Electronic Transport Studies of InAs Quantum Well

Google researchers have recently demonstrated quantum advantage in a superconducting quantum computer by solving a specific problem that is beyond the most powerful classical computers. The next step is to construct a universal quantum computer to solve real world problems such as new-drug design and discovery. This formidable advance will require a much larger number of fully functional qubits. Unfortunately, a relatively low average qubit gate fidelity of ~ 99% in current transmon qubits has been detrimental in this pursuit.<br/>A different approach, topological quantum computing, may overcome these difficulties, due to its enhanced tolerance to errors. In a topological quantum computer, a qubit would be constructed out of four Majorana quasiparticles (MQPs), with a gate performed by moving one MQP around another, or braiding MQPs. Because the braiding is topological and nonlocal, Majorana-based qubits would be intrinsically robust against local decoherence sources and thereby enable fault-tolerant quantum computing.<br/>InAs has emerged as a promising material platform to realize topological superconducting states (TSSs) which can host MQPs: (1) It can form a highly transparent interface with aluminum (Al, a superconductor); (2) the strength of spin-orbit-coupling (SOC) is large and tunable, a key ingredient for realizing TSSs. Indeed, recent work by Microsoft Quantum shows exciting results in InAs-Al hybrid devices that are consistent with the observation of TSSs and MQPs.<br/>In this work, we will present our recent low temperature electronic transport characterization in a high quality InAs quantum well (QW), grown by molecular-beam epitaxy. A specimen of a standard 5mm × 5mm geometry is cleaved from an as-grown wafer. Eight indium contacts are diffused symmetrically around the perimeter of the specimen to form ohmic contacts to the 2D electron gas (2DEG) realized in the InAs QW. The specimen is then cooled down to the liquid helium temperature, and the magneto-resistance Rxx and the Hall resistance Rxy are measured as a function of magnetic (B) fields. Rxx displays the typical Shubnikov-de Haas oscillations. For Rxy, it is linear with B in the low field range but displays quantized plateaus at high B fields.<br/>Our low temperature measurements demonstrate high quality 2DEG in our InAs QW. In the future, we will examine the SOC strength in InAs by analyzing the weak-antilocalization effect. Results from this study will provide critical information for the realization of MQPs.