Extended Quantum Computing Patterns
Intent
Transform a quantum state from one basis to another so that the next operation can be performed in a more suitable representation.
Context
An algorithm contains an operation that is easier to express or apply in a basis different from the current one.
Forces
The transformation adds gates and may need to be reversed later. Approximate transformations can reduce circuit depth at the cost of accuracy.
Solution
Apply a unitary transformation that maps the state to the required basis. Examples include the quantum Fourier transform, the Hadamard transform, and quantum discrete cosine or sine transforms.
Result
The state is represented in a basis suited to the next part of the computation.
Examples
Quantum Fourier transform, inverse quantum Fourier transform, Hadamard transform, quantum DCT, and quantum DST.
Related Patterns
Uniform Superposition; Quantum Phase Estimation (QPE)
Known Uses
QFT implementations in Qiskit, PennyLane, and Classiq, and the DCT and DST routines provided by Classiq.