We study the emission spectrum and absorption spectrum of a quantum emitter when it is driven by various pulse sequences. We consider the Uhrig sequence of $π_x$ pulses, the periodic sequence of $π_xπ_y$ pulses and the periodic sequence of $π_z$ pulses (phase kicks). We find that, similar to the periodic sequence of $π_x$ pulses, the Uhrig sequence of $π_x$ pulses has emission and absorption that are, with small variations, analogous to those of the resonance fluorescence spectrum. In addition, while the periodic sequence of $π_z$ pulses produces a spectrum that is dependent on the detuning between the emitter and the pulse carrier frequency, the Uhrig sequence of nonequidistant $π_x$ pulses and the periodic sequence of $π_xπ_y$ pulses have spectra with little dependence on the detuning as long as it stays moderate along with the number of pulses. This implies that they can also, similar to previously studied periodic sequence of $π_x$ pulses, be used to tune the emission or absorption of quantum emitters to specific frequencies, to mitigate inhomogeneous broadening and to enhance the production of indistinguishable photons from emitters the solid state.
We investigate how entanglement can enhance two-photon absorption in a three-level system. First, we employ the Schmidt decomposition to determine the entanglement properties of the optimal two-photon state to drive such a transition, and the maximum enhancement which can be achieved in comparison to the optimal classical pulse. We then adapt the optimization problem to realistic experimental constraints, where photon pairs from a down-conversion source are manipulated by local operations such as spatial light modulators. We derive optimal pulse shaping functions to enhance the absorption effi…
In this tutorial we provide a short review of attosecond pulse characterization techniques and a pedagogical account of a recently proposed method called Pulse Analysis by Delayed Absorption (PANDA) [Pabst and Dahlström, Phys. Rev. A, 94, 13411 (2016)]. We discuss possible implementations of PANDA in alkali atoms using either principal quantum number wave packets or spin-orbit wave packets. The main merit of the PANDA method is that it can be used as a pulse characterization method that is free from atomic latency effects, such as scattering phase shifts and long-lived atomic resonances. Final…
Periodic-Pulse Control of Collective Emission and Photon Statistics in Interacting Quantum Emitters
Middle Tennessee State University（中田纳西州立大学）；Quantum Research, Interdisciplinary Science, and Education (QRISE) Center, Middle Tennessee State University（中田纳西州立大学量子研究、跨学科科学与教育中心）
We provide a compendium of the quantum mechanical equations for photon emission rates, photon absorption cross sections, and photon scattering cross sections. For each case, the different equations that apply for discrete or continuous electron states of the emitting, absorbing, or scattering material are given.
We present a spin-adapted time-dependent coupled cluster singles and doubles model for the molecular response to a sequence of ultrashort laser pulses. The implementation is used to calculate the electronic response to a valence-exciting pump pulse, and a subsequent core-exciting probe pulse. We assess the accuracy of the integration procedures used in solving the dynamic coupled cluster equations, in order to find a compromise between computational cost and accuracy. The transient absorption spectrum of lithium fluoride is calculated for various delays of the probe pulse with respect to the p…
We demonstrate time-resolved nonlinear extreme-ultraviolet absorption spectroscopy on multiply charged ions, here applied to the doubly charged neon ion, driven by a phase-locked sequence of two intense free-electron laser pulses. Absorption signatures of resonance lines due to 2$p$--3$d$ bound--bound transitions between the spin-orbit multiplets $^3$P$_{0,1,2}$ and $^3$D$_{1,2,3}$ of the transiently produced doubly charged Ne$^{2+}$ ion are revealed, with time-dependent spectral changes over a time-delay range of $(2.4\pm0.3)\,\text{fs}$. Furthermore, we observe 10-meV-scale spectral shifts o…
Using the Brink-Axel hypothesis we derive the rate $R$ for nuclear dipole excitation by a laser pulse carrying $N \gg 1$ photons with average energy $\hbar ω_0 \approx 5$ MeV. As expected $R \propto (\hbar ω_0)^3$. The rate is also proportional to the aperure $α$ of the laser pulse. Perhaps less expected is the fact that $R \propto N$, irrespective of the degree of coherence of the laser pulse. The expression for $R$, derived for a nearly stationary laser pulse, is valid also for short times and can, thus, be used in simulations via rate equations of multiple nuclear dipole excitations by a si…
We present a combined experimental and theoretical study on the photodissociation dynamics of ion-pair formation in O$_2$ following resonant two-photon absorption of a 9.3 eV femtosecond pulse, where the resulting O$^+$ ions are detected using 3-D momentum imaging. Ion-pair formation states of $^3Σ^-_g$ and $^3Π_g$ symmetry are accessed through predissociation of optically dark continuum Rydberg states converging to the B $^2Σ^-_g$ ionic state, which are resonantly populated via a mixture of both parallel-parallel and parallel-perpendicular two-photon transitions. This mixture is evident in th…
The recent demonstration of isolated attosecond pulses from an X-ray free-electron laser (XFEL) opens the possibility for probing ultrafast electron dynamics at X-ray wavelengths. An established experimental method for probing ultrafast dynamics is X-ray transient absorption spectroscopy, where the X-ray absorption spectrum is measured by scanning the central photon energy and recording the resultant photoproducts. The spectral bandwidth inherent to attosecond pulses is wide compared to the resonant features typically probed, which generally precludes the application of this technique in the a…
