ExperimentsExperiment 5 · Quantum basics

Quantum Coin

Flip a classical coin and a quantum coin 10, 100 or 1000 times.

① What is the problem?

Is a quantum coin different from an ordinary coin?

② How does a classical computer approach it?

A classical coin flip is random because of unknown details of the throw (modelled with a pseudo-random generator).

③ How does the quantum approach differ?

A qubit in H|0⟩ gives 50/50 outcomes from the Born rule. Applying H twice gives 0 every time — no classical coin can 'un-flip' itself.

🔮 Make a prediction

With 100 flips, how close to 50% heads will the quantum coin be?

Heads / Tails from a pseudo-random generator (a model of a physical toss).

Result

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Qubit |0⟩ → H (superposition) → measurement. Heads = 0, Tails = 1.

Result

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A classical coin tossed twice is still 50/50. Apply H twice to the qubit and measure:

④ What is happening mathematically?

P(heads) = |⟨0|H|0⟩|² = 1/2. For n flips, the number of heads has standard deviation √n/2.

⑤ What does the simulation show?

Side-by-side histograms from actual draws, and the 'double flip' interference test.

⑥ What did we learn?

A single quantum flip's statistics look like a fair coin; the difference appears when quantum operations are combined.

⑦ What can you experiment with?

Predict how close to 50% you'll get with 10 vs 1000 flips.

📓 Record: my lab notebook

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