What is a quantum kernel?

Question: What is a quantum kernel often used for? A) Cooling a quantum chip B) Storing all backend passwords C) Measuring temperature only D) Measuring similarity between data points after mapping them into quantum feature states Correct: D Explanation: A quantum kernel maps classical data into quantum states and computes similarity between those states. This can be used with kernel-based machine learning methods. Topic: quantum computing / quantum kernels / machine learning