2026 Nils Asplund FAST Prize
The 2026 Nils Asplund FAST Prize has been awarded to graduate student Max Tao in Andrei Faraon's research group. Max's proposal on "Hybrid transmon-optics interconnects using micro-transfer printing of rare-earth doped thin films". Max will work with KNI technical staff members Dr. Guy DeRose and Dr. Yonghwi Kim on this project, which will enable micro-transfer printing technology in the KNI Lab, allowing for the fabrication and integration of rare-earth ion crystals and superconducting microwave circuits onto a single device.
The prize comes with $30,000 in unburdened funding for materials and supplies, and up for $10,000 to cover KNI Lab fees for this project during the two year performance period. Congratulations, Max!
Background: Superconducting qubit technologies, particularly transmon qubits, have rapidly emerged as one of the industry's leading platforms for quantum computation. However, these systems still face a major challenge of scaling quantum processors to commercially viable sizes. Quantum networks provide a promising solution to these problems by enabling the long-range connection between a large number of processors via microwave-to-optical transducers. Rare-earth-ion (REI) devices are especially promising for this task due to their long coherence times and ultranarrow optical transitions, which allow efficient coupling to both microwave and optical modes. Thin-film-based implementations would further boost transduction performance due to the lower optical depth of the crystal. However, direct fabrication of thin film REI-doped crystals on superconducting platforms is challenging due to conflicting fabrication requirements. In this project, Max aim's to develop a hybrid transducer that employs micro-transfer printing to heterogenously integrate thin film crystals onto superconducting resonators.
Quantum technologies made rapid developments in quantum computing, communication, and sensing. Additionally, several different platforms have emerged for various applications, such as superconducting qubits for fast, high-fidelity operations, solid-state defects for quantum memories, and photonic integrated circuits for scalable production. Meanwhile, REI-based devices have shown promise for high-efficiency, low-noise transduction and quantum memories with coherences up to hours.
The core challenge for developing these devices is the difficulty in monolithic fabrication since REI crystals and superconducting microwave circuits require mutually incompatible processing conditions. Hybrid integration provides a general solution by allowing each material to be fabricated under optimal conditions and later assembled into a single device. Among hybrid-integration techniques, micro-transfer printing is uniquely promising since it allows deterministic pick-and-place integration of structures with high spatial precision and alignment accuracy. Since the integration occurs after fabrication, we may also take advantage of post-characterization. This is especially important for devices which have low fabrication yield or high fabrication variance, where the best samples may be chosen for integration. Additionally, the post-processing capabilities allow for effective use of valuable materials, such as the REI-doped crystals in Max's case, since only the local device area is affected during the transfer.
Micro-transfer printing has already been employed to demonstrate integration of superconducting single-photon detectors on lithium niobate, quantum dots for single photon emission on silicon oxide, and thin film lithium niobate on silicon nitride for fast modulation. Finally, transfer printing is already an industrially mature technology, supporting array-scale printing, computer-assisted alignment, and high-yield integration, all of which will be necessary for future quantum networks and distributed quantum systems.
Overall, this project will establish a scalable, high-precision hybrid-integration pathway that overcomes fabrication incompatibility and enables the next generation of REI-based quantum transducers and hybrid quantum technologies.
Thin film device fabrication and mounting. (a) Fabrication flow for thin film samples. A sacrificial layer is coated on bulk Yb:YVO4 chips and then bonded to a Si carrier wafer for mechanical grinding and polishing. Then the sacrificial layer is underetched to suspend the thin film for transfer printing. (b) Hybrid thin film device consisting of the thin film on top of a Nb superconducting microwave resonator. We then deposit DBR on top to reflect the optical signal for collection.