Probability before quantum
Read a probability distribution and distinguish a prediction from a sample.
Intuition
A probability describes how likely an outcome is. A probability of 1 means certainty; 0 means impossible. A 50% chance does not promise an alternating sequence of zeros and ones.
For a two-outcome experiment the probabilities add to one. A fair classical coin and a measured |+⟩ state can both give 50/50 counts. That matching histogram does not make a spinning coin a quantum superposition. Later we will use interference to distinguish quantum states with identical probabilities.
The mathematics
Look a little deeper
For independent, repeated fair trials, the expected number of ones in n shots is n/2. The observed count can differ. Repeating a quantum trial includes preparing its initial state again.
Use it
Prepare equal measurement probabilities with H. Compare 10 and 1,000 shots in Measurements; inspect the unchanged ideal Probabilities tab.
This exercise uses the same server-side state and circuit checks as its linked practice problem.
Build your circuit
Click a gate to append it, or drag it onto a wire. CX uses the selected control; SWAP uses it as the second operand. Basis order: |qₙ … q₀⟩.
Returned logical circuit · before transpilation · q0 on top
Connect to code
qc = QuantumCircuit(1) qc.h(0)
These operations go inside a circuit-building program. Practice problems provide a complete solve() template.
Check your understanding
First complete the circuit exercise successfully.