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Robust high-fidelity coherent control of two-state systems by detuning pulses
摘要： Coherent control of two-state systems is traditionally achieved by resonant pulses of specific Rabi frequency and duration, by adiabatic techniques using level crossings or delayed pulses, or by sequences of pulses with precise relative phases (composite pulses). Here we develop a method for high-fidelity coherent control which uses a sequence of detuning pulses. By using the detuning pulse areas as control parameters, and driving on an analogy with composite pulses, we report a great variety of detuning pulse sequences for broadband and narrow-band transition probability profiles.
关键词： composite pulses,narrow-band,coherent control,broadband,detuning pulses,two-state systems
更新于2025-09-23 15:22:29
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Coherently controlled generation of single-cycle terahertz pulses from a thin layer of nonlinear medium with low-frequency resonances
摘要： We propose a scheme to generate single-cycle terahertz (THz) pulses via reflection of an optical femtosecond pulse train from a thin layer of nonlinear resonant medium. Our method is based on the coherent control of low-frequency oscillations and free induction decay in the medium. The specific single-cycle shape of generated THz pulses requires a plane wave front and detection in the near field. Our theoretical results pave the way to a new, simple, and highly efficient way to generate single-cycle waveshape-tunable THz pulses.
关键词： nonlinear resonant medium,coherent control,single-cycle waveshape-tunable,free induction decay,terahertz pulses
更新于2025-09-23 15:19:57
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Control of the populations and phases of two-level quantum systems by a single frequency-chirped laser pulse
摘要： We present an analytical electric field expression to simultaneously control the population and phase dynamics of two-level quantum systems. The presented electric field is obtained by a reverse engineering technique after the desired population and phase evolution pathways of the system have been specified. Upon application of this laser field, the system is driven from an arbitrary quantum state superposition to the desired population distribution; meanwhile the phase of one of the states proceeds according to a predefined path. The robustness of the engineered electric field is demonstrated by numerical simulations on the example of the 3s → 3p transition of atomic sodium. Furthermore, the limitations of the presented technique, which arise due to the application of the rotating wave approximation, are thoroughly analyzed and discussed.
关键词： two-level systems,coherent control,pulse-engineering
更新于2025-09-19 17:13:59
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Coherent light matter interactions in nanostructure based active semiconductor waveguides operating at room temperature
摘要： Light matter coherent interactions require that the coherent state induced in the matter be maintained for the duration of the observation. The only way to induce and observe such interactions in room temperature semiconductors, where the coherence time is of the order of a few hundred femtoseconds, is to use ultrashort pulse excitations and an ultrafast characterization technique. For media comprising an ensemble of nanostructure semiconductors such as self-assembled quantum dots, the gain broadening inhomogeneity also affects the interaction. Moreover, when gain media in the form of an active waveguide, such as optical amplifiers, are used, the interaction is distributed and includes nonresonant incoherent phenomena that occur simultaneously with the coherent effects. Such a complex system can exhibit, nevertheless, clear coherent interactions even at room temperature. Using InAs/InP quantum dot and wirelike quantum dash amplifiers, Rabi oscillations, self-induced transparency, coherent control using spectral pulse shaping, Ramsey interference, and photon echo have been demonstrated. The characterization employed cross frequency resolved optical gating, and the experiments were accompanied by a comprehensive finite difference time domain model that solves the Maxwell and Lindblad equations. This work has major implications on the understanding of the details of dynamical processes in active semiconductor devices, on short pulse generation from semiconductor lasers, and on various future quantum devices.
关键词： active semiconductor waveguides,coherent control,self-induced transparency,Rabi oscillations,coherent light matter interactions,nanostructure,Ramsey interference,photon echo,room temperature
更新于2025-09-16 10:30:52
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Phase control of plasmon enhanced two-photon photoluminescence in resonant gold nanoantennas
摘要： Plasmonic nanoantennas emit two-photon photoluminescence, which is much stronger than their second harmonic generation. Unfortunately, luminescence is an incoherent process and therefore generally not explored for nanoscale coherent control of the antenna response. Here, we demonstrate that, in resonant gold nanoantennas, the two-photon absorption process can be coherent, provided that the excitation pulse duration is shorter than the dephasing time of plasmon mode oscillation. Exploiting this coherent response, we show the pure spectral phase control of resonant gold nanoantennas, with effective read-out of the two-photon photoluminescence.
