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X gate

As explained in Building Quantum Software with Python

The X gate is a single-qubit quantum gate that swaps the amplitudes associated with the two computational-basis outcomes.

The X gate, also called the NOT gate, swaps the amplitudes associated with the two computational-basis outcomes of a single-qubit state. section 3.2.2

Simulating an X gate

Represent the state as a two-item list and exchange its entries: state = [state[1], state[0]]. This directly models the amplitude swap. section 3.2.2

Applying the gate twice

Starting with the default state [0, 1], one X transformation produces the swapped state, and applying the same transformation again returns [1, 0]. section 3.2.5

How Building Quantum Software with Python covers it

How deep it goes
Defines the amplitude swap, implements it with a list assignment, and verifies reversibility by applying the transformation twice.
Examples
Demonstrates the gate with two-item state lists, the default state [0, 1], and successive swaps returning [1, 0].
What it assumes
Assumes a single-qubit state represented by a pair of amplitudes and distinguishes computational-basis outcomes.
What you can do after
Builds a direct state-list simulation and verifies that applying the X gate twice restores the initial amplitudes.
How it connects
Connects the X gate to the NOT gate, single-qubit gates, inverse gates, and two-by-two matrix transformations.
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This explainer was generated by Manning's knowledge graph from the text of Building Quantum Software with Python. The section links point to the parts of the book it draws on.