Report
Teaser, summary, work performed and final results
Periodic Reporting for period 1 - QUINTESSENS (QUantum INTErface between Superconducting circuits and Spin ENSemble)
Teaser
Dopants in silicon appear as a key building block for quantum information processing as they can be used to store quantum information thanks to the long coherence time of the spin of the donor nucleus. Dopants also have the potential to serve as quantum nodes, providing...
Summary
Dopants in silicon appear as a key building block for quantum information processing as they can be used to store quantum information thanks to the long coherence time of the spin of the donor nucleus. Dopants also have the potential to serve as quantum nodes, providing interfaces between different quantum systems. The quantum state of their electron spins can be exchanged with their nuclear spins, or with microwave photons. The coupling to microwave photons brings about the tantalising opportunity to create a long-lived solid-state quantum memory for superconducting circuits which are particularly efficient at manipulating quantum information but so far lack the possibility to store it for long times.
In order to achieve such a spin memory for superconducting circuits, it is necessary to be able to transfer a qubit between the two systems much more rapidly than it decoheres in either system. The goal of this project is to create such an interface. Indeed this part is still missing and is of crucial importance to build scalable devices for quantum information. Fabrication of a scalable quantum device able to process quantum information and store the quantum information is of prime importance and would have a tremendous impact for various field of the society ranging from cryptography to simulation of complex systems for climate modeling, chemistry, …
The overall objectives for this project are to :
i) optimize dopants implantation in silicon,
ii) design, fabricate and characterize high-quality-factor tunable superconducting resonators able withstand magnetic field,
iii) build a setup to characterize spin-superconductor interaction,
iv) demonstrate coherent exchange.
Work performed
During this project, the two folds of the hybrid system have been explored. A set of implantations with various parameters have been performed in a partner university in order to optimize the dopants’ implantation. The implanted samples were then characterized by ESR, in the host institution. The effect of strain generated by the superconducting film deposited on top of the silicon has also been studied. It is of prime importance because strain can drastically alter the properties of the dopants.
On the resonator part, the design was optimized through simulation. Devices were then fabricated using the clean room facilities at the host institution. This part included the development of a multi-step process to achieve high quality factor superconducting resonators. On some samples a Ne-FIB process has been develop to create nanoSQUID, a new an essential development for high-Q tunable resonators. Low temperature measurements of Nb and NbN resonator demonstrated magnetic field tunable resonator able to withstand magnetic field while maintaining a high enough quality factor to allow for the coherent exchange between the superconducting resonators and spins of dopants.
A microwave measurement setup was also implemented in a dilution fridge in order to characterize superconducting resonators at low temperature.
Final results
This work was a first demonstration of tunable superconducting resonators able to withstand magnetic field while maintaining a relatively high quality factor. These specific properties are of prime importance for building and realization of hybrid spin-superconducting devices and it will benefit the whole quantum information community.
The superconducting devices developed here also has strong benefits for ESR magnetometry applications, probing small number of spins, it could potentially allow to increase significatively the sensitivity of these detectors. Finally the resonator with embedded nanoSQUID established and validated an emerging fabrication technique for superconducting circuits: namely Neon-FIB.
We made the first demonstration of realization of a highly tunable superconducting resonator fabricated with Ne-FIB, able to withstand magnetic field while maintain high quality factor. The implementation and validation of Ne-FIB technique will benefit to a broad community using nanodevices, beyond the sole field of quantum information.