物理學(xué)家們終于制造出一種量子X射線裝置

物理學(xué)家們終于制造出一種量子X射線裝置

A team of researchers has just demonstrated quantum enhancement in an actual X-ray machine, achieving the desirable goal of eliminating background noise for precision detection.

一組研究人員剛剛在一臺實際的X光機上演示了量子增強，實現(xiàn)了消除背景噪聲以進行精確檢測的理想目標。

The relationships between photon pairs on quantum scales can be exploited to create sharper, higher-resolution images than classical optics. This emerging field is called quantum imaging, and it has some really impressive potential - particularly since, using optical light, it can be used to show objects that can't usually be seen, like bones and organs.

量子尺度上的光子對之間的關(guān)系可以用來產(chǎn)生比經(jīng)典光學(xué)更清晰、更高分辨率的圖像。這一新興領(lǐng)域被稱為量子成像，它有著令人印象深刻的潛力——特別是因為，利用光，它可以用來顯示通?？床灰姷奈矬w，比如骨骼和器官。

Quantum correlation describes a number of different relationships between photon pairs. Entanglement is one of these, and is applied in optical quantum imaging.

量子相關(guān)描述了光子對之間的許多不同關(guān)系。糾纏就是其中之一，并應(yīng)用于光學(xué)量子成像。

But the technical challenges of generating entangled photons in X-ray wavelengths are considerably greater than for optical light, so in the building of their quantum X-ray, the team took a different approach.

但是在x射線波段產(chǎn)生糾纏光子的技術(shù)挑戰(zhàn)遠大于光，因此在構(gòu)建它們的量子x射線時，研究小組采取了不同的方法。

They used a technique called quantum illumination to minimise background noise. Usually, this uses entangled photons, but weaker correlations work, too. Using a process called parametric down-conversion (PDC), the researchers split a high-energy - or "pump" - photon into two lower-energy photons, called a signal photon and an idler photon.

他們使用了一種稱為量子照明的技術(shù)來最小化背景噪聲。通常，這會產(chǎn)生糾纏光子，但較弱的相關(guān)性也會起作用。研究人員使用一種稱為參數(shù)下轉(zhuǎn)換(pdc)的過程，將一個高能或“泵”光子分裂成兩個低能光子，稱為信號光子和空轉(zhuǎn)光子。

"X-ray PDC has been demonstrated by several authors, and the application of the effect as a source for ghost imaging has been demonstrated recently," the researchers write in their paper.

研究人員在他們的論文中寫道:“幾位作者已經(jīng)證明了x射線PDC，最近也證明了這種效應(yīng)作為鬼影成像的來源的應(yīng)用。”

"However, in all previous publications, the photon statistics have not been measured. Essentially, to date, there is no experimental evidence that photons, which are generated by X-ray PDC, exhibit statistics of quantum states of radiation. Likewise, observations of the quantum enhanced measurement sensitivity have never been reported at X-ray wavelengths."

“然而，在以前的所有出版物中，光子統(tǒng)計數(shù)據(jù)都沒有被測量過。實際上，到目前為止，還沒有實驗證據(jù)表明由x射線PDC產(chǎn)生的光子具有輻射量子態(tài)的統(tǒng)計特性。同樣，量子增強測量靈敏度的觀測從未在x射線波長上報道過。”

The researchers achieved their X-ray PDC with a diamond crystal. The nonlinear structure of the crystal splits a beam of pump X-ray photons into signal and idler beams, each with half the energy of the pump beam.

研究人員用鉆石晶體實現(xiàn)了x射線PDC。晶體的非線性結(jié)構(gòu)將一束泵浦x射線光子分裂成信號和空轉(zhuǎn)光束，每一束的能量只有泵浦光束的一半。

Normally, this process is very inefficient using X-rays, so the team scaled up the power. Using the SPring-8 synchrotron in Japan, they shot a 22 KeV beam of X-rays at their crystal, which split into two beams, each carrying 11 KeV.

通常情況下，使用X射線的這個過程效率非常低，所以團隊擴大了能量。利用日本的spring-8同步加速器，他們向晶體發(fā)射了一束22 kev的x射線，晶體分裂成兩束，每束攜帶11 kev。

The signal beam is sent towards the object to be imaged - in the case of this research, a small piece of metal with three slits - with a detector on the other side. The idler beam is sent straight to a different detector. This is set up so that each beam hits its respective detector at the same place and at the same time.

信號束被發(fā)送到被成像的物體上——在本研究中，是一小塊有三個狹縫的金屬片——另一邊有一個探測器。空轉(zhuǎn)光束被直接發(fā)送到另一個檢測器。這樣設(shè)置是為了讓每束光束在同一時間、同一地點擊中各自的探測器。

"The perfect time-energy relationship we observed could only mean that the two photons were quantum correlated," said physicist Sason Sofer of Bar-Ilan University in Israel.

以色列巴伊蘭大學(xué)的物理學(xué)家Sason Sofer說:“我們觀察到的完美的時間-能量關(guān)系只能說明這兩個光子是量子相關(guān)的。”

For the next step, the researchers compared their detections. There were only around 100 correlated photons per point in the image, and around 10,000 more background photons. But the researchers could match each idler to a signal, so they could actually tell which photons in the image were from the beam, thus easily separating out the background noise.

下一步，研究人員比較了他們的檢測結(jié)果。圖像中每個點只有大約100個相關(guān)光子，還有大約10000個背景光子。但是研究人員可以將每一個引導(dǎo)輪與一個信號匹配，這樣他們就可以真正分辨出圖像中的哪些光子來自光束，從而很容易地分離出背景噪聲。

They then compared these images to images taken using regular, non-correlated photons - and the correlated photons clearly produced a much sharper image.

然后，他們將這些圖像與使用規(guī)則的、非相關(guān)光子拍攝的圖像進行了比較——相關(guān)光子明顯產(chǎn)生了更清晰的圖像。

It's early days yet, but it's definitely a step in the right direction for what could be a greatly exciting tool. Quantum X-ray imaging could have a number of uses outside the range of current X-ray technology.

雖然現(xiàn)在還處于早期階段，但這絕對是朝著正確的方向邁出的一步，這將是一個非常令人興奮的工具。量子x射線成像可以在當前x射線技術(shù)范圍之外有許多用途。

One promise is that it could lower the amount of radiation required for X-ray imaging. This would mean that samples easily damaged by X-rays could be imaged, or samples that require low temperatures; less radiation would mean less heat. It could also enable physicists to X-ray atomic nuclei to see what's inside.

其中一個希望是它可以降低x射線成像所需的輻射量。這意味著容易被x射線損壞的樣品可以成像，或者需要低溫的樣品;更少的輻射意味著更少的熱量。它還能讓物理學(xué)家用x射線來觀察原子核內(nèi)部。

The research has been published in Physical Review X.

這項研究發(fā)表在《物理評論X》上。