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One quantum problem solved, many more to go

By Liz Tay
May 6, 2007 12:00 PM ET

Computerworld Australia - Researchers in Japan have developed new circuit technology touted to be the vital next step towards the realization of a practical quantum computer.

A collaborative effort between the Japan Science and Technology Agency, the Institute of Physical and Chemical Research (RIKEN) and electronics vendor NEC Corp., the technology is said to be the world's first quantum bit (qubit) circuit that can control the strength of coupling between qubits.

Current electronics rely on the manipulation of binary bits between two states -- on and off, or one and zero -- to store information. In quantum computing, information is stored in qubits, which can exist in a much larger range of states.

While previous advances have been made in establishing qubits and quantum logic gates, the coupling of qubits so far has been difficult to control.

"It has hitherto been difficult to switch the movement of one bit and two bits in the same quantum bit, although the bit's movements in the state of one single bit and the coupling of two bits have been confirmed," explained Jaw-Shen Tsai, an NEC researcher.

The new technology enables the coupling of qubits to be controlled by employing an additional qubit in between the coupled qubit pair. The additional qubit acts as a nonlinear transformer that is able to turn on and off the magnetic coupling between the two coupled qubits.

Using the new scheme, researchers have successfully employed a coupled two-qubit system to carry out a multiquantum control experiment involving the turning on and off of the coupling.

Quantum computing is expected to be a vast improvement on today's most modern supercomputers due to its potential to perform functions exponentially faster than any current computer.

But there is still a long way to go before quantum computing becomes a reality, Tsai said. With ongoing improvements in conventional computers and their applications, Tsai expects the development of a practical quantum computer to be more than 10 years away.

Meanwhile, the researchers are making plans for more complicated quantum computations that involve more steps and more qubits, to create a more realistic system and keep abreast of competition from other laboratories in the U.S. and Europe.

Reprinted with permission from Computerworld Australia Story copyright 2012 Computerworld New Australia. All rights reserved.
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