Compare two runs
Did the 0 and 1 counts change? Explain why different samples can still fit the same 50/50 probability model.
A free taste of Quantum Explorers
One qubit.
What will it do?
Build a tiny circuit, make a prediction, then run your experiment. This is the same ideal simulator used in the course. No account or coding required.
Teaching simulatorThe results come from a mathematical model, not a physical quantum computer. Your written prediction is not submitted, saved to an account or included in analytics.
The idea
Prepare. Change. Measure.
A qubit is a unit of quantum information. Here, we prepare it in the state called |0⟩. A gate changes its state. A measurement gives an ordinary bit: 0 or 1.
An H gate applied to |0⟩ creates equal chances of measuring 0 and 1 in this ideal model. Each shot starts again with a freshly prepared qubit. Repeating shots lets us look for a pattern.
Built-in circuit lab
Build from left to right
Start with one qubit, add an H gate, and guess the result. Then press Run simulator. Each “shot” is a fresh preparation followed by one measurement.
This beginner lab measures at the end of the circuit. Add M last; gates after measurement are not supported here. Run simulator always measures all qubits, even if you have not added M.
- No instructions yet.
Your guess is not graded. A single 0 or 1 is enough to start.
Initial state: every qubit is prepared as |0⟩.
Circuit results
Simulator| Result | Exact chance | Count | Sample percent |
|---|---|---|---|
| 0 | 100% | — | — |
Run the simulator to create a text summary of the chart.
Bit-order legend
Pi Leo labels wires q0, q1 and q2 from top to bottom. In displayed result strings, the highest-numbered bit is written on the left, so a two-qubit result is shown as q1q0. This matches the convention used in the Pi Leo simulator and common Qiskit count strings.
Gate definitions
- X
- Exchanges the |0⟩ and |1⟩ reference states in these examples.
- H
- Changes the state direction and can create equal 0/1 measurement probabilities from |0⟩.
- Z
- Changes relative phase. Its effect may appear only after a later analysing gate.
- CX
- Applies X to a target when its control is in the |1⟩ reference state.
- Measurement
- Produces a classical bit result.
Make sense of your evidence
What changed? What stayed the same?
Try a certain result
Reset, add X, then M. Predict again. Starting at |0⟩, X changes the state to |1⟩, so every shot gives 1 in this ideal model.
Try two H gates
Reset, add H, another H, then M. Two consecutive H gates return |0⟩ to |0⟩. Every ideal shot gives 0.
Check your explanation
For H then measurement, exact probabilities stay 50% 0 and 50% 1, while observed counts can vary. More shots usually make the observed proportions closer to the model's probabilities, but do not guarantee an exact split. X then measurement gives 1 with certainty in this model. H followed by H then measurement gives 0 with certainty.
This simulator models ideal operations. Real devices can introduce noise and errors. A sample histogram is evidence from one simulated experiment, not proof of how every physical device will behave.
Keep asking good questions
That is the rhythm of Quantum Explorers.
Meet an idea, predict, experiment, explain. The full course builds from ordinary bits through 17 lessons, with quizzes and a completion certificate earned by passing every lesson.