Generating dark and entangled states in optical cavities: unlocking new possibilities in quantum metrology

Physicists have been working hard to improve the accuracy of atomic clocks, which are the most precise timing devices currently available. A promising way to achieve higher accuracy is to utilize spin squeezed states in clock atoms.

Spin squeezed states are entangled quantum states in which particles work together to counteract their inherent quantum noise. These states provide incredible potential for quantum enhanced measurement and metrology. However, creating spin squeezed states with minimal external noise in optical transitions has always been a challenging task.

The research team led by Anna Maria Ray has been focusing on using optical cavities to generate spin squeezed states. These chambers are composed of mirrors, allowing light to reflect back and forth multiple times. In the cavity, atoms can synchronize their photon emission, producing much brighter light than individual atoms alone. This phenomenon is called superradiance. According to the control method of superradiance, it may lead to entanglement or destruction of the required quantum state.

In their previous work, Rey and her team found that multi-level atoms with two or more internal energy states provided unique opportunities for utilizing superradiance emission. By inducing atoms to cancel each other's emission, they can produce dark states that are not affected by superradiance.

Now, in two recently released studies, the team has revealed a method that can not only generate dark states in optical cavities, but also spin compress these states. This breakthrough opens up exciting possibilities for the generation of entangled clocks and the advancement of quantum metrology.

Researchers have discovered two methods for preparing highly entangled spin squeezed states in atoms. One method is to use a laser to power atoms and place them at special points on a superradiance potential called saddle points. At these points, atoms reshape their noise distribution and become highly compressed. Another method is to transfer the superradiance state to the dark state, utilizing specific points where atoms approach bright spots with zero curvature.
The fascinating aspect of these findings is that even without external laser drive, spin squeezing can be retained. This conversion of compressed state to dark state not only maintains the reduced noise characteristics, but also ensures their survival.

These findings provide new avenues for quantum metrology, enabling more precise measurements and enhancing the capabilities of atomic clocks. By utilizing dark and entangled states within optical cavities, researchers can unleash the potential of quantum enhancement technology and delve deeper into the fascinating world of quantum physics.

Source: Laser Net