Monthly Archives: November 2011

Wheeler’s delayed choice experiment

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Quantum decoherence 5.3
 
 
In the delayed choice experiment, the wave function of the system (the photons and the environment) is also in a superposition of eigenstates, not just the wave functions of the individual photons are.

All the past is there, but our present measurement “chooses” which part to see. 

— Me@2011.10.21
 
 
The chosen part must be a consistent story, according the quantum mechanics.

The chosen part is what we called “an observer”.

— Me@2018-01-22 09:35:02 PM
 
 
 
2011.11.20 Sunday (c) All rights reserved by ACHK

Delayed choice quantum eraser

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Quantum decoherence 5.2 | Event Realism 5 | 事件實在論 5

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For a delayed choice quantum eraser, both interference patterns are there.

But since they overlap each other, you cannot see them individually.

— Me@2011.10.21

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One of the easiest ways of “making sense” of the delayed-choice paradox is to examine it using Bohmian mechanics. The surprising implications of the original delayed-choice experiment led Wheeler to the conclusion that “no phenomenon is a phenomenon until it is an observed phenomenon”, which is a very radical position. Wheeler famously said that the “past has no existence except as recorded in the present“, and that the Universe does not “exist, out there independent of all acts of observation”.

— Wikipedia on Wheeler’s delayed choice experiment

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What we do in the present does not change the past, but change we can see/say about the past.

— Wheeler on Delayed choice quantum eraser

— paraphrased

— Me@2018-02-04 03:40:27 PM

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2011.11.19 Saturday (c) All rights reserved by ACHK

EPR paradox

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Einstein–Podolsky–Rosen paradox | Quantum decoherence 5

How does quantum decoherence achieve EPR?

1. Everything is entangled, not just for those pairs of photons.

2. The measuring device is part of the system, the universe.

— Me@2011.10.21

2011.11.19 Saturday (c) All rights reserved by ACHK

Khan Academy 2

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“The school of the future will not resemble the school of today,” Khan says. “In the past, the assembly-line, lecture-homework-exam model existed because that’s what was possible in the no-tech and low-tech classrooms of their day.”

— Salman Khan (educator)

2011.11.19 Saturday ACHK

全像記憶 2

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這段改編自 2010 年 5 月 18 日的對話。

Photographic memory（過目不忘）非常重要。

當年（2007），我重返大學讀物理碩士。第一科是一科數學科目。那科非常深。曾經有一份功課的題目，深到即使我對著筆記，也近乎完全看不明白。於是，我唯有暫停該份功課。那天是星期六。我花了當天的一整天，先把那份筆記的數十頁內容，都全部背誦下來。星期日，我才再開始嘗試做那一份功課。

我發現，背了整份筆記後，我開始明白那些功課問題的意思，從而可以嘗試解答它們。最後，那份功課我大概奪得一半的分數。如果我不是靈機一觸，想到用「把整份筆記也背下來」這個方法的話，我就一分也拿不到。

為什麼對著筆記逐頁閱讀就看不明題目，而背了整份筆記就可以呢？

有些題目之所以深，是它要求你同時察覺和運用到（例如）七個要點。但是，如果你只憑逐頁閱讀筆記，你在同一刻只能閱讀到一頁。而一頁之中又可能只有（例如）三個要點。更壞的情況是，功課題目所要求的那七個要點，原來散佈在筆記中的（例如）第一、第十、第十七 和 第二十三頁中。那樣，那七個要點就近乎沒有機會，在你的思考中同時出現。

把整份筆記（之中的要點）都背誦下來，方能化解這個問題。所以，photographic memory 非常重要。

— Me@2011.11.17

2011.11.17 Friday (c) All rights reserved by ACHK

Wave function 2

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Wavefunction collapse can be viewed as an epiphenomenon of quantum decoherence, which in turn is nothing more than an effect of the underlying local time evolution of the wavefunction of a system and all of its environment.

— Wikipedia on EPR paradox

Quantum decoherence: only the wave function that describes the whole universe is real.

A wave function that describes part of the universe is only partially real.

— Me@2011.10.21

2011.11.18 Friday (c) All rights reserved by ACHK

Google 10

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That’s why it made utter sense to me that Google would try to dig itself out of its patent hole with a plan that wound up to encompass much more than the problem itself. After being rebuffed in its efforts to nab an expensive patent portfolio to defend Android against “bogus” (in David Drummond’s phrase) claims, it decided not only to get a better portfolio but an entire company and new business model as well.

— Why the Motorola Mobility Deal is like the Google Book Search Settlement

— Steven Levy

2011.11.16 Wednesday ACHK

電燈膽 2.2

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這段改編自 2010 年 3 月 6 日的對話。

一個人時有一個利益團體；兩個人時有三個利益團體：甲、乙、甲乙；三個人時有七個利益團體；四個人時有十五個利益團體；如此類推。

利益團體數目的增長，遠比人數的增長快。所以，要把一個多人團體管理得好，你需要一個奇蹟。

— Me@2011.11.16

2011.11.16 Wednesday (c) All rights reserved by ACHK

Quantum chaos 2

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Quantum chaos theory studies how the correspondence between quantum mechanics and classical mechanics works in the context of chaotic systems.

