EXECUTIVE SUMMARY

Quantum Information Processing and Communication (QIPC) has the potential to revolutionize many areas of science and technology. It exploits fundamentally new modes of computation and communication, because it is based on the physical laws of quantum mechanics instead of classical physics. It holds the promise of immense computing power beyond the capabilities of any classical computer, it guarantees absolutely secure communication, and it is directly linked to emerging quantum technologies, such as, for example, quantum based sensors. The worldwide interest in the subject may be gauged by the recent significant increase of funding in quantum information technology; in particular in the United States, Canada, Australia and in some countries in Asia (see section 2.2). Europe has played a leading role in the early development of QIPC, and, given appropriate research infrastructure and suitable funding, European researchers are well positioned to maintain Europe at the forefront of the field. However, this requires a significant effort at national level and a consolidation, coordination and unification of many national projects and initiatives under one common European umbrella with the lead of the research program of the European Commission. For Europe to remain competitive in this field in the future there is an urgent need for a substantial EU-programme in QIPC.

GOALS OF QIPC RESEARCH IN THE COMING FIVE TO TEN YEARS

While QIPC belongs mainly to basic research, where key advances are often outcomes of curiosity driven research, there is nonetheless a clear set of goals for QIPC in the coming five to ten years:

• In quantum computing the goal for the next ten years is to develop a few-qubit general-purpose quantum processor including error correction, as a model system to demonstrate quantum algorithms and various quantum computing architectures, and with emphasis on potential scalability. While at present certain physical systems can be identified as prime candidates, it is essential to pursue this goal on a broad basis of competing approaches, allowing hybridization and cross fertilization between different fields (e.g., quantum optics, individual atoms and ions, as well as solid state). In addition, interfaces (with direct relevance for quantum communication) and model systems should be developed for connecting quantum computers in small networks. Parallel to these developments special purpose quantum computers with a few tens of qubits, or more, should be developed, e.g. to act as quantum simulators. The ultimate goal is to construct laboratory models of quantum computers which outperform classical computers on whatever nontrivial problem.

• In quantum communication, the short-term goal is to develop quantum cryptography towards becoming an established technology and a commercial product. A scientific goal is to demonstrate long-distance quantum communication both in optical fiber and in free space. On the 5-10 year time scale, the goals are to gain several orders of magnitude on the secret bit rate and to demonstrate quantum repeaters. The latter will require the implementation of error correction, entanglement purification, quantum interfaces and quantum memories. Each of the mentioned four requirements constitutes a serious scientific challenge. In particular, the main challenge will be the development of a quantum memory that outperforms the simple, but insufficient, "photon in a fiber loop" technique.

• Theory must on one hand continue to play a leading role in guiding and supporting experimental developments. On the other hand fundamental theoretical issues must be pursued. The most important one is the formulation of a quantum information theory, a quantum counterpart to the classical theory of information, computation and communication. This implies the search for new quantum algorithms, new computational models and architectures, as well as quantum communication and entanglement manipulation protocols. A key element is a deeper understanding of entanglement in quantum theory. This includes the understanding of decoherence (an intrinsic property of quantum systems interacting with their environment), which leads to the detrimental effects of imperfections and noise. It is necessary to find ways to overcome them, for example with quantum error correction and purification. It will lead both to a deeper understanding of quantum theory per se, but it is also in direct connection to experimental implementations. Finally, the links of quantum information theory to other branches of physics must be developed, e.g. to condensed matter physics.

THE LEADING ROLE OF EUROPEAN RESEARCHERS IN QIPC

European researchers have been from the outset prominent in setting the agenda of, and leading, the worldwide research efforts in quantum information science, in friendly competition with similar efforts and programs in the US, Australia, Canada, Japan and China. This includes pioneering work on the foundations of the quantum theory of computation, quantum algorithms, and the discovery of entangled state quantum cryptography, which generated a spate of new research that established a vigorously active new area of physics, computer science and cryptology. Many subsequent seminal contributions, inspired by the 1994 Shor's quantum factoring algorithm, such as ways of implementing quantum computation using ion traps, quantum dots, cavity QED, optical lattices and a number of other technologies, novel computational architectures, methods of error correction and fault tolerant quantum computation originated in Europe. A unique feature and strength of European research is the broad range of activities and expertise, linking coherently efforts from experimental realization all the way to basic theoretical questions in quantum information science and quantum physics.

RECOMMENDATIONS FOR FUNDING ON THE EU AND NATIONAL LEVEL

QIPC has established itself as one of the key new multidisciplinary fields between theoretical and experimental physics, computer science and mathematics. Continued competitiveness of the EU and its member nations requires a significant effort both on the European and national level

• QIPC must take a prominent and established position in EU research efforts, e.g. in the Seventh Framework Programme for Research of the European Commission (FP 7), and find its counterpart in national programs.

• The structure of the funding must account for the interdisciplinary character of the field, and must support a spectrum of activities across different disciplines from experimental to theoretical physics, computer sciences and mathematics.

• Links with industry must be developed, both on the level of possible commercial exploitation, and in research programs making new technologies available, outside the capabilities and know-how of traditional QIPC basic-research oriented laboratories. In particular, links with micro- and nano-fabrication facilities and related technology centers must be strengthened, and QIPC spin-off new quantum technologies like quantum sensors and high precision measurement devices ought to be encouraged.

References: The US Roadmap for Quantum Computing and Quantum Cryptography is available at http://qist.lanl.gov