Scientists Trapped an Antimatter Particle for Months to Study Its Secrets

Antimatter is not known for being easy to get ahold of. That’s part of why these particles remain so cryptic. But recently, a team of physicists at Northwestern University managed to trap a single antimatter particle for months. Cooling it to temperatures near absolute zero, they could control its quantum states with great precision without even touching it. The experiment, published in Physical Review Letters, represents a breakthrough in our understanding of one of the great mysteries of physics.

反物质向来以难以捕捉而著称，这也是这些粒子至今仍充满神秘色彩的部分原因。但最近，西北大学的一支物理学家团队成功地将单个反物质粒子捕获了数月之久。通过将其冷却至接近绝对零度的温度，研究人员能够在不接触它的情况下，极其精确地控制其量子态。这项发表在《物理评论快报》上的实验，标志着我们在理解物理学这一重大谜题方面取得了突破。

In theory, antimatter should be everywhere. Mathematics predicts that every particle of matter has an equivalent antiparticle, a fact that scientists have verified experimentally. The universe should therefore contain similar amounts of both, but almost everything we observe is made up of ordinary matter, and we still don’t know why.

从理论上讲，反物质应该无处不在。数学预测每一种物质粒子都有一个对应的反粒子，这一事实已得到科学家的实验验证。因此，宇宙中应该包含等量的物质和反物质，但我们观察到的几乎所有事物都是由普通物质构成的，而我们至今仍不知道原因。

It is possible to produce antimatter particles in laboratories, but studying them is still incredibly difficult. When an antiparticle comes into contact with ordinary matter, the two annihilate each other and release energy. To prevent research facilities from exploding, scientists use vacuum chambers and electromagnetic fields that suspend the antiparticles in isolation. But this only partially solves the problem. Studying these particles, especially experimenting with their behavior on a quantum scale, remains challenging.

虽然在实验室中制造反物质粒子是可能的，但对其进行研究仍然极其困难。当反粒子与普通物质接触时，两者会发生湮灭并释放能量。为了防止研究设施爆炸，科学家们使用真空室和电磁场将反粒子悬浮在隔离状态中。但这只能部分解决问题。研究这些粒子，特别是在量子尺度上对其行为进行实验，依然充满挑战。

For this experiment, researchers at Northwestern trapped a positron, the antimatter counterpart of electrons. The team, led by Gerald Gabrielse, developed a device known as a single-positron quantum cyclotron, which used electric and magnetic fields to hold the positron in a vacuum at a temperature close to absolute zero. This means the antimatter particle was at its lowest energy state, allowing the researchers to induce controlled changes in its quantum behavior. Unlike other methods in particle physics, this approach didn’t destroy the particle. The researchers were therefore able to keep the single antiparticle trapped for months, allowing them to repeat measurements.

在这次实验中，西北大学的研究人员捕获了一个正电子，即电子的反物质对应物。由杰拉德·加布里埃尔斯（Gerald Gabrielse）领导的团队开发了一种被称为“单正电子量子回旋加速器”的装置，利用电场和磁场将正电子保持在接近绝对零度的真空中。这意味着反物质粒子处于其最低能量状态，使研究人员能够对其量子行为进行受控诱导。与其他粒子物理学方法不同，这种方法不会破坏粒子。因此，研究人员能够将单个反粒子捕获数月，从而进行重复测量。

So what can taming antimatter particles actually teach us? Scientists know that matter and antimatter have very similar properties. For example, an electron and a positron have exactly the same mass, although their electric charges are opposite. However, questions still remain about exactly how similar these two forms of matter are and whether there are small differences that have gone unnoticed in experiments conducted to date.

那么，驯服反物质粒子究竟能教会我们什么呢？科学家们知道，物质和反物质具有非常相似的特性。例如，电子和正电子的质量完全相同，尽管它们的电荷相反。然而，关于这两种物质形式究竟有多相似，以及在迄今为止进行的实验中是否有一些细微的差异未被察觉，这些问题仍然存在。

To this end, researchers want to compare the magnetic properties of both particles. Physicists have already made very precise measurements with electrons, but achieving the same level of precision with positrons has proven more difficult. According to the American Physical Society, the new device could enable measurements of antimatter particles about 30 times more precise than scientists were capable of before.

为此，研究人员希望比较这两种粒子的磁性。物理学家已经对电子进行了非常精确的测量，但要对正电子达到同样的精度则更为困难。据美国物理学会称，这种新装置能够使反物质粒子的测量精度比科学家以往的能力提高约 30 倍。

So far, the experiment has not revealed any unexpected differences between the two particles. What the researchers have achieved is an improvement in their ability to detect these differences in antimatter particles. If future measurements find that a positron responds to magnetic fields differently than an electron, scientists would have to revise some of the laws they use to explain the behavior of matter and antimatter.

到目前为止，该实验尚未发现这两种粒子之间存在任何意料之外的差异。研究人员所取得的成就是提高了他们检测反物质粒子中这些差异的能力。如果未来的测量发现正电子对磁场的反应与电子不同，科学家们将不得不修改他们用来解释物质和反物质行为的部分定律。

This story originally appeared in WIRED en Español and has been translated from Spanish.

本文最初发表于《连线》西班牙语版（WIRED en Español），由西班牙语翻译而来。