# How to know if any two arbitrary qubits are entangled? [duplicate]

Suppose there are two quits called q1 and q2. They are in two different superposition states. If we represent their states on the Bloch sphere surface, q1 is located at point_1 and q2 is placed at point_2. Please note that point_1 is different from point_2 and we know where point1 and point2 are. Now, my question consists of two parts:

1. How to make q1 and q2 entangled?
2. After making them entangled, how to check if they are entangled indeed?