Non-catastrophic Encoders and Encoder Inverses for Quantum Convolutional Codes

We present an algorithm to construct quantum circuits for encoding and inverse encoding of quantum convolutional codes. We show that any quantum convolutional code contains a subcode of finite index which has a non-catastrophic encoding circuit. Our work generalizes the conditions for non-catastrophic encoders derived in a paper by Ollivier and Tillich (quant-ph/0401134) which are applicable only for a restricted class of quantum convolutional codes. We also show that the encoders and their inverses constructed by our method naturally can be applied online, i.e., qubits can be sent and received with constant delay.Comment: 6 pages, 1 figure, submitted to 2006 IEEE International Symposium on Information Theor

FRESH – FRI-based single-image super-resolution algorithm

In this paper, we consider the problem of single image super-resolution and propose a novel algorithm that outperforms state-of-the-art methods without the need of learning patches pairs from external data sets. We achieve this by modeling images and, more precisely, lines of images as piecewise smooth functions and propose a resolution enhancement method for this type of functions. The method makes use of the theory of sampling signals with finite rate of innovation (FRI) and combines it with traditional linear reconstruction methods. We combine the two reconstructions by leveraging from the multi-resolution analysis in wavelet theory and show how an FRI reconstruction and a linear reconstruction can be fused using filter banks. We then apply this method along vertical, horizontal, and diagonal directions in an image to obtain a single-image super-resolution algorithm. We also propose a further improvement of the method based on learning from the errors of our super-resolution result at lower resolution levels. Simulation results show that our method outperforms state-of-the-art algorithms under different blurring kernels

On list decoding of wavelet codes over finite fields of characteristic two

Доказывается, что вейвлет-код над полем GF(2m) c длиной кодовых и информационных слов n = 2m — 1 и (n — 1)/2 соответственно, у которого среди коэффициентов спектрального представления порождающего многочлена имеется d + 1 последовательных нулей, 0 < d < (n — 3)/2, допускает списочное декодирование за полиномиальное время. Шаги алгоритма, осуществляющего списочное декодирование с исправлением до e < n — д/n(n — d — 2) ошибок, реализованы в виде программы. Приведены примеры её применения для списочного декодирования зашумленных кодовых слов. Отмечено, что неравенство Варшамова — Гилберта при достаточно больших n не позволяет судить о существовании вейвлет-кодов c максимальным кодовым расстоянием (n — 1) /2

Списочное декодирование вейвлет-кодов

В работе обсуждается возможность списочного декодирования вейвлет-кодов и приводится утверждение, согласно которому вейвлет-коды над полем $GF(q)$ нечетной характеристики с длиной кодовых и информационных слов $n=q-1$ и $n/2$ соответственно, а также над полем четной характеристики с длиной кодовых и информационных слов $n=q-1$ и $(n-1)/2$ соответственно допускают списочное декодирование, если среди коэффициентов спектрального представления их порождающих многочленов имеется $d+1$ последовательных нулей, $0$ &lt; $d$ &lt; $n/2$ для полей нечетной характеристики и $0$ &lt; $d$ &lt; $(n-3)/2$ для полей четной характеристики. Также описывается алгоритм, позволяющий выполнять списочное декодирование вейвлет-кодов при соблюдении перечисленных условий. В качестве демонстрации его работы приводятся пошаговые решения модельных задач списочного декодирования зашумленных кодовых слов вейвлет-кодов над полями четной и нечетной характеристики. Помимо этого, в работе построена вейвлет-версия квазисовершенного троичного кода Голея, длины его кодовых и информационных слов равны 8 и 4 соответственно, кодовое расстояние равно 4, минимальный радиус шаров с центрами в кодовых словах, покрывающих пространство слов длины 8, равен 3

Spread spectrum-based video watermarking algorithms for copyright protection

Merged with duplicate record 10026.1/2263 on 14.03.2017 by CS (TIS)Digital technologies know an unprecedented expansion in the last years. The consumer can now benefit from hardware and software which was considered state-of-the-art several years ago. The advantages offered by the digital technologies are major but the same digital technology opens the door for unlimited piracy. Copying an analogue VCR tape was certainly possible and relatively easy, in spite of various forms of protection, but due to the analogue environment, the subsequent copies had an inherent loss in quality. This was a natural way of limiting the multiple copying of a video material. With digital technology, this barrier disappears, being possible to make as many copies as desired, without any loss in quality whatsoever. Digital watermarking is one of the best available tools for fighting this threat. The aim of the present work was to develop a digital watermarking system compliant with the recommendations drawn by the EBU, for video broadcast monitoring. Since the watermark can be inserted in either spatial domain or transform domain, this aspect was investigated and led to the conclusion that wavelet transform is one of the best solutions available. Since watermarking is not an easy task, especially considering the robustness under various attacks several techniques were employed in order to increase the capacity/robustness of the system: spread-spectrum and modulation techniques to cast the watermark, powerful error correction to protect the mark, human visual models to insert a robust mark and to ensure its invisibility. The combination of these methods led to a major improvement, but yet the system wasn't robust to several important geometrical attacks. In order to achieve this last milestone, the system uses two distinct watermarks: a spatial domain reference watermark and the main watermark embedded in the wavelet domain. By using this reference watermark and techniques specific to image registration, the system is able to determine the parameters of the attack and revert it. Once the attack was reverted, the main watermark is recovered. The final result is a high capacity, blind DWr-based video watermarking system, robust to a wide range of attacks.BBC Research & Developmen