Search apparatus, search method, and search program

1. A search device comprising a processor configured to perform the steps of:

specifying a function for identifying whether or not a posture of a robot comprising a robot arm satisfies a predetermined condition, wherein the robot arm includes a joint which rotates a portion of the robot arm closer to a tip of the robot;

setting a quantum computer so as to search for a state of a plurality of qubits corresponding to an angle of the joint of the robot arm satisfying the predetermined condition, by setting the plurality of qubits to an initial state in which all possible quantum states for the plurality of the qubits are superposed, and by applying unitary transformations formed based on the function to the plurality of qubits in the initial state a number of times according to the number of the plurality of qubits; and

calculating the angle corresponding to a measurement value of the plurality of qubits,

wherein the unitary transformations include a first unitary transformation for inverting a phase of a quantum state corresponding to the angle of the joint of the robot arm satisfying the predetermined condition, and a second unitary transformation for inverting a quantum state with respect to a predetermined quantum state, and

wherein the calculated angle is transmitted to a robot control device to control the robot.

2. The search device according to claim 1 , wherein

the predetermined condition includes a condition indicating that a position of an end effector provided on the robot is closest to a target position.

3. The search device according to claim 1 , wherein

the predetermined condition includes a condition indicating that a trajectory of an end effector provided on the robot is closest to a target trajectory.

4. The search device according to claim 1 , wherein

the predetermined condition includes a condition indicating that the joint does not interfere with an obstacle.

5. The search device according to claim 4 , wherein the processor is further configured to perform the step of

setting, in the quantum computer, a counter qubit that corresponds to whether or not the joint interferes with the obstacle.

6. The search device according to claim 5 , wherein

the first unitary transformation is for

inverting a phase of a direct product state of the plurality of qubits and the counter qubit when the angle corresponding to the plurality of qubits satisfies the predetermined condition and the counter qubit corresponds to the joint not interfering with the obstacle; and

leaving the phase of the direct product state of the plurality of qubits and the counter qubit unchanged when the angle corresponding to the plurality of qubits does not satisfy the predetermined condition or when the counter qubit corresponds to the joint interfering with the obstacle; and

the second unitary transformation is for inverting the direct product state of the plurality of qubits and the counter qubit with respect to a predetermined quantum state.

7. The search device according to claim 1 , wherein

the angle is represented by a bit string according to a CORDIC algorithm.

8. A computer-implemented search method comprising:

specifying a function for identifying whether or not a posture of a robot comprising a robot arm satisfies a predetermined condition, wherein the robot arm includes a joint which rotates a portion of the robot arm closer to a tip of the robot;

setting a quantum computer so as to search for a state of a plurality of qubits corresponding to an angle of the joint of the robot arm satisfying the predetermined condition, by setting the plurality of qubits to an initial state in which all possible quantum states for the plurality of the qubits are superposed, and by applying unitary transformations formed based on the function to the plurality of qubits in the initial state a number of times according to the number of the plurality of qubits; and

calculating the angle corresponding to a measurement value of the plurality of qubits,

wherein the unitary transformations include a first unitary transformation for inverting a phase of a quantum state corresponding to the angle of the joint of the robot arm satisfying the predetermined condition, and a second unitary transformation for inverting a quantum state with respect to a predetermined quantum state, and

wherein the calculated angle is transmitted to a robot control device to control the robot.

9. A non-transitory computer-readable storage medium storing a program which, when executed by a processor provided in a search device, performs:

specifying a function for identifying whether or not a posture of a robot comprising a robot arm satisfies a predetermined condition, wherein the robot arm includes a joint which rotates a portion of the robot arm closer to a tip of the robot;

setting a quantum computer so as to search for a state of a plurality of qubits corresponding to an angle of the joint of the robot arm satisfying the predetermined condition, by setting the plurality of qubits to an initial state in which all possible quantum states for the plurality of the qubits are superposed, and by applying unitary transformations formed based on the function to the plurality of qubits in the initial state a number of times according to the number of the plurality of qubits; and

calculating the angle corresponding to a measurement value of the plurality of qubits,

wherein the unitary transformations include a first unitary transformation for inverting a phase of a quantum state corresponding to the angle of the joint of the robot arm satisfying the predetermined condition, and a second unitary transformation for inverting a quantum state with respect to a predetermined quantum state, and

wherein the calculated angle is transmitted to a robot control device to control the robot.