BlueFors Lab Tackles Quantum Interconnection For Scalable Computers

Researchers at the University of Central Florida are addressing a critical hurdle in the development of scalable quantum computers: interconnectivity.

Assistant Professor Jing Xu’s Experimental Quantum Magnetics Laboratory (EQMag Lab) is focusing on an unconventional approach, utilizing magnetic excitations known as magnons to bridge communication gaps between disparate quantum systems. Superconducting qubits, optical photons, mechanical resonators, and spin systems all excel at different tasks but currently struggle to communicate. This work mirrors the challenges of global communication, where signals require conversion for efficient travel; just as a phone message shifts from wireless to optical, quantum systems need translation. “Magnons are useful for quantum systems because they can interact with many different quantum platforms and excitations, such as photons, phonons, and superconducting qubits,” explains Jing, suggesting this method could integrate seamlessly with existing quantum technologies. EQMag Lab Investigates Interconnecting Quantum Modalities This research extends beyond achieving quantum communication; it’s a focused effort to engineer a physics-based solution for interconnectivity, addressing a core challenge hindering the scalability of quantum technologies. The difficulty EQMag Lab is tackling mirrors the complexities of global communication networks, where signals require translation to traverse different mediums. However, unlike classical signal conversion, maintaining the delicate quantum state during transfer presents a significant hurdle. “Our main objective is to build an interface between magnons and microwave photons, which is quantized by the superconducting qubit in quantum circuits,” shares Jing, highlighting the lab’s specific focus on coupling these distinct platforms.

The team is actively designing, fabricating, and testing hybrid chips integrating magnetic materials with superconducting circuits, and in some instances, optical or mechanical components, all on a single substrate to enable precise control and signal transfer analysis. A key challenge lies in the inherent incompatibility between magnetic fields and superconductivity; magnetic fields can disrupt the superconducting state. However, the EQMag Lab team is employing innovative strategies to mitigate this issue. “Superconducting systems don’t necessarily function well when affected by a magnetic field, but we can make them work together,” explains Jing, detailing their use of Type II superconductors, which allow magnetic field penetration in the form of vortices. They are fabricating microstructures with holes to act as pinning centers for these vortices, slowing their movement and preserving superconductivity, and exploring superconductors with higher critical temperatures and utilizing high-frequency signals to control quantum circuits. To facilitate rapid iteration and experimentation, the lab relies on comprehensive nanofabrication capabilities available on campus. “Having full nanofabrication capability on campus is valuable because a fast turnaround is very important for new research areas like quantum magnetics,” Xu explains, emphasizing the importance of a streamlined workflow for this emerging field.

The team’s work is supported by a Bluefors LD400 dilution refrigerator, the first dedicated to quantum information science research in Florida, capable of reaching temperatures of just a few millikelvin, essential for maintaining quantum coherence. “If we can’t reliably achieve this temperature, random thermal excitation will break the quantum coherence and destroy all the quantum states we’ve prepared,” Jing cautions, underscoring the critical role of cryogenic infrastructure in their research. Magnon Behavior as a Quantum Information Carrier The pursuit of scalable quantum computing increasingly focuses on interconnectivity; disparate quantum systems, each adept at specific tasks, require reliable communication pathways to function as a cohesive whole. This approach, still relatively unexplored, aims to bridge the gap between these otherwise incompatible quantum platforms. Magnons, described as atomic-scale waves arising from collective shifts in magnetic moments within a material, offer a unique potential for quantum transduction. Unlike traditional signal conversion reliant on transitioning between wireless and optical formats, utilizing magnons requires maintaining delicate quantum states during transfer, a challenge EQMag Lab is actively addressing through innovative device design and nanofabrication. The lab’s research isn’t solely theoretical; it’s a tightly integrated cycle of device design, nanofabrication, measurement, and iterative refinement, all conducted in-house to accelerate progress. Currently, the EQMag Lab team concentrates on coupling magnons with microwave photons, quantized by superconducting qubits, and exploring interactions with phonons and optical photons. Techniques include fabricating pinning centers within the superconductor and utilizing magnetic materials to attract and slow vortex movement, alongside employing superconductors with higher critical temperatures. Our main objective is to build an interface between magnons and microwave photons, which is quantized by the superconducting qubit in quantum circuits.

