Semiconductor spin qubits based on spin-orbit states are responsive to electric field excitation allowing for practical, fast and potentially scalable qubit control. Spin-electric susceptibility, however, renders these qubits generally vulnerable to electrical noise, which limits their coherence time. Here we report on a spin-orbit qubit consisting of a single hole electrostatically confined in a natural silicon metal-oxide-semiconductor device. By varying the magnetic field orientation, we reveal the existence of operation sweet spots where the impact of charge noise is minimized while preserving an efficient electric-dipole spin control. We correspondingly observe an extension of the Hahn-echo coherence time up to 88 $μ$s, exceeding by an order of magnitude the best reported values for hole-spin qubits, and approaching the state-of-the-art for electron spin qubits with synthetic spin-orbit coupling in isotopically-purified silicon. This finding largely enhances the prospects of silicon-based hole spin qubits for scalable quantum information processing.

Semiconductor-based architectures where quantum information is encoded in the spin degrees of freedom of electrons or holes form an appealing platform for quantum computing. Here we present the current state-of-the-art and discuss prospects and challenges at scientific and technological level.

We discuss the status, challenges and perspectives of "Quantum CAD" for the design and exploration of spin qubits. We highlight the similarities and differences with conventional TCAD for micro-electronics, and focus on design, physics and variability of silicon-on-insulator qubits as an illustration.

The next step after ITER is the demonstration of stable electricity production with a fusion reactor. Key design performance will have to be met by the corresponding power plant demonstrator (DEMO), fulfilling a large number of constraints. System codes such as SYCOMORE, by simulating all the fusion power plant sub-systems, address these questions. To be able to perform design optimizations, simplified models relying on physical and technological assumptions have to be used, resulting in a large number of input parameters. As these parameters are not always exactly known, the impact of their associated uncertainties on final design performance has to be evaluated. Sensitivity methods, by measuring the relative influence of inputs on the figures of merit of the design, allow the dominant parameters to be selected. This information helps the search for optimal working points, guides the priority for technical improvements and finally allows meaningful inputs for uncertainty propagation to be selected. A full set of sensitivity methods and their application to an ITER and DEMO design will be presented, discussing both the statistical method behaviours and the physical results. Plasma shape parameters (minor radius and plasma elongations) share half of the net electricity power sensitivity for the DEMO 2015 design, while the toroidal magnetic field and the 95% safety factor are responsible for 23% and 17% of the electric power sensitivity, respectively. The plasma minor radius is responsible for 45% of the pulse duration sensitivity for the DEMO 2015 design, while plasma physics parameters drive % of the pulse duration sensitivity.

The next step for fusion energy after the ITER tokamak is the demonstration power plant DEMO. In this framework, system codes are used to address high-level key design issues for the DEMO pre-conceptual phase. They aim at capturing the interactions between the subsystems of a fusion reactor. SYCOMORE is a modular system code which includes physics and technology models coupled to an optimizer in order to explore a large design parameter space. In the present paper, trade-off studies focused on technology modules are reported including the influence of some design-driving assumptions on the reactor performances and size, starting from a European DEMO1-like design (more than 500MW net electric power and 2 h burn duration). The increase of the mechanical stress limits in TF and CS magnets can help reducing the reactor size, slightly more when high temperature superconductors are used in the TF coil. The tritium breeding ratio can be improved to more than 1.10 by a moderate increase of the size, but the tritium burn-up ratio needs one additional meter of major radius for every percent increase. Divertor coolant options are also compared, showing some differences between helium, hot and cold water scenarios at various incident divertor heat fluxes.

In the framework of prospective activities for a demonstration power plant, DEMO will be the next step for fusion energy following ITER tokamak. Some of the key design top-level questions can be addressed using macroscopic system-level codes. Those system codes aim to model the whole fusion plant with all its subsystems and identify the impact of their interactions on the design choices. The code SYstem COde for MOdelling REactors (SYCOMORE) is a modular system code developed to address key questions relevant to the tokamak fusion reactor design by giving a global view of technology and physic domains. Among all components, SYCOMORE provides a representation of the magnet system, which is of importance regarding some factor of merits, e.g., fusion power or cost. SYCOMORE is ultimately coupled with an optimizer, scanning a high number of operation configurations and ranking them along selected merits. This scanning requires fast computation for each scanned point, so the magnets modeling must meet a tradeoff between simplicity and accuracy. In this paper, we describe that the way toroidal field (TF), central solenoid (CS), and poloidal field (PF) systems modeling in SYCOMORE was chosen taking into consideration the driving design criteria used in usual magnet design method (temperature margin, copper maximum temperature during quench, mechanical resilience in stainless steel structural parts, etc). The specificities of the reduced magnet representation chosen approach will be exposed, and the benchmarking of the simplified model of the two main systems (TF and CS) applied on DEMO reactor configuration will be compared with the output of a more sophisticated design method using an elaborated tool (CEA design tool) that is used to establish the CEA design of DEMO magnets. Together with this benchmark, a discussion on the limits of this approach will be conducted. PF system implementation being in an early stage, the winding pack design module will be exposed (with its associated benchmarking part with CEA design tool), but not the part of PF current reconstruction with respect to system features. Parametric explorations of DEMO configurations will be reported along different conceptual choices related to the magnets (e.g., superconductor material and performances, and structure resilience limits), and the impact on the magnet system main design features will be exposed. Main lines of the future development work will also be presented.