Coherently converting information between the microwave frequencies used in wireless networks and quantum computers and the optical frequencies ideal for long-distance communications is a formidable technical challenge. This is because the phase information is 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 solid-state device 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 opto-mechanical resonator to build a highly efficient converter capable 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 the mechanical mode via magneto-elasticity and with the microwave antenna via contactless inductive coupling. The cost of the increased complexity is the gain of a substantial increase in the effective coupling strength: through magneto-elasticity and opto-mechanics we combine the best of both worlds, i.e. a much stronger coupling to microwaves compared to purely mechanical systems and to optical modes 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 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.
