While most students have no clue what Dirac electrons, quantum computers and copper-doped bismuth selenide are, a new breakthrough by University physicists could eventually change that.
Physics Prof. Lu Li, along with University doctoral student Benjamin Lawson and Yew San Hor, a professor at the Missouri University of Science and Technology, have confirmed that material copper-doped bismuth selenide contains Dirac-like electrons, which could prove significant in increasing the speed and capabilities of quantum computing.
In a typical computer, like the ones students use daily to post on Facebook and work on class assignments, information is stored in a binary format as zeroes and ones, which are called bits. Calculations are performed as different sequences of binary encoding information.
Quantum computers, however, can store these sequences as zeroes and ones separately like a traditional computer, but can also store sequences with both zeroes and ones at the same time, called qubits.
Lawson, who assisted in contrasting the measurement methods and collected much of the project’s data, said the concept could be easily explained by visualizing a device with rows of switches.
“You can think of it like this: I am trying to convey a message to you with a bunch of switches,” Lawson said. “In a classical computer, you look at the switches which are all either up or down and translate a message. In a quantum computer, all the switches are either up, down, or a single switch could be both up and down. With the third option, I can encode much more information with fewer switches.”
The idea of quantum computing is not new — Li said it’s been around for more than a decade. But Li, Lawson and Hor’s recent discovery uncovered the copper-doped bismuth selenide that contains Dirac electrons, or electrons that can outperform regular electrons by allowing “switches” to be up, down or both at the same time.
Lawson compared the material to silicon for classic computers, and said it could be the key building block for quantum computers. Copper-doped bismuth selenide is considered a topological superconductor, meaning they conduct energy indefinitely and have enough energy to process classical and quantum physics.
“That’s the beauty of that scheme,” Li said.
Although Li and his team were not the first researchers to theorize copper-doped bismuth selenide could contain the Dirac electrons needed for quantum computation, they were the first to actually detect them, thus proving the theory correct.
But students shouldn’t expect to complete their CTools assignments on a quantum computer anytime soon. Lawson said students don’t interact with quantum computers because they don’t yet work as efficiently as classical computers.
Still, many students use classical computers to do complicated calculations, which takes a long time.
“Quantum computers hold the promise of being able to do these computations much faster,” Lawson said. “The technology is not there yet, but there is a lot of potential.”
Lawson said further experiments are necessary to ensure potential topographical superconductors behave in ways the initial research has shown. Further research initiatives will then attempt to find ways to employ their properties in user-friendly quantum computers.
UofM’s Dirac electrons point way to quantum computer
In this post we attempt to wander into the tall grass known as quantum computing. Some of this confusing jungle has been cut away by Professor Lu Li (Physics) of the University of Michigan. In a U of M press release (December 4, 2012) he/they report that Dirac Electrons have been directly observed in an exotic material - copper-doped bismuth selenide (Cu0.25Bi2Se3). The doped bismuth selenide has been studied before and is known for having some unique properties; an "insulating topological superconductor".
`In the flurry of research activity on CuxBi2Se3 (same thing) Professor Li has picked up on this work. Professor Li cooled the exotic stuff to ultra-cold temperatures ("cryogenic") and was able to somehow directly observe the until-then-theoretical Dirac electrons. That is to say that other researchers had proposed the existence of the Dirac electrons but U of M's Li was the first to observe them. He describes them as superconducting electrons that can "clump together" and have "no electrical resistance". These properties/this property makes them desirable to investigate as qubits - the quantum computing equivalent of bits.
This also means that the Dirac electrons also have "a leg in each world" - the world of the classical physical and the world of the quantum. That such a beast so uniquely quantum and classical has been observed for the first time is itself remarkable. The property of such a thing being directly observable also means it may be suitable for the quantum computers' qubits. The quantum computer user will be able to process quantum calculations without changing them via observation - another remarkable property.
However, just observing the copper-doped bismuth selenide material is challenging in that we have located no images of the exact material. At least not yet. Also images of Dirac electrons will likely be impossible or not available online as yet. The best we can do is provide a video of Dirac Fermions (to which Dirac electrons should belong). As far as an image of a topological superconductor of bismuth selenide the Berkeley Lab News Center might have the best representation so far. An actual working quantum computer of Dirac electrons from the University of Michigan may be a long way off .
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