Quantum Computers Move Closer to Reality, Thanks to Highly Enriched and Highly Purified Silicon

ScienceDaily  — The quantum computer is a futuristic machine that could operate at speeds even more mind-boggling than the world's fastest super-computers.

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SFU physicist Mike Thewalt and grad student Kamyar Saeedi with a sample of highly isotopically enriched silicon - its unique properties could advance quantum computing. (Credit: Image courtesy of Simon Fraser University)

Research involving physicist Mike Thewalt of Simon Fraser University offers a new step towards making quantum computing a reality, through the unique properties of highly enriched and highly purified silicon.

Quantum computers right now exist pretty much in physicists' concepts, and theoretical research. There are some basic quantum computers in existence, but nobody yet can build a truly practical one -- or really knows how.

Such computers will harness the powers of atoms and sub-atomic particles (ions, photons, electrons) to perform memory and processing tasks, thanks to strange sub-atomic properties.

What Thewalt and colleagues at Oxford University and in Germany have found is that their special silicon allows processes to take place and be observed in a solid state that scientists used to think required a near-perfect vacuum.

And, using this ²⁸Si they have extended to three minutes -- from a matter of seconds -- the time in which scientists can manipulate, observe and measure the processes.

"It's by far a record in solid-state systems," Thewalt says. "If you'd asked people a few years ago if this was possible, they'd have said no. It opens new ways of using solid-state semi-conductors such as silicon as a base for quantum computing.

"You can start to do things that people thought you could only do in a vacuum. What we have found, and what wasn't anticipated, are the sharp spectral lines (optical qualities) in the 28Silicon we have been testing. It's so pure, and so perfect. There's no other material like it."

But the world is still a long way from practical quantum computers, he notes.

Quantum computing is a concept that challenges everything we know or understand about today's computers.

Your desktop or laptop computer processes "bits" of information. The bit is a fundamental unit of information, seen by your computer has having a value of either "1" or "0."

That last paragraph, when written in Word, contains 181 characters including spaces. In your home computer, that simple paragraph is processed as a string of some 1,448 "1"s and "0"s.

But in the quantum computer, the "quantum bit" (also known as a "qubit") can be both a "1" and a "0" -- and all values between 0 and 1 -- at the same time.

Says Thewalt: "A classical 1/0 bit can be thought of as a person being either at the North or South Pole, whereas a qubit can be anywhere on the surface of the globe -- its actual state is described by two parameters similar to latitude and longitude."

Make a practical quantum computer with enough qubits available and it could complete in minutes calculations that would take today's super-computers years, and your laptop perhaps millions of years.

The work by Thewalt and his fellow researchers opens up yet another avenue of research and application that may, in time, lead to practical breakthroughs in quantum computing.

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Journal Reference:

1. M. Steger, K. Saeedi, M. L. W. Thewalt, J. J. L. Morton, H. Riemann, N. V. Abrosimov, P. Becker, H.- J. Pohl.Quantum Information Storage for over 180 s Using Donor Spins in a ²⁸Si 'Semiconductor Vacuum'.Science, 2012; 336 (6086): 1280 DOI:10.1126/science.1217635

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Cassini Plasma Spectrometer Turns Off

ScienceDaily — The Cassini plasma spectrometer instrument (CAPS) aboard NASA's Cassini spacecraft was turned off between Friday, June 1 and Saturday, June 2, when a circuit breaker tripped off after the instrument experienced some unexpected voltage shifts.

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Artist concept of Cassini spacecraft. Image credit: NASA/JPL Artist concept of Cassini spacecraft. (Credit: NASA/JPL)

 

Engineers are currently investigating this issue, which they believe is due to short circuits in the instrument. In June 2011, the instrument was turned off because of similar problems, but was switched on again in March 2012 once investigators determined that tin plating on electronic components had grown "whiskers" large enough to contact another conducting surface and carry electrical current, resulting in a voltage shift. At that time, it was believed that these "whiskers" were not capable of carrying sufficient current to cause any damage, and the voltage shifts didn't have any effect on normal spacecraft operations because the power subsystem is designed to operate in the presence of such shifts.
More details about whiskers on the CAPS instrument can be found here: http://www.jpl.nasa.gov/news/news.cfm?release=2012-078 .
The cause is still under investigation, but engineers will be looking into this issue over the next few months.
Cassini launched in 1997 and has been exploring the Saturn system since 2004. The project completed its original prime mission in 2008 and has been extended twice. Cassini is now in its solstice mission, which will enable scientists to observe seasonal change in the Saturn system through the northern summer solstice.??
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington.
For more information about the Cassini mission, visit: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .

