Engineered platforms for topological superconductivity and Majorana zero modes

Abstract

Among the major approaches that are being pursued for realizing quantum bits, the Majoranabased platform has been the most recent to be launched. It attempts to realize qubits which store quantum information in a topologically-protected manner. The quantum information is protected by its nonlocal storage in localized and well-separated Majorana zero modes, and manipulated by exploiting their nonabelian quantum exchange properties. Realizing these topological qubits is experimentally challenging, requiring superconductivity, helical electrons (created by spin-orbit coupling) and breaking of time reversal symmetry to all cooperate in an uncomfortable alliance. Over the past decade, several candidate material systems for realizing Majorana-based topological qubits have been explored, and there is accumulating, though still debated, evidence that zero modes are indeed being realized. This paper reviews the basic physical principles on which these approaches are based, the material systems that are being developed, and the current state of the field. We highlight both the progress made and the challenges that still need to be overcome.

Multi-particle scattering and breakdown of the Wiedemann-Franz law at a junction of N interacting quantum wires

“…Based on the results of this paper, in [55] we conclude that the emergence of MZMs and their action in inducing the topological Kondo effect becomes the effective mechanism triggering the (universal) breakdown of the WFL at the junction and that such phenomenon can be exploited for detection of the presence of MZMs at the junction. While standard charge transport experiments cannot presently distinguish MZMs from other effects unambiguously [57][58][59][60][61], our proposal provides a new experimental test, aimed at ruling out such ambiguities.…”

Corner states, hinge states and Majorana modes in SnTe nanowires

“…Majorana zero modes are intensively-searched non-Abelian quasiparticles which hold a promise for topological quantum computing [43][44][45]. The key ingredients for realizing Majorana zero modes are usually thought to be spin-orbit coupling (spin-rotation-symmetry breaking field), magnetic field (time-reversal-symmetry breaking field) and superconductivity [46], and there exists a number of candidate platforms for studying Majorana zero modes including chains of adatoms [47][48][49] and various strong spin-orbit coupling materials in the presence of superconductivity and magnetism [50][51][52][53]. SnTe materials are particularly promising candidates for this purpose because in addition to the strong spin-orbit coupling they offer flexibility for introducing symmetry breaking fields such as superconductivity, magnetism and inversion-symmetry breaking fields.…”

Yu-Shiba-Rusinov qubit

“…While superconducting-circuit based qubits have been at the forefront of the immense recent progress, proposals that utilize the low-energy bound states in superconductors, i. e. the Andreev levels, have been also under intense scrutiny for quantum computing [15][16][17][18][19][20][21]. The reasons are two-fold: (i) the dimensions of Andreev states-based qubits (∼ µm) are typically much smaller than the sizes of the conventional superconducting qubits (∼mm), which facilitates designing quantum registers with higher qubit densities and (ii) they constitute the building blocks of topological quantum computers based on Majorana zero modes, which have experienced significant theoretical and experimental research efforts [22][23][24][25][26][27].…”