Nanocomputing - For real

Last week Nature magazine published an article describing how scientists at IBM's Almaden Research Center managed to transform a billion-billion (10^18) custom-designed molecules into a quantum computer that finds a number's factors, a major issue in cryptographic systems.

The IBM site doesn't explain in detail how things were done, saying that "a quantum computer gets its power by taking advantage of certain properties of atoms or nuclei that allow them to work together as quantum bits, or qubits, which serve simultaneously as the computer's processor and memory". Scientist Isaac Chuang, leader of the research team and now an associate professor at MIT, called attention to the core of the problem: "Now we have the challenge of turning quantum computation into an engineering reality".

The conquest is a further step in a series of experiments which started after quantum computers were proposed by Richard Feynman, Paul Benioff, David Deutsch and Charles Bennett, and it was greatly advanced by the description (in 1994) by Peter Shor of a quantum algorithm for factoring large numbers exponentially faster than conventional computers. Chuang "led the team that demonstrated the world's first 2-qubit quantum computer in 1998 at University of California (Berkeley). At IBM, Chuang and colleagues were first to demonstrate important quantum computing algorithms with 3-qubit and 5-qubit quantum computers."

David Di Vincenzo, research staff member at IBM's Watson lab, has promulgated five criteria necessary for a practical quantum computer: (a) a scalable physical system with well characterized qubits; (2) the ability to initialize the qubits state; (3) decoherence times much longer than the quantum gate operation time; (4) a universal set of quantum gates; and (5) the ability to measure specific qubits.

The thing in itself is a seven-qubit quantum computer designed to have seven nuclear spins - the nuclei of five fluorine and two carbon atoms - which can interact with each other as qubits, be programmed by radiofrequency pulses and be detected by nuclear magnetic resonance (NMR) instruments similar to those commonly used in hospitals and chemistry labs. We must investigate this matter more carefully.

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