Periodic Reporting for period 2 - LONGSPIN (Long-range coupling of hole spins on a silicon chip)
Reporting period: 2019-09-01 to 2021-02-28
While spins are excellent quantum bits, their long-range coupling remains a challenge to tackle towards complex quantum computing architectures. LONGSPIN plans to take up this challenge using a microwave photon as a quantum mediator between spin-orbit qubits. The LONGSPIN project presents a unique approach by leveraging a standard silicon-on-insulator CMOS process for the implementation of the qubits co-integrated with superconducting microwave resonators.
This research project will provide a CMOS quantum toolkit with optimized designs and materials for fast and coherent qubits with a profound understanding of the physical limitations to spin-orbit coherence and qubit gate fidelity in silicon. Eventually a microwave photon used as a quantum bus will allow the transfer of quantum information between distant spin-orbit qubits.
Measurements on hole spin-orbit qubit in silicon have allowed LONGPSIN to explore the physical mechanism behind the electrically driven spin resonance (Crippa et al. PRL 2018). With the understanding of this driving mechanism it should be possible to engineer devices to get faster and more coherent spin-orbit qubits.
LONGSPIN also managed to readout a silicon hole spin-orbit qubit by low frequency dispersive gate reflectometry (Crippa et al. Nature Communications 2019). This readout proof-of-concept realized on an isolated double quantum dot should pave the way towards qubit readout in dense array of quantum dots.
LONGSPIN has also started to co-integrate high impedance superconducting microwave resonator and CMOS silicon qubit devices. The resonators are made from Nobium Nitride thin films patterned as coplanar microwave cavities. Impedance as high as 4.5kOhms with internal quality factor above 20.000 under a static magnetic field of 1T has been demonstrated. These microwave cavity characteristics should allow the strong coupling of microwave photons and spin-orbit qubits towards long distance qubit interaction.