EuroSQIP stands for European Superconducting Quantum Information Processor and is coordinated by Profesor Göran Wendin at Chalmers University of Technology in Sweden. EuroSQIP is a close collaboration between fourteen European universities and research institutes in Sweden, Germany, the Netherlands, France, Italy, Switzerland, Austria and Russia. The EC contribution is 6 million Euros, representing about half of the budget for the project.

EuroSQIP is now on its way since four months and the partners will gather in Paris at the Institut Henri Poincaré during 22-24 March to present results and compare notes, and to listen to invited talks from prominent scientists in neighbouring fields. A major activity will involve the planning of research during the remaining part of 2006. Although integrated projects like EuroSQIP involve long-term and high-risk research, the organizational form promotes close collaboration between partners to meet the challenges in the work plans, with reviews and revision every twelve months. This creates interesting perspectives, considering that EuroSQIP concerns fundamental research, the true objectives of which may take ten to twenty years to approach, and maybe fifty years to accomplish.

The purpose of the EuroSQIP project is to fabricate a prototype solid state, superconducting “computer” with 3-5 quantum bits – qubits – complete with control and readout circuitry, including designs for memory devices and communication buses. Actually, this means experimenting with a single register with 3-5 qubits. The ancestor of the microprocessor, the Intel 4004 from 1971, also had 4-bit registers, but it had quite a few of them; this made it possible to shift data sequentially between registers and to add and subtract their contents, achieving amazing things on a chip in those days. On the other hand, a 4-bit quantum computer will basically have one single 4-qubit register, but it will be coherent, and one will be able to superpose all bit configurations. That is a little bit like playing on all of the strings of a violin at the same time, making use of all possible effects of overtones, interference, chords and harmonies. There is however an additional – quantum – quality that a classical violin can never have – entanglement. That describes relations – correlations – between the strings that Einstein described as spooky action at a distance. Spooky or not, it remains an experimental fact, and entanglement may be what gives a quantum computer its ultimate power.

A quantum computer of tomorrow will need at least 50-100 qubits to become really useful in the sense of solving hard problems that ordinary supercomputers will never be able to solve. With 5 qubits things become more modest, and we only need to handle simultaneously 32 interfering memory states of the computer. But they are coherent, and can play chords and produce some amazing music! For a short while, before the interference effects and the entanglement die out, on can influence that music by manipulating the strings. Finally, the music stops, and one must use the bow again to strike a new chord. So, the overall objective of EuroSQIP to is to make a single 3-5 qubit register in such a coherent manner that one can perform a significant number of operations during the lifetime of a musical chord, to solve problems that are hard for ordinary computers (and classical violinists). The sad fact is that in order really to compete with the best ordinary computers of today, a quantum computer must be able to handle at least 30 qubits during long times. However, such achievements lie far ahead – currently the largest qubit registers contain 8 qubits, in ion traps, and a major problem will be to scale up the size of the qubit registers. There the solid-state solutions may have an advantage through micro/nanofabrication technologies. A fair perspective is probably to start from the first integrated circuit, in 1963. This suggests that we may have to wait for 40 years for quantum computer technology to show what it can do.

The different EuroSQIP partners work with three variations of superconducting qubits based on Josephson junctions. The current situation is that single qubit registers are quite well understood, and that work is in progress with 2-4 coupled qubits at different levels of sophistication. The critical milestone for the first year is to be able to operate a 2-qubit register during “long” times (around a microsecond) in general ways required for building quantum logic circuits. In four years the ambition is to be able to perform advanced general operations on a 3-5 qubit register, and to understand the conditions for building larger circuits, like 10-qubit registers, in a not too distant future.

The EuroSQIP qubits make use of the phenomenon of macroscopic quantum coherence to create electronic circuits that are governed by the laws of quantum physics in spite of not being smaller than the computer circuits of today. The price one has to pay is to have to cool down the circuits to temperatures close to absolute zero. The benefit is to be able to design and optimise “artificial atom” qubits. Once the design criteria for quantised electronic circuits with small clusters of 3-10 qubits are understood, one can expect opportunities for large-scale integration to open up.

The development of a quantum information processor on a chip represents one aspect of the evolution of nanoelectronics and quantum devices that can be expected strongly to influence future information, sensor and measurement technologies.

EuroSQIP, European Superconducting Quantum Information Processor is one of three integrated EU projects within the FP6 IST-FET program Quantum Information Processing and Communication (QIPC). The others are SCALA and QAP, and soon the Coordination Action programme QUROPE will start up, forming a cohesive framework for all the European QIPC activities.

Kick-off meeting – Quantum Computation and Coherence
Paris, 22-24 March 2006, Institut Henri Poincaré, Paris.
Organizers: D.Esteve, D.L.Shepelyansky, G.Wendin

Further information on IST FP6-015708 EuroSQIP
Professor Göran Wendin, tel: +46 31 772 3189;
Ass. professor Göran Johansson, tel: +46 31 772 3237;