Optical modulator, optical receiver, conversion device, spin orbital direct product state generation device, and quantum computer

An optical receiver that receives a coherent laser beam in a superposition state of two orthogonal angular momentum states, the optical receiver comprising:

• a first optical element on which light in any angular momentum state is incident and which is configured to separate the light into two laser beams in the two orthogonal angular momentum states;
• a first waveguide on which one of the laser beams from the first optical element is incident;
• a second waveguide on which the other of the laser beams from the first optical element is incident;
• a first phase shifter provided in one or both of the first and second waveguides and configured to control a phase of the laser beam incident on the waveguide;
• a second optical element configured to combine the laser beam propagating through the first waveguide and the laser beam propagating through the second waveguide and separate the combined laser beam into two laser beams;
• a third waveguide on which one of the laser beams separated by the second optical element is incident;
• a fourth waveguide on which the other of the laser beams separated by the second optical element is incident;
• a second phase shifter provided in one or both of the third and fourth waveguides and configured to control a phase of the laser beam incident on the waveguide;
• a third optical element configured to combine the laser beam propagating through the third waveguide and the laser beam propagating through the fourth waveguide and separate the combined laser beam into two laser beams;
• a fifth waveguide on which one of the laser beams separated by the third optical element is incident;
• a sixth waveguide on which the other of the laser beams separated by the third optical element is incident;
• a first receiver configured to detect the laser beam propagating through the fifth waveguide;
• and
• a second receiver configured to detect the laser beam propagating through the sixth waveguide.

A conversion device that converts a coherent laser beam in a superposition state of orthogonal spin angular momentum states into a coherent laser beam in a superposition state of orthogonal orbital angular momentum states or converts a coherent laser beam in a superposition state of orthogonal orbital angular momentum states into a coherent laser beam in a superposition state of orthogonal spin angular momentum states, the conversion device comprising:

• a coupler of photonic crystal with a rectangular planar shape;
• a first waveguide coupled with a first side surface of the coupler;
• a second waveguide coupled with a second side surface adjacent to the first side surface of the coupler;
• and
• a ring waveguide disposed between the first and second waveguides,
• wherein an inner circumference of the ring waveguide has a periodic structure and a period of the periodic structure has magnitude which is an integral multiple of a wavelength of the laser beam in the ring waveguide.

A spin orbital direct product state generation device comprising:

• a first waveguide on which a coherent laser beam in a superposition state of two orthogonal spin angular momentum states is incident;
• a first optical element configured to separate the laser beam propagating through the first waveguide into two laser beams with identical intensity;
• a second waveguide on which one of the laser beams from the first optical element is incident;
• a third waveguide on which the other of the laser beams from the first optical element is incident;
• a first phase shifter provided in one or both of the second and third waveguides and configured to control a phase of the laser beam incident on the waveguide;
• a second optical element configured to combine the laser beam propagating through the second waveguide and the laser beam propagating through the third waveguide and separate the combined laser beam into two laser beams;
• a fourth waveguide on which one of the laser beams separated by the second optical element is incident;
• a fifth waveguide on which the other of the laser beams separated by the second optical element is incident;
• a second phase shifter provided in one or both of the fourth and fifth waveguides and configured to control a phase of the laser beam incident on the waveguide;
• a third optical element on which the laser beam propagating through the fourth waveguide is incident and which is configured to emit the laser beam in a first angular momentum state;
• a fourth optical element on which the laser beam propagating through the fifth waveguide is incident and which is configured to emit the laser beam in a second angular momentum state orthogonal to the first angular momentum state;
• and
• a fifth optical element configured to combine the laser beam in the first angular momentum state and the laser beam in the second angular momentum state.