每一种粒子都有一个和它的质量、寿命、自旋严格相等，而电荷却正好相反的反粒子存在，这是狄拉克在他的正电子预言中提出来的。狄拉克方程预言了一种新的电子——正电子，从而开创了反原子、反物质、反世界的研究。
1932年美国物理学家安德森在宇宙线的研究中发现了正电子，这是人类发现的第一个反粒子。1932年由美国物理学家卡尔·安德森在实验中证实了正电子的存在。随后又发现了负质子和自旋方向相反的反中子。到目前为止，已经发现了300多种基本粒子，这些基本粒子都是正反成对存在的，也就是说，任何粒子都可能存在着反粒子。由反粒子组成的物质被称为反物质。正反粒子和物质如果相遇，会发生湮灭，并全部变成能量。
这些都是大家比较熟悉的，其实，在物理学领域，理论上也存在一种更为奇特的粒子，就是正反粒子（非学术名），就是正反粒子共同存在的一种粒子，这是1937年意大利理论物理学家马约拉纳（Ettore Majorana）提出一种观点，所以这种粒子叫马约拉纳粒子，物理学的语言，这种粒子叫马约拉纳费米子（Majorana fermion）是一种费米子，它的反粒子就是它本身。与此相反，狄拉克费米子（Dirac fermion）则是指反粒子与自身不同的费米子。这一概念由马约拉纳于1937年提出，他对狄拉克方程式改写得到了马约拉纳方程式，可以描述中性自旋1/2粒子，因而满足这一方程的粒子为自身的反粒子。
从那以后，物理学家一直试图能捕捉到这种神秘的马约拉纳费米子，现在终于有了很强的证据证明这种马约拉纳费米子确实存在于超导材料内，这一发现将帮助科学家研究新型量子计算机。来自普林斯顿大学Ali Yazdani小组的这一新发现昨天发表在《科学》杂志上。这一发现具有重要意义，将启动新型粒子发现的热潮，将来科学家会试图发现非超导情况下的马约拉纳费米子。
Theresearch team placed a long chain of iron atoms, which are magnetic, on top ofa superconductor made of lead. Normally, magnetism disrupts superconductors,which depend on a lack of magnetic fields for their electrons to flowunimpeded. But in this case the magnetic chain turned into a special type ofsuperconductor in which electrons next to one another in the chain coordinatedtheir spins to simultaneously satisfy the requirements of magnetism andsuperconductivity. Each of these pairs can be thought of as an electron and anantielectron, with a negative and a positive charge, respectively. Thatarrangement, however, leaves one electron at each end of the chain without aneighbor to pair with, causing them to take on the properties of both electronsand antielectrons — in other words, Majorana particles.
Asopposed to particles found in a vacuum, unattached to other matter, theseMajoranas are what’s called emergent particles. They emerge from the collectiveproperties of the surrounding matter and could not exist outside thesuperconductor.
Thediscovery could have implications for searches for free Majorana particlesoutside of superconducting materials. Many physicists suspect neutrinos — verylightweight particles with the strange ability to alter their identities, orflavors — are Majorana particles, and experiments are ongoing to investigatewhether this is the case.
Thefinding could also be useful for constructing quantum computers that harnessthe laws of quantum mechanics to make calculations many times faster thanconventional computers. One of the main issues in building a quantum computeris the susceptibility of quantum properties such as entanglement (a connectionbetween two particles such that an action on one affects the other) to collapsedue to outside interference. A particle chain with Majoranas capping each endwould be somewhat immune to this danger, because damage would have to be doneto both ends simultaneously to destroy any information encoded there.
