[Paleopsych] Magnetic resonance goes nano

[Steve Hovland]

http://www.trnmag.com/Stories/2005/060105/Magnetic_resonance_goes_nano_B  
rief_060105.html


June 1/8, 2005
The magnetic resonance imaging devices that hospitals use to diagnose 
illnesses provide detailed pictures of the insides of the human body by 
measuring the unique responses of the atoms and molecules in specific types 
of tissue to particular sequences of radio waves and magnetic pulses.

The technology also gives scientists a way to control the spins, or 
magnetic orientations of atoms; this ability has led to several prototype 
quantum computers. Although nuclear magnetic resonance quantum computer 
prototypes have been among the most advanced quantum devices built, such 
systems are generally limited to about 10 quantum bits, which is well short 
of the thousands needed for practical systems.

Researchers from NTT Basic Research Labs in Japan and the Japan Science and 
Technology Agency have built a nuclear magnetic resonance device that has 
the potential to overcome the limit because it is small enough to fit on a 
computer chip. It could also be tapped to allow nuclear magnetic resonance 
devices used in chemistry, biology and medicine to examine smaller samples, 
according to the researchers.

Quantum computers use properties like spin to represent the 1s and 0s of 
digital information. In theory, quantum computers would be able to solve 
certain types of very large problems, including those underpinning today's 
encryption technologies, many orders of magnitude faster than today's 
classical computers.

The researchers' device measures spin by measuring electrical resistance 
across a 200-by-200-nanometer area of semiconductor material rather than 
using a centimeter-scale coil to pick up radio waves. This allows it to 
control and measure a much smaller number of atomic spins and to control 
and measure six distinct types of spin.

The researchers' next step is to fabricate a quantum integrated circuit by 
connecting several nuclear magnetic resonance devices. Even without links 
to each other, the devices could be used as quantum memory, according to 
the researchers.

It will be 10 or 20 years before quantum computers that contain 100 to 
10,000 qubits are ready for commercial use, according to the researchers. 
The work appeared in the April 21, 2005 issue of Nature (Controlled 
Multiple Quantum Coherences of Nuclear Spins in a Nanometer-Scale Device).