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Quantum decoherence is the loss of quantum coherence. In quantum mechanics, particles such as electrons are described by a wave function, a mathematical representation of the quantum state of a system; a probabilistic interpretation of the wave function is used to explain various quantum effects. As long as there exists a definite phase relation between different states, the system is said to be coherent.
量子態的數學表示 --> 波涵數 --> 概率 --> 量子效應 --> 態間「相關係」固定 --> 系統相干（coherent）。這一定就是所謂墾丁優美海景沒人在看的狀態。所有一切上下夸克、電子、光子、膠子、希格子一體 cohere 在那裡好端端沒事。
Coherence is preserved under the laws of quantum physics, and this is necessary for the functioning of quantum computers. If a quantum system is perfectly isolated, it would be impossible to manipulate or investigate it.
無觀測／量度的孤立量子系統的量子「相干」（coherent）狀態會被完整保存。
If it is not perfectly isolated, for example during a measurement, coherence is shared with the environment and appears to be lost with time, a process called quantum decoherence.
一旦觀測行爲發生，相干性將會被分布到環境（我們人在看就是環境的一種）裡以致隨時間消失，這叫做「量子不相干」—— 可以想成系統量子態的「純度」被破壞。
As a result of this process, quantum behavior is apparently lost, just as energy appears to be lost by friction in classical mechanics.
結果是量子行爲的喪失。（然後宏觀效應就來了嗎？）
Decoherence has been developed into a complete framework, but it does not solve the measurement problem.
「量子不相干」（quantum decoherence）沒解決量子系統的觀測問題。（什麼問題？是不是波涵數崩塌的問題？）
Decoherence can be viewed as the loss of information from a system into the environment.
「量子不相干」可以被看成是量子系統資訊消失到環境裡的現象。（所以系統行爲就不再量子了，是不是這樣？「不量子」就宏觀：浪花、礁石、海景，眼前一切的一切「凝」出樣貌）
Thus the dynamics of the system alone are irreversible. As with any coupling, entanglements are generated between the system and environment. These have the effect of sharing quantum information with—or transferring it to—the surroundings.
此系統動態發展無可逆轉。系統和環境（包括你我等觀測者）產生量子糾纏（entanglement）。量子系統資訊被分享、傳播、散布到環境裡。
Decoherence has been used to understand the collapse of the wave function in quantum mechanics. Decoherence does not generate actual wave-function collapse. It only provides an explanation for the observation of wave-function collapse, as the quantum nature of the system "leaks" into the environment.
量子不相干被用來解釋量子波涵數崩塌現象，但本身並不產生量子崩塌，只是用來解釋波涵數崩塌所觀測到的現象 —— 量子系統狀態被「漏」到環境裡。
That is, components of the wave function are decoupled from a coherent system and acquire phases from their immediate surroundings.
波涵數的部份被從相干、完整的量子系統中解構，開始從環境中獲取相、態。（融爲一體）
Specifically, decoherence does not attempt to explain the measurement problem. Rather, decoherence provides an explanation for the transition of the system to a mixture of states that seem to correspond to those states observers perceive.
這段有點重複，意思是 decouple/decohere 後的量子混合狀態就是觀測者看見的宏觀樣貌 —— 浪花、礁石、海景 etc.
Moreover, our observation tells us that this mixture looks like a proper quantum ensemble in a measurement situation, as we observe that measurements lead to the "realization" of precisely one state in the "ensemble".
沒錯，量子系統與環境混合後我們所見的就是整個量子總態「凝」出來的現實世界，不再量子，只有一種宏觀狀態 —— 墾丁美不勝收的海景。
維基的解釋往下開始複雜艱深，需要先弄懂許多專有名詞，就此打住，以後慢慢再說。但許多量力名詞像「波涵數」、「態」、「相」、「概率」、「相干／不相干」、「並／解構」、「總／分貌」、「量子糾纏」、「量子崩塌」等已經十分清楚。
這樣欣賞墾丁海景有點奇怪，但你得了解，量子世界是沒有浪花、礁石、美景、你我這些「東西」的，只有上下夸克加電子，光子膠子希格子 etc.，奇怪的是我們自己和宏觀世界這些「大東西」。量子崩塌／多重世界不論，coherence/decoherence, entanglement, coupling/decoupling 都是真的。這樣想就不但不奇怪好像還頗順理成章說。
至此堪稱滿意。活到老學到老，沒人教我自己教自己；可以安心去睡覺了。
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