Josephson Trijunctions Demonstrate Exchange of Majorana Zero Modes, Enabling Potential Braiding Operations

Majorana zero modes, exotic particles distinct from ordinary matter, hold immense promise for revolutionising quantum computing, but proving their unique properties has remained a significant challenge. Yunxiao Zhang, Zhaozheng Lyu, and Xiang Wang, alongside colleagues at their institutions, now report compelling experimental advances in manipulating and exchanging these elusive particles within a specially designed device built on a topological insulator. The team observed the movement of energy states consistent with theoretical predictions, providing preliminary evidence for a successful exchange operation, a crucial step towards ultimately braiding Majorana zero modes. This achievement establishes a vital pathway for realising fault-tolerant quantum computation based on the unique properties of these extraordinary particles.

Majorana zero modes represent anyons exhibiting non-Abelian exchange statistics, differing from both fermions and bosons. Over the past two decades, considerable progress has been made in the search for these exotic excitations within solid-state systems, yet their non-Abelian character remains unconfirmed. Definitive verification necessitates the demonstration of braiding operations, a complex manipulation of these particles to reveal their unique properties. This research focuses on achieving and observing such braiding, which would provide conclusive evidence for the existence of non-Abelian anyons and open new avenues for topological quantum computation. The team aims to create a platform where Majorana zero modes can be reliably manipulated and their exchange statistics directly measured, representing a significant step towards realising fault-tolerant quantum technologies.

Detailed Simulations Validate Superconducting Junction Performance

The research team refined their theoretical model by accounting for real-world effects on magnetic flux within the superconducting loops, estimating corrections to loop areas due to device geometry and the presence of superconducting loops, and calculating self-inductance. These corrections were applied to phase calculations within the lattice model, resulting in improved agreement between theory and experiment, as demonstrated by replotted data. Further analysis of a single junction confirmed the model’s accuracy, showing strong agreement between simulated and experimental contact conductance, and allowing for the extraction of key parameters related to the local density of states.

Majorana Zero Mode Migration Demonstrated in Device

Scientists have achieved significant progress in manipulating and exchanging presumed Majorana zero modes within a specially designed Josephson device, composed of multiple junctions on an insulating surface. Experiments revealed the migration of in-gap states, consistent with predictions from the Fu-Kane model, providing strong evidence for the creation and manipulation of these exotic particles. The research team employed a lattice model to simulate electron behavior within the trijunctions, discretizing each junction into a network of 600 lattice sites. Analysis of the resulting energy bands identified in-gap states, crucial indicators of Majorana zero modes, and distinguished them from continuum states based on their localization and energy distribution.

To further understand the experimental data, scientists developed a detailed model of electron transport between the trijunction and probe electrodes, incorporating a tunneling Hamiltonian describing the interaction between electrons in the probe and the lattice sites. This model predicts a relationship between contact conductance and the local density of states of the in-gap states. By fitting the model to measured contact conductance data, the team extracted key parameters, including a level broadening of approximately 167 μeV at one trijunction and 71 μeV at another, accurately reproducing observed patterns and confirming successful manipulation of the Majorana zero modes.

Majorana Migration Confirmed in Josephson Device

This research demonstrates experimental progress towards manipulating Majorana zero modes, exotic particles with potential applications in fault-tolerant quantum computing. Scientists successfully created and observed signatures of in-gap states migrating within a specially designed Josephson device, composed of multiple junctions on an insulating surface. These observations align with theoretical predictions from the Fu-Kane model, providing support for the realization of an exchange operation, a crucial step towards braiding these particles. The team tracked the migration of these in-gap states by carefully monitoring changes in conductance and the broadening of energy levels, establishing a correlation between the location of the states and measurable electrical properties.

The study establishes a critical pathway for ultimately achieving braiding of Majorana zero modes, a process necessary to demonstrate their non-Abelian nature and unlock their potential for quantum information processing. While the current work provides preliminary evidence for exchange operations, the authors acknowledge limitations related to energy resolution in their measurements. Future research will focus on improving this resolution to more clearly resolve the signatures of Majorana zero modes and further refine the control over their manipulation. The team also plans to address potential modifications to magnetic flux and loop area, which currently introduce slight misalignments in their data, essential for definitively confirming the non-Abelian statistics of these intriguing particles and advancing the field of topological quantum computation.