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Quantum Circuits, Algorithms, and Industry · Module 3/8: Quantum Gates and Circuit Design

Learning objectives
  • Explain the core ideas in quantum gates and circuit design.
  • Apply the concepts to a small circuit or business/technical evaluation.
  • Identify limitations and appropriate benchmarks.
Tap Next (or use your arrow keys) to move one idea at a time. A fixed three-question check waits at the end: the course's own checkpoint, same questions every attempt. The ← up top exits whenever you like; progress keeps.

Single-qubit gates

X flips |0⟩ and |1⟩. Z changes the phase of |1⟩. H creates or recombines equal superpositions. S and T apply phase rotations. Rx, Ry, and Rz provide continuous rotations.

Gates transform amplitudes and phase through unitary matrices.

Controlled gates

CNOT flips a target when the control is |1⟩. Combined with H, it creates a Bell state. Controlled operations are central to entanglement, arithmetic, phase kickback, and error correction.

Two-qubit gates create conditional structure and are usually noisier than single-qubit gates.

Circuit depth and compilation

A logical circuit must be mapped to the device's native gate set and connectivity. Compilation inserts swaps, decomposes gates, and optimizes depth. Hardware-aware compilation can determine whether a circuit is practical.

The same abstract algorithm can perform very differently after hardware mapping.

Applied activity

Complete a simulator or analysis exercise: reproduce the lesson's central example, record assumptions and outputs, and explain one source of error or limitation.

Module check: Quantum Gates and Circuit Design

3 questions: drawn fresh from the bank every attempt. Pass mark 60%. Unlimited retakes.

Read the full lesson text

1. Single-qubit gates

X flips |0⟩ and |1⟩. Z changes the phase of |1⟩. H creates or recombines equal superpositions. S and T apply phase rotations. Rx, Ry, and Rz provide continuous rotations.

Gates transform amplitudes and phase through unitary matrices.

2. Controlled gates

CNOT flips a target when the control is |1⟩. Combined with H, it creates a Bell state. Controlled operations are central to entanglement, arithmetic, phase kickback, and error correction.

Two-qubit gates create conditional structure and are usually noisier than single-qubit gates.

3. Circuit depth and compilation

A logical circuit must be mapped to the device's native gate set and connectivity. Compilation inserts swaps, decomposes gates, and optimizes depth. Hardware-aware compilation can determine whether a circuit is practical.

The same abstract algorithm can perform very differently after hardware mapping.

4. Applied activity

Complete a simulator or analysis exercise: reproduce the lesson's central example, record assumptions and outputs, and explain one source of error or limitation.

Quantum, But Friendly

How Small Is Small?The Spinning CoinBit vs QubitSpooky Friends Final test

Inside a Quantum Computer

The Golden ChandelierHow It ThinksGood At, Bad At Final test

Quantum in the Real World

Quantum You Already OwnThe Great Quantum RaceFollowing the Quantum Money Final test

The Academy

Quantum Computing FoundationsQuantum Circuits, Algorithms, and IndustryFault-Tolerant Quantum Computing and Technical Strategy The full curriculum

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