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New Law for Quantum Computers Disclosed

March 06, 2000

Arun Kumar Pati, who is currently at the University, but who is based at the Bhaba Atomic Research Centre, Mumbai, India, and Samuel L. Braunstein, at the School of Informatics have published a paper in the current issue of the International Journal, Nature [9 March 2000], describing their discovery of a new law, which they call the quantum no-deleting principle.

"The advances in conventional computer technology have seen an incredible increase in speed together with the production of microchips to ever smaller scales. When these scales approach the sizes of atoms, then different laws, described by quantum physics, come into play. Computers working at the atomic scale designed to specially utilize the weirdness of the quantum world are predicted to achieve startling speed-ups in processing power. These are called quantum computers." says Dr. Braunstein.

"Although it may take several decades to build quantum computers, many scientists around the world are already working towards their realization. For such long-range planning to succeed it is essential to grasp the boundaries of capability of such quantum technology. For example, the established no-cloning principle, states that if we tried building a copying machine for quantum objects we would fail, because we cannot measure a quantum state precisely enough," says Dr. Braunstein. "This principle is now recognized by scientists to be an important milestone in the realization of quantum computers."

"To understand our result, let us recall a simple task for any conventional computer. If we had stored several copies of some data, then anyone could easily delete one or more of these copies, leaving the rest intact. By contrast, our new principle states that, if we had stored several copies of our quantum data on a quantum computer, then only we, the original owners, could delete any of them. No-one else could delete even a single copy," explains Dr. Pati. "This task looks very much like running a copying machine in reverse; starting with two identical copies and leaving a single original and a blank sheet. Like cloning, this task is impossible in the quantum world. To our surprise, the no-deleting principle, describes a new boundary for the quantum world, and is different from that described by no-cloning."

Dr. Pati says "I am sure that this quantum no-deleting principle will play a pivotal role in our present understanding of quantum information and further our ability to handle and manipulate quantum information" He explains," the fact that it is impossible to delete quantum information, means that in principle the information is very secure, in the sense that it cannot be accidentally tampered with. It does however, present the problem of //over... removing information completely, when that is what you want to do."

In this burgeoning era of quantum information science, Bangor scientists have disclosed another law, hitherto unnoticed. Though the quantum no-deleting principle puts a limitation on quantum information it may lead to new ways of harnessing quantum information. ENDS.
2.3.00



Wales Bangor, University of