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Deep Q-Networks in AI

Deep Q-Networks (DQN) are a class of deep reinforcement learning algorithms used for learning optimal policies in Markov decision processes (MDPs). DQN combines deep learning with Q-learning, a classic reinforcement learning algorithm, to approximate the optimal action-value function (Q-function) for a given environment.

The key idea behind DQN is to use a deep neural network to approximate the Q-function, which maps states to action values. The neural network takes the state as input and outputs a Q-value for each possible action. During training, DQN uses a variant of Q-learning called experience replay, where it stores transitions (state, action, reward, next state) in a replay buffer and samples mini-batches of experiences to update the Q-network. This helps stabilize training and improve sample efficiency.

DQN also uses a target network to stabilize learning. The target network is a copy of the Q-network that is updated less frequently and is used to compute target Q-values during training. This helps prevent the target Q-values from oscillating during training.

DQN has been successfully applied to a wide range of tasks, including playing Atari games from raw pixel inputs, learning to play board games like Go and chess, and controlling robotic systems. It has become a foundational algorithm in the field of deep reinforcement learning and has inspired many subsequent advancements and extensions.

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