Building a ubiquitous high-speed Internet from anywhere in the world or a long-range quantum network are two technological challenges that both require the development of a phase-sensitive transducer that can interconvert information from microwave frequencies at which wireless networks or quantum computers operate to optical frequencies, the optimal telecommunications band for long-distance information exchange. However, wireless or quantum signals are extremely fragile and weak, so the coherence between the microwave and optical signals is easily lost. The EU-funded PALANTIRI project aims to create an integrated microchip that performs an embedded coherent up-conversion from microwave to optical frequencies. The idea is to combine microwave photons, acoustic phonons, magnons and optical photons in a single low-loss platform to build a highly efficient device for phase-coherent transduction. The effort is focused on a highly efficient opto-mechanical resonator made of suspended optical cavities, with the ultimate goal of achieving a unity conversion rate.
In PALANTIRI, we propose a radically new approach to opto-mechanics by inserting a magnetic element that maintains high cooperativity both with a mechanical mode through magneto-acoustic coupling and with the microwave antenna through contactless inductive coupling, while exploiting the magnetic texture to achieve perfect matching with an optical mode. The cost of the increased complexity is the gain of a substantial increase in the effective coupling strength: through magneto-acoustic and optomechanical effects we combine the best of both worlds, i.e. a much stronger coupling to microwaves compared to purely mechanical systems and to optical lasers than the purely magnetic systems. This is made possible by recent advances in materials science that allow the fabrication of free-standing micron-sized disks of the ultra-high quality magnetic insulator yttrium iron garnet. The suspension greatly suppresses any leakage of phononic or photonic vibrational energy through the substrate. The subsequent challenge is the implementation of this idea in the form of an on-chip integrated device. The scientific goal of PALANTIRI is to deliver a proof-of-principle on-chip analog coherent frequency converter with high efficiency within 42 months. The delivered phase-sensitive device will provide the breakthroughs needed to radically expand the connectivity capacity of a backhaul network, enabling high-speed Internet access for anyone, anywhere. It will also provide the fundamental building block for the quantum-capable Internet infrastructure of the future.
Project website: PALANTIRI
Contact at SPINTEC: Olivier KLEIN
