Laser oscillator

1. A laser oscillator comprising:

a ring resonator including an optical fiber ring in which an optical fiber is connected in a ring shape;

an incident laser light control unit that enters a laser pulsed light as a qubit string on the ring resonator;

a laser light detection unit that detects a polarization state of the laser pulsed light oscillating by the ring resonator;

an optical amplifier that is connected to the optical fiber ring and maintains an amplitude of the laser pulsed light propagating through the optical fiber ring;

a first optical fiber that is connected with a first polarization controller, after changing a polarization state of the laser pulsed light being a first qubit and a second qubit, which are continuous to each other and extracted from the optical fiber ring at a predetermined branch ratio, by the first polarization controller, and couples the laser pulsed light whose polarization state has been changed with the laser pulsed light being the first qubit and the second qubit, which are continuous to each other and propagate on the optical fiber ring;

a second optical fiber that is connected with a second polarization controller, after changing a polarization state of the laser pulsed light being the first qubit and the second qubit, which are continuous to each other and extracted from the optical fiber ring at a predetermined branch ratio, by the second polarization controller, and couples the laser pulsed light whose polarization state has been changed with the laser pulsed light being the first qubit and the second qubit, which are continuous to each other and propagate on the optical fiber ring; and

a third optical fiber that is connected with a third polarization controller, after changing a polarization state of the laser pulsed light being the first qubit and the second qubit, which are continuous to each other and extracted from the optical fiber ring at a predetermined branch ratio, by the third polarization controller, and couples the laser pulsed light whose polarization state has been changed with the laser pulsed light being the first qubit and the second qubit, which are continuous to each other and propagate on the optical fiber ring,

wherein the polarization state of the laser pulsed light is represented as a state vector in a Poincaré sphere having an S 1 axis, an S 2 axis, and an S 3 axis which are orthogonal to each other, the first polarization controller rotates the state vector representing the polarization state of the laser pulsed light as a rotation axis on the S 1 axis, the second polarization controller rotates the state vector representing the polarization state of the laser pulsed light as a rotation axis on the S 2 axis, and the third polarization controller rotates the state vector representing the polarization state of the laser pulsed light as a rotation axis on the S 3 axis.

2. The laser oscillator according to claim 1 ,

wherein the polarization state of the laser pulsed light is represented as a state vector having a base with the S 1 axis as the Z axis, the S 2 axis as the X axis, and the S 3 axis as the Y axis,

each of the first to third polarization controllers includes:

a polarization beam splitter that separates a laser pulse as the qubit into a horizontal polarization component and a vertical polarization component;

an optical rotator that adjusts an amplitude ratio between the horizontal polarization component and the vertical polarization component;

an optical modulator array that gives a phase difference between the horizontal polarization component and the vertical polarization component, which are adjusted by the optical rotator; and

a polarization beam coupler that couples the horizontal polarization component with the vertical polarization component, which are given the phase difference by the optical modulator array.

3. The laser oscillator according to claim 1 , wherein the incident laser light control unit makes a laser pulsed light having a small portion of amplitude formed between the qubits incident into the ring resonator as a laser pulsed light being the qubit string.

4. The laser oscillator according to claim 1 ,

wherein the polarization state of the laser pulsed light is represented as a state vector having a base with the S 1 axis as the Z axis, the S 2 axis as the X axis, and the S 3 axis as the Y axis,

the laser light detection unit includes a fourth polarization controller and a delay line, and

the fourth polarization controller changes the polarization state of one of the laser pulsed light being the first qubit and the laser pulsed light being the second qubit, which are oscillated by the ring oscillator, and then detects the other polarization state of the laser pulsed light being the first qubit and the laser pulsed light being the second qubit.

5. A laser oscillator comprising:

a ring resonator that includes an optical fiber ring in which the optical fiber is coupled in a ring shape and partially branched into a first path and a second path having equal optical path lengths;

an incident laser light control unit that enters a laser pulsed light as a qubit string on the ring resonator;

a laser light detection unit that detects a polarization state of the laser pulsed light oscillating by the ring resonator;

an optical amplifier that is connected to the optical fiber ring and maintains an amplitude of the laser pulsed light propagating through the optical fiber ring; and

a polarization controller that is connected to the first path of the optical fiber ring,

wherein the laser pulsed light that becomes the qubit string passing through the first path is coupled with the laser pulse that becomes the qubit string that has passed through the second path without receiving the control of the polarization state, after changing the polarization states of the laser pulsed light being an i th qubit and the laser pulsed light being a j th qubit by the polarization controller, and

the polarization state of the laser pulsed light is represented as a state vector in a Poincaré sphere having an S 1 axis, an S 2 axis, and an S 3 axis, which are orthogonal to each other, and the polarization controller rotates the state vector representing the polarization state of the laser pulsed light around one of the S 1 axis, the S 2 axis, and the S 3 axis as a rotation axis.

6. The laser oscillator according to claim 5 ,

wherein the polarization controller is controlled by a control computer,

the polarization controller oscillates the ring resonator while rotating the polarization states of the laser pulsed light being the i th qubit and the laser pulsed light being the j th qubit with a first rotational amount around one of the S 1 axis, the S 2 axis, and the S 3 axis as the rotation axis, and then oscillates the ring resonator while rotating in a reverse direction the polarization states of the laser pulsed light being the i th qubit and the laser pulsed light being the j th qubit with the first rotational amount around the rotation axis.

7. A laser oscillator comprising:

a ring resonator including an optical fiber ring in which an optical fiber is connected in a ring shape;

an incident laser light control unit that enters a laser pulsed light as a qubit string on the ring resonator;

a laser light detection unit that detects a polarization state of the laser pulsed light oscillating by the ring resonator;

an optical amplifier that is connected to the optical fiber ring and maintains an amplitude of the laser pulsed light propagating through the optical fiber ring;

a first polarization interferometer that outputs the laser pulsed light being the first qubit or the laser pulsed light being the second qubit according to the polarization state of the laser pulsed light being a first qubit and the polarization state of the laser pulsed light being a second qubit, which are extracted from the optical fiber ring at a predetermined branch ratio, and couples the output laser pulsed light with the laser pulsed light propagating on the optical fiber ring;

a second polarization interferometer that outputs the laser pulsed light being the first qubit or the laser pulsed light being the second qubit according to the polarization state of the laser pulsed light being the first qubit and the polarization state of the laser pulsed light being the second qubit, which are extracted from the optical fiber ring at a predetermined branch ratio, and couples the output laser pulsed light with the laser pulsed light propagating on the optical fiber ring;

a third polarization interferometer that outputs the laser pulsed light being the first qubit or the laser pulsed light being the second qubit according to the polarization state of the laser pulsed light being the first qubit and the polarization state of the laser pulsed light being the second qubit, which are extracted from the optical fiber ring at a predetermined branch ratio, and couples the output laser pulsed light with the laser pulsed light propagating on the optical fiber ring;

a first input delay line that delays the laser pulsed light being the first qubit according to a delay amount of the laser pulsed light being the second qubit with respect to the laser pulsed light being the first qubit in the optical fiber ring, and inputs the delayed laser pulsed light to the first polarization interferometer;

a first output delay line that delays the laser pulsed light being the second qubit output from the first polarization interferometer according to the delay amount of the laser pulsed light being the second qubit with respect to the laser pulsed light being the first qubit in the optical fiber ring;

a second input delay line that delays the laser pulsed light being the first qubit according to a delay amount of the laser pulsed light being the second qubit with respect to the laser pulsed light being the first qubit in the optical fiber ring, and inputs the delayed laser pulsed light to the second polarization interferometer;

a second output delay line that delays the laser pulsed light being the second qubit output from the second polarization interferometer according to the delay amount of the laser pulsed light being the second qubit with respect to the laser pulsed light being the first qubit in the optical fiber ring;

a third input delay line that delays the laser pulsed light being the first qubit according to a delay amount of the laser pulsed light being the second qubit with respect to the laser pulsed light being the first qubit in the optical fiber ring, and inputs the delayed laser pulsed light to the third polarization interferometer; and

a third output delay line that delays the laser pulsed light being the second qubit output from the third polarization interferometer according to the delay amount of the laser pulsed light being the second qubit with respect to the laser pulsed light being the first qubit in the optical fiber ring,

wherein the polarization state of the laser pulsed light is represented as a state vector in a Poincaré sphere having an S 1 axis, an S 2 axis, and an S 3 axis, which are orthogonal to each other,

the first polarization interferometer maximizes a gain when a Stokes parameter S 1 of the first qubit is 1 and the Stokes parameter S 1 of the second qubit is −1, or when the Stokes parameter S 1 of the first qubit is −1 and the Stokes parameter S 1 of the second qubit is 1,

the second polarization interferometer maximizes the gain when a Stokes parameter S 2 of the first qubit is 1 and the Stokes parameter S 2 of the second qubit is −1, or when the Stokes parameter S 2 of the first qubit is −1 and the Stokes parameter S 2 of the second qubit is 1, and

the third polarization interferometer maximizes the gain when a Stokes parameter S 3 of the first qubit is 1 and the Stokes parameter S 3 of the second qubit is −1, or when the Stokes parameter S 3 of the first qubit is −1 and the Stokes parameter S 3 of the second qubit is 1.

8. The laser oscillator according to claim 7 ,

wherein the polarization state of the laser pulsed light is represented as a state vector having a base with the S 1 axis as the Z axis, the S 2 axis as the X axis, and the S 3 axis as the Y axis, and

the first polarization interferometer maximizes the gain both when the laser pulsed light being the first qubit interferes with the laser pulsed light being the second qubit rotated 180° around the S 2 axis, and when the laser pulsed light being the first qubit interferes with the laser pulsed light being the second qubit rotated 180° around the S 3 axis.

9. The laser oscillator according to claim 8 , wherein the second polarization interferometer includes:

a second of the first polarization interferometer;

a quarter wave reverse rotator around the Y axis which rotates the polarization states of the laser pulsed light being the first qubit and the laser pulsed light being the second qubit −90° around the S 3 axis, and inputs the rotated laser pulsed lights to the second first polarization interferometer; and

a quarter wave rotator around the Y axis which rotates the polarization state of the output of the second first polarization interferometer 90° around the S 3 axis.

10. The laser oscillator according to claim 8 , wherein the third polarization interferometer includes:

a third of the first polarization interferometer;

a quarter wave rotator around the X axis which rotates the polarization states of the laser pulsed light being the first qubit and the laser pulsed light being the second qubit 90° around the S 2 axis, and inputs the rotated laser pulsed lights to the third first polarization interferometer; and

a quarter wave reverse rotator around the X axis which rotates the polarization state of the output of the third first polarization interferometer −90° around the S 2 axis.

11. The laser oscillator according to claim 7 ,

wherein the polarization state of the laser pulsed light is represented as a state vector having a base with the S 1 axis as the Z axis, the S 2 axis as the X axis, and the S 3 axis as the Y axis,

the first polarization interferometer includes:

a first X-axis half-wave plate that rotates the polarization state of the laser pulsed light being the first qubit 180° around the S 2 axis;

a first Y-axis half-wave plate that rotates the polarization state of the laser pulsed light being the first qubit 180° around the S 3 axis;

a second X-axis half-wave plate that rotates the polarization state of the laser pulsed light being the second qubit 180° around the S 2 axis; and

a second Y-axis half-wave plate that rotates the polarization state of the laser pulsed light being the second qubit 180° around the S 3 axis,

wherein the first polarization interferometer couples the laser pulsed light being the first qubit passing through the first X axis half-wave plate with the laser pulsed light being the first qubit passing through the first Y axis half-wave plate, and outputs the coupled laser pulsed light as the laser pulsed light being the second qubit, and

the second polarization interferometer couples the laser pulsed light being the second qubit passing through the second X axis half-wave plate with the laser pulsed light being the second qubit passing through the second Y axis half-wave plate, and outputs the coupled laser pulsed light as the laser pulsed light being the first qubit.

