Stationary states and spectral superposition
For a time-independent Hamiltonian, an energy eigenstate evolves by a phase exp(−iEt/ħ).
Key knowledge
For a time-independent Hamiltonian, an energy eigenstate evolves by a phase exp(−iEt/ħ). In a complete discrete orthonormal energy basis a state evolves as a sum of those phases with its initial expansion coefficients; relative phases can change observable probabilities.
Values and equations
Hφ_n=E_nφ_n; |ψ(t)⟩=Σ_n c_n exp(−iE_nt/ħ)|n⟩; Σ_n|c_n|²=1
- H,E_n
- Hamiltonian and eigenenergy J
- t
- Elapsed time s
- ħ
- Reduced Planck constant J s
- φ_n,|n⟩,c_n
- Normalized eigenstate and dimensionless expansion coefficient
Conditions and scope
- Discrete complete basis and normalized square-summable coefficients; continua need spectral integrals.
- A stationary energy eigenstate has time-independent probabilities for time-independent observables, not zero motion in a classical trajectory.
Sources · 1
References
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Evidence and review
Quantum Mechanics (2010): Stationary states: Separation in the time-independent potential, energy phases and expansion in stationary eigenstates.
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Entry details
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