| The light-matter interaction is an important topic in the field of atomic,molecular and optical physics and is related to the disciplines of physics,chemistry,electronic engineering and so on.Within the framework of classical electrodynamics,it is em-phasized that the state of the system follows the classical mechanics and the Maxwell's equations.As found by scientists,the problem of black body radiation and atomic spectroscopy cannot be interpreted using the classical mechanics,but needs the quan-tum theory.Now scientists are capable of using light as a tool for observing and ma-nipulating matter on the atomic scale.The light-matter interaction in semiconductor nanostructures involves the light at subwavelength scales,which is useful not only for developing novel quantum optics and quantum electronics devices,but also for explor-ing the effects of the light to control the internal motions of molecules.The light-matter interaction in superconducting quantum circuits involves the interaction of photons at microwave frequencies with artificial atoms made of Josephson junctions.These arti-ficial atoms make it easier to study the known phenomena of quantum optics and can also be used to explore the novel phenomena that are not found in natural atoms.The hybrid cavity quantum electrodynamics(QED)system combines the advantages of two or more quantum systems.It is not only of fundamental importance,but also opens up exciting possibilities for quantum technologies,such as quantum computation and quantum information.This Ph.D.thesis theoretically studies the light-matter interaction in a semicon-ductor quantum dot system and experimentally studies the light-matter interaction in a superconducting quantum circuits system and in a cavity magnon-polariton system.Our main results are summarized as follows:(1)Theoretical investigation of the eigenenergy spectrum and linear optical absorp-tion response spectrum of the weak probe field in a triple-quantum-dot system.By analyzing the eigenenergy spectrum of the system Hamiltonian,we can discriminate tunneling-induced transparency(TIT)and double TIT from Autler-Townes(AT)dou-blet and triplet,respectively.For the resonant case,the presence of the TIT does not exhibit distinguishable anticrossing in the eigenenergy spectrum in the weak-tunneling regime,but the occurrence of double anticrossings in the strong-tunneling regime shows that the TIT evolves to the AT doublet.For the off-resonance case,the appearance of a new detuning-dependent dip in the absorption spectrum leads to the double TIT be-havior in the weak-tunneling regime due to no distinguished anticrossing occurring in the eigenenergy spectrum.However,in the strong-tunneling regime,a new detuning-dependent dip in the absorption spectrum results in AT triplet owing to the presence of triple anticrossings in the eigenenergy spectrum.Our results can be applied to quantum measurement and quantum-optics devices in solid-state systems.(2)Theoretical study of the linear and nonlinear dispersion responses of a probe field in an asymmetrical triple quantum dot system.It is shown that the linear and nonlinear dispersion responses of the probe field are significantly sensitive to both the detunings and the tunneling strength of the indirect-excitonic(IX)states.In particular,the nonlinear dispersion properties of the probe field are dominated by the enhanced cross-Kerr nonlinearity from one of the IX states.Meanwhile,by varying the detunings of the other IX state,we reveal the realization of the enhanced-cross-Kerr-nonlinearity induced self-focusing and self-defocusing effects for the probe field.Moreover,by taking into account the effect of the longitudinal-acoustic-phonon induced dephasing of the IX states,it is possible to modulate the height and position of the peak of the self-focusing or self-defocusing effect.Our results may have potential applications in nonlinear-optics and quantum-optics devices based on the enhanced nonlinearities in this solid-state system.(3)Experimental investigation of the time-domain Young's double-slit(YDS)ex-periment in a superconducting quantum circuits system.We show that a YDS exper-iment can be realized by modulating the symmetrical-trigger-square-wave probe and control pulsed fields in a tunable three-dimensional transmon.An analytical model based on Bessel feature picture is developed to explain the interference and diffraction patterns.In particular,the diffraction function depends on the detuning of the probe field,which is in analogy with regulating the slit width in the conventional YDS ex-periment.In addition,we also demonstrate that the generalized Van-Vleck degenerate perturbation model captures all the relevant features of the YDS experiment,which suggests the existence of motional narrowing in the strongly driven regime.This work promises new avenues for investigating the physics of systems interacted with modu-lated fields and offers a new way to explore the wave-particle duality of photons.(4)Experimental study of the exceptional point in a cavity magnon-polariton sys-tem.Magnon-polaritons are hybrid light-matter quasiparticles originating from the strong coupling between magnons and microwave photons in a cavity QED system.They have emerged as a potential candidate for implementing quantum transducers and memories.Owing to the dampings of both photons and magnons,the polaritons have limited lifetimes.However,stationary magnon-polariton states can be reached by a dy-namical balance between pumping and losses,so the intrinsical nonequilibrium system may be described by a non-Hermitian Harmiltonian.Here we design a tunable cavity quantum electrodynamics system with a small ferromagnetic sphere in a microwave cavity and engineer the dissipations of photons and magnons to create cavity magnon-polaritons which have non-Hermitian spectral degeneracies.By tuning the magnon-photon coupling strength,we observe the polaritonic coherent perfect absorption and demonstrate the phase transition at the exceptional point.Our experiment offers a nov-el macroscopic quantum platform to explore the non-Hermitian physics of the cavity magnon-polaritons. |
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