Periodic Reporting for period 1 - PALANTIRI (Phase-sensitive Alteration of Light colorAtioN in quadri-parTIte gaRnet cavIty)
Período documentado: 2022-10-01 hasta 2023-09-30
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 the 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 a 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 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 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.
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 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.
Developing schemes for ecient and broadband frequency conversion of quantum signals is an ongoing challenge in the eld of modern quantum information. The coherent conversion between microwave and optical signals is an especially important milestone towards long-distance quantum communication. In this work, we propose a two-stage conversion protocol, employing a resonant interaction between magnetic and mechanical excitations as a mediator between microwave and optical photons. During the first period, the consortium has largely laid the groundwork to focus the consortium's efforts for the remainder of the project. It has demonstrated its ability to build high quality suspended garnet structures. It has also begun to build the various spectrometers that will be needed to characterize the physical properties, both magnetic and elastic, of these suspended structures. It has also identified the spatio-temporal vector field pattern of the eigenmode with the most efficient quadripartite coupling. This achievement is the result of a combined effort of 4 technical WPs.
WP1 – Processing and integration (MLU):
The optimal geometry of both the microwave antenna and the suspended disk has been designed and fabricated. The development of a material recipe for the growth of high quality garnet films on Si has been also initiated in parallel.
WP2 – Finesse (CNRS):
The spectral signature of a suspended YIG slabs detached from is pedestal has been measured by magnetic resonance force microscopy. While the preliminary results shows significant inhomogeneous broadening. It is not yet clear at this stage if the broadening results from relaxation of constraint once the crystal is detached from the growth substrate. In order to reduce the sensitivity to deformation, we have started a new process to produce thicker suspended magnetic structures.
WP3 – Coherent coupling (CNRS):
During the first period, two new home-made experimental setups were built to measure the opto-mechanical coupling. The first is a dedicated Brillouin light scattering spectrometer operating inside an electromagnet. The seond is a scanning interferometer to map the elastic deformation oscillating at microwave frequencies with a spatial resolution reaching the diffraction limit and a sensitivity of a few picometers. Both setup will allow both a spectral and spatial characterization of the opto-mechanical mechanism.
WP4 – Selection rules (TUD):
An analytical framework for optimizing the quandripartite hybridization has been formulated. The magneto-elsatic coupling in the analytically optimized geometry has been calculated by finite element methods, predicting a coupling strength greater than the expected damping rate in these structures, thus ensuring that a strong coupling regime can be achieved in the chosen geometry..
WP5 – Management, Dissemination & Exploitation (CEA):
The management of PALANTIRI has defined the working environment of the consortium, in particular the sharing and storage of internal data and documents, as well as the external outreach to a broader audience in a public relations effort to promote the goals of the project. A logo and website have been designed in order to create a brand image. https://project-palantiri.eu/
WP1 – Processing and integration (MLU):
The optimal geometry of both the microwave antenna and the suspended disk has been designed and fabricated. The development of a material recipe for the growth of high quality garnet films on Si has been also initiated in parallel.
WP2 – Finesse (CNRS):
The spectral signature of a suspended YIG slabs detached from is pedestal has been measured by magnetic resonance force microscopy. While the preliminary results shows significant inhomogeneous broadening. It is not yet clear at this stage if the broadening results from relaxation of constraint once the crystal is detached from the growth substrate. In order to reduce the sensitivity to deformation, we have started a new process to produce thicker suspended magnetic structures.
WP3 – Coherent coupling (CNRS):
During the first period, two new home-made experimental setups were built to measure the opto-mechanical coupling. The first is a dedicated Brillouin light scattering spectrometer operating inside an electromagnet. The seond is a scanning interferometer to map the elastic deformation oscillating at microwave frequencies with a spatial resolution reaching the diffraction limit and a sensitivity of a few picometers. Both setup will allow both a spectral and spatial characterization of the opto-mechanical mechanism.
WP4 – Selection rules (TUD):
An analytical framework for optimizing the quandripartite hybridization has been formulated. The magneto-elsatic coupling in the analytically optimized geometry has been calculated by finite element methods, predicting a coupling strength greater than the expected damping rate in these structures, thus ensuring that a strong coupling regime can be achieved in the chosen geometry..
WP5 – Management, Dissemination & Exploitation (CEA):
The management of PALANTIRI has defined the working environment of the consortium, in particular the sharing and storage of internal data and documents, as well as the external outreach to a broader audience in a public relations effort to promote the goals of the project. A logo and website have been designed in order to create a brand image. https://project-palantiri.eu/
WP1 – Processing and integration (MLU):
We have achieved the fabrication of suspended YIG mushrooms.
WP2 – Finesse (CNRS):
MRFM has provided the measurement of the linewidth in a frrestanding slab of YIG deposited on a microwave antenna
WP3 – Coherent coupling (CNRS):
We have built home-made setup to measure the spatio-temporal profile of acoustic waves
WP4 – Selection rules (TUD):
We have identified the optimal process to enhance the efficiency of the interconversion. An analytical framework on the optimization of the four cooperativities of the quadripartite coupling has been formulated. Based on estimates for the coupling strengths under optimized conditions for yttrium iron garnet, we predict close to unity conversion eciency without the requirement of matching cooperativities. We predict a conversion band- width in the regions of largest eciency of the order of magnitude of the coupling strengths that can be further increased at the expense of reduced conversion eciency.
WP5 – Management, Dissemination & Exploitation (CEA):
3 publications have been submitted during the first period, with one paper published in the high impact journal Phys. Rev. X. In parallel the work performed in the project has been presented at 3 international workshops : Cavitronics in Erlangen, MMM in Sendai, and Magnonics in Le Touquet.
A patent has been filed on the use magnetic elements as transducer of elastic modes with well-defined angular momenta.
We have achieved the fabrication of suspended YIG mushrooms.
WP2 – Finesse (CNRS):
MRFM has provided the measurement of the linewidth in a frrestanding slab of YIG deposited on a microwave antenna
WP3 – Coherent coupling (CNRS):
We have built home-made setup to measure the spatio-temporal profile of acoustic waves
WP4 – Selection rules (TUD):
We have identified the optimal process to enhance the efficiency of the interconversion. An analytical framework on the optimization of the four cooperativities of the quadripartite coupling has been formulated. Based on estimates for the coupling strengths under optimized conditions for yttrium iron garnet, we predict close to unity conversion eciency without the requirement of matching cooperativities. We predict a conversion band- width in the regions of largest eciency of the order of magnitude of the coupling strengths that can be further increased at the expense of reduced conversion eciency.
WP5 – Management, Dissemination & Exploitation (CEA):
3 publications have been submitted during the first period, with one paper published in the high impact journal Phys. Rev. X. In parallel the work performed in the project has been presented at 3 international workshops : Cavitronics in Erlangen, MMM in Sendai, and Magnonics in Le Touquet.
A patent has been filed on the use magnetic elements as transducer of elastic modes with well-defined angular momenta.