利用人造钻石做实验或将改写经典热力学定律

据本周的中国科技报报道，英国量子物理学家正在利用人造钻石做实验，试图证明一种几年前刚被理论化的效应：量子推动可使钻石的功率输出高于经典热力学限定的水平。

只有鲁莽的物理学家，才敢于尝试打破热力学定律。不过，事实证明，或许真有改变这些定律的办法。在英国牛津大学的一间实验室里，量子物理学家正试图利用一小块人造钻石做到这一点。起初，这颗淹没在乱七八糟的光学纤维和镜子中的钻石几乎不可见。不过，当研究人员打开绿色激光器时，钻石中的缺陷被照亮，晶体开始发出红色的光。

在这束光线中，科学家发现了一种几年前刚被理论化的效应存在的初步证据：量子推动可使钻石的功率输出高于经典热力学限定的水平。如果结论成立，它们将给量子热力学研究带来实实在在的好处。量子热力学是一个相对较新的领域，旨在原子尺度上揭示控制热量和能量流动的定律。

经典热力学定律的发展要追溯到 19 世纪。它们诞生于理解蒸汽机和其他宏观系统所做的努力。诸如温度、热量等热力学变量本质上是统计性的，并且根据大型粒子群的平均运动被定义。但回到上世纪 80 年代，该领域的早期先驱、以色列希伯莱大学研究人员 Ronnie Kosloff 开始思考这种状况对于小很多的系统来说是否仍行得通。

在量子领域中，人们相信量子热力学定律同基于大多数粒子行为的经典理论是不同的，许多量子热力学家希望能找到可以适用于实际目的的传统热力学之外的行为，包括改进基于实验室的制冷技术，创造具有增强能力的电池和精炼量子计算技术。如果这一实验结果成立，它们将成为量子热力学研究中的一个大突破。

这样的钻石实验最先是由 Ronnie Kosloff 、Raam Uzdin 以及同样来自希伯来大学的 Amikam Levy 提出。按照他们的设想散布在钻石中的由氮原子造成的缺陷可以作为一个热机，与高温源（此次实验中用的是激光）接触，来实现电子的激发跃迁从而释放出光子能量。通过激光和微波辐射都可以激发出光子，但 Kosloff 和他的同事们更期待的是，这样的“发动机”可以在一种增强模式下来运作，即通过量子效应改善热力学性能。

在这次试验中，牛津大学的研究者受到上述想法的启发，结合脉冲激光与微波辐射方法研究了存在量子效应（相干性）的钻石热机实验，通过脉冲激光而不是连续的光来得到一些电子的叠加态，结合微波辐射可以使晶体能够更快的发射出光子。

研究者利用具有氮空位缺陷的钻石研究了两种类型的量子热机与不存在量子效应的经典热机做比较。最后，他们发现，测量到的输出功率与普通热机的输出功率相比高出四个标准差，从而打破了经典理论的限制。

他们还注意到，当相干性减弱时，输出功率就会减小到经典限制以下，这表明量子效应有利于热机功率的提升，也证明了量子效应在应用方面存有积极性。

领导开展钻石试验的牛津大学实验室的Ian Walmsley 也对该领域的未来持谨慎态度。尽管 Walmsley 和其他实验人员近年来一直被量子热力学研究吸引，但他表示，他们的兴趣在很大程度上 " 带有机会主义 "。他们发现了开展相对快速和简单试验的机会，即借助出于其他用途已经安装成功的装置。例如，钻石缺陷试验装置已被广泛用于研究量子计算和传感器应用。Walmsley 认为，目前量子热力学领域正在蓬勃发展。" 但它能否继续活跃下去，或者最终什么都不是，我们将拭目以待。"

随着CVD合成技术的提高，洛阳誉芯金刚石通过采用气体原料（氢气、甲烷）在低于1个气压，800-1200℃的温度下采用外延生长的方式获得完全透明无色大尺寸金刚石单晶，其成分、硬度、密度等与天然钻石基本一致，而价格远远低于天然钻石；与高温高压法（HTHP）不同，CVD人工成合技术不需要使用催化剂，杜绝了生产中形成的金属夹杂、裂隙、孔洞等。

