# Quantum Information Theory

**- Overview**

Quantum information theory is defined as the study of how to use quantum mechanical systems to achieve information processing tasks. It focuses on utilizing the properties of quantum mechanics to achieve efficient storage and transmission of information, thus fundamentally different from classical information theory.

Quantum information science is a field that combines the principles of quantum mechanics with information theory to study the processing, analysis and transmission of information. It covers the theoretical and experimental aspects of quantum physics, including the limits of what quantum information can achieve.

The term quantum information theory is sometimes used, but it does not include experimental studies and may be confused with the subfield of quantum information science that deals with quantum information processing.

Please refer to the following for more information:

- Wikipedia:
**Quantum Information Science**

**- Random Unitaries**

Random unitaries are a fundamental concept in quantum information theory and quantum many-body physics. They are quantum analogs of random numbers, and are used in many applications, including: Randomized benchmarking, Mixing in black holes, Quantum communication, Superdense coding, and Remote state preparation.

Random unitaries are often constructed using a random unitary matrix, which can be expensive to decompose. However, some methods have been proposed that are easier to implement on quantum hardware.

**[More to come ...]**