
English: 
To really understand what is special about
quantum bits and why they can provide such
a large computational power, we have to look
at what happens when we take more than one qubit.
Let's take the example of a spin which
we know how to visualise.
The super position of the 0 and 1 state of a single spin is simply the spin pointing to the right.
So that doesn't seem so strange.
But now, let's take two spins
and make them interact with each other.
This can happen for example because each spin produces a tiny magnetic field in its vicinity
and this field changes the energy of the other spin.
Remember that we can rotate a spin by applying an oscillating magnetic field
at the frequency proportional to the energy difference between the 1 and the 0 state
but if there is another spin in the vicinity, the total energy depends also on the state of that spin.

Chinese: 
要真正理解量子比特的特殊之处并且为何拥有如此强大的计算能力
我们就得看看当超过一个比特时会发生什么
让我们拿自旋做例子这样更直观
一个单独自旋粒子在0 1之间的态叠加就是自旋粒子指向右边
所以看起来不是很奇怪
但现在
我们让两个自旋粒子产生互动
这是可以发生的
因为举例来说
个自旋粒子在周围制造一个小型磁场然后磁场会改变其他自旋粒子的能量
记住我们能够翻转自旋
可以通过应用振动磁场在频繁区域1和0之间的能量不同来实现
但是如果附近有其他自旋
那么总能量就也取决于那个自旋粒子了
我们这样说我在0值准备两个自旋粒子

English: 
Let's say I prepare both spins in the 0 state and then I put spin A in the super position of 0 and 1.
Now I try to flip spin B by applying the frequency it would respond to if spin A is in the 0 state.
But actually, since A is in both the 0 and the 1 state, then spin B both flips and doesn't flip.
The resulting state is a super position of 0-1 and 1-0.
The 0-1 branch of the super position is created because spin B flips to 1 when spin A is 0
and the 1-0 branch is created because spin B remains 0 when A is in the state 1.
This kind of super position is perfectly legitimate but it's really special.
In this state I have absolutely no idea of where the two spins are pointing
but I do know that they point
in opposite directions.
This is called an entangled state.
If I separate the two spins after I have prepared the entangled state

Chinese: 
之后我把A自旋放在0和1的态叠加
现在我要试图B自旋世家的频率为A自旋处在0基态时B自旋会翻转的频率
但事实上因为A自旋既在0也在1
那么B自旋既倒转也不倒转
结果就是0-1和1-0的态叠加
0-1态叠加的分支出现因为B自旋倒转到1
当A自旋在0
1-0分支出现因为B自旋仍然在0当A在1的时候
这种态叠加很完美合理但它很特殊
在这种情况下我完全不知道两个自旋的指向
但我能确定它们指向是相反的
这就叫纠缠自旋
在我准备好两个纠缠状态后如果我分离它们
并且我对A自旋进行测量

English: 
and I measure for example spin A and I find it in the 0 state, then instantly, spin B
acquires the 1 state no matter how far apart
it is when the measurement takes place.
This is what Einstein called dismissively, 'The spooky action at the distance' but now we
know from many experimental tests, that this
is the way quantum mechanics really works.
In the context of quantum computing, entangled states represent a strikingly non-classical computer code.
There is no way you can write in your desktop computer a code where
two bits have no value but have the opposite value,
but you can do so in a quantum computer
and the more qubits you have, the more these entangled quantum computer codes
proliferate  and grow exponentially with the number of qubits.
Gaining access to these entangled quantum states is the key
to exploiting the exponentially large computational power of quantum systems.

Chinese: 
我发现它处在0值
那么立刻B自旋需要1基态不论多远当测量开始的时候
这就是爱因斯坦所不以为然的距离间不可思议的作用
经过许多实验我们现在知道了
这是量子计算产生作用的方式
就其来说纠缠状态代表一种显著的非经典电脑代码
你是没办法用你的电脑写出当两个比特没有参照值的代码但你可以通过量子计算来实现
比特越多
量子纠缠会随着比特的数量显著增长
解析量子纠缠是开发量子计算系统的主要途径

Chinese: 
同时纠缠状态是很脆弱并可以轻易被外界的干扰所破坏掉
这也就是为什么建立一个量子计算机需要这么多的努力与投资
我们需要建立一个绝对稳定的环境
可以用来制造大量量子纠缠并不受干扰
字幕由新南威尔士大学翻译专业提供
刘帅制作

English: 
At the same time, entangled states are very fragile
and can easily be destroyed by unwanted interference from the outside world.
This is why building a quantum computer requires so much effort and investment.
We need to create a perfectly
controlled environment where large entangled states
can be produced and manipulated without interference.
