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Driven two-state quantum dynamics University Quantum Mechanics II · Time-dependent perturbation theory

Resonance Switch

Time a coherent drive and tune its detuning to route a two-state ensemble into the excited state.

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Challenge 1 of 3

Resonant inversion

A perfectly resonant coherent drive starts with every system in its lower state.

Mission targetExpected excited-state population95–100 %
SETUP PREVIEWRESONANTEXCITED-STATE PROBABILITY10Pulse time: 0–10.0 μsMaximum 100.0%ENSEMBLE POPULATION6.1%Ω = 1.00 rad/μsΔ = 0.00 rad/μsCoherent two-level model · Populations, not particle flight paths.

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Coupling Ω₀1 rad/μs
Detuning Δ0 rad/μs
Initial statelower state

Stop the pulse with 95–100% expected excited-state population.

Build your setup

Test 1

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0.5 μs
0.1 μs10 μs

3 stars on your first test; 2 within three; 1 after that. A first clear earns 100 XP plus 10 per star. Better star records earn the difference; repeating a record earns no extra XP.

Your experiment is ready.

Use the exact two-state Rabi probability, distinguish detuning's probability ceiling from timing error, and locate a later population peak.

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The physics behind the game

Use the exact two-state Rabi probability, distinguish detuning's probability ceiling from timing error, and locate a later population peak.

Pₑ(t) = Ω₀²/(Ω₀² + Δ²) · sin²[½√(Ω₀² + Δ²)t]

Model assumptions. An initially lower-state, isolated two-level system with a coherent rotating drive, or a linearly driven system within the rotating-wave approximation. Ω₀ and Δ are angular frequencies in rad/μs, and time is in μs. Probabilities describe an ensemble; relaxation, decoherence and sampling noise are omitted.