Control Of Wave Packets Research Articles

Terahertz Spatiotemporal Wave Synthesis in Random Systems.

Complex media have emerged as a powerful and robust framework to control light-matter interactions designed for task-specific optical functionalities. Studies on wavefront shaping through disordered systems have demonstrated optical wave manipulation capabilities beyond conventional optics, including aberration-free and subwavelength focusing. However, achieving arbitrary and simultaneous control over the spatial and temporal features of light remains challenging. In particular, no practical solution exists for field-level arbitrary spatiotemporal control of wave packets. A new paradigm shift has emerged in the terahertz frequency domain, offering methods for absolute time-domain measurements of the scattered electric field, enabling direct field-based wave synthesis. In this work, we report the experimental demonstration of field-level control of single-cycle terahertz pulses on arbitrary spatial points through complex disordered media.

Optimal control of wave-packets: a semiclassical approach

We studied the optimal quantum control of a molecular rotor in tilted laser fields using the time-sliced Herman–Kluk propagator for the evaluation of the optimal pulse and the light–dipole interaction as the control mechanism. The proposed methodology was used to study the effects of an optimal pulse on the evolution of a wave-packet in a double-well potential and in the effective potential of a molecular rotor in a collinear tilted fields setup. The amplitude and frequency of the control pulse were obtained in such a way that the transition probability between two rotational wave-packets was maximised.

Control of wave packets in Li2 by shaping the pump and probe pulses for a state-selected pump-probe analysis of the ionization continuum

Wave packet signals in Li(2) prepared by shaped pump pulses are also detected with state-selected shaped probe pulses in the ionization continuum. The results show that the final states are discrete Rydberg states instead of continuum states. Final autoionizing states in the continuum are observed and characterized. By selecting specific resonant rovibrational electronic transitions from the superposition states prepared in the wave packets to the final autoionizing states with the pulse shaping system, the modulation depths of the wave packet signals are increased by as much as 5.20+/-0.03 times. Control of the wave packets is also realized by shaping the probe pulses to select specific resonant transitions between the states in the wave packets and the highly excited Rydberg states. The detected amplitude ratio of one specific vibrational quantum beat to one specific rotational quantum beat can be decreased by ten times.

Quantum logic in coarse grained control of wavepackets

We describe ‘coarse-grained’ control of wavepackets with finite resolution in phase space and show how this control can be approached as quantum information processing. To this end, we introduce the wavepacket analogues of qubits, designed to represent the information recorded within a wavepacket, and show how they can be addressed within a single wavepacket. The control is implemented both for non-dispersive wavepacket propagation using linear optical elements, illustrated for the classical waves, and for the dispersive evolution using fractional wavepacket revivals and AC Stark shifts as control tools, illustrated for the revivals of molecular alignment.

Quantum logic approach to wave packet control.

We study control of wave packets with a finite accuracy, approaching it as quantum information processing. For a given control resolution, we define the analogs of several quantum bits within the shape of a single wave packet. These bits are based on wave packet symmetries. Analogs of one- and two-bit gates can be implemented using only free wave packet evolution and coordinate-dependent ac Stark shifts applied at the moments of fractional revivals. As in quantum computation, the gates form a logarithmically small set of basis operations which can be used to approximate any unitary transformation desired for quantum control of the wave packet dynamics. Numerical examples show the application of this approach to control vibrational wave packet revivals.

Control of wave packet dynamics in quantum wells: Effects of Coulomb interactions

We present a theoretical investigation of the effects of Coulomb interactions on the control of wave packets in quantum wells. In particular, we consider the attractive interactions between electrons and holes in an asymmetric double-quantum well. The goal of this work is to clarify the extent to which this interaction affects the controllability of wave packets in quantum-well structures. We find that significant control is attained using simple, experimentally feasible laser pulses. The optimal fields in the presence and absence of the Coulomb interaction are quite similar. The primary effect of the Coulomb interaction is to modify the energy splittings, which induces a small change in the oscillation period and eigenstate composition of the wave packet. Our results indicate that the electron–hole interaction does not substantially affect the controllability of the system dynamics, and that small adjustments in laser parameters can compensate for the interaction.

Extraction of potentials and dynamics from condensed phase pump–probe spectra: Application to I2 in Kr matrices

The many-body dynamics in the condensed phase often leads to structureless absorption spectra while vibrational recurrences in localized coordinates are preserved. A scheme is presented to directly extract anharmonicities and energy relaxation from the varying vibrational periods in pump–probe spectra. For the B state of I2 a constant anharmonicity and a vibrational energy relaxation rate decreasing by one order of magnitude in the wavelength range from 540 to 583 nm are obtained. An analytical expression for compensating the wave packet dispersion due to the anharmonicity is derived and it is applied to the control of wave packets by chirped pulses. Focusing of the wave packet is experimentally observed in accordance with the anharmonicity and even after significant energy relaxation. Predissociation rates are determined from the envelopes of the pump–probe spectra.