353 research outputs found
Recommended from our members
Local search: A guide for the information retrieval practitioner
There are a number of combinatorial optimisation problems in information retrieval in which the use of local search methods are worthwhile. The purpose of this paper is to show how local search can be used to solve some well known tasks in information retrieval (IR), how previous research in the field is piecemeal, bereft of a structure and methodologically flawed, and to suggest more rigorous ways of applying local search methods to solve IR problems. We provide a query based taxonomy for analysing the use of local search in IR tasks and an overview of issues such as fitness functions, statistical significance and test collections when conducting experiments on combinatorial optimisation problems. The paper gives a guide on the pitfalls and problems for IR practitioners who wish to use local search to solve their research issues, and gives practical advice on the use of such methods. The query based taxonomy is a novel structure which can be used by the IR practitioner in order to examine the use of local search in IR
Toward an improved understanding of software change
Structural changes, including moving, renaming, merging and splitting are important design change decisions made by programmers. However, during the process of software evolution, this information often gets lost. Recovering instances of structural changes in the past, as well as understanding them, are essential for us to achieve a better understanding of how and why software changes.
In this thesis, we propose an approach that helps to recover and understand the lost information of structural changes
Faster-than-Clifford Simulations of Entanglement Purification Circuits and Their Full-stack Optimization
Quantum Entanglement is a fundamentally important resource in Quantum
Information Science; however, generating it in practice is plagued by noise and
decoherence, limiting its utility. Entanglement distillation and forward error
correction are the tools we employ to combat this noise, but designing the best
distillation and error correction circuits that function well, especially on
today's imperfect hardware, is still challenging. Here, we develop a simulation
algorithm for distillation circuits with gate-simulation complexity of
steps, providing for drastically faster modeling compared to
Clifford simulators or wavefunction
simulators over qubits.
This new simulator made it possible to not only model but also optimize
practically interesting purification circuits. It enabled us to use a simple
discrete optimization algorithm to design purification circuits from raw
Bell pairs to purified pairs and study the use of these circuits in the
teleportation of logical qubits in second-generation quantum repeaters. The
resulting purification circuits are the best-known purification circuits for
finite-size noisy hardware and can be fine-tuned for specific hardware error
models. Furthermore, we design purification circuits that shape the
correlations of errors in the purified pairs such that the performance of the
error-correcting code used in teleportation or other higher-level protocols is
greatly improved. Our approach of optimizing multiple layers of the networking
stack, both the low-level entanglement purification, and the forward error
correction on top of it, are shown to be indispensable for the design of
high-performance second-generation quantum repeaters
- …