Scientists from the University of California in Los Angeles, who were funded by the U.S. Army, have discovered a proverbial smoking gun signature of the elusive Majorana particle. The researchers believe this discovery could block intruders on vulnerable communication networks.
Italian theoretical physicist Ettore Majorana had predicted the Majorana particles over eight decades ago. Owing to their remarkable properties, which enable them to avert quantum information loss and be immune to external interference, these particles could turn out to be the critical building blocks for quantum computers.
Besides solving an ancient physics problem, the finding also paves a potential pathway to manipulate Majorana fermions to achieve robust topological quantum computing, noted Dr. Joe Qiu, manager of the Solid-State Electronics Program within the Engineering Sciences Directorate at the Army Research Office, a U.S. Army Research Laboratory subsidiary, situated at Research Triangle Park in Durham, North Carolina.
When compared to classical computers, quantum computers can solve problems much more efficiently and rapidly, potentially resulting in the considerable development in situational awareness with the ability to process huge amounts of available data, a basic priority research area for the U.S. Army.
Prior experimental approaches based on semiconductor nanowires on superconductors have produced inconclusive signals which could also be attributed to other effects. The UCLA experiment using stacked layers of magnetic topological insulator and superconductor has demonstrated the clearest and most unambiguous evidence of the particles as predicted by theory so far.
Dr. Joe Qiu
The study leading to the breakthrough signifies a close interdisciplinary partnership among a group of scientists including material scientists, physicists, and electrical engineers. An Army Multidisciplinary University Research Initiative (MURI) award, jointly managed by Electronics (Dr. Joe Qiu), Physics (Dr. Marc Ulrich), and Materials (Dr. John Prater) divisions at ARO, funded the UCLA research team. ARO supports research to instigate scientific and comprehensive technological breakthroughs in private industry, nonprofit organizations, educational institutions, and extramural organizations that can make prospective American Soldiers safer and stronger.
The study was headed by Professor Kang Wang, a UCLA distinguished professor of electrical engineering, of physics, and of materials science and engineering, who also holds the Raytheon Chair in Electrical Engineering of UCLA.
The research featured in an invited talk presented by Professor Wang along with two other associated invited talks by his collaborators during the American Physical Society March Meeting and was first published in the prestigious journal Science in July 2017.
Because the Majorana particle is its own anti-particle—carrying zero electrical charge - it is viewed as the best candidate to carry a quantum bit, or qubit, the unit of data that would be the foundation of quantum computers. Unlike ‘bits’ of data in standard computers, which can be represented as either 0s or 1s, qubits have the ability to be both 0s and 1s, a property that would give quantum computers exponentially more computing power and speed than today’s best supercomputers.
Dr. Joe Qiu
The Majorana particle has been at the center of attention for quantum computing chiefly because it has a neutral charge, which makes it resistant to external interference and provides the ability to leverage and sustain a quantum property—entanglement. Entanglement enables two physically separate particles to simultaneously encode information, which could create massive computing power.
“Imagine that bits of data in standard computers are like cars traveling both ways on two-lane highways,” stated Wang, who also serves as the director of the Center of Excellence in Green Nanotechnology of the King Abdulaziz City for Science and Technology. “A quantum computer could have many lanes and many levels of ‘traffic’, and the cars could hop between levels and travel in both directions at the same time, in every lane and on every level. We need stable, armored quantum ‘cars’ to do this and the Majorana particles are those supercars.”
To conduct their study, the team arranged a superconductor, a material that allows free flow of electrons across its surfaces with virtually zero resistance; over it, they positioned a thin film of a new quantum material called topological insulator, to enable the engineers to control the particles into a specific pattern. Subsequent to sweeping a very small magnetic field over the installation, the team discovered the discrete quantized signal of the Majorana particles—the unique attribute of a particular kind of quantum particle—in the electrical traffic between the two materials.
“The Majorana particles show up and behave like halves of an electron, although they aren’t pieces of electrons,” stated Qing Lin He, a postdoctoral scholar at UCLA and co-lead author of the paper published in the Science journal. “We observed quantum behavior, and the signal we saw clearly showed the existence of these particles.”
During the experiment, Majorana particles propagated along the edges of the topological insulator in a discrete braid-like pattern. The researchers stated that the subsequent step in their study will be to investigate how to use Majorana particles in quantum braiding, which would knit them together to enable the storage and processing of information at tremendous speeds.
Lei Pan, the other co-lead author of the paper and a UCLA doctoral student in electrical engineering, stated that the distinctive properties of Majorana particles would apparently make them particularly valuable for topological quantum computers.
“While conventional quantum systems have sophisticated schemes to correct errors, information encoded in a topological quantum computer cannot be easily corrupted,” he added. “What’s exciting about using Majorana particles to build quantum computers is that the system would be fault-tolerant.”
The research group also had collaborating members from UC Irvine, UC Davis, and Stanford University.