Abstract: An optical waveguide includes a cladding layer, a Si layer, a REO layer, and a cap layer. The REO layer is made of a single-crystal rare earth oxide, and is formed on the Si layer. The cap layer is formed on the REO layer. The cap layer may be made of a material transparent to light to be guided. The cap layer has a stripe shape extending in a direction in which light is guided.

Abstract: In an embodiment method for growing a rare earth oxide crystal, a surface of a Si substrate is cleaned by carrying out treatments using chemical solutions such as a mixed sulfuric acid-hydrogen peroxide solution, hot nitric acid, or diluted hydrofluoric acid several times to remove impurities on the surface of the Si substrate. A silicon oxide layer including amorphous SiOx is formed on the Si substrate. A metal layer including a rare earth metal is formed in contact with an upper surface of the silicon oxide layer. The silicon oxide layer is reacted with the metal layer through heating to form a first crystal layer including a rare earth oxide crystal obtained by oxidizing the rare earth metal on the Si substrate.

Abstract: A solid-state quantum memory includes a vibrator supported in a displaceable (vibratable) manner on a substrate and a vibration exciter configured to excite the vibrator to vibrate. A rare-earth element is introduced into the vibrator and the introduced rare-earth element forms an electronic two-level system in the vibrator. The vibrator is supported on the substrate by a support. The substrate including a piezoelectric element formed from a piezoelectric material, as well as a first electrode and a second electrode formed by sandwiching the piezoelectric element, serves as the vibration exciter.

Abstract: In an embodiment method for growing a rare earth oxide crystal, a surface of a Si substrate is cleaned by carrying out treatments using chemical solutions such as a mixed sulfuric acid-hydrogen peroxide solution, hot nitric acid, or diluted hydrofluoric acid several times to remove impurities on the surface of the Si substrate. A silicon oxide layer including amorphous SiOx is formed on the Si substrate. A metal layer including a rare earth metal is formed in contact with an upper surface of the silicon oxide layer. The silicon oxide layer is reacted with the metal layer through heating to form a first crystal layer including a rare earth oxide crystal obtained by oxidizing the rare earth metal on the Si substrate.