Scientists Optically Levitate Tiny Nanodiamond in Free Space

There may be a new technique that could have implications for the field of quantum information and computing. Scientists have measured for the first time light emitted by photoluminescence from a nanodiamond levitating in free space.

In this latest experiment, the researchers were able to levitate a diamond as small as 100 nanometers (about one-thousandth the diameter of a human hair) in free space. How did they manage it? They used a technique called laser trapping. Essentially, they trapped nanodiamonds in space and, using another laser, caused the diamonds to emit light at certain frequencies. The light emitted by the nanodiamonds was due to photoluminescence. The defects inside the nanodiamonds absorbed photons from the second laser, which excited the system and changed the spin. The system then relaxed and other photons were emitted.

While levitating nanodiamonds doesn't seem like it would have useful applications, it certainly does. It could be used to create optomechanical resonators, which are structures in which the vibrations of the system can be controlled by light. In theory, it could allow researchers to encode information in the vibrations of the diamonds and extract it using the light that they emit.

In the long-term, these nano-optomechanical resonators could include the creation of what are known as Schrödinger Cat states. These macroscopic, or large-scale, systems are in two quantum states at once. In theory, these resonators could also be used as extremely sensitive sensors of forces, measuring tiny displacements in the positions of metal plates or mirrors in configurations used in microchips.

"Levitating particles such as these could have advantages over other optomechanical oscillators that exist, as they are not attached to any large structures," said Nick Vamivakas, one of the researchers, in a news release. "This would mean they are easier to keep cool and it is expected that fragile quantum coherence, essential for these systems to work, will last sufficiently long for experiments to be performed."

Currently, the researchers are looking forward to future experiments. They plan to link the laser cooling of the crystal resonator with the spin of the internal defect to monitor the changes in spin configuration of the internal defect.

The findings are published in the journal Optics Letters.