets. Moreover, it pushes further the
performance of highly optimised hand-crafted early-exit CNNs, delivering up to
5.11x speedup over lightweight models on imposed latency-driven SLAs for
embedded devices.Comment: Accepted at the 39th International Conference on Computer-Aided
Design (ICCAD), 202
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