Quantum Registers¶

QCGPU provides a class to represent the register, qcgpu.State. The register class stores (on the OpenCL device) a state vector. This state vector is a chunk of memory, the size of which is:

\[64 \cdot 2^n \text{ bits}.\]

This means you would need just 2kb of memory to have a 5 qubit register, a 30 qubit register would take up 9gb of memory.

This is something to be aware of, as the state vector must fit in the memory of the device you wish to use.

Using the `State` class¶

To create a new register, you can use

import qcgpu

register = qcgpu.State(5)

This will create a 5 qubit register.

When you run this, you may be prompted to choose a device. This is normal, as you can have more than 1 device that supports OpenCL in your computer. Just choose the one you want.

Mathematical Description¶

This class represents a state vector \(\lvert \psi \rangle\) with

\[\lvert \psi \rangle = \sum_{j = 0}^{2^n - 1} \alpha_j \lvert j \rangle\]

where \(n\) is the number of qubits, \(\alpha_j\) is the amplitude and the state is \(j\) runs overall \(2^n\) basis states.

Quantum Registers¶

Using the State class¶

Mathematical Description¶

Using the `State` class¶