Years 3–6 · Week 6 of 12
Superposition
Learning goals
By the end, you can…
- Name superposition as a kind of quantum state.
- Connect a prepared superposition with possible measurement outcomes.
- Use repeated preparations to compare predicted 0 and 1 chances.
- Describe a Hadamard gate as one way to prepare a balanced superposition from 0.
What you already know
Connect to a familiar idea
Different qubit preparations can produce different 0-and-1 patterns. Superposition is the quantum-state idea used to describe these possibilities.
- Know that a qubit measurement can produce 0 or 1.
- Compare outcome counts from repeated trials.
Opening story
Start with something familiar
A virtual qubit is prepared in the same way one hundred times. About half the measurements give 0 and about half give 1. The superposition predicts that repeated pattern, not a blurred reading on the detector.
Plain-English explanation
Build the idea carefully
Contributions to possible outcomes
A qubit can be prepared in a quantum state called a superposition. A superposition is described using contributions associated with possible measurement outcomes.
Prepare the same state many times
A measurement in the computational basis produces one recorded outcome, 0 or 1. Repeating the same preparation many times reveals the probability pattern; a Hadamard gate can prepare a balanced superposition from 0.
Try the model
Balance a superposition
Move the balance control, predict the result chart, then measure many freshly prepared virtual qubits.
Ready. Adjust a control, then run the model.
What this model shows: The balance control is a simplified visual representation of outcome probabilities and does not show every part of a quantum state.
Text alternative for this interactive
Compare balanced and biased prepared-state cards with supplied 100-run histograms.
Expected observation: A balanced preparation gives roughly equal 0 and 1 counts over many runs, although each measurement records only one outcome.
Guided activity
Predict three preparations
- Predict charts for 0-heavy, balanced and 1-heavy preparations.
- Run one hundred measurements for each preparation.
- Compare the ordering of the three charts with your predictions.
Evidence to collect: The three histograms change with the preparation, and the balanced state has counts near half 0 and half 1 across many runs.
Glossary
Words to know
- superposition
- A quantum state described by contributions for possible outcomes.
- balanced
- Giving equal predicted chances for 0 and 1 in the chosen measurement.
- Hadamard gate
- A quantum gate that can make a balanced superposition from 0.
- phase
- A part of a quantum state that affects interference.
Short recap
Keep these ideas
- Superposition is a quantum-state description.
- One computational-basis measurement produces 0 or 1.
- A balanced superposition gives an approximately even pattern over many fresh runs.
Knowledge check
4 clear questions
Choose an answer for immediate feedback. You may retry, and your best submitted score is kept.
Explore More Optional extension for Years 5–6
Applying a Hadamard gate to 0 makes a balanced superposition in the ideal model. Equal measurement chances do not describe everything: phase can change what later gates do.
Try this
Prepare 0, apply H, record the predicted balance, then leave a note explaining why the balance picture is incomplete.
Adult support Teacher and parent notes
Discuss
- Use 'contributions associated with outcomes' before introducing amplitudes.
- Do not rely on 'both 0 and 1 at once' as the explanation.
- State that the probability slider omits phase.
Answer guidance
Look for one outcome per measurement, repeated preparation and cautious language such as 'roughly equal across many runs'.
Offline activity
Sort prepared-state cards beside pre-generated histograms. Paper work cannot reproduce quantum superposition, so label it as data interpretation.
Safety
No physical quantum apparatus is required. Use only the ideal simulator or printed result cards.
Sources and further reading
Checked references for this lesson
These sources support the lesson’s main scientific claims. Links open on the source organisation’s site.
- The qubit in quantum computing Microsoft Learn · official documentation · checked 2026-08-02
- Quantum information IBM Quantum Learning · official learning module · checked 2026-08-02
- Circuits IBM Quantum Learning · official learning module · checked 2026-08-02
Content review: Reviewed on 2026-08-02.