量子點cQED系統(tǒng)中的聲子效應(yīng)研究
發(fā)布時間：2018-10-31 09:33
【摘要】：空腔量子電動力學(xué)(cavity Quantum Electrodynamics,c QED)是量子光學(xué)研究領(lǐng)域的一個重要分支。近年來,固態(tài)的c QED系統(tǒng),即量子點-微腔系統(tǒng)引起了人們的研究興趣。新的系統(tǒng)在量子信息處理中同樣具有廣泛的應(yīng)用,范圍包含量子位的實現(xiàn)到單光子源的建立。固態(tài)系統(tǒng)中的一個重要問題是會受到聲子庫的影響。這些影響主要表現(xiàn)在三個方面,即聲子引起的重整化、純退相和失諧聲子散射。本文首先是介紹了基本的光與原子相互作用模型:J-C模型,以及聲子庫對量子點c QED系統(tǒng)的影響。聲子庫的影響主要來自于電子與聲子的耦合,這種耦合包含兩種機(jī)制:壓電耦合和形變勢耦合。由粒子的波函數(shù)出發(fā)來計算相應(yīng)的聲子譜函數(shù),從得到的結(jié)果中發(fā)現(xiàn)壓電耦合作用對系統(tǒng)的影響至少比形變勢耦合小了一個數(shù)量級,這個結(jié)果支持了聲子庫對系統(tǒng)的影響主要來源于LA聲子的結(jié)論。量子點的形狀受到制造技術(shù)的影響會有所不同,這意味著在實際系統(tǒng)中量子點形狀的影響是一個重要的問題。由波函數(shù)出發(fā)通過計算得到了三種典型形狀:球形、橢球形和圓盤形的量子點的聲子譜函數(shù)和相應(yīng)的聲子效應(yīng)曲線。這些結(jié)果表明了聲子效應(yīng)與量子點形狀有較強(qiáng)的依賴關(guān)系。在三種形狀量子點中,圓盤形量子點具有最強(qiáng)的電聲子耦合和最寬的聲子譜分布,相應(yīng)地,其聲子效應(yīng)也是最明顯的。聲子庫對系統(tǒng)的影響與溫度是直接相關(guān)的,由于存在耦合重整化,隨著溫度升高,系統(tǒng)將會從強(qiáng)耦合轉(zhuǎn)變到弱耦合狀態(tài)。從約化密度矩陣主方程出發(fā),通過計算可以得到這種轉(zhuǎn)變的判定條件。受聲子庫的影響,量子點的衰減率與溫度直接相關(guān),當(dāng)溫度在40-50K時,衰減率會隨著溫度升高迅速上升。本文的計算表明在這種溫度依賴關(guān)系下,系統(tǒng)狀態(tài)的變化在某些情況下會出現(xiàn)反常,如隨著溫度升高,系統(tǒng)會出現(xiàn)強(qiáng)耦合→弱耦合→強(qiáng)耦合→弱耦合的變化情況。這表明聲子庫所帶來的影響會使量子點c QED系統(tǒng)出現(xiàn)一些新的與原子c QED系統(tǒng)不同的現(xiàn)象。文章最后計算了發(fā)射譜隨溫度的變化曲線,對一些相關(guān)問題進(jìn)行了討論。
[Abstract]:Cavity quantum electrodynamics (cavity Quantum Electrodynamics,c QED) is an important branch of quantum optics. In recent years, the solid-state c QED system, called quantum dot-microcavity system, has attracted much attention. The new system also has a wide range of applications in quantum information processing, ranging from the realization of quantum bits to the establishment of single photon sources. An important problem in solid state systems is the influence of phonon libraries. These effects are mainly reflected in three aspects: phonon induced renormalization pure dephase and detuning phonon scattering. In this paper, we first introduce the basic model of the interaction between light and atom: J-C model, and the effect of phonon library on the c QED system of quantum dots. The effect of phonon library mainly comes from the coupling of electrons and phonons, which consists of two mechanisms: piezoelectric coupling and deformation potential coupling. The corresponding phonon spectrum function is calculated from the wave function of the particle. It is found that the effect of piezoelectric coupling on the system is at least one order of magnitude less than that of the deformation potential coupling. This result supports the conclusion that the effect of phonon library on the system is mainly derived from LA phonon. The shape of quantum dots will be affected differently by manufacturing technology, which means that the shape of quantum dots is an important problem in practical systems. The phonon spectral functions and the corresponding phonon effect curves of spherical ellipsoid and disk quantum dots are obtained from the wave function. These results indicate that the phonon effect is strongly dependent on the shape of quantum dots. Among the three kinds of quantum dots, the disk quantum dots have the strongest phonon coupling and the widest phonon spectrum distribution, and the phonon effect is also the most obvious. The effect of phonon library on the system is directly related to temperature. Due to the existence of coupling renormalization, the system will change from strong coupling to weak coupling state with the increase of temperature. Based on the main equation of reduced density matrix, the decision conditions of this transformation can be obtained by calculation. Under the influence of phonon pool, the decay rate of quantum dots is directly related to temperature. When the temperature is 40-50K, the attenuation rate will rise rapidly with the increase of temperature. The calculation in this paper shows that under this temperature dependence, the variation of system state will be abnormal in some cases, for example, with the increase of temperature, there will be strong coupling and weak coupling and strong coupling and weak coupling in the system. It is suggested that the effect of phonon library will lead to some new phenomena in the quantum dot c QED system which are different from those in the atomic c QED system. Finally, the curve of emission spectrum with temperature is calculated, and some related problems are discussed.
