雙場量子密鑰分發協議之研究

Abstract

近期，一種全新的量子密鑰分發協議:雙場協議 (TFQKD protocol) 被提出，並宣稱其可以密鑰分發速率可以打破在沒有量子中繼器下量子通訊通道容量的上界。在此協議提出後不久，便引發了熱烈的關注。 在這篇論文中，我們首先檢視了現存的協議方案，並與雙場協議比較，探討各協議所使用的原理。此外，我們整理了近期相關的研究論文，在各種被提出的雙場協議中，大致可分為兩類:相位匹配型 (PM) 協議、送-不送型 (SNS) 協議。我們分別回顧協議裡的安全性證明，並模擬了在不同情況下兩種協議的密鑰分發速率，比較兩者的優劣。 為了探討在實作上的可行性，我們也討論了在有限筆資料數量下，協議中各數值受統計波動的影響。最後，結果顯示在現今的設備及科技下，雙場協議仍然可以超越無中繼器的通道容量上界。

Recently, a new protocol, the twin-field QKD (TFQKD) protocol, has been proposed and is claimed to overcome the fundamental limits of quantum repeater-less communications. Soon after its appearance, the related research has gained lot of focus. In this thesis, we first review the existing protocol and make a comparison between them and the TFQKD protocol. Furthermore, we classify recent papers related to the TFQKD protocols into two main types: the phase-matching-type (PM) protocol and the sending-or-not-sending-type (SNS) protocol. We review the arguments for the security and simulate the key rate versus distance for both types of protocols under different conditions. Then we compare their performances between the two types of protocols. To investigate the feasibility for practical implementation, we also discuss the finite-size effect for the post-processing block size. The results show both protocols are capable of overcoming the repeater-less bound with current devices and technology.