open-standards/wai/wai-quantum/course/lessons/bell/lesson.en.md
Transaction Science fb230d8a62 wai-quantum: the circuits course as data, each exercise checked by the engine, and wai-quantum learn in English and Chinese
engine::course reads the course from wai-quantum/course/: 21 lessons from a
first circuit through superposition, entanglement, interference, the standard
algorithms, noise and mitigation, error correction and fault tolerance to
resource estimates, each a Markdown text in English and Simplified Chinese and
an exercise.json with a schema. A check runs each case of an exercise (a
generator's inputs) with its intent and the verdict, measures its constraints
(the gates allowed, counts, the T count, the critique's smells, the resource
estimate's counts), and says what went wrong from the diagnostics, the verdict
and the critique, never from the solution. The tests hold every solution to
pass by proof, every known wrong answer to fail for its stated reason, and
every locale to every text and message.

wai-quantum learn shows, starts, checks, hints and explains a lesson, keeps
progress only on this machine, and speaks the language --lang or LANG names;
the command summaries and docs topics have Chinese translations held to the
English they came from. The verdict gains of_diagnostic for a generator's
refusal. llms.txt names the course.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
2026-10-28 08:42:54 -04:00

748 B

Two qubits can be in a state that is not one state for each: the Bell state

(|00⟩ + |11⟩)/√2.

Measured, it gives 00 or 11, each half the time, and never 01 or 10. Each qubit on its own looks like a fair coin, yet the two always agree. No pair of separate one-qubit states gives this; the qubits are entangled.

The gate that entangles here is the controlled-NOT, cx control, target. It flips the target exactly when the control is |1⟩. On a control in superposition it acts on both parts at once.

The engine runs a circuit of h, cx and the other Clifford gates on the stabilizer tableau, which follows thousands of qubits exactly without writing out 2ⁿ amplitudes. Try wai-quantum plan on your solution to see it chosen.