本文選題：量子糾纏 + 糾纏突然死亡　； 參考：《哈爾濱工業(yè)大學》2014年博士論文

【摘要】：量子糾纏是量子信息領(lǐng)域中的一種重要資源，但是它又是極其脆弱的�，F(xiàn)實量子系統(tǒng)不可能孤立于周圍環(huán)境單獨存在，必須考慮量子噪聲對量子系統(tǒng)糾纏的影響。量子噪聲會導致量子糾纏衰減甚至突然死亡，影響量子信息處理過程，有必要對不同量子噪聲環(huán)境下的系統(tǒng)糾纏演化進行研究。 控制量子系統(tǒng)的糾纏演化，了解量子噪聲對量子系統(tǒng)糾纏演化的影響將為量子信息處理過程中維持量子糾纏的最大存在提供有力理論支撐，是量子信息技術(shù)得以應用的重要環(huán)節(jié)。與此同時，由于量子噪聲等因素而產(chǎn)生的糾纏混態(tài)在實際量子信息處理過程中呈主導作用，因此研究糾纏混態(tài)在量子噪聲環(huán)境下的糾纏演化特性對量子信息技術(shù)的應用具有重大現(xiàn)實意義。 本文針對量子信息中糾纏突然死亡現(xiàn)象，給出了一類可控二原子量子系統(tǒng)糾纏演化模型，重點研究了量子信息中常見的兩類特殊二粒子糾纏混態(tài)在局域獨立（或局域共同）Pauli和退極化量子噪聲環(huán)境下的糾纏演化特性，特別是當量子信道受上述量子噪聲環(huán)境影響時的單量子比特量子隱形傳輸理論。本論文的主要研究內(nèi)容如下： 研究了囚禁于腔場中的二原子糾纏動力學。討論了分別以兩類不可以通過局域操作和經(jīng)典通信相互轉(zhuǎn)化的三原子W態(tài)為原子初始態(tài)以及不同粒子數(shù)態(tài)為腔場初始態(tài)時二原子糾纏并發(fā)度和負值度的演化。分析了系統(tǒng)糾纏演化過程中出現(xiàn)糾纏突然死亡的原因。結(jié)果發(fā)現(xiàn)原子初始態(tài)和腔場粒子數(shù)態(tài)對原子糾纏突然死亡現(xiàn)象的出現(xiàn)有重要影響。 研究了兩類特殊二粒子糾纏態(tài)在局域獨立（或局域共同）Pauli和退極化量子噪聲環(huán)境下的糾纏動力學。一類為Bell態(tài)與|00（或|11）混合情況下的二粒子糾纏態(tài)，另一類為擴展的類Werner態(tài)。針對每一類量子系統(tǒng)，均利用量子主方程的方法給出了其密度矩陣在不同噪聲環(huán)境下演化的解析表達式，并就每種量子噪聲環(huán)境，依次給出了局域獨立和局域共同環(huán)境下系統(tǒng)并發(fā)度隨各參量的變化規(guī)律，同時對這兩種情況下的并發(fā)度進行了比較分析，評估了混合比例和純度對各自量子系統(tǒng)糾纏演化的影響，，分析了系統(tǒng)在糾纏演化過程中出現(xiàn)糾纏突然死亡和糾纏得以保持的原因。結(jié)果發(fā)現(xiàn)無論哪種量子系統(tǒng)，在某些局域共同Pauli量子噪聲環(huán)境下，均存在一個特定區(qū)域使量子系統(tǒng)糾纏度始終保持與初始狀態(tài)一致。 研究了量子信道在不同Pauli和退極化量子噪聲環(huán)境下的單量子比特量子隱形傳輸理論。結(jié)合量子隱形傳輸量子線路模型給出了當量子信道（分別以四個不同Bell態(tài)為量子信道）經(jīng)歷局域獨立（或局域共同）Pauli和退極化量子噪聲環(huán)境時量子隱形傳輸?shù)谋Ｕ娑群推骄Ｕ娑�，針對每種噪聲環(huán)境，比較分析了局域獨立和局域共同環(huán)境下的平均保真度。發(fā)現(xiàn)當量子信道受到不同Pauli和退極化噪聲環(huán)境影響時，四個Bell態(tài)中只有一個最適合作為量子信道。 本論文的研究工作對加深糾纏突然死亡出現(xiàn)原因的理解以及實際量子信息傳輸過程中如何保持糾纏提供了一定的理論參考，為獲得高平均保真度量子隱形傳輸提供了理論依據(jù)。
[Abstract]:Quantum entanglement is an important resource in the field of quantum information, but it is extremely fragile. The real quantum system can not isolate in the surrounding environment alone. We must consider the effect of quantum noise on the entanglement of quantum systems. Quantum noise can cause quantum entanglement attenuation or even sudden death, affecting the process of quantum information processing. It is necessary to study the entanglement evolution of systems under different quantum noise environments.
To control the entanglement evolution of quantum systems and to understand the influence of quantum noise on the entanglement evolution of quantum systems will provide a powerful theoretical support for the maximum existence of quantum entanglement in the process of quantum information processing. It is an important link in the application of quantum information technology. At the same time, the entanglement state produced by quantum noise and other factors is real. It is of great practical significance to study the entanglement and the evolution characteristics of entanglement and mixed state in quantum noise environment for the application of quantum information technology.
In this paper, the entanglement evolution model of a class of controllable two atom quantum systems is given in quantum information. The entanglement evolution characteristics of two special two particle entangled states in quantum information in the local independent (or local common) Pauli and depolarized quantum noise environment are studied emphatically, especially when the quantum signal is used as a quantum letter. The single qubit quantum teleportation theory is affected by the above quantum noise environment. The main contents of this paper are as follows:
