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《理解量子力学》#2 波函数 – 译学馆
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《理解量子力学》#2 波函数

The Wave Function | Quantum Mechanics 2

上次我们学了量子力学
Last time we met quantum mechanics,
认识了它的两个规则
and got aquatinted to the two rules of the theory.
如果你还没看过那个介绍视频
If you haven ’ t seen that introduction video yet,
得先去看看它
do go watch that first.
接下来的视频中
In the next few videos I ’ ll
我将教你们如何正确运用那些规则
teach you how to use those rules properly and then we can
并很好地将其应用于量子力学
start applying it in awesome ways.
上个视频我们讨论了双缝实验
Last video we talked about the double slit experiment,
我得再提一次
and I ’ ll just remind you of
那个实验的含义
the moral of that story.
我们学过 不管什么原因
We learnt that, for whatever reason,
物体在被观察以及不被观察时
objects seem to act differently when they ’ re not
似乎表现的并不一样
being watching them compared to when theyare.
也就是说一个粒子会处于它可能有的几种状态
Say a particle has several possible statesit could be in.
通常我们认为
Normally we ’ d think,
不管是否被观测 它一定表现得正常
regardless of whether its being watched, it must act normal- doing
——处于那些可能性中的一种
just one of those things,
但这个实验告诉我们并非如此
but this experiment showed us that that can ’ t be true.
然而我们不知道的是……
What we don ’ t know though is…
我们看不到的时候它们到底在做什么
what exactly are they doing behind our backs?
量子力学主要从侧面来解释这个问题
Quantum mechanics deals with this by basicallyside stepping the issue.
它完全放弃
It totally gives up
讨论整个物体实际上在做什么
on talking about what the object is actually doing all together.
相反它只讨论与粒子相关的所谓波函数
Instead it only talks about something called the wavefunction associated with that particle.
什么是波函数?呃
What is this wavefunction? Umm,
好吧
well.
首先来说它是做什么的
Let me tell you what it does first.
为了说明这个问题
To do that,
我们需要叠加原理——这次我会讲得更明确点
we need the superposition principle- which I ’ ll explain more precisely this time.
回到这个场景 这个规则告诉我们波函数长什么样
Going back to this situation, this rule tells us how the wavefunction looks.
它指出波函数存在于每一个可能状态
It says the wavefunction is in each of thepossible states.
我们这样写
We write that like this,
波函数等于粒子在状态1的情况加上
the wavefunction equals the particle ’ s state in option 1
在状态2的情况 等等
plus in option 2 etc:
这个a b和c只是一些数字 下个视频我会讲
That a, b, and c are just some numbers- and they ’ re the subject
但现在忽略他们
of the next video but we’ll ignore themfor now.
重点是:这个波函数 以某种方式
The important part is:This wavefunction, that is somehow associated
和粒子联系起来
with the particle,
包含了粒子可能存在的每一种状态
contains each of the possible things states the particle could be in.
比如 我们看双缝实验
For example, if we looked at the double slit experiment,
我们不知道粒子要通过
we don ’ t know which door the
哪个门
particle took.
也就意味着这个粒子的波函数
That means the wavefunction
是通过门1和门2的
for that particle is a superposition of going through door 1
叠加
and door 2.
因此 从下一个视频起 我们开始看到
As we ’ ll start to see from the next video onwards,
这个波函数理论相当有用
this wavefunction idea is incredibly
——我们可以用它预测
useful- we can use it to predict the outcome
任何目前做过的实验的结果
of any experiment done so far, and it ’ s
它也是我们所获得的量子现象的原因
the reason we get all the quantum phenomena
有的你可能听过 比如量子缠结
that you may have heard of, like entanglement,
海森堡不确定原理 等等
the Heisenberg uncertainty principle etc.
这很有用……但是得说它有点不令人满意
It’s very useful… but hopefully it’sa little unsatisfying.
关于粒子的状态波函数告诉了我们什么呢?
What does this wavefunction tell us about what the particle is doing?
有很多可能的解释
There are plenty possible interpretations.
也许它意味着在我们没去看的时候