12. The laser oscillator according to claim 11 ,

wherein the second polarization interferometer includes:

a third Y-axis half-wave plate that rotates the polarization state of the laser pulsed light being the first qubit 180° around the S 3 axis;

a first Z-axis half-wave plate that rotates the polarization state of the laser pulsed light being the first qubit 180° around the S 1 axis;

a fourth Y-axis half-wave plate that rotates the polarization state of the laser pulsed light being the second qubit 180° around the S 3 axis; and

a second Z-axis half-wave plate that rotates the polarization state of the laser pulsed light being the second qubit 180° around the S 1 axis,

wherein the second polarization interferometer couples the laser pulsed light being the first qubit passing through the third Y axis half-wave plate with the laser pulsed light being the first qubit passing through the first Z axis half-wave plate, and outputs the coupled laser pulsed light as the laser pulsed light being the second qubit, and

the second polarization interferometer couples the laser pulsed light being the second qubit passing through the fourth Y axis half-wave plate with the laser pulsed light being the second qubit passing through the second Z axis half-wave plate, and outputs the coupled laser pulsed light as the laser pulsed light being the first qubit.

13. The laser oscillator according to claim 11 , wherein the third polarization interferometer includes:

a third Z-axis half-wave plate that rotates the polarization state of the laser pulsed light being the first qubit 180° around the S 1 axis;

a third X-axis half-wave plate that rotates the polarization state of the laser pulsed light being the first qubit 180° around the S 2 axis;

a fourth Z-axis half-wave plate that rotates the polarization state of the laser pulsed light being the second qubit 180° around the S 1 axis; and

a fourth X-axis half-wave plate that rotates the polarization state of the laser pulsed light being the second qubit 180° around the S 2 axis,

wherein the third polarization interferometer couples the laser pulsed light being the first qubit passing through the third Z axis half-wave plate with the laser pulsed light being the first qubit passing through the third X axis half-wave plate, and outputs the coupled laser pulsed light as the laser pulsed light being the second qubit, and

the third polarization interferometer couples the laser pulsed light being the second qubit passing through the fourth Z axis half-wave plate with the laser pulsed light being the second qubit passing through the fourth X axis half-wave plate, and outputs the coupled laser pulsed light as the laser pulsed light being the first qubit.

14. A laser oscillator comprising:

a ring resonator including an optical fiber ring in which an optical fiber is connected in a ring shape;

an incident laser light control unit that enters a laser pulsed light as a qubit string on the ring resonator;

a laser light detection unit that detects a polarization state of the laser pulsed light oscillating by the ring resonator;

an optical amplifier that is connected to the optical fiber ring and maintains an amplitude of the laser pulsed light propagating through the optical fiber ring; and

an XYZ spin operator that outputs the laser pulsed light being the first qubit and the laser pulsed light being the second qubit according to the polarization state of the laser pulsed light being the first qubit and the polarization state of the laser pulsed light being the second qubit, which are extracted from the optical fiber ring at a predetermined ratio, and couples the output laser pulsed lights with the laser pulsed light being the first qubit and the laser pulsed light being the second qubit, which propagate on the optical fiber ring,

wherein an optical path length on the optical fiber ring from a branch position to a coupling position is equal to an optical path length of a path through the XYZ spin operator for the laser pulsed light being the first qubit and the laser pulsed light being the second qubit, and an optical path length corresponding to a delay amount of the laser pulsed light being the second qubit with respect to the laser pulsed light being the first qubit is provided between the branch position of the laser pulsed light being the first qubit and the branch position of the laser pulsed light being the second qubit, and between the coupling position of the laser pulsed light being the first qubit and the coupling position of the laser pulsed light being the second qubit, on the optical fiber ring,

the polarization state of the laser pulsed light is represented as a state vector in a Poincaré sphere having an S 1 axis, an S 2 axis, and an S 3 axis, which are orthogonal to each other, and

the XYZ spin operator maximizes a gain when the stokes parameters S 1 , S 2 , and S 3 of the first qubit are 1 and the stokes parameters S 1 , S 2 , and S 3 of the second qubit are −1, or when the stokes parameters S 1 , S 2 , and S 3 of the first qubit are −1 and the stokes parameters S 1 , S 2 , and S 3 of the second qubit are 1.