Physicists at Purdue University have achieved a groundbreaking milestone in levitated optomechanics, observing the Berry phase of electron spins in nano-sized diamonds levitated in vacuum. Led by Professor Tongcang Li, the team successfully levitated a diamond in high vacuum using a special ion trap and observed how fast rotation affected the spin qubits inside the levitated diamond.
The fluorescent nanodiamonds, with an average diameter of about 750 nm, were produced through high-pressure, high-temperature synthesis and irradiated with high-energy electrons to create nitrogen-vacancy color centers hosting electron spin qubits. By rotating the diamonds at incredibly fast speeds – up to 1.2 billion times per minute – the team was able to observe the Berry phase, a unique phenomenon that helps us better understand quantum physics.
This breakthrough has significant implications for precision measurements and studying the mysterious relationship between quantum mechanics and gravity. The research was supported by the National Science Foundation, the Office of Naval Research, and the Gordon and Betty Moore Foundation, among others.
Levitated Optomechanics: A New Milestone in Quantum Physics
The field of levitated optomechanics has reached a new milestone with the observation of the Berry phase of electron spins in nano-sized diamonds levitated in vacuum by Prof. Tongcang Li’s group at Purdue University. This achievement marks a significant breakthrough in the study of rotating quantum systems and levitodynamics.
The Experiment
The experiment involved levitating fluorescent nanodiamonds, with an average diameter of about 300 nm, above a surface ion trap using alternating voltages applied to four corner electrodes. The diamonds were driven to rotate at high speeds, up to 1.2 billion revolutions per minute (rpm), inducing a phase in the nitrogen-vacancy electron spins inside the diamond. The team used a commercial software, COMSOL Multiphysics, to perform 3D simulations and optimize the design of the integrated surface ion trap.
Controlling the Spin Direction
The researchers demonstrated that they can adjust the spin direction and levitation by controlling the driving voltage. The levitated diamond can rotate around the z-axis (perpendicular to the surface of the ion trap) either clockwise or counterclockwise, depending on the driving signal. If no driving signal is applied, the diamond will spin omnidirectionally.
Implications for Quantum Gravity and Industrial Applications
Levitated nanodiamonds with embedded spin qubits have been proposed for precision measurements and creating large quantum superpositions to test the limit of quantum mechanics and the quantum nature of gravity. This discovery could have significant implications for our understanding of quantum gravity, which remains one of the biggest unsolved problems in modern physics.
Furthermore, levitated micro and nano-scale particles in vacuum can serve as excellent accelerometers and electric field sensors, with potential applications in industrial settings. For example, the US Air Force Research Laboratory (AFRL) is using optically-levitated nanoparticles to develop solutions for critical problems in navigation and communication.
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