Levitation has historically captivated both the imaginations of magicians and the precise interests of physicists. The visual spectacle of objects floating seemingly unsupported in midair conjures a sense of wonder, but beyond the spectacle lies a profound utility for scientific experimentation. Levitation allows researchers to isolate objects from physical contact and environmental interference, an essential factor for studying delicate phenomena and for enhancing measurement sensitivity. In particular, levitating rotors have attracted extensive attention due to their ability to detect subtle physical forces by relying on meticulously controlled angular momentum and torque. Recent advances in magnetic levitation are now pushing these devices into new regimes of performance, dramatically reducing frictional losses and opening doors to quantum-level investigations.
Traditional microscale levitation systems often employ optical or electrical methods to suspend particles, requiring highly sophisticated and sensitive apparatuses. Far from the lab bench’s fragile environments, macroscopic magnetic levitation systems offer a compelling alternative. These systems operate at room temperature and are far more resilient against environmental perturbations such as vibrations or air currents. Magnetically levitated macroscopic rotors, unlike microscale atomic particles, must contend with Earth’s gravitational pull directly, making them uniquely suitable for practical applications like gravimetry – the precise measurement of gravitational fields – as well as foundational inquiries into the crossover between classical physics and quantum phenomena. However, persistent physical challenges have historically limited their performance.
A key limitation in magnetic levitation systems stems from eddy-current damping. When a conductor moves through a non-uniform magnetic field, circulating currents, known as eddy currents, arise within the material. These currents generate secondary magnetic fields that oppose the rotor’s movement, effectively acting as friction and thereby dissipating energy and disrupting precision measurements. Although eddy-current damping serves useful purposes in various industrial applications, such as power tool brakes and train systems, it represents a formidable barrier for researchers aiming to measure physical effects with ultra-high sensitivity. Overcoming this obstacle has remained a long-standing challenge in rotor levitation technology.
Recently, researchers from the Okinawa Institute of Science and Technology (OIST) have unveiled a novel approach that elegantly circumvents eddy-current damping, marking a significant breakthrough for macroscopic levitating rotors. The team, led by professor Jason Twamley and including PhD student Daehee Kim, developed a graphite rotor disk paired with rare-earth magnets, arranged with perfect axial symmetry to eliminate the usual eddy-current friction during rotation. Rather than reducing damping by material modifications alone, this approach leverages fundamental geometric and electromagnetic principles to achieve near frictionless rotation in an idealized setup, as verified through comprehensive mathematical modeling, numerical simulations, and experimental validation.
The conventional wisdom surrounding eddy currents dictates that any movement of a conductive object in a varying magnetic field generates opposing currents that drain energy and cause drag. However, the OIST team found a profound exception: if the object’s rotation axis perfectly aligns with the symmetry axis of the magnetic field, the rotor experiences no change in magnetic flux during spin. Because the flux remains constant, eddy currents cannot form in response to rotation, effectively nullifying this source of damping. Their experiments used a centimeter-scale disk made solely of graphite, a diamagnetic conductor with favorable levitation properties and low mass, maximizing the levitative force without adding heavier composite materials.
This research builds on earlier developments by the OIST Quantum Machines Unit, who previously engineered composite graphite plates embedded in silica and wax matrices to reduce eddy-current damping. While that design confined eddy currents within microscopic grains of graphite, greatly reducing friction, the inclusion of wax compromised the levitative strength, limiting the device’s utility when weight was added—such as mirrors or other components needed for rotation tracking and measurement tasks. The new purely graphite rotor eliminates these constraints, combining strong magnetic suspension with an intrinsic evasion of eddy-current losses.
Achieving ultra-low friction in a levitated rotor is a paramount goal because it directly correlates with the device’s sensitivity to subtle forces and its potential to approach quantum mechanical behavior. The OIST rotor can be spun up with minimal energy loss, making it a candidate for high-precision gyroscopes capable of detecting infinitesimal rotational changes. Conversely, the rotor can be gradually spun down and cooled, aiming to reach the quantum regime where macroscopic superposition and quantum gravity effects might be observed. Such experiments could provide unprecedented insights into the foundation of quantum physics as it bridges to classical phenomena.
Realizing the ideal system relies heavily on precise engineering. Any imperfections in the rotor disk or asymmetries in the magnetic field can reintroduce flux variations, triggering eddy currents and damping. The researchers emphasize that the limiting factors now become mechanical machining precision and ambient air friction, which can be minimized by operating under near-perfect vacuum conditions. Advances in magnet fabrication and refined machining techniques will further enhance the symmetry and stability of the levitated rotor, pushing the boundaries of measurable precision to scales of mere millimeters or even beyond.
From a practical standpoint, this breakthrough paves the way for next-generation sensors and instruments that operate with unprecedented sensitivity and stability at room temperature. Unlike microscale levitation systems that demand intricate lasers or cryogenic environments, the OIST rotor’s macroscopic magnetic levitation operates in accessible laboratory conditions and remains robust against environmental noise. This combination makes it an attractive candidate for diverse applications, including precise inertial navigation, gravimetric mapping, and fundamental physics experiments that test the limits of wave-particle duality and the nature of vacuum gravity.
Looking forward, the implications of achieving near-zero eddy-current damping in magnetically levitated rotors span scientific disciplines. Precise measurement apparatuses based on this technology could be deployed aboard spacecraft or satellites, where microgravity environments enhance operational stability and where extreme sensitivity is needed for probing dark matter interactions, gravitational waves, or subtle deviations in fundamental constants. The platform may also enable experimental tests of rotational quantum superposition states at scales never before possible, potentially shedding light on how classical macroscopic objects transition to quantum behavior.
The OIST team’s comprehensive study was published in Communications Physics in October 2025, marking a milestone in macroscopic quantum rotor development. By blending rigorous theoretical analysis with hands-on experimental insights, they have demonstrated a path forward that blends elegant physics with practical engineering to eradicate one of the longest-standing obstacles in magnetic rotor levitation research. Their work exemplifies how precision engineering guided by fundamental electromagnetic theory can unlock new frontiers of measurement and quantum science accessible at room temperature and human-friendly scales.
In summary, the creation of a diamagnetically levitated graphite rotor that completely sidesteps eddy-current damping effects represents a landmark achievement. This advances the state-of-the-art from complex, fragile microscale levitation setups toward robust, scalable macroscopic systems with ultra-low frictional losses. Such systems hold promise not only for refined classical sensing applications but also for pioneering quantum mechanical research. The elegant exploitation of axial symmetry to suppress rotational eddy currents unlocks a realm where frictionless, nearly ideal macroscopic rotors operate, merging the dream of levitation with the rigorous demands of experimental physics in unprecedented ways.
Subject of Research: Not applicable
Article Title: A magnetically levitated conducting rotor with ultra-low rotational damping circumventing eddy loss
News Publication Date: 10-Oct-2025
Web References:
- Communications Physics: https://doi.org/10.1038/s42005-025-02318-4
References:
Kim, D., Twamley, J., et al. (2025). “A magnetically levitated conducting rotor with ultra-low rotational damping circumventing eddy loss,” Communications Physics. https://doi.org/10.1038/s42005-025-02318-4
Image Credits: Adrian Skov (OIST)
Keywords: Magnetic levitation, eddy-current damping, diamagnetic rotor, graphite disk, rare earth magnets, quantum regime, ultra-low friction, gyroscope, quantum machines, precision sensors, axial symmetry, vacuum gravity
