Professor Mitsuru Takenaka and his team, in collaboration with the National Institute of Advanced Industrial Science and Technology (AIST), have succeeded in developing a low-loss, nonvolatile optical phase shifter using a new phase-shift material, Ge2Sb2Te3S2 (GSTS). The refractive index change per unit loss generated when GSTS is converted from amorphous to crystalline is more than 20 times larger than that of conventional technology. The optical computations using silicon optical circuits with many GSTSs integrated are expected to be applied to deep learning, quantum computation, etc., because the optical loss is extremely small and the integration conditions for low power consumption due to small size and non-volatility are met. The research results were published in “Technical Digest” published at the IEEE International Electron Devices Meeting (IEDM) held on the West Coast of the United States from December 3 to 7 (U.S. Pacific Standard Time).