本文關(guān)鍵詞：基于冷原子系統(tǒng)的量子糾纏態(tài)產(chǎn)生與存儲(chǔ)　出處：《山西大學(xué)》2016年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 量子中繼 窄帶可預(yù)言偏振糾纏光子對(duì) 量子存儲(chǔ) 動(dòng)力學(xué)退耦合

【摘要】：量子中繼器是量子信息中重要的組成環(huán)節(jié)。在量子網(wǎng)絡(luò)中,脆弱的量子信息從發(fā)射方傳遞到接收方,不可避免的要經(jīng)歷退相干過(guò)程,其中包括光纖損耗和環(huán)境干擾。由此量子信息傳遞的直接距離被限制在約200km之內(nèi),而量子中繼器就是用來(lái)擴(kuò)展量子信息傳遞距離的重要儀器。一般量子中繼包含量子糾纏交換,量子存儲(chǔ)和量子糾纏純化三個(gè)部分。其中量子糾纏的交換用來(lái)聯(lián)結(jié)糾纏子區(qū)間,以避免長(zhǎng)距離傳輸?shù)墓庾訑?shù)損耗,量子存儲(chǔ)用來(lái)解決概率性事件帶來(lái)的資源指數(shù)消耗,量子糾纏純化用來(lái)解決退相干過(guò)程帶來(lái)糾纏品質(zhì)的下降。本論文的主要內(nèi)容是基于冷原子系綜的量子中繼器的研究,其中包括以下幾個(gè)方面的研究?jī)?nèi)容：(1)窄帶糾纏光源的產(chǎn)生：利用自發(fā)拉曼散射的辦法,在冷原子系綜中同時(shí)產(chǎn)生兩對(duì)光和原子的糾纏態(tài),通過(guò)對(duì)其中的這兩個(gè)光子進(jìn)行Bell測(cè)量,我們將存儲(chǔ)中的兩個(gè)自旋波投影到一個(gè)Bell態(tài)上,形成一對(duì)偏振糾纏光子對(duì)的存儲(chǔ)。在一段存儲(chǔ)時(shí)間之后,可預(yù)言的讀出一對(duì)偏振糾纏光子對(duì),利用雙光子量子態(tài)Tomography和Bell測(cè)量等方法驗(yàn)證了產(chǎn)生的糾纏光的品質(zhì)。利用類似的實(shí)驗(yàn)方法,還可以實(shí)現(xiàn)三光子GHZ態(tài)的建立。這樣,我們?cè)趯?shí)驗(yàn)上實(shí)現(xiàn)了窄帶的糾纏光的制備。(2)任意偏振單光子存儲(chǔ)：在冷原子系綜上施加一個(gè)中等強(qiáng)度的軸向磁場(chǎng),將原子的Zeeman簡(jiǎn)并態(tài)分離,經(jīng)過(guò)光泵浦過(guò)程,建立兩互相正交的磁不敏感態(tài)。利用電磁感應(yīng)透明過(guò)程,將任意偏振的單光子量級(jí)信號(hào)光,存儲(chǔ)為冷原子系綜中的自旋波疊加態(tài)。利用自制的濾波系統(tǒng)(模清潔器等),對(duì)控制光進(jìn)行高效的噪聲抑制,對(duì)信號(hào)光進(jìn)行高信噪比的濾波。實(shí)現(xiàn)了長(zhǎng)存儲(chǔ)壽命高保真度的量子存儲(chǔ)。在4.5ms的存儲(chǔ)時(shí)間,量子偏振態(tài)保真度為78.4%。(3)動(dòng)力學(xué)退耦合延長(zhǎng)量子信息在冷原子系綜中的壽命：利用Raman雙光子躍遷過(guò)程,對(duì)存儲(chǔ)在冷原子系綜中的自旋波疊加態(tài)施加CPMG序列的退耦合操控。量子過(guò)程保真度在8001μs的存儲(chǔ)時(shí)間依然大于80%,相比于沒(méi)有施加退耦合操控的存儲(chǔ)壽命提高了3.4倍。
[Abstract]:Quantum repeater is an important part of quantum information. In quantum network, the fragile quantum information is transferred from the emitter to the receiver, and it is inevitable to undergo the process of decoherence. This includes optical fiber loss and environmental interference. The direct distance of quantum information transmission is limited to about 200 km. Quantum repeater is an important instrument to extend the transmission distance of quantum information. Generally quantum relay contains quantum entanglement exchange. Quantum storage and quantum entanglement purification, in which the exchange of quantum entanglement is used to link the entangled sub-region to avoid the loss of photon number in long distance transmission. Quantum storage is used to solve the resource exponent consumption caused by probabilistic events. Quantum entanglement purification is used to solve the degradation of entanglement quality caused by decoherence. The main content of this thesis is based on the research of quantum repeater with cold atom ensemble. It includes the following aspects: the generation of narrowband entangled light sources: using the method of spontaneous Raman scattering, the entangled states of two pairs of light and atoms are produced simultaneously in cold atomic ensemble. By Bell measurements of these two photons, we project the two spin waves onto a Bell state to form a pair of polarization-entangled photons, after a period of storage time. A pair of polarization-entangled photon pairs can be read out predictably. The quality of the generated entangled light is verified by two-photon quantum state Tomography and Bell measurements. Similar experimental methods are used. It is also possible to establish a three-photon GHZ state. We have experimentally realized the fabrication of narrow band entangled light. 2) arbitrary polarization single photon storage: applying a medium intensity axial magnetic field to the cold atomic system to separate the Zeeman states of atoms. Two mutually orthogonal magnetically insensitive states are established through the optical pumping process, and the arbitrary polarization of single-photon signal light is obtained by using the electromagnetic induction transparency process. It is stored as the superposition state of spin wave in the cold atomic ensemble. The noise suppression of the control light is carried out efficiently by using the self-made filter system (mode cleaner, etc.). The signal light is filtered with high signal-to-noise ratio (SNR). Quantum storage with long storage life and high fidelity is realized. The storage time is 4.5 Ms. The fidelity of quantum polarization state is 78.4%.) Kinetic decoupling prolongs the lifetime of quantum information in cold atomic ensemble: using Raman two-photon transition process. The decoupling operation of the CPMG sequence is applied to the spin wave superposition state stored in the cold atomic ensemble. The storage time of the quantum process fidelity at 8001 渭 s is still greater than 80%. The storage life is 3.4 times longer than that without decoupling control.
【學(xué)位授予單位】：山西大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：O413

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2 ;Quantum storage of optical signals and coherent manipulation of quantum states based on electromagnetically induced transparency[J];Chinese Science Bulletin;2012年16期

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本文編號(hào)：1381555