Short Answer
A system remains in its instantaneous eigenstate if the Hamiltonian changes slowly enough is the best answer.
Quantum questions reward precision with language. Identify whether the prompt is about wave behaviour, measurement, states, operators, or quantised energy levels before choosing a formula or interpretation.
If the Hamiltonian changes infinitely slowly (adiabatically), the system stays in that eigenstate — it doesn't jump to another.
Why This Answer Is Correct
This is a Hard-level question in Quantum Physics. The prompt is really testing whether you can connect the concept to its defining physical relationship instead of picking a nearby-but-wrong term.
When a quantum question feels ambiguous, translating it into state, observable, probability, and evolution language usually clarifies the answer.
Choices At A Glance
- A. Energy is conserved exactly
- B. A system remains in its instantaneous eigenstate if the Hamiltonian changes slowly enough
- C. Entropy never decreases
- D. Wavefunctions collapse slowly
When similar options appear on an exam, eliminate the ones that break the core law, use the wrong units, or confuse a definition with a consequence.
Topic Snapshot
Topic: Quantum Physics
Difficulty: Hard
Best next move: Re-state the governing law in your own words, then solve one more example from the same topic before moving on.