Quantum computing advances - September 27, 2007
Scientists in the UK have made a major step in quantum computing by demonstrating that superconducting electrical circuits can be used to send information between two stores of quantum information (AFP, Reuters). The advance is detailed in two papers in this week's Nature – one by Silanpaa and colleagues and the other by Johannes Majer and colleagues.
Silanpaa and co connected their storage mechanisms for quantum information (qubits) via a cavity in which an electromagnetic wave had been established. Majer and co did a similar thing, but using ‘virtual’ photons (“weak perturbations of their cavity's quantum light field” according to an accompanying News and Views article, subscription required). As if quantum computing wasn’t difficult enough, another paper from last week’s Nature is also relevant, one authored by Houck et al. They detailed a ‘single-photon gun’ that can be used to generate and guide photons in an electrical circuit
What does this all mean though? Basically, for quantum computing to work we need to be able to transfer information stored in qubits to other qubits. Previously this had only been done between qubits that were (relatively) close to each other; this work shows it can be done over (relatively) large distances. Here’s what the News and Views piece makes of it all: “these papers represent confident steps towards the ultimate goal of a viable, large-scale quantum computer.”.
Yale, where many of these researchers are based, has a press release on this too.
Image: “coplanar waveguide cavity connecting two superconducting phase qubits at each end” / Michael Kemper
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Source: http://www.sciencedaily.com/releases/2007/10/071008103647.htm
Scientists at Florida State University's National High Magnetic Field Laboratory and the university's Department of Chemistry and Biochemistry have introduced a new material that could be to computers of the future what silicon is to the computers of today.
The material -- a compound made from the elements potassium, niobium and oxygen, along with chromium ions -- could provide a technological breakthrough that leads to the development of new quantum computing technologies. Quantum computers would harness the power of atoms and molecules to perform memory and processing tasks on a scale far beyond those of current computers.
"The field of quantum information technology is in its infancy, and our work is another step forward in this fascinating field," said Saritha Nellutla, a postdoctoral associate at the magnet lab and lead author of the paper published in Physical Review Letters.
Semiconductor technology is close to reaching its performance limit. Over the years, processors have shrunk to their current size, with the components of a computer chip more than 1,000 times smaller than the thickness of a human hair. At those very small scales, quantum effects -- behaviors in matter that occur at the atomic and subatomic levels -- can start playing a role. By exploiting those behaviors, scientists hope to take computing to the next level.
In current computers, the basic unit of information is the "bit," which can have a value of 0 or 1. In so-called quantum computers, which currently exist only in theory, the basic unit is the "qubit" (short for quantum bit). A qubit can have not only a value of 0 or 1, but also all kinds of combinations of 0 and 1 -- including 0 and 1 at the same time -- meaning quantum computers could perform certain kinds of calculations much more effectively than current ones.
How scientists realize the promise of the theoretical qubit is not clear. Various designs and paths have been proposed, and one very promising idea is to use tiny magnetic fields, called "spins." Spins are associated with electrons and various atomic nuclei.
Magnet lab scientists used high magnetic fields and microwave radiation to "operate" on the spins in the new material they developed to get an indication of how long the spin could be controlled. Based on their experiments, the material could enable 500 operations in 10 microseconds before losing its ability to retain information, making it a good candidate for a qubit.
Putting this spin to work would usher in a technological revolution, because the spin state of an electron, in addition to its charge, could be used to carry, manipulate and store information.
"This material is very promising," said Naresh Dalal, a professor of chemistry and biochemistry at FSU and one of the paper's authors. "But additional synthetic and magnetic characterization work is needed before it could be made suitable for use in a device."
Dalal also serves as an adviser to FSU chemistry graduate student Mekhala Pati, who created the material.
Note: This story has been adapted from material provided by Florida State University.
Fausto Intilla
http://www.oloscience.com
Posted by: Fausto Intilla | October 17, 2007 04:46 PM