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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.

一组研究人员刚刚在一台实际的X光机上演示了量子增强，实现了消除背景噪声以进行精确检测的理想目标。

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.

量子尺度上的光子对之间的关系可以用来产生比经典光学更清晰、更高分辨率的图像。这一新兴领域被称为量子成像，它有着令人印象深刻的潜力——特别是因为，利用光，它可以用来显示通常看不见的物体，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.

量子相关描述了光子对之间的许多不同关系。纠缠就是其中之一，并应用于光学量子成像。

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射线波段产生纠缠光子的技术挑战远大于光，因此在构建它们的量子x射线时，研究小组采取了不同的方法。

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.

他们使用了一种称为量子照明的技术来最小化背景噪声。通常，这会产生纠缠光子，但较弱的相关性也会起作用。研究人员使用一种称为参数下转换(pdc)的过程，将一个高能或“泵”光子分裂成两个低能光子，称为信号光子和空转光子。

\"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.

研究人员在他们的论文中写道:“几位作者已经证明了x射线PDC，最近也证明了这种效应作为鬼影成像的来源的应用。”

\"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，光子统计数据都没有被测量过。实际上，到目前为止，还没有实验证据表明由x射线PDC产生的光子具有辐射量子态的统计特性。同样，量子增强测量灵敏度的观测从未在x射线波长上报道过。”

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.

研究人员用钻石晶体实现了x射线PDC。晶体的非线性结构将一束泵浦x射线光子分裂成信号和空转光束，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.

通常情况下，使用X射线的这个过程效率非常低，所以团队扩大了能量。利用日本的spring-8同步加速器，他们向晶体发射了一束22 kev的x射线，晶体分裂成两束，每束携带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.

信号束被发送到被成像的物体上——在本研究中，是一小块有三个狭缝的金属片——另一边有一个探测器。空转光束被直接发送到另一个检测器。这样设置是为了让每束光束在同一时间、同一地点击中各自的探测器。

\"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.

以色列巴伊兰大学的物理学家Sason Sofer说:“我们观察到的完美的时间-能量关系只能说明这两个光子是量子相关的。”

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，研究人员比较了他们的检测结果。图像中每个点只有大约100个相关光子，还有大约10000个背景光子。但是研究人员可以将每一个引导轮与一个信号匹配，这样他们就可以真正分辨出图像中的哪些光子来自光束，从而很容易地分离出背景噪声。

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，他们将这些图像与使用规则的、非相关光子拍摄的图像进行了比较——相关光子明显产生了更清晰的图像。

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.

虽然现在还处于早期阶段，但这绝对是朝着正确的方向迈出的一步，这将是一个非常令人兴奋的工具。量子x射线成像可以在当前x射线技术范围之外有许多用途。

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.

其中一个希望是它可以降低x射线成像所需的辐射量。这意味着容易被x射线损坏的样品可以成像，或者需要低温的样品;更少的辐射意味着更少的热量。它还能让物理学家用x射线来观察原子核内部。

The research has been published in Physical Review X.

这项研究发表在《物理评论X》上。

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