Newly discovered quantum particles have unique memory properties that improve computers

Researchers at Purdue University have discovered that a collection of electrons under extreme conditions can form quasiparticles called "anyons," which have unique "memory" properties and could advance quantum computing. 

The team first reported the possible detection of anyons in early July but have confirmed new experimental evidence of their existence, as well as specific properties. 

Postdoctoral research associate James Nakamura made the discovery, assisted by Shuang Liang and Geoffrey Gardner. The work was conducted at a laboratory headed by Michael Manfra, distinguished professor of physics and astronomy.

Anyons were so named in the 1980s by Frank Wilczek, a Nobel Prize-winning physicist at MIT, because of their ability to "adopt 'any' quantum phase when their positions are exchanged." They are not subatomic particles, such as bosons and fermions (the more basic particles that make up the nucleons of atoms), but "quasiparticles that exist in two dimensions."

"Anyons only exist as collective excitations of electrons under special circumstances," Manfra said, as reported by Phys.org. 

Their behavior is not observed in other subatomic particles and unlike bosons and fermions, anyons can preserve a "memory" of their interactions with other quasiparticles during quantum mechanical phase transitions (QPTs are changes that happen at, or close to, absolute zero). On a macro scale, think of a phase transition like water turning into ice. 

"The quasiparticles’ unusual behaviour when switching places means that if one moves in a full circle around another… [It] will retain a memory of that motion in its quantum state," the study said. 

They are able to retain memories of these interactions due to quasi-property's fractional charge and fractional statistics (subatomic particles produce a charge that is an integer). The interferometer, a device made of matrices of gallium arsenide and aluminum gallium arsenide, prevents electric currents from running through the device but instead allows currents to run along the side. This is what gives the quasiparticles a one-third, or fractional charge. 

Another "characteristic difference between fermions and bosons is how the particles act when they are looped, or braided, around each other," Scientist Study reported. Fermions (made up of electrons) and bosons (made up of photons) interact in straightforward ways when "braided" around each other. But when the electrons are placed in a device called an interferometer, cooled to near absolute zero and placed under a powerful magnet, and confine to a two-dimensional path, an environment that allows quasi-particle arises. Anyons can be braided around each other in more complex ways.

"Theorists have suggested that the ability of these particles to retain information could be useful in developing ultra-fast quantum computing systems that don’t require error correction [a major stumbling block in quantum computers]," the study noted.

Quantum computers are superior to traditional computers in that they make use of the special properties of particles in a quantum state, namely, superposition, entanglement and interference, and store information on qubits – the basic unit of information in quantum computing. These special properties allow quantum computers to store and process more data than even the most powerful supercomputer ever could. However, each qubit requires more bits for error correction. Because an anyon's "behavior depends on the number of times the particles are braided, or looped, around each other, they are more robust in their properties than other quantum particles," the researchers said.

The system is said to be "topological" as it depends on the "geometry" of any system built using anyons, which researchers are currently working on scaling up. A topological quantum computer would be more stable than a standard quantum computer. 

The next step, according to Manfra, is a more complicated interferometer that will give researchers greater "control [over] the location and number of quasiparticles in the chamber." This will also allow them to change the number of quasiparticles in the device on demand and "change the interference pattern as [they] choose."

Perhaps the future of computing isn't in the standard qubit, but the more versatile and stable anyon.