【學(xué)位授予單位】：暨南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：O471.1
本文編號：2301685
[Abstract]:Cavity quantum electrodynamics (cavity Quantum Electrodynamics,c QED) is an important branch of quantum optics. In recent years, the solid-state c QED system, called quantum dot-microcavity system, has attracted much attention. The new system also has a wide range of applications in quantum information processing, ranging from the realization of quantum bits to the establishment of single photon sources. An important problem in solid state systems is the influence of phonon libraries. These effects are mainly reflected in three aspects: phonon induced renormalization pure dephase and detuning phonon scattering. In this paper, we first introduce the basic model of the interaction between light and atom: J-C model, and the effect of phonon library on the c QED system of quantum dots. The effect of phonon library mainly comes from the coupling of electrons and phonons, which consists of two mechanisms: piezoelectric coupling and deformation potential coupling. The corresponding phonon spectrum function is calculated from the wave function of the particle. It is found that the effect of piezoelectric coupling on the system is at least one order of magnitude less than that of the deformation potential coupling. This result supports the conclusion that the effect of phonon library on the system is mainly derived from LA phonon. The shape of quantum dots will be affected differently by manufacturing technology, which means that the shape of quantum dots is an important problem in practical systems. The phonon spectral functions and the corresponding phonon effect curves of spherical ellipsoid and disk quantum dots are obtained from the wave function. These results indicate that the phonon effect is strongly dependent on the shape of quantum dots. Among the three kinds of quantum dots, the disk quantum dots have the strongest phonon coupling and the widest phonon spectrum distribution, and the phonon effect is also the most obvious. The effect of phonon library on the system is directly related to temperature. Due to the existence of coupling renormalization, the system will change from strong coupling to weak coupling state with the increase of temperature. Based on the main equation of reduced density matrix, the decision conditions of this transformation can be obtained by calculation. Under the influence of phonon pool, the decay rate of quantum dots is directly related to temperature. When the temperature is 40-50K, the attenuation rate will rise rapidly with the increase of temperature. The calculation in this paper shows that under this temperature dependence, the variation of system state will be abnormal in some cases, for example, with the increase of temperature, there will be strong coupling and weak coupling and strong coupling and weak coupling in the system. It is suggested that the effect of phonon library will lead to some new phenomena in the quantum dot c QED system which are different from those in the atomic c QED system. Finally, the curve of emission spectrum with temperature is calculated, and some related problems are discussed.
【學(xué)位授予單位】：暨南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：O471.1
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相關(guān)期刊論文 前3條
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