Chin Blog

其實在下的背景是資訊科技出身，只是也涉獵一點物理學的領域。那麼聊量子網路之前，我們對量子、網路應該要先有基本的認識。

何謂網路？末學認為任意2個節點之間不論以有線或無線的方法，並以相同格式相互傳輸訊號，就是網路。有一門特定學問稱「計算機網路」就是討論這些東西。

你將手機裡的檔案透過USB傳輸線連接到電腦，算不算網路？當然算，然而很少人這樣講。電腦和手機是2個節點，檔案從手機傳到電腦的過程中就是資料(訊號)的傳輸。

何謂量子？我們應該先認識「基本粒子」，因為科學不斷進步，所以每個時代對基本粒子的定義不同。基本粒子是構成物質的基本單位，無法再分解。

以前認為原子是基本粒子，後來發現原子還能被切割而得知質子、中子與電子等等。難道現代科學能夠確定量子不會再被切割嗎？我認為量子是一種相對性的概念，而不是像原子是絕對性的概念。

那麼量子網路在近代非常熱門，我認為是訊號傳遞在網路安全的本質上與過去的電腦網路標準與技術有極大差異。

常見的電腦網路在資料的傳輸與安全保護資料往往是兩回事、分開做。尤其是乙太網路，因為乙太網路是一種多重存取網路(廣播網路)，在乙太網路上的節點經常以廣播形式送出資料，所以其他節點要監聽你送出的資料並非難事。通常會基於安全目的對資料做加密，而加密方法隨著時間不斷加強，駭客也越來越難將從中偷聽來的資料做解密，實際上很難但理論上還是可行。

量子網路就不是了！基於量子力學原理，量子節點之間利用「量子密鑰發佈(QKD)」以形成安全通訊的網路，若有第三方以任何方法嘗試監聽，將導致量子位元產生變化，使訊號傳遞的內容被改變，使其不可能被克隆(clone複製)。

量子狀態之特性有兩種：測量態、糾纏態。我認為後者是前者的延伸，測量態是說A粒子與B粒子的狀態是同步的；糾纏態是說粒子利用量子糾纏效應(相互依賴)，當A粒子產生變化，B粒子也同步產生相應的變化。這便是量子通訊安全的本質。

然而有一種現象稱「量子的不確定性」，量測未知的量子態必定改變量子態，意即我只是量測它而不改變它，但它還是被改變。這使我們需要去觀察其某種規律(如公式)。

還有一種現象稱「量子衰減效應(quantum decoherence)」，這是量子計算機必須面臨的挑戰。在量子系統，粒子會因為量子糾纏效應隨著時間逐漸流失，也可以說量子糾纏跟量子衰減存在因果關係。

量子技術或特性本身不代表好壞，就像電腦工程師做壞事變駭客、駭客做好事變電腦工程師。量子技術道理亦同，量子計算可做攻、量子通信可做守。

目前量子電腦處於研究階段，不過已經有一些量子廣域網路進入應用階段。2017年9月中國建立量子通信骨幹，連接了北京、上海、濟南、合肥，稱「京滬幹線」，並應用於商務、金融等領域。

美國也投資大量資金在量子研究，如「量子資訊科學國家戰略概述」，這份概述對量子技術分為4個研究領域：量子感測與運算、量子模擬、量子網路、量子硬體。美國不只在小學投入程式教育，還計畫投入量子教育。筆者真覺得美國小學生好累阿！哈哈！

Actually, my background is information technology. Additionally, I had also discovery field of physics. First, we should know the quantum and network before start quantum network.

What is network? I think any wired or wireless method between any two nodes, and they transport signal by same format, that is network. The "computer network" is a knowledge, it is discuss these things.

You transport file to computer by USB cable, is it network? of course. But, few people say it. Computer and phone are two nodes, file was transported to computer from phone that is transport of data(signal).

What is quantum? First we should know "elementary particle". The science keep on progress, so different definitions of elementary particles in each era.
Elementary particle is the basic unit of matter, it can not decompose.

Previously, thought the atom is elementary. Later, the atom can be decompose and get protons, neutrons, electron and so on. Can science able to sure quantum not be decompose? I think the quantum is a concept of relativity, not absolute like atom.

Then quantum network is very popular now. I think reason for nature of network security that signal transmission is very different from past computer network standards and technologies.

In common computer network, transport data and protect data are two different things. The ethernet especially. Because ethernet is a multiaccess network(broadcast network).
The node often use broadcast method to transmit data in ethernet. It cause other nodes want to monitor your data that not difficult.
Usually, security-based so we encrypted data. Encryption methods keep on grow over time. It is also increasingly difficult for hacker to decrypt data they have eavesdropped. Actually difficult but theoretically feasible.
Quantum network is not it! Quantum-mechanics based principle, each quantum nodes utilize "Quantum Key Distribution(QKD)" to form secure communication network.
If third node attempt to monitor them over any method that cause quantum bit be changed. So the content passed by the signal is changed. Make it impossible to be cloned.

There are two characteristics of quantum states: quantum measure and quantum entanglement.
I think the latter is an extension of the former.
Quantum measure that particle A and particle B, their state is synchronize.
Quantum entanglement that particles utilize entanglement effect(interdependence). When particle A be changed, particle B also synchronize form corresponding state.
It is essence of quantum communication security

However, there is a phenomenon that "quantum uncertainty". To measure unknown quantum state cause it be changed.
I have only measure and not change it, but it still be changed. It make we need to obsere some regular(formula).
And other phenomenon that "quantum decoherence". It is a must face challenge for quantum computer.
In Quantum system, the particles will gradual loss over time because quantum decoherence. Also there is a causal relationship between quantum entanglement and quantum decoherence.

Quantum technology or it characteristic are not represent good or bad. It like computer engineer do bad some things that form hacker, hacker do good some things that form computer engineer.
Quantum technology too, quantum computing can be attack, quantum communication can be defense.

Currently, quantum computer is researching phase. But some quantum WAN have entered application phase.
China builds backbone of quantum communication in Sep 2019, and that connect Beijing, Shanghai, Jinan and Hefei. It be call "Beijing and Shanghai trunk line".
It used in business, finance and other fields.

The US has also invested heavily in quantum research, such as "Subcommittee on Quantum Information Science(SCQIS)".
The document divide quantum technology into 4 research fields: quantum sense and computing, quantum simulation, quantum network, quantum hardware.
The US is not only invest programming education in elementary school, but also to planning invest quantum education.
I feel that elementary students of US are so tired! haha!