Scientists Create First Working Model of a Two-Qubit Electronic Quantum Processor

[David Farber <dave () farber net>]

Scientists Create First Working Model of a Two-Qubit Electronic  
Quantum Processor

Model uses the power of quantum mechanics in a processor similar to  
that found in computers and cell phones

June 30, 2009

<http://www.nsf.gov/news/news_summ.jsp?cntn_id=115089&govDel=USNSF_51>

A team led by Yale University researchers has successfully implemented  
simple algorithms using a quantum processor based on microwave solid- 
state technology--similar to that found in computers and cell phones.  
The new processor is far from conventional, however, in that it uses  
the potent power of quantum mechanics to bring the dream of quantum  
computing a small but significant step closer to reality.

The work was supported in part by the Yale Center for Quantum and  
Information Physics (CQUIP), funded by a grant from the National  
Science Foundation's Division of Materials Research and Division of  
Physics, and by the Army Research Office and National Security Agency.  
The findings were published online in the June 28 issue of Nature.

"This result is an important step forward towards all-electronic  
quantum information processing," said Wendy Fuller-Mora, program  
director for the NSF Division of Materials Research/Condensed Matter  
Physics.

"Our experiment can only perform a few very simple quantum tasks,  
which have been demonstrated before using other systems such as  
photons, trapped ions, and nuclear magnetic resonance," said Robert  
Schoelkopf, a principal investigator and professor of applied physics  
and physics at Yale. "But this is the first time it has been done in  
an all-electronic device, which looks and feels much more like a  
regular microprocessor."

The team used artificial atoms as quantum bits, or qubits. Although  
made from over a billion aluminum atoms in a superconducting  
electronic circuit, these qubits behave as single atoms. The  
difference is that the manufactured atoms are much larger and  
therefore easier to control than single atoms or other types of qubits.

Just like a single atom, an artificial atom can be stimulated into  
different energy states, akin to the "on" and "off" states of the bits  
in conventional computers. But following the counterintuitive laws of  
quantum mechanics, the scientists can also place these artificial  
atoms in "superpositions" of quantum states-both "off" and "on" at the  
same time. This wider variety of possible states allows for greater  
information storage and processing power.

As an example, imagine searching through a set of four phone numbers,  
including one for a friend, without knowing which number belonged to  
the friend. "It's like being able to place one phone call that  
simultaneously tests all four numbers, but only goes through to the  
right one," Schoelkopf said.

To perform this kind of "reverse phone book" search, the scientists  
used logic gates made from two qubits, which communicated with one  
another using a "quantum bus" design previously developed by members  
of the team.

[snip]


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