关键词： two-photon photoluminescence,gold nanoantennas,plasmonic nanoantennas,spectral phase control,coherent control
更新于2025-09-10 09:29:36
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A quantum retrograde canon: complete population inversion in <i>n</i> <sup>2</sup> -state systems
摘要： We present a novel approach for analytically reducing a family of time-dependent multi-state quantum control problems to two-state systems. The presented method translates between related n2-state systems and two-state systems, such that the former undergo complete population inversion (CPI) if and only if the latter reach specific states. For even n, the method translates any two-state CPI scheme to a family of CPI schemes in n2-state systems. In particular, facilitating CPI in a four-state system via real time-dependent nearest-neighbors couplings is reduced to facilitating CPI in a two-level system. Furthermore, we show that the method can be used for operator control, and provide conditions for producing several universal gates for quantum computation as an example. In addition, we indicate a basis for utilizing the method in optimal control problems.
关键词： quantum state transfer,quantum computation,coherent control,quantum information,complete population transfer,quantum control
更新于2025-09-09 09:28:46
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Coherent control of femtosecond spin current investigated by polarization dependent terahertz emission spectroscopy in ferromagnetic heterostructures
摘要： Approaches towards highly-efficient generation of controllable ellipitical ferromagnetic nano-heterostructures are demonstrated. The mechanism for the coherent control of femtosecond spin current in ferromagnetic heterostructures are discussed.
关键词： coherent control,ferromagnetic heterostructures,terahertz emission spectroscopy,femtosecond spin current
更新于2025-09-09 09:28:46
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Direct excitation of molecular vibrational motion by intense broadband THz pulses
摘要： We theoretically investigate molecular vibrational dynamics driven by intense and broadband THz pulses. The light-nuclei interaction is derived from a fully quantum-mechanical minimal coupling Hamiltonian to analyse direct excitation of vibrational modes by the THz pulses. We show that for diatomic molecules a "vibrational moment" can be defined in a manner similar to the dipole moment and that it has non-zero values only for heteronuclear diatomic molecules. Taking ultra-cold heteronuclear diatomic molecules as examples, we show that vibrational-mode excitation by THz pulse irradiation occurs almost stepwisely, especially for low vibrational modes. Coherent control method using frequency-controlled THz pulse sequence is also proposed.
关键词： quantum-mechanical minimal coupling Hamiltonian,vibrational moment,heteronuclear diatomic molecules,coherent control,molecular vibrational dynamics,THz pulses
更新于2025-09-09 09:28:46
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Time dependent spatial entanglement in atom-field interaction
摘要： By using stochastic ensembles of walkers in physical and in one-body Hilbert spaces the recently proposed time-dependent quantum Monte Carlo (TDQMC) method offers the unique capability to calculate one-body density matrices at fully correlated level, without referencing the many-body quantum state. Here TDQMC is applied to study entanglement of simple systems such as Moshinsky atom (oscillator potentials) and atoms with Coulomb potentials in one spatial dimension. Our findings indicate that the dynamic entanglement of atoms exposed to powerful ultrashort laser pulse can be easily manipulated by introducing an appropriate phase modulation where the negative chirp enhances the entanglement while the positive one suppresses it. These findings can be used to explore the correlation properties of different constituents of complex quantum systems subjected to appropriately shaped laser radiation.
关键词： ultrashort pulses,entanglement,coherent control
更新于2025-09-04 15:30:14
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Electronically programmable photonic molecule
摘要： Physical systems with discrete energy levels are ubiquitous in nature and are fundamental building blocks of quantum technology. Realizing controllable artificial atom- and molecule-like systems for light would enable coherent and dynamic control of the frequency, amplitude and phase of photons. In this work, we demonstrate a ‘photonic molecule’ with two distinct energy levels using coupled lithium niobate microring resonators and control it by external microwave excitation. We show that the frequency and phase of light can be precisely controlled by programmed microwave signals, using concepts of canonical two-level systems including Autler–Townes splitting, Stark shift, Rabi oscillation and Ramsey interference. Through such coherent control, we show on-demand optical storage and retrieval by reconfiguring the photonic molecule into a bright–dark mode pair. These results of dynamic control of light in a programmable and scalable electro-optic system open doors to applications in microwave signal processing, quantum photonic gates in the frequency domain and exploring concepts in optical computing and topological physics.
关键词： topological physics,coherent control,optical computing,microring resonators,lithium niobate,optical storage,microwave excitation,photonic molecule,quantum photonics
更新于2025-09-04 15:30:14