Physicists throw world’s smallest disco party with levitating nanodiamonds

A new milestone in levitate optomechanics has been reached by Professor Donggang Li’s group, who observed the Perry phase of electron spins in nanoscale diamonds levitated in vacuum.

Physicists at Purdue are hosting the world’s smallest disco party. A disco ball is a glowing nanodiamond that spins and spins at an incredibly high speed. The glowing diamond emits and scatters multi-colored lights in different directions as it rotates. The party continues to study the effects of fast spin on the spin qubits in their system and observes the Berry phase.

A team led by Donggang Li, professor of physics and astronomy and electrical and computer engineering at Purdue University, published their results. Natural communication. Critics of the publication He described the work as „an exciting moment for the study of rotating quantum systems and levodynamics” and „a new milestone for the levitate optomechanics community”.

„Imagine tiny diamonds floating in empty space or a vacuum. Inside these diamonds are spin qubits that scientists can use to make precise measurements and explore the mysterious relationship between quantum mechanics and gravity,” explains Li, who is a member of Purdue’s Institute for Quantum Science and Engineering. Experiments with floating diamonds have had trouble preventing their loss to vacuum and studying spin qubits. However, in our work, we successfully extrude a diamond in high vacuum using a special ion trap. For the first time, we can observe and control the behavior of spin qubits inside a levitated diamond in high vacuum.

Observation of the Berry phase

The team made the diamonds spin at an incredible speed – 1.2 billion times per minute! By doing this, they were able to observe how the rotation affected the spin qubits in a unique way known as Perry phase.

„This advance enables us to better understand and study the fascinating world of quantum physics,” he says.

Fluorescent nanodiamonds with an average diameter of 750 nm were produced by high-pressure, high-temperature synthesis. These diamonds are then irradiated with high-energy electrons to create nitrogen-vacant colored centers that provide electron spin qubits. When illuminated by a green laser, they emit red light, which can be used to read their electron spin states. An additional infrared laser was shone on the levitated nanodiamond to monitor its rotation. Like a disco ball, as the nanodiamond spins, the direction of the scattered infrared light changes, carrying information about the nanodiamond’s rotation.

The authors of this paper are mostly from Purdue University and are members of Li’s research group: Yuanbin Jin (postdoc), Kunhong Shen (PhD student), Jingyu Gao (PhD student), and Peng Zhu (recent PhD graduate). Li, Jin, Shen and Zhu conceived and designed the project and Jin and Shen developed the system. Jin then performed the measurements and calculations and the group discussed the results collectively. The two non-Purdue authors are Alejandro Crain, a principal member of the technical staff at Sandia National Laboratories, and Chong Zhu, an assistant professor at Washington University in St. Louis. Li’s group discussed the experimental results with Crain and Zhu, who provided suggestions for improving the experiment and manuscript.

Jin explains, „For the design of our integrated surface ion trap, we used the commercial software COMSOL Multiphysics to perform 3D simulations. We calculated the trap state and microwave transmittance using different parameters to optimize the design. We added additional electrodes to conveniently control the motion of the levitated diamond. And for fabrication, we used photolithography to create a A surface ion trap is fabricated on a sapphire wafer A 300-nm-thick layer of gold is deposited on the sapphire wafer to form the electrodes of the surface ion trap.

Diamond controls spin

So which way do diamonds spin and can they manipulate speed or direction? Shen says yes, they can adjust spin direction and levitation.

„The driver can adjust the voltage to change the direction of rotation,” he explains. „The levitated diamond can rotate around the z-axis (perpendicular to the surface of the ion trap), either clockwise or counterclockwise depending on our driving signal. If no driving signal is applied, the diamond will rotate in all directions like a ball of yarn.

Levitating nanodiamonds with embedded spin qubits have been proposed for precise measurements and to create large quantum superpositions to test the limits of quantum mechanics and the quantum nature of gravity.

„General relativity and quantum mechanics were two of the most important scientific breakthroughs of the 20th century.^Th century However, we still don’t know how gravity will be measured,” says Li. „Achieving the ability to experimentally probe quantum gravity will be a huge breakthrough. Additionally, rotating diamonds with embedded spin qubits provide a platform to study the connection between mechanical motion and quantum spins.

This discovery could have a ripple effect in industrial applications. Levitating micro- and nano-scale particles in a vacuum could serve as ideal accelerometers and electric field sensors, Li says. For example, the US Air Force Research Laboratory (AFRL) is using optically-levitate nanoparticles to develop solutions to critical problems in navigation and communications.

„At Purdue University, we have state-of-the-art facilities for our research on levitate optomechanics,” says Li. „We have two specialized, home-built systems dedicated to this area of ​​research. Additionally, we have access to shared facilities at the Birk Nanotechnology Center, which enables us to develop and characterize an integrated surface ion trap on campus. We are fortunate to have talented students and postdocs capable of conducting cutting-edge research. More , my team has been working in this field for ten years and our extensive experience has allowed us to move forward quickly.

Reference: Yuanbin Jin, Kunhong Shen, Peng Zhu, Xingyu Gao, Chong Zhu, Alejandro J. Crain and Donggong Li, 13 June 2024, “Quantum control and Perry phase electron-spinning levitate diamonds in high vacuum” Natural communication.
DOI: 10.1038/s41467-024-49175-3

This research was supported by the National Science Foundation (grant number PHY-2110591), the Office of Naval Research (grant number N00014-18-1-2371), and the Gordon and Betty Moore Foundation (grant DOI 10.37807/gbmf12259). The project is also partially supported by the Laboratory Directed Research and Development Program at Sandia National Laboratories.