聖誕小禮物：六個同時順時針，逆時針轉的離子

Image credit: Bill Pietsch, Astronaut 3 Media Group, Inc.

NIST researchers have succeeded in coaxing six ions into an unusual quantum 「cat」 state in which their nuclei are collectively spinning clockwise and counterclockwise at the same time. View an animation simulating six entangled ions in simultaneous "cat" states. Requires the free Quicktime player or free Real player).

美國 NIST (Commerce Department』s National Institute of Standards and Technology) 的科學家於2005年成功地讓6個鈹離子系統實現了自旋方向完全相反的宏觀量子疊加態，也就是量子力學理論中的「薛定諤貓」態。

按這裡可看到六個同時順時針，逆時針轉的「薛定諤貓態」離子的動畫片。如你不能看到，請下載免費的free Quicktime player 或者免費的free Real player.

[ 本帖最後由 自由之靈 於 2008-12-23 23:08 編輯 ]

俺怎麼看到它一動不動滴

俺也是！

對不起，我也發覺了。再試試。

謝啦。

是不是俺一觀察它，它就不動了？

最後那道藍光是啥意思？

50微妙已過，貓態不再？

原帖由 618o382 於 2008-12-24 01:58 發表 [聖誕小禮物：六個同時順時針，逆時針轉的離子 - 信仰天地 -  backchina.com]  
是不是俺一觀察它，它就不動了？

是飛機看就不動，基看就動，要不八福同學不會謝啦 看來有聖靈內駐真滴不一樣

各位稍等，抱歉！應該可以看到動的。

原帖由 自由之靈 於 2008-12-24 02:04 發表 [聖誕小禮物：六個同時順時針，逆時針轉的離子 - 信仰天地 -  backchina.com]  
各位稍等，抱歉！應該可以看到動的。

靈姐你乾脆貼個鏈接讓大夥兒自個看吧。
鏈接如下：
http://www.nist.gov/public_affai ... atStates_embed.html

謝謝蚊子。 正急著，偏偏我的 Window Vista 出了毛病。對，就是這個鏈接。

[ 本帖最後由 自由之靈 於 2008-12-23 15:36 編輯 ]

把作者的解釋拷貝過來，很多問題就明白了：

The above animation simulates six ions in "cat" states, spinning in two opposite directions at the same time. Each ion spins both left (clockwise, shown in blue) and right (counter-clockwise, shown in red) simultaneously, a condition called a superposition. The six ions are also entangled with each other, so their properties are correlated. If one ion is measured with a laser (shown as a blue beam), that ion's delicate superposition will "collapse" and it will spin in only one direction (clockwise/blue in the animation). Entanglement causes the other five ions to immediately spin in the same direction (they all turn blue).

謝謝轉帖。

不過看起來好像又不是 「概率」 的解釋了……

黃金分割網友？你的理論需要修改下……這裡還有個 「坍縮」 呢……

我的理解是概率問題。

期待學物理的大蝦指教。

這個問題挺有趣。有趣在怎樣理解一個離子如何同時順時針和逆時針轉，有趣在量子力學的特性上。但不是有趣在邏輯關係上，也不是有趣在於宗教，哲學問題上，哈。

以下是NIST的科學家對做這一實驗時的描述：

http://www.nist.gov/public_affairs/releases/cat_states.htm

Background: Creating Entangled Cat States with Six Ions

STEP 1

Ions have a property called spin. Spin can be visualized as a rotating top, which can be pointing up, down, or any direction in between to represent a combination of up and down at the same time. (The spin can point in any direction, so there are many possibilities.)

The NIST experiment begins with all six ions spin down. Then they are hit with two parallel laser pulses, which places each of the ions in an equal superposition of spin up and spin down. This means that each ion would have a 50/50 chance of being measured as spin up or spin down. (A measurement always causes a superposition to collapse to one direction or the other.) A measurement of all six ions would have 64 (26) possible outcomes, or combinations of up and down spins. But the ions are not measured at this point in the experiment. Instead, they remain in the superposition of all 64 possibilities.

STEP 2

All six ions are entangled using a NIST technique originally developed several years ago to entangle two or three ions. Two laser beams are positioned at right angles to apply an oscillating force to all six ions. The lasers are tuned so the difference between their frequencies is very close to the frequency of one of the natural vibrational motions of the six-ion string. Based on differences in the spin up and spin down components of the evolving 64 states, the ions 「feel」 a differing laser force that cause the ions to oscillate in a particular way. This coupling of the superposition of spin states to the motion of the ion string has the global effect of entangling the ions in a controlled way.

「During this process the ions all 'talk』 to each other at the same time, like in a conference call,」 says NIST physicist Dietrich Leibfried. 「The common motion can be thought of as the 『phone line.』 (The Austrian experiment is more like a series of individual phone calls to 『the boss,』 or the motion.)"

STEP 3
A final laser pulse places all six entangled ions in the cat state, where they stop evolving and remain briefly in the superposition of all spins up (rotating to the right) and all spins down (rotating to the left); that is, the original 64 possibilities have been reduced to two.

VERIFICATION

NIST scientists used two techniques to prove indirectly that the ions were in cat states. (Direct measurements would cause the cat states to collapse.) Both techniques rely on the fact that any spinning object oscillates in an external magnetic field at a rate proportional to its internal magnetic properties.

In a superposition of all six spins up and down simultaneously (a cat state), the 「all up」 component will oscillate at six times the rate of a single spin up, and the 「all down」 component will oscillate at six times the rate of a single spin down—but in the direction opposite to 「all up.」 Therefore, a cat-like superposition of six ions will spin apart six times faster than a superposition of a single atom. Scientists can evaluate how cleanly the prepared cat states execute the oscillation at the sixfold speed, and thus determine how purely the original 「all up and all down」 state was prepared.

[ 本帖最後由 自由之靈 於 2008-12-23 23:02 編輯 ]

如在上述引文中 Step 1 提到，離子具有自轉的特性。自轉可以看作是一個旋轉的陀螺，轉軸向下或向上。轉軸向下時，離子向左轉，即為順時針轉（從上往下看。用右手法則），如圖中的藍色。轉軸向上時，離子向右轉，即為逆時針轉，如圖中的紅色。

當這個轉軸指向任何在上，下中間的方向時，這時的離子旋轉被認為是順時針和逆時針轉的組合。即所謂的「順時針和逆時針轉同時旋轉」。此現象被稱為量子力學中的態疊加。

我也不是學物理的，歡迎大蝦們指正和補充！

[ 本帖最後由 自由之靈 於 2008-12-23 23:09 編輯 ]

那道藍光是測量用的激光脈衝。當用它測量時，離子不穩定的疊加態會被擊垮而變為向一個方向旋轉（這裡是藍色）。又因為量子糾纏，導致其他五個離子也馬上向同一方向旋轉(都呈藍色）。

[ 本帖最後由 自由之靈 於 2008-12-23 22:24 編輯 ]

嗯，這個解釋看起來更具體些。

不過，照這個解釋，影片里畫成平躺著旋轉不就得了，幹嘛還紅的、藍的、又 collapse……故弄玄虛啊？