Since the breakthrough discovery of the Majorana particle in 2012 in Delft, the group of professor Leo Kouwenhoven at QuTech and Microsoft have collaborated with theorists and material scientists of various institutes to understand the next steps required to improve the experiments. Now, the scientists have provided a definite proof for the existence of the Majorana, paving the way toward Majorana quantum bits. They have published their work in Nature.

In 1937, Ettore Majorana predicted a new, fundamental particle that was later named after him. The Majorana particle has the property of being its own anti-particle. Researcher Hao Zhang says, “Usually, there is an opposite property in the antiparticle, such as charge—the antiparticle of the electron is the positron.” Majorana quasiparticles appear in materials in extremely restricted conditions. When a nanowire made from a semiconductor is connected to a superconductive material, researchers see a so-called zero-bias peak in the case of certain electric and magnetic fields. This signal is the main characteristic of the presence of Majoranas.

In the first 2012 experiment, the zero-bias peak was noisy and difficult to see, and the results were debatable. In the years that followed, researchers worked very hard on improving the theory, materials and the experimental fabrications. In recent months, multiple breakthroughs ensued. Transport in the required materials is improved in two steps: high-quality interfaces and superclean Majorana transport. Furthermore, the design of nano-hashtags allowed for future exchange of Majorana particles, the final step required for topological quantum computing.

Now, the researchers in Delft have combined all improvements in an experiment to show the quantized conductance of the zero-bias peak. This perfect quantization of Majorana conductance is the final proof of the existence of the Majorana. Zhang says, “It is a direct consequence of the particle-antiparticle property.”

This experiment closes a chapter in the quest for Majorana particles, and opens a new chapter to work toward quantum information processing based on their properties. Their unique physical characteristics make the Majorana particles much more stable than the majority of other qubits. Making and regulating these Majoranas on the way to creating a topological quantum computer is still challenging. The level of control and understanding now reached allows for the exploration of Majorana quantum computing. The researchers aim to combine the previous breakthroughs into one experiment to realize a qubit based on four Majorana particles.

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“For that, we need to scale up to more complicated networks such as the nano-hashtags,” Hao Zhang explains, “and then we finally have a qubit that is protected by its own topology.”

Provided by:
Delft University of Technology

More information:
Quantized Majorana conductance, Nature (2018).

Perfect quantization of the Majorana conductance is the final proof of the existence of the Majorana’s.
Credit: TU Delft