The two atom entanglement dynamics in a cavity field are studied. The concurrency of the entanglement and the negative value of the two atom in the initial state of the three atom W state which can not be transformed by the local operation and the classical communication can not be transformed by the local operation and the classical communication are discussed respectively. The evolution process of the entanglement in the system is analyzed. The cause of entanglement sudden death is found. It is found that the initial state of atoms and the number of states in the cavity have important effects on the sudden death of entanglement.
The entanglement dynamics of two special two particle entangled states in local independent (or local common) Pauli and depolarized quantum noise environment are studied. A class of entangled states of two particles in the mixture of Bell States and |00 (or |11), and another class of extended Werner states. The analytic expression of its density matrix evolves under different noise environment, and each quantum noise environment is given in order to give the variation of the system concurrency with each parameter in local independent and local common environment. At the same time, the concurrency of the two cases is compared and analyzed, and the mixture ratio and purity are evaluated for each quantum system. The influence of entanglement evolution is analyzed. The cause of the entanglement sudden death and entanglement in the process of entanglement evolution is analyzed. It is found that no matter which quantum system, in some local common Pauli quantum noise environment, there is a particular region that keeps the entanglement of quantum system consistent with the initial state.
The quantum teleportation theory of quantum channel in different Pauli and depolarized quantum noise environment is studied. Combining quantum teleportation quantum circuit model, a quantum channel (four different Bell states as a quantum channel) is given to experience local independent (or local common) Pauli and depolarized quantum noise environment The fidelity and average fidelity of the subsurface transmission are analyzed for each noise environment, and the average fidelity in local independent and local common environment is compared and analyzed. It is found that only one of the best cooperative quantum channels in the four Bell states when the quantum channel is affected by different Pauli and depolarizing noise environment.
The research work in this paper provides a theoretical reference for deepening the understanding of the cause of the sudden death of entanglement and how to maintain entanglement in the actual quantum information transmission process, and provides a theoretical basis for obtaining high average fidelity quantum teleportation.

【學位授予單位】：哈爾濱工業(yè)大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：O413;TN918

【參考文獻】

相關(guān)期刊論文 前3條

1 苗純;楊名;曹卓良;;Controlled Quantum Teleportation Through Noisy GHZ Channel[J];Communications in Theoretical Physics;2010年03期

2 計新;呂天全;張壽;;Entanglement dynamics of two distant atoms in two detuning cavities[J];Chinese Physics B;2010年11期

3 潘長寧;李飛;方見樹;方卯發(fā);;Entanglement dynamics of two-qubit systems in different quantum noises[J];Chinese Physics B;2011年02期

本文編號：1880446