Quantum Dynamics of a Kicked Harmonic Oscillator
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Huntley, Laura Ingalls
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A classical system of two masses connected by a spring and subjected to a time dependent pulse is used to model a kicked quantum harmonic oscillator. This model is of interest because it is related to the M¨ossbauer effect where the kick is due to the emission of a photon -. Furthermore, the model can be solved analytically and results in coherent states. The solution to this model is found by writing the Schr¨odinger equation in terms of center of mass and relative coordinates . The wave function is found after performing two extended Galilean transformations  and applying separation of variables . The force applied to the system is specified as a Gaussian pulse, and the expectation value of the energy is calculated to agree with Ehrenfest’s theorem . The probability that the system is in the unperturbed harmonic oscillator state is found to have a form that indicates coherent states . We find that any force acting on the system in a stationary state will produce coherent states once the force has gone to zero, except in the case where the force is turned off at the moment when the oscillator is in its equilibrium position with zero velocity. In this case, the wave function returns to the original stationary state. We further show that the wave packet of the system keeps its shape with time, which is another indicator of coherent states for the harmonic oscillator. Finally, we examine the case of a delta-function pulse acting on the system for the harmonic oscillator potential as well as a general potential. We find a form for the wave function of the harmonic oscillator case using three techniques and determine that the wave packet does not keep its shape for the general potential case.
Franklin and Marshall College Archives, Undergraduate Honors Thesis 2007
- F&M Theses Collection