A research team has discovered the first multiple Majorana zero modes (MZMs) within a single vortex of the superconducting topological crystalline insulator SnTe. They used crystal symmetry to manage the connections between these MZMs, paving the way for advancements in fault-tolerant quantum computers. This significant finding has been published in Nature.
A team of researchers led by Prof. Junwei Liu, Associate Professor in the Physics Department at the Hong Kong University of Science and Technology (HKUST), along with Prof. Jinfeng Jia and Prof. Yaoyi Li from Shanghai Jiao Tong University (SJTU), have made a breakthrough by discovering multiple Majorana zero modes (MZMs) in one vortex of the superconducting topological crystalline insulator SnTe. They utilized the crystal symmetry to control how these MZMs interact with each other. This discovery opens new avenues for developing reliable quantum computers, as detailed in their publication in Nature.
MZMs are unique quasiparticles with zero energy that behave according to non-Abelian statistics, which allows for different sequences of braiding without changing the overall number of exchanges. This is different from typical particles like electrons and photons, where diverse movements result in the same final state. Such characteristics make MZMs resilient to local disturbances, making them well-suited for stable fault-tolerant quantum computing. Despite progress in creating artificial topological superconductors, manipulating and braiding MZMs has been difficult due to their spatial separation, complicating the movements needed for them to merge.
The collaborative research, merging theoretical and experimental expertise from HKUST and SJTU, took a novel approach by leveraging the special features of crystal-symmetry-protected MZMs to overcome existing challenges. They successfully demonstrated the existence and merging of multiple MZMs, protected by magnetic mirror symmetry, in a single vortex of SnTe without needing real-space movement or strong magnetic fields. Their methods utilized skills in low-temperature scanning tunneling microscopy, high-quality material growth, and extensive theoretical simulations.
The experimental team at SJTU noticed significant variations in the zero-bias peak, which is a key indicator of MZMs, in the SnTe/Pb heterostructure when subjected to tilted magnetic fields (Fig 4a-b). In response, the theoretical team at HKUST conducted detailed numerical simulations to confirm that these variations linked directly to the crystal-symmetry-protected MZMs. By employing the kernel polynomial method, they effectively simulated large vortex systems with hundreds of millions of orbitals, enabling further investigation into new properties within vortex systems beyond just the crystal-symmetry-protected MZMs. This research opens new possibilities for identifying and working with multiple MZMs safeguarded by crystal symmetry. Their discoveries lay the foundation for demonstrating non-Abelian statistics experimentally and for creating innovative topological qubits and quantum gates based on these multiple MZMs.
*Note: Prof. Junwei Liu from HKUST, Prof. Yaoyi Li, and Prof. Jinfeng Jia from SJTU are the corresponding authors. Chun Yu Wan from HKUST, Dr. Tengteng Liu, and Dr. Hao Yang, both from SJTU, share the role of co-first authors.
