Materials for Silicon Quantum Dots and their Impact on Electron Spin Qubits

Abstract

Quantum computers have the potential to efficiently solve problems in logistics, drug and material design, finance, and cybersecurity. However, millions of qubits will be necessary for correcting inevitable errors in quantum operations. In this scenario, electron spins in gate‐defined silicon quantum dots are strong contenders for encoding qubits, leveraging the microelectronics industry know‐how for fabricating densely populated chips with nanoscale electrodes. The sophisticated material combinations used in commercially manufactured transistors, however, will have a very different impact on the fragile qubits. Here some key properties of the materials that have a direct impact on qubit performance and variability are reviewed.

Coherent control of electron spin qubits in silicon using a global field

“…Note that for SiMOS spin qubit devices, the qubit frequencies are different due to the variability in spin-orbit effects caused by the imperfections (e.g. surface roughness) in the Si-SiO 2 interface 37 . By monitoring how the qubit frequencies change due to Stark shifts from voltages applied to the different gates (see analysis in the Supplementary Note 5), we deduce that the spin resonance signal at the higher frequency (for a fixed B 0 ) corresponds to the spin under gate D1, whilst the other resonance belongs to the spin under D2.…”

Transition metal quantum dots for the electrocatalytic hydrogen evolution reaction: recent progresses and challenges

“…5) like photochemical reagents, 66 light emitting diodes, 67 catalysis, 68 solar cells, 69 due to their properties such as photochemical, 70-72 magnetic, [73][74][75][76] optoelectrical, [77][78][79] piezoelectrical. [80][81][82][83] QDs with enhancing properties exhibited by the semiconductors are proved as an effective electrocatalysts in HER in the current research. Predominantly, due to reduction in size, the metallic materials will have a wider surface area, less mechanical fracture and larger active sites, amidst the above attractive characteristics, metallic QDs lack good electrical conductivity and have a higher tendency to agglomerate, 84,85 thus making them inefficient as a single-component electrocatalyst, but QDs effectively work when they are engineered in composites.…”

Quintet formation and exchange fluctuations: The role of stochastic resonance in singlet fission

“…Our results, presented in Fig. 2 for a particular choice of zero-field splitting and exchange parameters [31], show the average population p 5 (t) of the quintet manifold 5…”

“…Exchange noise can arise from many sources, including thermally-driven structural fluctuations, switching in nearby charge centres [1,2], and electrical noise in voltages applied to control gates [3] in engineered systems. Quantum dot systems [4,5] are a prime example of this and, due to their potential applications in quantum information processing, advanced approaches to quantifying the impact of exchange noise have been developed [6]. Fundamentally, these approaches have sought to efficiently model open quantum systems (OQS), i.e., quantum systems coupled to their environment [7], as a way to understand and improve fidelity of gate operations [8,9].…”

“…Since SF proceeds rapidly from a singlet state, it is assumed to form the net-singlet triplet-pair 1 (TT) , i.e., a pair of triplets whose spins couple with zero net spin. However, recent spectroscopic studies have revealed that the triplet-pair undergoes spin dynamics, forming triplet 3 (TT) and quintet 5 (TT) multiexcitons [20,21], before dissociating into uncorrelated triplet excitons. High-spin states such as quintets have fundamental implications for the use of SF in photovoltaics [21], and have also been considered for quantum information processing applications [22]; understanding how these high-spin states form in SF, and how material design can affect their formation, presents an important unanswered question in the field [22].…”