Curriculum / Quantum Foundations / Bell State Capstone

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Bell State Capstone

Build all four Bell states and verify their properties.

Bell State Capstone

The Four Bell States

There are four maximally entangled two-qubit states, called the Bell basis:

  • Φ+ = (|00⟩ + |11⟩)/√2, H then CNOT
  • Φ- = (|00⟩ - |11⟩)/√2, H, Z, then CNOT
  • Ψ+ = (|01⟩ + |10⟩)/√2, H, X on qubit 1, then CNOT
  • Ψ- = (|01⟩ - |10⟩)/√2, X on both qubits, then H on qubit 0, then CNOT

Your Project

Create the Φ+ Bell state (the one we made before) and verify it produces only |00⟩ and |11⟩. Print the counts and a verification message.

Bonus challenge: Try creating all four Bell states!

How this lesson works

A multi-step project that combines several concepts into one larger build, checked checkpoint by checkpoint as you go.

Part of: Quantum Foundations

Learn the basics: qubits, gates, superposition, and measurement.

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