InAs-Al Hybrid Devices Passing the Topological Gap Protocol



We present measurements and simulations of semiconductor-superconductor heterostructure devices that are consistent with the observation of topological superconductivity and Majorana zero modes. The devices are fabricated from high-mobility two-dimensional electron gases in which quasi-one-dimensional wires are defined by electrostatic gates. These devices enable measurements of local and non-local transport properties and have been optimized via extensive simulations for robustness against non-uniformity and disorder. Our main result is that several devices, fabricated according to the design’s engineering specifications, have passed the topological gap protocol defined in Pikulin {\it et al.}\ [arXiv:2103.12217 (opens in new tab)]. This protocol is a stringent test composed of a sequence of three-terminal local and non-local transport measurements performed while varying the magnetic field, semiconductor electron density, and junction transparencies. Passing the protocol indicates a high probability of detection of a topological phase hosting Majorana zero modes. Our experimental results are consistent with a quantum phase transition into a topological superconducting phase that extends over several hundred millitesla in magnetic field and several millivolts in gate voltage, corresponding to approximately one hundred micro-electron-volts in Zeeman energy and chemical potential in the semiconducting wire. These regions feature a closing and re-opening of the bulk gap, with simultaneous zero-bias conductance peaks at {\it both} ends of the devices that withstand changes in the junction transparencies. The measured maximum topological gaps in our devices are 20-30μeV. This demonstration is a prerequisite for experiments involving fusion and braiding of Majorana zero modes.

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InAs-Al Hybrid Devices Passing the Topological Gap Protocol

Dr. Chetan Nayak, Distinguished Engineer of Quantum at Microsoft, met with leaders in the Quantum industry to discuss Microsoft’s recent hardware progress in July 2022. In this session, Dr. Nayak presents the measurements and simulations that are detailed in his recent arXiv submission. This publication follows Microsoft’s announcement in March 2022 that they discovered that they could produce the topological superconducting phase and its concomitant Majorana zero modes, clearing a significant hurdle toward building a scaled quantum machine.