Aug 11 2009
Under a targeted basic research program of the Japan Science and Technology Agency (JST), Hiroshi Imamura of the National Institute of Advanced Industrial Science and Technology (AIST), and Nobuhiko Yokoshi of JST have developed a new method for electrically measuring a quantum superposition spin state of two electrons captured in a gallium arsenide (GaAs) based semiconductor artificial molecule (double quantum dots).
In addition to its electrical property, "electric charge", an electron has a magnetic property referred to as "electron spin". A new approach called "spintronics", which attempts to exploit this magnetic property for electronics applications, is attracting considerable attention. Above all, it is expected that the electron spins captured in artificial semiconductor atoms or molecules can be used as the basis for future quantum information processing devices.
This group established the theoretical foundation for a method to electrically measure the quantum superposition of the two spin states (singlet and triplet) of two electrons captured in a double quantum dot. With the conventional methods, only the probability of singlet and triplet spin states could be measured. Since the new method can also detect the quantum-mechanical relative phase of the two states, the two-electron spin states are fully measured. This method is valuable not only in the context of basic physics but also as a means for confirming the initialization of the quantum states and reading out the computed results that are necessary to develop a quantum information processing device. Therefore, this method is expected to contribute to the development of quantum information processing devices based on semiconductor artificial molecules.
The research was conducted in collaboration with Hideo Kosaka (Associate Professor) of the Research Institute of Electrical Communication (RIEC), Tohoku University.
The results have been accepted by the American Physical Society's "Physical Review Letters" and will be published online in the near future.