Hybrid Chip Design Overcomes Superconductivity Challenges EQMag Lab’s approach centers on utilizing magnons, magnetic excitations, as potential intermediaries, a relatively unexplored avenue in quantum interconnectivity. To preserve superconductivity, the EQMag Lab team employs several strategies, including the fabrication of nanoscale holes within the superconducting film to “pin” these vortices, preventing their movement. “We can fabricate holes on the thin film of the superconductor so that it acts as a pinning center for the superconducting vortices,” says Jing. They leverage higher critical temperature superconductors and utilize high-frequency signals, in the gigahertz or even terahertz range, to maintain quantum coherence. This accelerated workflow not only advances research but also provides students with invaluable hands-on experience, preparing them for future roles in the evolving field of quantum technology. Magnons are useful for quantum systems because they can interact with many different quantum platforms and excitations, such as photons, phonons, and superconducting qubits. Type II Superconductors Enable Magnetic Field Integration Researchers are now focusing on materials that can withstand the inherent conflict between magnetic fields and superconductivity, paving the way for more complex and powerful quantum architectures. This approach requires careful material selection; conventional Type I superconductors are quickly rendered non-superconducting by magnetic fields. The key lies in controlling these vortices to prevent them from disrupting the superconducting state. Several strategies are employed to manage these magnetic intrusions. The lab utilizes nanofabrication techniques to create physical barriers within the superconducting film. Additionally, strategically placed magnetic materials can attract and slow the vortices, preserving superconductivity, and the use of superconductors with higher critical temperatures further enhances stability.

The team leverages high-frequency signals, reaching gigahertz and even terahertz ranges, to maintain quantum circuit control while simultaneously preserving the superconducting state. This integrated approach allows for precise control over interactions and rigorous testing of magnon-based signal transfer between different quantum modalities. The lab’s ability to rapidly design, fabricate, and test these devices is bolstered by on-campus nanofabrication facilities. “We can fabricate a device using the on-campus facilities, cool it down in our cryostat, measure it with electronics, study the result, optimize the parameters, and repeat the process,” Xu explains. Having full nanofabrication capability on campus is valuable because a fast turnaround is very important for new research areas like quantum magnetics. Bluefors LD400 Dilution Refrigerator Accelerates Research Cycles The pursuit of practical quantum technologies often clashes with the realities of experimental timelines; while theoretical advancements progress rapidly, physical validation can lag significantly behind. This isn’t simply about achieving extremely low temperatures, but about dramatically compressing the research cycle, allowing for more rapid iteration and experimentation in a field where precision and stability are paramount. The ability to quickly test and refine designs is crucial for EQMag Lab, which focuses on quantum magnonics and the use of magnetic excitations, known as magnons, to interconnect diverse quantum systems.

The team’s work necessitates a delicate balance between controlling magnetic fields and preserving the superconducting states essential for qubit operation. This complex interplay demands a reliable cryogenic environment, and the LD400 has proven instrumental in achieving that. Prior to its installation, achieving the necessary millikelvin temperatures for quantum coherence could take days or even weeks, severely limiting experimental throughput. “I really appreciate the Bluefors system – it goes from room temperature to 10 millikelvin in about 22 hours,” Jing notes, highlighting the substantial time savings. This accelerated cooldown, coupled with the refrigerator’s overall stability, has fundamentally altered the lab’s workflow.

The team can now dedicate weeks to continuous testing, with minimal downtime for cooling or warming, significantly increasing the amount of data collected and analyzed. “Because the Bluefors refrigerator is so convenient and so stable, we can spend weeks testing devices in a stable environment, bookended by less than one day for cool down and less than one day for warm up,” shares Jing. This efficiency extends beyond research output; it directly impacts the training of the next generation of quantum scientists. The increased experimental access afforded by the LD400 allows students to gain hands-on experience with all stages of the research process, from device design and nanofabrication to measurement and analysis. The lab’s commitment to blending fundamental physics with practical engineering is further strengthened by this capability, enabling a more dynamic and iterative approach to quantum innovation. We also want to couple with other degrees of freedom, such as phonons and optical photons. Source: https://bluefors.com/stories/quantum-magnonics-toward-interconnected-quantum-systems/ Tags: