Preparation And Properties Of Non-classical States In Double Quantum Dot-cavity Coupling Systems

In the development of quantum information science,the preparation of non-classical s-tates has always been a very important link.For a long time,people have tried to prepare non-classical states in systems such as atoms,photonic molecules and semiconductor quantum dots.And applied them to many fields such as quantum cryptography,quantum metrology and quantum communication.Since the single quantum dot-cavity coupling system has a longer coherence time,its high integration and high stability make it a single photon source prepa-ration platform.Due to the hyperradiance in the double quantum dot-cavity coupling system,the preparation of multiphoton nonclassical states is expected in this system.Based on this,this paper presents a scheme for preparing multiphoton nonclassical states in a double quantum dot-cavity coupling system.And the effects of double quantum dots on the collective emission behaviors,intensity-amplitude correlation,and resonance fluorescence spectrum of the system are revealed.First,we propose a new scheme to generate the multiphoton nonclassical states in which the single-and two-photon excitation processes are suppressed by cavity induced transparency(CIT)effect.Due to the slight deviation of the natural frequencies of the two quantum dots,an independent transition channel is generated in the energy level diagram.Although the single-and two-photon states are suppressed by the CIT effect,there are still single-and two-photon populations in the independent transition channel.So that the system is in a regime of hy-perradiance.In the hyperradiance regime,although the second-order correlation function is far greater than 1,the photon statistic of the system still exhibits high-order nonclassical effects.By examining the Klyshko's figures of merit,we found that only the third and higher order photon number distributions exhibit nonclassicality,so we call this nonclassical state as three-photon nonclassical state.Subsequently,we further extended this scheme to the case of strong driv-ing,and proposed a scheme for preparing multiphoton nonclassical state with a three-photon probability of 10-4.In order to further study the nonclassicality of the non-identical double quantum dot-cavity coupling system,we then analyzed the intensity-amplitude correlation of the system,and found that non-Gaussian fluctuations will cause the time asymmetry of the intensity-amplitude corre-lation function.From the perspective of complete-collapse and partial-collapse of the single-photon state,we reveal the physical origin of time asymmetry.In the system of identical double quantum dot,the single-photon transition is far from resonance,thus the difference between complete-and partial-collapse of the single-photon state has little effect on the system,and the time asymmetry is not obvious.However,for non-identical double quantum dot,as the detuning between the eigenfrequency of two quantum dots increases,the single-photon transition tends to resonate,and the corresponding population increases.At this time,the difference between complete-collapse due to strength measurements and partial-collapse due to amplitude mea-surements is apparent,which makes the time asymmetry more obvious.In addition,we also used the homodyne cross-correlation criterion to verify the nonclassicality of the system,and found that the output light will still exhibit nonclassical effects in the region of photon bunching and uncompressed.Finally,we explored the ultranarrow spectral line in the resonance fluorescence spectrum and its non-Gaussian features of the double quantum dot-cavity coupling system under ultra-strong coupling(USC)regime.In the regime of USC,the rotating wave approximation(RWA)breaks down and the counter-rotating terms in the Hamiltonian cause the level crossing and avoided-level crossing in the energy spectrum.We choose the frequency of diving field that res-onates with the cavity frequency when the avoided-crossing occurs,and an equivalent four-level dressed states model driven by Rabi frequency can be obtained.In the case of avoided-level-crossing,due to the electron shelving effect on the two metastable states,the decay rates of the incoherent terms in the density matrix elements slows down,thus an ultranarrow peak shows up.Moreover,the vacuum-induced quantum interference couples the incoherent terms with the coherent terms.When we detecting the fluorescence radiated by the sidebands,an ultranarrow peak appears at the line center of the resonance fluorescence spectrum.For the case of level-crossing,the additional inner sidebands in the resonance fluorescence spectrum becomes more prominent as compared to the Mollow triplet.Finally,we use the intensity-amplitude corre-lation function to analyze the non-Gaussian feature of the system,and found that the double quantum dot-cavity ultrastrong coupling system has obvious non-Gaussian properties,and with the increases of driving strength and coupling strength,the non-Gaussian feature of the system will be further enhanced.