What is the Difference Between Q Learning and Deep Q Learning?

What is the Difference Between Q Learning and Deep Q Learning?

Artificial Intelligence & Machine Learning

Deep Q-Learning vs Q-Learning: A Comprehensive Essay

The fields of artificial intelligence and machine learning are continuously evolving, with various techniques being developed to solve complex problems. Among these techniques, Q-Learning and Deep Q-Learning stand out as powerful methods for decision-making and learning in environments with sequential decision-making processes. This essay delves into the background, mechanics, and real-world applications of both Q-Learning and Deep Q-Learning.

Background and Calculation of Q-Learning

Introduction to Q-Learning: Q-Learning is a model-free reinforcement learning algorithm introduced by Christopher Watkins in 1989. It is used to find the optimal action-selection policy in a given environment. Q-Learning operates by learning a Q-value function that maps state-action pairs to rewards.

Calculation in Q-Learning: The core of Q-Learning is the Q-value function, represented as Q(s, a), where ‘s’ is a state, and ‘a’ is an action. The algorithm updates its Q-values using the Bellman equation:

Real-World Application of Q-Learning: Q-Learning has been successfully applied in areas like robotics, automated control systems, and gaming, where the environment can be modeled as a Markov Decision Process (MDP), and the goal is to maximize the cumulative reward.

Background and Calculation of Deep Q-Learning

Introduction to Deep Q-Learning: Deep Q-Learning, introduced by the DeepMind team in 2015, is an extension of Q-Learning that uses deep neural networks to approximate the Q-value function. This approach is particularly useful in dealing with high-dimensional input spaces, where traditional Q-Learning falls short.

Calculation in Deep Q-Learning: In Deep Q-Learning, the Q-value function is approximated using a deep neural network. The network takes the state as input and outputs Q-values for each action. The loss function used to train the network is based on the temporal difference (TD) error, given by:

Real-World Application of Deep Q-Learning: Deep Q-Learning has been effectively used in complex environments like playing video games (e.g., Atari games) and in robotics. Its ability to handle high-dimensional sensory inputs makes it suitable for visual perception tasks in autonomous vehicles and complex strategy games.

Comparison: Deep Q-Learning vs Q-Learning

  1. Capacity to Handle High-Dimensional Spaces:
    • Q-Learning struggles with environments having high-dimensional state spaces.
    • Deep Q-Learning, with its neural network, excels in handling high-dimensional inputs.
  2. Stability and Efficiency:
    • Q-Learning is more stable but less efficient in large or continuous spaces.
    • Deep Q-Learning, while powerful, can be unstable and requires techniques like experience replay and target networks for stability.
  3. Complexity and Overhead:
    • Q-Learning is simpler and easier to implement.
    • Deep Q-Learning is more complex, requiring careful tuning and more computational resources.
  4. Applicability:
    • Q-Learning is well-suited for simpler problems with discrete, low-dimensional spaces.
    • Deep Q-Learning is designed for complex problems where the state space is large or continuous, such as real-world vision-based tasks.


Both Q-Learning and Deep Q-Learning are significant in the landscape of reinforcement learning, each with its strengths and ideal use cases. Q-Learning offers a robust framework for learning policies in environments with discrete, manageable state spaces. Deep Q-Learning, on the other hand, extends the capabilities of traditional Q-Learning to handle complex, high-dimensional environments, making it a powerful tool for state-of-the-art AI applications. The choice between the two depends on the specific requirements and constraints of the problem at hand.

Diagram showing the components in a typical Reinforcement Learning (RL) system. An agent takes actions in an environment which is interpreted into a reward and a representation of the state which is fed back into the agent. Incorporates other CC0 work: https://openclipart.org/detail/202735/eye-side-view https://openclipart.org/detail/191072/blue-robot and https://openclipart.org/detail/246662/simple-maze-puzzle



What is the Difference Between Q Learning and Deep Q Learning? What is the Difference Between Q Learning and Deep Q Learning?