The Longer Term: Quantum Information Processing and Communication

P. Zoller, Thomas Beth, Daniele Binosi +36 more

W J Munro, Kae Nemoto, T P Spiller

Quantum information processing (QIP) offers the promise of being able to do things that we cannot do with conventional technology. Here we present a new route for distributed optical QIP, based on generalized quantum non-demolition measurements, providing a unified approach for quantum communication and computing. Interactions between photons are generated using weak nonlinearities and intense laser fields—the use of such fields provides for robust distribution of quantum information. Our approach only requires a practical set of resources, and it uses these very efficiently. Thus it promises to be extremely useful for the first quantum technologies, based on scarce resources. Furthermore, in the longer term this approach provides both options and scalability for efficient many-qubit QIP.

Travis Roland Beals

William J. Munro, Kae Nemoto, Timothy P. Spiller

Quantum information processing (QIP) offers the promise of being able to do things that we cannot do with conventional technology. Here we present a new route for distributed optical QIP, based on generalized quantum non-demolition measurements, providing a unified approach for quantum communication and computing. Interactions between photons are generated using weak non-linearities and intense laser fields--the use of such fields provides for robust distribution of quantum information. Our approach requires only a practical set of resources, and it uses these very efficiently. Thus it promises to be extremely useful for the first quantum technologies, based on scarce resources. Furthermore, in the longer term this approach provides both options and scalability for efficient many-qubit QIP.

C. H. Bennett

Philippe Jorrand

Information is physical: the laws which govern its encoding, processing and communication are those of its unavoidable physical embodyment. In today's computing, information obeys the laws of Newton's and Maxwell's classical physics: this assertion holds all the way from commercial computers down to their most abstract models, e.g. Turing machines and lambda-calculi. Today's computation is classical.Research in quantum information processing and communication (QIPC) was born some twenty years ago, as a child of two major scientific achievements of the 20th century, namely quantum physics and information sciences. The driving force of this interdisciplinary research is that of looking for the consequences of having information encoding, computation and communication obey the laws of quantum physics, i.e. the ultimate knowledge that we have, today, of the foreign world of elementary particles, as described by quantum mechanics. Breakthroughs in algorithmics, cryptography, information theory and abstract computational models have shown that this rerooting of information from classical to quantum has far reaching consequences, both quantitative and qualitative, and opens new avenues for research within the foundations of computer science.The aim of this tutorial is to give a survey of the principles, main results and long term perspectives of current research in QIPC, from a computer science point of view. No prior knowledge in quantum mechanics is required to follow this tutorial. There will be two parts:1 - Computation, the quantum way: quantum bits and quantum operations; two major quantum algorithms: quadratic speedup for unordered database search (Grover's algorithm), exponential speedup for integer factoring (Shor's algorithm);2 - Communication, the quantum way, and longer term perspectives: quantum state teleportation; a quantum cryptographic protocol for secret key distribution. Hot topics in QIPC research, state of the art in physical implementation of quantum computers.