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Story Source:
The above story is reprinted from materials provided by NASA/Jet Propulsion Laboratory.

Splitting the Unsplittable: Physicists Split an Atom Using Quantum Mechanics Precision

ScienceDaily  — Researchers from the University of Bonn have just shown how a single atom can be split into its two halves, pulled apart and put back together again. While the word "atom" literally means "indivisible," the laws of quantum mechanics allow dividing atoms -- similarly to light rays -- and reuniting them. The researchers want to build quantum mechanics bridges by letting the atom touch adjacent atoms while it is being pulled apart so that it works like a bridge span between two pillars.

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Maximilian Genske, Noomen Belmechri, Andreas Steffen and Dr. Andrea Alberti working. (Credit: Copyright Barbara Frommann/Uni Bonn)

 

The results have just been published in the journal Proceedings of the National Academy of Sciences.
Dividing atoms? What sounds like nuclear fission and radioactivity is, however, a precision process using quantum mechanics. The laws of quantum mechanics allow objects to exist in several states simultaneously. This is what the so-called double-slit experiment is based on, where a particle can go through two slits at the same time. The Bonn scientists working with Prof. Dr. Dieter Meschede from the Institute for Applied Physics of the University of Bonn succeeded in keeping a single atom simultaneously in two places that were more than ten micrometers, or one hundredth of a millimeter, apart. This is an enormous distance for an atom. Afterwards, the atom was put back together undamaged.
The atom has a split personality
The fragile quantum effects can only occur at the lowest temperatures and with careful handling. One method is cooling a cesium atom enormously using lasers -- to a temperature of a tenth of a million above absolute zero -- and then holding it with another laser. This laser beam is key to splitting the atom. It works because atoms have a spin that can go in two directions. Depending on the direction, the atom can be moved to the right or the left by the laser like on a conveyor. Key is that the atom's spin can be in both directions simultaneously. So, if the atom is moved to the right and left at the same time, it will split. "The atom has kind of a split personality, half of it is to the right, and half to the left, and yet, it is still whole," explained Andreas Steffen, the publication's lead author.
The parts compare their "experiences"
But you cannot see the split directly; if you shine a light on the atom to take a picture, the split will collapse immediately. The atom can then be seen in several images; sometimes on the left, sometimes on the right -- but never in both places. And yet, the split can be proved successfully by putting the atom back together. Thus an interferometer can be built from individual atoms that can, e.g., be used to measure external impacts precisely. Here, the atoms are split, moved apart and joined again. What will become visible, e.g., are differences between the magnetic fields of the two positions or accelerations since they become imprinted in the quantum mechanical state of the atom. This principle has already been used to very precisely survey forces such as Earth's acceleration.
Quantum systems as tools?
The Bonn scientists, however, are looking for something else: simulating complex quantum systems. Many physicists have been hoping for a long time to be able to simulate so-called topological isolators or plant photosynthesis -- phenomena that are hard to capture with modern super computers -- using small quantum systems. The first steps on the way to such simulators could consist of modeling the movement of electrons in solid bodies, thus gaining insights for innovative electronic devices. Examples for this are Dirac motion of electrons in a single graph-layer or the emergence of artificial molecules from interacting particles. But for this purpose, individual atoms would not only have to be well controlled, but also linked according to quantum mechanical laws since where the crux of the matter lies is exactly in a structure made up from many quantum objects.
A cog in a gearbox
"For us, an atom is a well-controlled and oiled cog," said Dr. Andrea Alberti, the team lead for the Bonn experiment. "You can build a calculator with remarkable performance using these cogs, but in order for it to work, they have to engage." This is where the actual significance of splitting atoms lies: Because the two halves are put back together again, they can make contact with adjacent atoms to their left and right and then share it. This allows a small network of atoms to form that can be used -- like in the memory of a computer -- to simulate and control real systems, which would make their secrets more accessible. The scientists believe that the entire potential of controlling individual atoms this precisely will become apparent over time.

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Journal Reference:

1. A. Steffen, A. Alberti, W. Alt, N. Belmechri, S. Hild, M. Karski, A. Widera, D. Meschede. Digital atom interferometer with single particle control on a discretized space-time geometry. Proceedings of the National Academy of Sciences, 2012; DOI: 10.1073/pnas.1204285109