— Wikipedia on Chaos theory

2011.11.16 Wednesday ACHK

The delusion

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The most powerful illusion, 2

February 12, 1950

Dear Mr. Marcus:

A human being is a part of the whole, called by us “Universe”, a part limited in time and space. He experiences himself, his thoughts and feelings as something separated from the rest — a kind of optical delusion of his consciousness. The striving to free oneself from this delusion is the one issue of true religion. Not to nourish the delusion but to try to overcome it is the way to reach the attainable measure of peace of mind.

With my best wishes,
sincerely yours,

Albert Einstein.

Mr. Robert S.Marcus
World Jewish Congress
1834 Broadway
New York 23,N.Y.

— Letters of Note

— Edited by Shaun Usher

2011.11.15 Tuesday ACHK

找例外 6.4

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這段改編自 2010 年 5 月 18 日的對話。

假設，你心目中的工作，並不是那些需要極端長時間 —— 超過五年 —— 訓練的專業工作，「找例外」這個技巧很可能會為你節省數年的時間。有時，它甚至可以為你奪得一份原本沒有機會得到的工作。

例如，你想做一位精算師。正路是大學選科時，選香港大學的精算系。但是，精算系的收生要求奇高。在我的年代，高考要考到 5A ，即全部甲等成績，才有機會入到。當年是那樣。現在的收生成績我不知道。但我相信，即使不是 5A，也仍會是十分高。

（HYC：中七的高考 5 個 A？）

無錯。

（HYC：那豈不是連中英文科也要 A？）

當然。

所以，如果你在高考時不能保證自己成績超卓，而又企圖選讀精算系的話，你在第零步就已經被拒諸門外。

如果你的成績不夠，而又堅決要做精算師的話，正確的思考方法是，先嘗試「找例外」：我要做精算師，所以理論上，我要在大學主修精算學，但是實際上，有沒有人曾經在沒有精算學學士學位的情況下，竟然做到一位精算師呢？

原來有。

大概而言，精算學是應用數學的一門。你可以在大學本科時主修數學。那有兩個好處。一來，數學系的收生要求雖然也不低，但不會像精算學系那麼高。二來，你可以保證你的數學能力堅厚，足以應付你在未來精算師工作的數學難題。大學之後，你才補讀一些精算學的文憑課程，然後，再逐一完成考精算師牌其他在學業和工作上的要求。

真正的重點是，你要保證你的學業和事業行程，可以接駁上投考精算師專業資格的道路。

— Me@2011.11.14

— A Careers Seminar on The Actuarial Profession

— Wai-Sum Chan, PhD, FSA, CERA

— Actuarial Society of Hong Kong

— 18 February, 2011

2011.11.14 Monday (c) All rights reserved by ACHK

iPod creator’s thermostat

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The Nest Thermostat also aces a task that traditional thermostats surprisingly don’t do very well at: measuring the temperature.

Many current thermostats can be routinely off by four or five degrees.

— Brave New Thermostat: How the iPod’s Creator Is Making Home Heating Sexy

— Steven Levy

2011.11.14 Monday ACHK

電燈膽 2.1

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這段改編自 2010 年 3 月 6 日的對話。

人單獨不好。其實，另一個極端都是不好。完整的全句應該是：

人單獨不好；人群體不好。

最理想的策略是，取其中道：在情義圈內有幾位知己。

（安：那我這個問題可能相關。我觀察到一個有趣的現象。Apple（蘋果電腦）由兩個人創辦而成。Microsoft（微軟公司）和 Google（谷歌公司）都是那樣，各自有兩個創辦人。為什麼極大成功的公司往往由兩個人創辦而成呢？

一個人很難成功。這個比較易理解。創辦一間公司的工作量非比尋常，並不是一個人所能承受。但是，為何偏偏要兩個人，而不可以三個人呢？）

麻煩很多。多人自然麻煩。

一人太辛苦，多人又麻煩。最小的不單獨人數是二。兩個人合作，很多時是最理想的設定。

三個人的政治結構，比兩個人的政治結構複雜很多倍。或者說，兩個人時，根本沒有所謂「政治結構」。三個人時，才開始有政治結構。

只有在「只有兩個人」時，才可以有「『對』話」。三個討論的話，就不再是真誠「『對』話」，因為甲乙對話時要考慮丙的感受；甲丙對話時又要考慮乙的感受；乙丙對話時再要考慮甲的感受。

兩個人如果選擇對方做夥伴，一定會是出於自願，因為那不會有來自第三方或者群眾的壓力。

— Me@2011.11.13

Friendship

* Two may talk and one may hear, but three cannot take part in a conversation of the most sincere and searching sort.

— Ralph Waldo Emerson

2011.11.13 Sunday (c) All rights reserved by ACHK

Dungeons & Dragons

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Dungeons & Dragons (abbreviated as D&D or DnD) is a role-playing game (RPG) in a fantasy setting originally designed by Gary Gygax and Dave Arneson, and first published in 1974 by Tactical Studies Rules, Inc. (TSR).

D&D’s publication is widely regarded as the beginning of modern role-playing games and the role-playing game industry.

— Wikipedia on Dungeons & Dragons

2011.11.11 Friday ACHK