特点：打磨后的净度一般为VVS及以上级别，色度为D-J色。

可提供克拉级的钻石原胚。

Impossible Things in Classical Thermodynamics

According to the China Science and Technology Daily this week, British quantum physicists are experimenting with artificial diamonds to try to prove a theory that was just a few years ago: Quantum propulsion can make the diamond's power output go above the classical thermodynamic limits.

Only reckless physicists dare to try to break the laws of thermodynamics. However, it turns out that there may really be a way to change these laws. In a lab at the University of Oxford in the UK, quantum physicists are trying to use a small piece of artificial diamond to do this. At first, the diamond, inundated with messy fibers and mirrors, was barely visible. However, when the researchers turned on the green laser, the defects in the diamond were illuminated and the crystals started to emit red light.

In this beam of light, scientists have found preliminary evidence of the theoretical effect just a few years ago: Quantum propulsion can make the power output of diamonds go beyond the classical thermodynamic limits. If the conclusions hold, they will bring tangible benefits to quantum thermodynamics. Quantum thermodynamics is a relatively new field that aims to reveal the laws governing the flow of heat and energy at the atomic scale.

The development of classical laws of thermodynamics dates back to the 19th century. They were born out of the effort to understand the steam engine and other macroscopic systems. Thermodynamic variables such as temperature, heat, etc. are statistical in nature and are defined by the average motion of large particle swarms. But back in the 1980s, Ronnie Kosloff, an early pioneer in the field and a researcher at Hebrew University in Israel, began to wonder if this situation still works for much smaller systems.

In the quantum field, it is believed that the laws of quantum thermodynamics are different from the classical theories based on the behavior of most particles, and many quantum thermodynamics hope to find something other than traditional thermodynamics that may be suitable for practical purposes, including improving laboratory-based refrigeration technology to create battery with enhanced capabilities and refined quantum computing technology. If the results of this experiment are valid, they will be a major breakthrough in quantum thermodynamics.

Such a diamond experiment was first proposed by Ronnie Kosloff, Raam Uzdin, and Amikam Levy, also from Hebrew University. According to their hypothesis, the nitrogen atoms scattered in diamonds can be used as a heat engine to contact with the high-temperature source (in this experiment, the laser) to realize the electronic excitation transition and release the photon energy. Photons can be excited by both laser and microwave radiation, but Kosloff and his colleagues are even more excited by the fact that such "engines" can operate in an enhanced mode that improves thermodynamic performance through quantum effects.

In this experiment, researchers at the University of Oxford, inspired by the above notion, studied diamond heat engine experiments with quantum effects (coherence) using pulsed and microwave radiation to obtain some electrons by pulsed laser rather than continuous light superposition state, combined with microwave radiation allows the crystal to emit photons faster.

The researchers used diamonds with nitrogen vacancy defects to investigate the comparison of two types of quantum heat engines with classical heat engines that do not have quantum effects. Finally, they found that the measured output power was four standard deviations above the output power of a typical heat engine, breaking the limits of classical theory.

They also noticed that when the coherence diminished, the output power was reduced below the classical limit, indicating that the quantum effect favored the increase of heat engine power and also demonstrated the positive effect of the quantum effect on the application.

Leadership in the diamond testing laboratory at Oxford University's Ian Walmsley also cautious about the future of the field. Although Walmsley and other experimenters have been drawn to quantum thermodynamics in recent years, he said their interest is "opportunistic" to a large extent. They found the opportunity to conduct relatively quick and simple trials with devices that have been installed successfully for other uses. For example, diamond defect testing devices have been widely used to study quantum computing and sensor applications. Walmsley believes that the current quantum thermodynamics is booming. "But whether it can continue to thrive or end up with nothing, we'll see."

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