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Quantum computing spins closer
November 24, 2008The promise of quantum computing is that it will dramatically outshine traditional computers in tackling certain key problems: searching large databases, factoring large numbers, creating uncrackable codes and simulating the atomic structure of materials.
A quantum step in that direction, if you'll pardon the pun, has been taken by Stanford researchers who announced their success in a paper published in the journal Nature. Working in the Ginzton Laboratory, they've employed ultrafast lasers to set a new speed record for the time it takes to rotate the spin of an individual electron and confirm the spin's new position.
Why does that matter? Existing computers, from laptops to supercomputers, see data as bits of information. Each bit can be either a zero or a one. But a quantum bit can be both zero and one at the same time, a situation known as a superposition state. This allows quantum computers to act like a massively parallel computer in some circumstances, solving problems that are almost impossible for classic computers to handle.
Quantum computing can be accomplished using a property of electrons known as "spin." A single unit of quantum information is the qubit, and can be constructed from a single electron spin, which in this experiment was confined within a nano-sized semiconductor known as a quantum dot.
An electron spin may be described as up or down (a variation of the usual zero and one) and may be manipulated from one state to another. The faster these electrons can be switched, the more quickly numbers can be crunched in a quantum fashion, with its intrinsic advantages over traditional computing designs.
The qubit in the Stanford experiment was manipulated and measured about 100 times faster than with previous techniques, said one of the researchers, David Press, a graduate student in applied physics.
The experiments were conducted at a temperature of almost absolute zero, inside a strong magnetic field produced by a superconducting magnet. The researchers first hit the qubit with laser light of specific frequencies to define and measure the electron spin, all within a few nanoseconds. Then they rotated the spin with polarized light pulses in a few tens of picoseconds (a picosecond is one trillionth of a second). Finally, the spin state was read out with yet another optical pulse.
Similar experiments have been done before, but with radio-frequency pulses, which are slower than laser-light pulses. "The optics were quite tricky," Press said. The researchers had to find a single, specific photon emitted from the qubit in order confirm the spin state of the electron. That photon, however, was clouded in a sea of scattered photons from the lasers themselves.
"The big benefit is to make quantum computing faster," Press said. The experiment "pushed quantum dots up to speed with other qubit candidate systems to ultimately build a quantum computer."
Quantum computers are still years away. In the shorter term, Press said, researchers would like to build a system of tens or hundreds of qubits to simulate the operation of a larger quantum system.
The other authors of the Nature paper were Bingyang Zhang of the Ginzton Lab, and Thaddeus Ladd and Yoshihisa Yamamoto of the Ginzton Lab and the National Institute of Informatics in Tokyo.
Stanford University
Quantum computing can be accomplished using a property of electrons known as "spin." A single unit of quantum information is the qubit, and can be constructed from a single electron spin, which in this experiment was confined within a nano-sized semiconductor known as a quantum dot.
An electron spin may be described as up or down (a variation of the usual zero and one) and may be manipulated from one state to another. The faster these electrons can be switched, the more quickly numbers can be crunched in a quantum fashion, with its intrinsic advantages over traditional computing designs.
The qubit in the Stanford experiment was manipulated and measured about 100 times faster than with previous techniques, said one of the researchers, David Press, a graduate student in applied physics.
The experiments were conducted at a temperature of almost absolute zero, inside a strong magnetic field produced by a superconducting magnet. The researchers first hit the qubit with laser light of specific frequencies to define and measure the electron spin, all within a few nanoseconds. Then they rotated the spin with polarized light pulses in a few tens of picoseconds (a picosecond is one trillionth of a second). Finally, the spin state was read out with yet another optical pulse.
Similar experiments have been done before, but with radio-frequency pulses, which are slower than laser-light pulses. "The optics were quite tricky," Press said. The researchers had to find a single, specific photon emitted from the qubit in order confirm the spin state of the electron. That photon, however, was clouded in a sea of scattered photons from the lasers themselves.
"The big benefit is to make quantum computing faster," Press said. The experiment "pushed quantum dots up to speed with other qubit candidate systems to ultimately build a quantum computer."
Quantum computers are still years away. In the shorter term, Press said, researchers would like to build a system of tens or hundreds of qubits to simulate the operation of a larger quantum system.
The other authors of the Nature paper were Bingyang Zhang of the Ginzton Lab, and Thaddeus Ladd and Yoshihisa Yamamoto of the Ginzton Lab and the National Institute of Informatics in Tokyo.
Stanford University
Quantum Computing Current Events and Quantum Computing News RSSUCSB physicists move 1 step closer to quantum computing
Physicists at UC Santa Barbara have made an important advance in electrically controlling quantum states of electrons, a step that could help in the development of quantum computing.
Rice ties in race for atomic-scale breakthrough
Everybody loves a race to the wire, even when the result is a tie. The great irony is the ultraprecise clocks that could result from this competition could probably break any tie.
NIST demonstrates 'universal' programmable quantum processor
Physicists at the National Institute of Standards and Technology (NIST) have demonstrated the first "universal" programmable quantum information processor able to run any program allowed by quantum mechanics-the rules governing the submicroscopic world-using two quantum bits (qubits) of information.
UA scientists discover quantum fingerprints of chaos
Chaotic behavior is the rule, not the exception, in the world we experience through our senses, the world governed by the laws of classical physics.
Diamonds may be the ultimate MRI probe, say Quantum physicists
Diamonds, it has long been said, are a girl's best friend. But a research team including a physicist from the National Institute of Standards and Technology (NIST) has recently found that the gems might turn out to be a patient's best friend as well.
A Police Woman Fights Quantum Hacking and Cracking
The first desktop computers changed the way we managed data forever. Three decades after their introduction, we rely on them to manage our time, social life and finances - and to keep this information safe from prying eyes and online predators.
Physicists find way to control individual bits in quantum computers
Physicists at the National Institute of Standards and Technology (NIST) have overcome a hurdle in quantum computer development, having devised* a viable way to manipulate a single "bit" in a quantum processor without disturbing the information stored in its neighbors.
NIST develops novel ion trap for sensing force and light
Miniature devices for trapping ions (electrically charged atoms) are common components in atomic clocks and quantum computing research. Now, a novel ion trap geometry demonstrated at the National Institute of Standards and Technology (NIST) could usher in a new generation of applications because the device holds promise as a stylus for sensing very small forces or as an interface for efficient transfer of individual light particles for quantum communications.
Scientists create first working model of a 2-qubit electronic quantum processor
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.
Scientists create first electronic quantum processor
A team led by Yale University researchers has created the first rudimentary solid-state quantum processor, taking another step toward the ultimate dream of building a quantum computer.
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