We are living at the beginning of a quantum revolution which will no doubt have a profound impact on all aspects of our lives. Quantum systems, which were once restricted to academic research, are now becoming a technological reality. This inevitable evolution is particularly well documented in the context of information and communication technologies where the first quantum devices are becoming available commercially.
This special theme of the ERCIM News brings quantum information science and technology closer to its readers via three invited and three contributed articles which explore various aspects of this fascinating field of research and its exciting applications.
Quantum computation, which is naturally a main focus of this issue, represents a highly unconventional and also extremely powerful computation paradigm. Quantum computation can provide immense computing power that reaches beyond the capabilities of any conventional computer. This power derives from the exotic properties of quantum systems, from quantum ‘weirdness’ which has no analog in the world of classical mechanics and thus no analog in the world we can perceive directly by our senses. This ‘weirdness’ reflects the counterintuitive facts that distinct quantum states of a system can coexist in what is called a quantum superposition and can also be entangled by strong correlations which have no classical analog.
Introduction into quantum information and related quantum engineering challenges is provided in the invited article by Thomas Busch from University College Cork who explores the essential principles which are common to all quantum information processing.
The realization of quantum computing faces highly complex challenges, the most important one being protection of quantum information against errors. Engineering approaches have been developed allowing us to achieve fault-tolerant quantum computation in principle. They are based on concatenated quantum error correction schemes, and as such, require a large amount of physical resources and extreme control over each component of the quantum computing process. An attractive alternative, topological quantum computation, has recently emerged which enables fault-tolerance to be built into quantum computing hardware.
Topological quantum computation is presented in the invited article by Joost Slingerland from National University of Ireland, Maynooth. It explains how the quantum ‘weirdness’ mentioned above can be even more exotic in certain two-dimensional quantum systems which permit quasiparticles called anyons, and how knotting trajectories of these anyons can be exploited for fault-tolerant quantum computation.
Efficient quantum algorithms are keys to harvesting the enormous power of quantum computing. Indeed quantum information science was highly accelerated by the discovery by Peter Shor of quantum algorithm for large number factorization which provides an exponential speedup of computation compared to any conventional (classical) algorithm. Tremendous progress in development of quantum algorithms have been experienced since then. Development of new algorithms is indeed closely related to study of novel paradigms for quantum computation.
Quantum random walks and their role in the development of quantum algorithms is presented in the invited article by Michael Mc Gettrick from National University of Ireland, Galway. The detailed understanding of quantum random walks, including for example the effect of memory on their controllability, is an important step towards new quantum algorithms.
The role of entanglement in the context of quantum algorithms and complexity is addressed in the article by Ashley Montanaro from University of Cambridge who investigates unentangled quantum proofs in Merlin-Arthur games and their applications for efficiently solving hard computational problems. Interesting results in this area have been obtained for example for the 3-SAT problem.
Important developments have taken place in other areas of quantum information processing, particularly in quantum communication and cryptography. While realization of quantum computing as the ultimate quantum information processor is challenging, quantum cryptography and its application for quantum key distribution provide commerically available quantum security.
New quantum cryptographic methods are explored in the article by Harry Buhrman, Serge Fehr, and Christian Schaffner from CWI. Quantum cryptography is also the topic of the article by Martin Stierle and Christoph Pacher from the Austrian Institute of Technology which focuses on high speed quantum key distribution and presents important recent developments towards commercial quantum cryptography.
National University of Ireland Maynooth / IUA