Marc Sanquer

We present recent progress in the implementation of scalable schemes for spin qubit readout in one dimensional quantum registers based on fully-depleted silicon-on-insulator (FDSOI) technology. We compare two schemes both based on rf gate reflectometry. The first one, denoted as dispersive readout, minimizes the device overhead thereby facilitating scale-up to large qubit registers. The second one, denoted as charge-sensing readout, requires additional readout components but is less sensitive to the strength of the interdot coupling facilitating operation in the few-electron regime. We demonstrate single-shot charge sensing with a fidelity of 97% in 5 μs. Finally, we propose a scalable device architecture for linear qubit registers relying on charge-sensing readout.

The recent development of arrays of quantum dots in semiconductor nanostructures highlights the progress of quantum devices toward a large scale. However, how to realize such arrays on a scalable platform such as silicon is still an open question. One of the main challenges lies in the detection of charges within the array. It is a prerequisite to initialize a desired charge state and read out spins through spin-to-charge conversion mechanisms. In this work, we use two methods based on either a single-lead charge detector or a reprogrammable single-electron transistor. By these methods, we study the charge dynamics and sensitivity by performing single-shot detection of the charge. Finally, we can probe the charge stability at any node of a linear array and assess the Coulomb disorder in the structure. We find an electrochemical potential fluctuation induced by charge noise comparable to that reported in other silicon quantum dots.

We fabricated quantum dot devices using a standard SOI CMOS process flow and demonstrated that the spin of confined electrons could be controlled via a local electrical-field excitation, owing to intervalley spin–orbit coupling. We discuss that modulating the confinement geometry via an additional electrode may enable switching a quantum bit (qubit) between an electrically addressable valley configuration and a protected spin configuration. This proposed scheme bears relevance to improve the tradeoff between fast operations and slow decoherence for quantum computing on a Si qubit platform. Finally, we evoke the impact of process-induced variability on the operating bias range.

The ability to manipulate electron spins with voltage-dependent electric fields is key to the operation of quantum spintronics devices, such as spin-based semiconductor qubits. A natural approach to electrical spin control exploits the spin–orbit coupling (SOC) inherently present in all materials. So far, this approach could not be applied to electrons in silicon, due to their extremely weak SOC. Here we report an experimental realization of electrically driven electron–spin resonance in a silicon-on-insulator (SOI) nanowire quantum dot device. The underlying driving mechanism results from an interplay between SOC and the multi-valley structure of the silicon conduction band, which is enhanced in the investigated nanowire geometry. We present a simple model capturing the essential physics and use tight-binding simulations for a more quantitative analysis. We discuss the relevance of our findings to the development of compact and scalable electron–spin qubits in silicon.

We present some recent progress towards the implementation of semiconductor spin quantum bits derived from a Si CMOS technology platform. Our approach consists in developing a foundry-compatible embodiment of the basic building block of quantum information, with a strong potential for large scale co-integration of a quantum core with its mandatory classical control and readout electronics. After introducing various qubit manipulation, coupling and readout schemes, we discuss some prospects for scalability, and in particular some potential advantages of the FDSOI technology.

The definition of the ampere will change in the next few years. This electrical base unit of the S.I. will be redefined by fixing the value of the charge quantum, i.e., the electron charge e. As a result electron pumps will become the natural device for the mise en pratique of this new ampere. In the last years semiconductor electron pumps have emerged as the most advanced systems, both in terms of speed and precision. Another figure of merit for a metrological device would be its ability to be predictible and shared. For that reason a mature fabrication process would certainly be an advantage. In this article we present electron pumps made within a CMOS (Complementary Metal Oxide Semiconductor) research facility on 300 mm silicon-on-insulator wafers, using advanced microelectronics tools and processes. We give an overview of the whole integration scheme and emphasize the fabrication steps which differ from the normal CMOS route.