Curriculum / Quantum Foundations / Creating Entanglement
Creating Entanglement
Build your first entangled state, the Bell state.
Creating Entanglement
The Bell State
Entanglement is one of the most profound quantum phenomena. When two qubits are entangled, measuring one reveals what the other will give, regardless of distance. The outcomes are perfectly correlated, but no usable signal travels between them: each measurement alone looks completely random, so entanglement cannot be used to communicate.
The simplest entangled state is the Bell state, created with H + CNOT:
- 1.Apply H to qubit 0 (superposition)
- 2.Apply CNOT with qubit 0 as control, qubit 1 as target
This creates: (|00⟩ + |11⟩)/√2
When you measure, you'll always get both qubits the same, either both 0 or both 1, with equal probability!
Your Challenge
Create a Bell state and verify you only see |00⟩ and |11⟩ in the results. You should NEVER see |01⟩ or |10⟩.
How this lesson works
A hands-on coding challenge. You write Qiskit-compatible Python in the browser editor, run it instantly via WebAssembly, watch the circuit and Bloch sphere react, and pass automatic output checks. The AI tutor Qubitus gives Socratic hints if you get stuck.
Part of: Quantum Foundations
Learn the basics: qubits, gates, superposition, and measurement.
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