Ever since 1981, scientists have been dreaming of a computer faster than the fastest supercomputer available today. Quantum computing, the idea of creating a computer that works by taking advantage of the properties of subatomic particles, would make these ultrafast computers available. Although this field is still in its infancy, it has been making quite some progress.
A step forward was recently taken by researchers at the Ruhr University Bochum in Germany, working with other researchers in Tokyo and Grenoble, France. These physicists have been able to transport a single electron from one quantum dot, which is a very small piece of a semiconductor, to another using a sound wave. The sound wave carries the electron along with it, at a speed of three micrometers per nanosecond, to the other quantum dot. Scientists were able to do this with a very high degree of accuracy.
The field of quantum electron optics looks at single elections. It aims to manipulate electrons at the single electron level. However, electrons are usually tightly packed together, making isolating and studying them nearly impossible. Fortunately for the field, quantum dots provide a good source of single electrons. While they do contain more than one electron, the electrons within quantum dots can be isolated close to the surface so that one can be trapped by a sound wave.
In the experiment, physicists moved the electron using an acoustic wave from the quantum dot through a quantum channel, where it was kept isolated from all other electrons. It was then deposited at another quantum dot spaced three micrometers apart. Electrodes were used to keep any extraneous electrons from entering the channel. The dot that the electron leaves is known as the single-electron source, and the dot that it enters is known as the single-electron detector.
Quantum dots are also convenient for use because it is easy to check if an electron is stored on one. A voltage pulse is sent through the single-electron detector to see if there are any electrons present. If there is one present, it is assumed that it came through the channel from the other quantum dot.
Researchers have also found that when starting with two electrons in the quantum dot source, they can transport one or both electrons to the quantum dot detector, depending ELECTRONS, from B7
set up around the source. Using the pulses of voltage through the second quantum dot, it was easy to tell whether one, two, or more electrons resided in the single-electron detector. Researchers believe that the ability to be able to separate two electrons is of interest in transporting quantum information.
Another important part of the experiment was keeping the orientation of the electron's spin the same as it was transferred and after it reached the second dot. This could have important implications for creating quantum bits in the future.
The physicists found that electrons in quantum dots keep the same spin for about 25 nanoseconds and that they could transfer an electron from one quantum dot to another in less than that time. Researchers hope that further experiments will be able to consistently keep electrons moving at the same spin after they are transferred from one quantum dot to another and use this in future quantum bits.
The process used by researchers was revealed to be highly efficient and accurate. Researchers at RUB hope that it can someday be used to produce complex quantum bits. Quantum bits are similar to the bits, strings of zeros and ones, used to store information in regular computers except that they are used in quantum computers.
