Bell’s theorem, 7

dools on Nov 21, 2014

When I watched the Leonard Susskind lectures on quantum entanglements he said the whole “communicating faster than light” thing is a bit misleading. The analogy he gives if imagine you have two coins and you ask someone to turn them over so one is heads and the other tails then you give them to 2 people without them knowing which is which, then they go to opposite ends of the universe, and they look at their coins, they instantly know the state of the other coin purely by deduction.

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hasenj on Nov 21, 2014 [-]

That’s what Einstein argued for, and it’s what Bell’s inequality proves to not be the case.

I actually remember seeing a Youtube video of Susskind talking about how “FTL” communication is a hack to try to force the quantum state to conform with our notions about the world. (he didn’t phrase it this way though; just my interpretation).

I don’t know the context it was said, but it seemed to imply that there’s a way of thinking about quantum states completely independent of set theory and our classical notions, and this way of thinking should not require FTL communication between entangled particles.

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evanb on Nov 21, 2014 [-]

While GP’s example is not what happens in QM (Bell’s inequality shows that the state of the two coins is not predetermined-but-secret), it is akin to that example, in the sense that because each person gets a random (though correlated) bit, they cannot transmit information to one another.

Bell’s inequality is a statement about the possible strength of the correlation, rather than about information transmission.

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pfortuny on Nov 21, 2014 [-]

Exactly. It is important to note that there is no information exchange if you do not have any information at all.

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— You can’t get entangled without a wormhole (2013)

— Hacker News

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2020.03.07 Saturday ACHK

反貼士搵笨大行動 1.2

幾個月後,考了物理科後的一晚,我和馬同學於電話傾談。他說他在見到試題時,十分生氣,因為不如傳說中的所謂「5 題貼中 4 題」。(根本就一題也沒有貼中,除非「貼中」的定義,就只是「同一課題」而已;例如,貼「力學」題目,又真是出了「力學」題目。)

我則不會有那樣的期望。我回答他說:「如果他真的可以貼中題目,他在平時又何須那麼用心去授課?他又何須在聖誕假和農曆年假中,再要不斷的補課呢?」

他:「真希望思考可以像你那麼成熟。那不是反話。那是我真正覺得。」

幾個月後,我有幸升到預科中六,打算再參加 Ken Chan 的補習班。他在我中五時,沒有同時開中六的課程。我估計,那是因為高考班的市場,只有會考班的五分之二。但是,在我中五後,傳說他會開中六班。所以,我打算去問一問,本來。

不幸,該補習社的負責人,在那時(1997 年的暑假)因涉嫌無牌經營補習社,被警方的重案組拘捕了。結果,我不了了之,中六時沒有再補物理。

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在我參加 Ken Chan 補習班的年代,在他的筆記中,每題 MC 題目方格的底部,都會有一句署名,大概是

This question set is prepared by Ken Chan. Please contact Ken Chan if you want to use it in your class.

我也不記得確實在哪時,但大概是在 1996 年底,他說:「最近的筆記,可能署名不是我,而是 MC Chan。我的手提電腦中了毒,所以需要問他借筆記。」

幾個月後,1997 年初,補習課程的尾聲時,Ken Chan 說:「今年我無開 intensive course(臨近正式公開試時的精修密集班),如果需要的話,你可以找市面上另一位導師。」

那另一位導師,因為在另一間補習社任教,Ken Chan 所以不好意思,直接開名介紹,唯有暗示:

「我係 Long Ques 陳,你估吓另一位係邊個。」

「Long Ques」即是長題目。相反就是「MC」,即 multiple choices(多項選擇題)。他所暗示的,其實就是 MC Chan。

Ken Chan 竟然會介紹其他導師,其實我有一點意外。他願意介紹的,必定和他的水平相當。但是,Ken Chan 對我來說是,半人半神。難以想像有另一個物理的半人半神。

在大約十年後,2007 年時,我是一位日校的數學教師。數學問題外,有空時,我也時常答學生物理問題。有一次,我向給有幾位學生解釋物理時,有一位學生突然講:「好似 Ken Chan 呀!」

她的意思是,我解釋物理時的說話風格,與 Ken Chan 的,十分相似。由於法例所限,日校教師不可介紹補習導師,所以,我沒有回應。我只能在心裡說:「梗係以啦,好細個嗰陣,係佢學生吖嘛。」(當然相似啦,因為我小時候是他學生。)

另一次那位學生問我物理。那份筆記我揭到封面看一看,原來是 Ken Chan 班的筆記。我感格外親切。

「咦,你識佢呀?」(你認識他嗎?)我的學生問。

又由於法例所限,我再沒有回應。但她再講多一句:「佢仲有個呀哥 MC Chan。」(他還有一個哥哥 MC Chan。)

雖然我不知其真假,但我覺得十分有可能,因為,那解釋了為何 Ken Chan 會信任他。

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中六時,我日校的同學中,有些在中五時和我一樣,都是補 Ken Chan 的物理班。升上中六後,他們大部分也補 MC Chan 的物理班。我在中六時則沒有補習。

— Me@2020-03-04 11:18:52 PM

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2020.03.07 Saturday (c) All rights reserved by ACHK