arXiv subjects

P. H. Bucksbaum

Publications and source records attributed to P. H. Bucksbaum.

26 records · Page 2Linked to original sources

arXiv2004

On the role of coupling in mode selective excitation using ultrafast pulse shaping in stimulated Raman spectroscopy

The coherence of two, coupled two-level systems, representing vibrational modes in a semiclassical model, is calculated in weak and strong fields for various coupling schemes and for different relative phases between initial state amplitudes. A relative phase equal to $π$ projects the system into a dark state. The selective excitation of one of the two, two-level systems is studied as a function of coupling strength and initial phases.

physics.chem-ph↗

arXiv2004

Control of trapped-ion quantum states with optical pulses

We present new results on the quantum control of systems with infinitely large Hilbert spaces. A control-theoretic analysis of the control of trapped ion quantum states via optical pulses is performed. We demonstrate how resonant bichromatic fields can be applied in two contrasting ways -- one that makes the system completely uncontrollable, and the other that makes the system controllable. In some interesting cases, the Hilbert space of the qubit-harmonic oscillator can be made finite, and the Schrödinger equation controllable via bichromatic resonant pulses. Extending this analysis to the quantum states of two ions, a new scheme for producing entangled qubits is discovered.

quant-ph↗

arXiv2003

Theory of selective excitation in Stimulated Raman Scattering

A semiclassical model is used to investigate the possibility of selectively exciting one of two closely spaced, uncoupled Raman transitions. The duration of the intense pump pulse that creates the Raman coherence is shorter than the vibrational period of a molecule (impulsive regime of interaction). Pulse shapes are found that provide either enhancement or suppression of particular vibrational excitations.

physics.chem-ph↗

arXiv2002

Supersonic strain front driven by a dense electron-hole plasma

We study coherent strain in (001) Ge generated by an ultrafast laser-initiated high density electron-hole plasma. The resultant coherent pulse is probed by time-resolved x-ray diffraction through changes in the anomalous transmission. The acoustic pulse front is driven by ambipolar diffusion of the electron-hole plasma and propagates into the crystal at supersonic speeds. Simulations of the strain including electron-phonon coupling, modified by carrier diffusion and Auger recombination, are in good agreement with the observed dynamics.

cond-mat.mtrl-sci↗

arXiv2001

Coherent control using adaptive learning algorithms

We have constructed an automated learning apparatus to control quantum systems. By directing intense shaped ultrafast laser pulses into a variety of samples and using a measurement of the system as a feedback signal, we are able to reshape the laser pulses to direct the system into a desired state. The feedback signal is the input to an adaptive learning algorithm. This algorithm programs a computer-controlled, acousto-optic modulator pulse shaper. The learning algorithm generates new shaped laser pulses based on the success of previous pulses in achieving a predetermined goal.

quant-ph↗

arXiv2001

Optimally shaped terahertz pulses for phase retrieval in a Rydberg atom data register

We employ Optimal Control Theory to discover an efficient information retrieval algorithm that can be performed on a Rydberg atom data register using a shaped terahertz pulse. The register is a Rydberg wave packet with one consituent orbital phase-reversed from the others (the ``marked bit''). The terahertz pulse that performs the decoding algorithm does so by by driving electron probability density into the marked orbital. Its shape is calculated by modifying the target of an optimal control problem so that it represents the direct product of all correct solutions to the algorithm.

quant-ph↗

arXiv2001

Probing impulsive strain propagation with x-ray pulses

Pump-probe time-resolved x-ray diffraction of allowed and nearly forbidden reflections in InSb is used to follow the propagation of a coherent acoustic pulse generated by ultrafast laser-excitation. The surface and bulk components of the strain could be simultaneously measured due to the large x-ray penetration depth. Comparison of the experimental data with dynamical diffraction simulations suggests that the conventional model for impulsively generated strain underestimates the partitioning of energy into coherent modes.

cond-mat↗

arXiv2000

Quantum phase retrieval of a Rydberg wave packet using a half-cycle pulse

A terahertz half-cycle pulse was used to retrieve information stored as quantum phase in an $N$-state Rydberg atom data register. The register was prepared as a wave packet with one state phase-reversed from the others (the "marked bit"). A half-cycle pulse then drove a significant portion of the electron probability into the flipped state via multimode interference.

quant-ph↗