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Scanning electron microscope micrograph of the micro-magnet deposited on the CMOS type device. A single electron is trapped in the CMOS device and its spin is manipulated by electric dipole spin resonance due to the magnetic field gradient created by the micro-magnet.
The advent of quantum computing requires the interconnection of millions of quantum bits, or "qubits". Several candidates are vying to be the best technology for this. Among them, semiconductor spin qubits offer long coherence times (during which they retain their quantum properties) and are compatible with CMOS structures (complementary metal-oxide-semiconductor), a technology that has enabled the integration of billions of transistors in classical microelectronics. This makes the spin qubit an ideal candidate for reliable and scalable fabrication of quantum processors.
A team from the Neel Institute (CNRS / University of Grenoble Alpes) in collaboration with the CEA (IRIG and Leti) has thus focused on the manufacture and characterization of intermediate solutions that allow the transition from laboratory design to qubits fully compliant with industrial CMOS standards. In particular, the scientists concentrated on the single electron spin qubit in a CMOS device, with an integrated micro-magnet in the manufacturing process.
This micro-magnet generates an inhomogeneous magnetic field in which the electron moves. When this movement occurs at a particular frequency, the electron's spin, which also acts as a nano-magnet, starts to rotate. These are the same principles employed in magnetic resonance measurements. This method enabled the study of the effect of the electron's environment on the spin's decoherence, such as charge fluctuations or nuclear spins, or the presence of excited states related to the silicon's crystal structure. The results indicate that the system's coherence is limited by magnetic noise induced by the nuclear spins of natural silicon, which could easily be improved by enriching the silicon with non-magnetic isotope 28.
This study, published in the journal NPJ Quantum Information, provides the first experimental evidence of coherent manipulation of an electron in a structure compatible with traditional microelectronics manufacturing.
References:
Electrical manipulation of a single electron spin in CMOS with micromagnet and spin-valley coupling,
Bernhard Klemt, Victor Elhomsy, Martin Nurizzo, Pierre Hamonic, Biel Martinez, Bruna Cardoso Paz, Cameron Spence, Matthieu C. Dartiailh, Baptiste Jadot, Emmanuel Chanrion, Vivien Thiney, Renan Lethiecq, Benoit Bertrand, Heimanu Niebojewski, Christopher Bäuerle, Maud Vinet, Yann-Michel Niquet, Tristan Meunier, and Matias Urdampilleta, NPJ Quantum Information, published on October 23, 2023.
Doi: 10.1038/s41534-023-00776-8
Open Archives: arXiv