Superconducting Silicon Qubit in CMOS Technology

Quantum technology for quantum computing builds on a deep understanding of the fundamental phenomena underlying the quantum properties as well as of the phenomena limiting the qubit performance. In addition, the chosen materials and integration technology need to offer a real potential of scalability and reproducibility, as in the case of CMOS compatible materials including silicon and CMOS process technology.

The aim of SIQUOS is to realise and study a Si gatemon qubit, a gate tuneable transmon qubit composed of a Si Josephson field-effect transistor (JoFET) coupled to a microwave resonator. It represents a valid integrable and scalable alternative to fully metallic superconducting qubits.

SIQUOS will focus on the Si JoFET, i.e., a Si transistor with superconducting source and drain (S&D) contacts, whose non-dissipative supercurrent can be modulated by an electrostatic gate. CMOS-compatible metal silicides, heavily boron (B) doped Si will be used as the superconducting S&D contacts. A comprehensive investigation of the superconductor/Si (S/Sm) interface by means of structural, chemical and low-temperature electronic transport characterisation will be performed. The first and foremost objective of SIQUOS is to optimise the S/Sm interface transparency so as to allow for the transfer of correlated charge carriers from the superconducting contacts into the Si channel and to reach large, reproducible supercurrents. The second objective is to realise Si JoFETs, demonstrating the gate tuneability of the Josephson supercurrent. Thereupon, the third and final objective is to integrate Si JoFETs in a transmon geometry including on-chip capacitors and resonators, and to realise the manipulation of quantum states in Si-gatemon devices. Additionally, the quantum performance of individual qubits will be measured when coupled to a limited number of other qubits to anticipate more complex quantum circuits. The control of the qubit properties in a scalable technology, and therefore the potential to directly assemble a large number of qubits in a functional quantum circuit, is an added major outcome of the project.

To achieve its successful realisation, SIQUOS relies on a multidisciplinary consortium with expertise in material and characterisation science, process integration and quantum nanoelectronics.

CONSORTIUM

• Coordinator: François Lefloch (Université Grenoble Alpes, FR)
• Francesca Chiodi (Université Paris-Saclay, Centre for Nanosciences and Nanotechnologies, FR)
• János Lábár (Centre for Energy Research, HU)
• Shi-Li Zhang (Uppsala University, SE)

PROJECT POSTER: SiQUOS