A University of Sussex scientist and his American colleagues have solved a mystery that limits the performance of the world's fastest computer, the quantum computer, after making an unexpected discovery.
Quantum technology is set to revolutionise our lives. Extremely fast computers that are based on this technology could solve mysteries in the understanding of our world, such as understanding chemical reactions and ultimately creating new medicines. The same technology already provides ultra-secure communications systems, and could be used in code-breaking to reveal answers to highly-complex questions, such as how the universe was created.
In the last few years ground breaking discoveries have been made showing great promise in a particular technology in which atoms are trapped and manipulated using laser and electric fields. These "ion traps", which are devices that trap single charged atoms (ions), can be used to process and transport vast amounts of information.
But while scientists have the knowledge of what a quantum computer could do, the challenge so far has been in how to build one on a small enough scale. An ion trap quantum computer would require millions of ion traps, resulting in a machine so large that it would fill a laboratory. The smaller the ion trap, the larger is the detrimental effect of "noise". Noise is the random motion of the atom created by electric fields that may prevent such a computer from working.
Now Dr Winfried Hensinger, lecturer in atomic molecular and optical physics at the University of Sussex, has worked with colleagues at the University of Michigan to successfully build a new type of ion trap. Louis Deslauriers, a graduate student at the University of Michigan (now a postdoctoral fellow at Stanford University) spearheaded the effort to build an ion trap that can change its size. Using this complicated experimental device, the scientists could measure exactly how the noise is related to the size of the ion trap and more importantly answer the question how small an ion trap computer could be made. In the process the team also made the world's smallest ion trap - just 0.023 mms from electrode to ion, equivalent to the width of a single hair.
In order to understand the mechanism behind such noise, the team tried cooling the electrodes that form the ion trap on either side of the ion to -120 degs C and made a surprising discovery. Most of the noise actually disappeared. This could mean that an ion trap quantum computer could be made much smaller than previously expected simply by cooling the electrodes.
Dr Hensinger said: "This is a very exciting discovery, and means that we now have a very realistic chance to develop the world's first large-scale quantum computer."
The latest successful research, which is published in Physical Review Letters (September 8, 2006), builds on previous work by Dr Hensinger and his colleagues on the chip fabrication of ion trap arrays and the microscopic manipulation of atoms. The research was carried out in the laboratory of Prof. Christopher Monroe at the University of Michigan.
Dr Hensinger, who heads the Ion Quantum Technology Group at the University of Sussex, says: "Quantum computer technology is likely to unlock some of science's biggest secrets, not only by processing information hundreds of times faster than current computers, but also by giving more accurate results. It is a very exciting and dynamic area of research and research at the University of Sussex will play an important role."
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