固定原子與傳輸原子量子位元的雙量子位元糾纏閘

Abstract

中性原子是易於發展可擴展的量子訊息處理平台的物理系統之一。本論文主要提出一個新穎的方案:用於量子訊息處理系統的原子被由一維光學晶格(optical lattice)和拉蓋爾-高斯光束(Laguerre-Gaussian beam)組成的光阱(opticaltrap)傳輸。此研究成果展示了在中性原子平台的量子訊息處理系統實現連結性(connectivity)的潛能。我們首先研究此新穎光阱的性質，並展示雙量子位元糾纏閘（two-qubit entangling gate）作用於一顆靜止的原子和另一顆被此傳輸的原子(被稱為Drive-Through方法)。在雙量子位元糾纏閘中，其中一顆移動的原子被藍頻失諧(blue-detuned)一維光學晶格和拉蓋爾-高斯光束捕捉和傳輸，另一顆靜止的原子僅被光鑷捕捉。此Drive-Through方法被應用於兩個雙量子位元糾纏方案：雷德堡阻礙（Rydberg blockade）方案和全耦合（global coupling）方案。當原子溫度達到10 微開爾文(microkelvin)時，兩種方案的保真度階分別可以達到0 .99和 0 .999。主要的誤差來源如原子溫度，都卜勒效應(Doppler effect)和雷射強度誤差也在此論文中被分析。本論文亦研究策畫移動原子的行徑以避免加熱原子。伴隨著適當的傳輸軌跡，此過程僅激發少於0.001個聲子(phonon)。

In this work, we theoretically investigate a novel scheme of quantum information processing via atom transportation. The scheme is based on a one-dimensional blue-detuned optical lattice and a blue-detuned Laguerre-Gaussian beam. We first studied the property of the relevant optical trap architecture. The implementation of two-qubit entangling gates on one stationary atom and one flying atom transported by a moving optical lattice, called as Drive-Through (DT) method, is also demonstrated. The DT method is implemented with two two-qubit entangling gate schemes, the Rydberg blockade scheme and the global coupling scheme, with gate fidelity 0. 99 and 0. 999, respectively, when the atomic temperature is about 10 microkelvin. Error sources like finite temperature, the Doppler effect, and laser intensity deviation are analyzed. Movement manipulation of the flying atom to avoid heating while accelerating is also studied. After atomic movement are optimized, <0.001 phonons are excited.