May 21 2010
Shiro Kawabata of Nanomaterials Theory Group, the Nanotechnology Research Institute of the National Institute of Advanced Industrial Science and Technology and his colleagues have discovered, from simulations of Josephson junction devices with a structure in which a ferromagnetic insulator is sandwiched between high-temperature superconductors, a phenomenon whereby two macroscopic quantum states of a junction device (0 junction and p junction) are alternately realized when the thickness of the ferromagnetic layer is changed in increments of one atomic layer.
The discovery that macroscopic properties over the whole device are changed drastically by differences in atomic-scale thickness is of great interest for basic science. On the basis of this discovery, we predict that macroscopic properties of superconducting devices can be artificially controlled by magnetic material thicknesses. We expect the application of such devices to lead to the future realization of quantum bits and quantum computers that are both robust to external noise.
Quantum computers have attracted great interest in recent years because of their potential for realizing massive parallel computation that greatly surpasses the capabilities of current computers. A major key to the realization of quantum computing is finding a way to eliminate the effects of external noise, which destroys quantum coherence. With the application of the phenomenon we have discovered, there is potential for realizing quantum bits that are completely unaffected by external noise and are capable of high-temperature operations. With such quantum bits, a possible road to practical quantum computers will be opened. In addition, we expect new applications to high-sensitivity magnetic sensors, quantum voltage standards, and suchlike.
This research was conducted as a part of the research project "Framework Development for Multiscale and Multiphysics Simulations toward Novel Applications of Superconductivity" (Research representative: Masahiko Machida) under the research area "High Performance Computing for Multi-scale and Multi-physics Phenomena" (Research leader: Genki Yagawa) of the Core Research for Evolutional Science and Technology (CREST) team research of Japan Science and Technology Agency.
The results of the research will be published in the electronic edition of Physical Review Letters, a scientific journal of the American Physical Society.