Quantum Mechanical Behavior of a Single Electron Recorded

The quantum mechanical behavior of a single electron in a nanoscale defect in a diamond was recorded for the first time. Electrons can be in many states at once and this new technique, which used ultrafast laser light pulses, allowed both observation of how the electron state changed over time and could also control the entire quantum state of the defect in diamond.

Traditional information processing uses binary logic; that is, zeros or ones, which is unambiguous. The state is either a zero or a one. In the emerging field of quantum information processing, the quantum world is employed. The quantum world can be described as ambiguous in terms of place and state with electrons possibly being in different states at once. A research team at the University of Chicago devised a new technique that employs quantum mechanical properties as a basis for bits of information. This new technique was described in a report published by Science Express and a print publication will be included in the journal Science this month.

The quantum mechanical property of an electron called spin was used. The spin state of a single electron was set as a quantum bit, or otherwise called a qubit. Qubits could be used in quantum computing. Quantum computing would be very fast; that is, much faster than computing using conventional zeros and ones. As reported, one development which could occur from the newly published study would be new materials that have appropriate quantum properties could be identified in the near future, and these new mataries would allow great advances in quantum computing.

What was special about this technique is it employed an atom-sized defect that exists naturally in diamond. This defect is a nitrogen-vacancy center, which is atom-sized. In this defect, there is a nitrogen atom that sits next to a vacant spot in the diamond’s crystal lattice. In the experiment, the scientists were able to harness the light and completely control the quantum state of the diamond defect at very high speeds. With this technique, a single nitrogen-vacancy center is located and then illuminated with very short pulses (a millionth of a second) of laser light. The initial pulse excites the defect-bound electron and then the electron states change in characteristic ways. A second laser light pulse stops the changes and captures a “picture” of the quantum state at that timepoint. When the elapsed time between two pulses is extended, a series of “snapshots”, or movie, is created. The vast range of possible timescales makes the new technique valuable because there are then interactions with the local environment in many different ways. Testing different timescales gives a more complete picture of the dynamics of the nitrogen-vacancy center.

Another interesting point about the technique is it also allows for control of the spin state of the electron, and not just observation. Also, it can be applied to quantum states of other types of matter, such as semiconductor materials. Control of new materials on an atomic level was reported as being possible.

The research was carried out by researchers at the Institute for Molecular Engineering at the University of Chicago and also by researchers at the University of California at Santa Barbara, the University of Pennsylvania and the University of Konstanz in Germany. Many are interested in the development of quantum computing methodology and moving beyond the limits of a binary system for computing. It has been reported that this new development in recording and controlling the quantum mechanical behavior of a single electron will have great repercussions for the future of quantum computing.

By Margaret Lutze

News Wise
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