Maybe it means that while we aren ’ t looking,
粒子真的分成若干部分
the particle really does split up and do all
做所有它的波函数包括的事情
the possible things in its wavefunction.
也许粒子实际上只做
Or perhaps the particle really only does one
那些事情中的一件——但是不同于经典物理学
of those things- but unlike in classical physics,
它仍然会有波函数中的其他选项
it still cares about the other options init’s wavefunction.
再或者 只有我们观测时
Or maybe, the particle doesn ’ t really exist
粒子才真的存在
at all until it ’ s measured.
我们不知道
We don’t know.
因此 如果我们说 粒子同时进行着所有可能行为 这种话就很草率
That’s why it’s very sloppy to say thingslike: the particle is doing all possible things
——事实上我们没有证据粒子在做什么
at once- actually we don ’ t have a clue what the particle is doing,
在量子力学中
in quantum mechanics
我们只知道波函数
we only know about the wavefunction.
另一种草率的描述是说粒子是一种波
Another example of this sloppiness is when people say the particle is a wave.
他们这么说的真正意思是在某些情况下波函数看起来是波状的
What they really mean is that the wavefunction looks wavelike in some circumstances. Again,
再说一次 我们并不真的了解那个理论
we don ’ t really understand what that says
对粒子的解释 因为我们
about the particle, because we don ’ t
没有真的了解波函数与粒子是怎样联系的
really know how the wavefunction is relatedto the particle.
关于量子力学 神奇的是
The crazy thing about quantum mechanics is,
我们不用理解它就能
we don ’ t need to understand it to be able
使用它
to use it.
事实上 一些人认为
In fact, some people think it doesn
讨论量子力学的含义完全没有意义
’ t make sense to talk about the meaning of quantum
因为所讨论的一切都只是没有证据的推断
mechanics at all, because anything said would just be speculation with no evidence.
但实际上我们会看到 通过深入研究量子力学
But actually we ’ ll see that by very carefully studying quantum mechanics,
人们至少已经推导出
people have derived
其涵义的一些具体内容——
at least some concrete things about the meaning- even
尽管我们离理解量子力学还很远
though we ’ re still a long way from
——如果我们能理解的话
understanding quantum mechanics- if it’seven possible at all.
就这样吧 今天就到这里吧
And with that, I ’ ll leave it for today,
但是到家庭作业时间了
but it ’ s time for your homework!
第一项 只需要你去思考
For the first task, I’d like you to justspeculate.
比如 说一些对波函数的理解
For example, make up some interpretations
或者告诉我关于波函数 你认为
for the wavefunction or tell me what you think
哪些解释很恰当 哪些不恰当
are nice or not nice interpretations for thewavefunction.
恰当的那些于你而言意味着什么
What does nice mean to you?
第二
The second question is,
你认为我们需要担心对于科学理论的
do you think we should even worry about the interpretation of scientific
理解吗
theories?
理论只要能
Isn ’ t it
给出正确的预测不就够了吗——即使我们不理解
enough that the theory makes the right predictions- even if we don ’ t understand
为什么它能预测
why it works?
关于科学理论的含义这种问题可以被认为是科学问题吗?
Can questions about the meaning of a theory be considered scientific questions at all?
请为你的回答自由举例
Feel free to bring up examples etc to back up your answer.
即使你只有部分答案或者你想要提问
Even if you only have partial answers or you want to ask a question,
请自由发表
feel free to leave
你的意见——我很乐意看
it as a comment- I love reading them.
离开之前 我想说
Before I go, can I just say,
你们上次作业回答得非常认真
I was blown away by how seriously you guys answered the questions
让我印象深刻
last time.
我读它们很开心
I had so much fun reading them,
我很骄傲你们为之花费了时间和精力
and I was so proud you put in the time and thought to
谢谢你们
do that- thank you.

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视频概述

量子力学 波函数 双缝实验 粒子的波动性 直白易懂的物理科普视频,长知识专用。

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视频来源

https://www.youtube.com/watch?v=02eZMf17wFs

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