Scalable Quantum Optical Interconnects

Projektinformationen

QUSCALE

ID Finanzhilfevereinbarung: 948265

DOI

10.3030/948265

EK-Unterschriftsdatum 3 November 2020

Startdatum 1 November 2021

Enddatum 31 Oktober 2026

Finanziert unter

• EXCELLENT SCIENCE - European Research Council (ERC)

Gesamtkosten

€ 2 047 500,00

EU-Beitrag

€ 2 047 500,00

Koordiniert durch

CHALMERS TEKNISKA HOGSKOLA AB
Sweden

Periodic Reporting for period 2 - QUSCALE (Scalable Quantum Optical Interconnects)

Berichtszeitraum: 2023-05-01 bis 2024-10-31

Zusammenfassung vom Kontext und den Gesamtzielen des Projekts

The invention of the transistor revolutionized technology, laying the foundation for modern electronic devices and the digital economy. Today, much of our information infrastructure and a significant portion of the global economy depend on this device. Yet, its creation seems almost serendipitous, suggesting that the landscape of possible inventions is far broader than what has been explored. For instance, transistors do not exploit quantum phenomena. Our research aims to develop hardware that harnesses the counter-intuitive properties of quantum superposition and quantum entanglement, paving the way for new technologies such as quantum communication links, quantum sensors, and quantum computers.

Achieving this vision will likely require the integration of various quantum hardware types. In this project, we focus on combining the advantages of optical and microwave quantum chips. Optical systems are adept at transferring information over long distances, while microwave quantum chips excel at performing fast, precise quantum operations. To leverage both, we aim to develop microwave-optical frequency converters, which can enable the seamless transfer of quantum information between microwave and optical frequencies. However, these converters require an optical pump, which generates heat and hampers the low-noise operation necessary for quantum devices.

Our objective is to overcome this limitation by designing frequency converters with enhanced thermal and power management, enabling faster and lower-noise conversion between microwave and optical quantum states. Additionally, we aim to expand the potential applications of these converters by developing new usage protocols, further advancing the field of quantum information processing.

Arbeit, die ab Beginn des Projekts bis zum Ende des durch den Bericht erfassten Berichtszeitraums geleistet wurde, und die wichtigsten bis dahin erzielten Ergebnisse

We have made significant progress in developing the sub-components of microwave-optical converters. Our approach involves first converting microwaves into mechanical motion, which is then transformed into optical waves. In essence, we utilize both electro- and optomechanical conversion processes to efficiently convert microwave photons into optical photons, or vice versa. To mitigate heating, we perform the optomechanical conversion in a fully clamped structure, attached to its substrate without suspension or release steps. Previous attempts with such clamped, or release-free, optomechanical converters have faced issues with weak conversion efficiency, which we address with our new designs. By employing mechanical waves with shorter wavelengths, we avoid energy leakage into the chip substrate. These devices have shown strong optomechanical interactions, and we are currently evaluating their impact on reducing heat.

For complete microwave-to-optics conversion, we use piezoelectricity to excite mechanical waves via microwaves. This step requires a material different from the one used in optomechanical conversion, prompting us to develop a process that integrates the best electromechanical and optomechanical materials. Additionally, we designed a release-free electromechanical structure to facilitate the conversion of microwaves into mechanical waves.

Moreover, we have designed a full microwave-optical converter by connecting the optomechanical and electromechanical sub-components. This design incorporates release-free lithium niobate electromechanical structures with silicon optomechanical structures on a sapphire substrate, enhancing thermal management and improving microwave and mechanical coherence. It relies on short-wavelength mechanical modes that are strongly guided along the chip surface.

We have also proposed and analyzed a novel theoretical scheme to generate optical entanglement using superconducting microwave quantum processors. This method enables small microwave quantum processors to create heralded entangled optical resource states for quantum computation, communication, and sensing, even with imperfect microwave-optical transducers.

Fortschritte, die über den aktuellen Stand der Technik hinausgehen und voraussichtliche potenzielle Auswirkungen (einschließlich der bis dato erzielten sozioökonomischen Auswirkungen und weiter gefassten gesellschaftlichen Auswirkungen des Projekts)

We advanced the state of the art in several areas: the release-free optomechanical converter, the release-free electromechanical converter, the release-free microwave-optical converter, and in understanding how to best apply these converters to quantum information processing tasks. Our optomechanical converter demonstrated an unprecedented interaction strength between light and mechanical waves, surpassing all previous release-free structures. This significant interaction strength has been experimentally confirmed. Similarly, the electromechanical structure exhibited an interaction strength between microwaves and mechanical waves that exceeds previous release-free structures, while maintaining compatibility with optomechanical converters.

Furthermore, our complete microwave-optical transducer design is expected to perform on par with suspended (released) devices, even without improvements in thermalization. We also achieved a breakthrough in understanding how to utilize microwave-optical converters by developing a novel scheme for generating optical entanglement from microwave operations.

By the end of the project, we expect to experimentally realize a fully functional release-free microwave-optical transducer. Our goal is to characterize its performance at cryogenic temperatures and begin using these release-free converters for practical tasks in quantum information processing.