Indian scientists develop a non-invasive method to measure quantum atom density

Indian scientists at the Raman Research Institute have developed a non-invasive technique to measure the local density of atoms in quantum systems without disturbing their fragile states, a breakthrough that could aid the development of quantum computing and sensing technologies.

The researchers demonstrated a method called Raman Driven Spin Noise Spectroscopy, or RDSNS, which allows scientists to determine how densely atoms are packed while preserving their quantum properties. The technique offers high accuracy, real-time measurement, and minimal disturbance, addressing a long-standing challenge in experimental quantum physics.

Quantum experiments often use clouds of atoms cooled to near absolute zero, where observing the atoms can disrupt or destroy their quantum states.

Conventional imaging methods, such as absorption and fluorescence imaging, can fail in dense or fast-changing systems due to heating, scattering, or long exposure requirements.

The RDSNS technique instead detects natural fluctuations in atomic spins. A weak laser beam passing through the atomic cloud picks up subtle changes in light polarisation caused by these fluctuations. The signal is enhanced using additional laser beams that gently drive atoms between nearby spin states, amplifying the signal significantly.

Using this method, researchers measured density changes in potassium atoms held in a magneto-optical trap and found that local density dynamics occurred faster than global measurements suggested. The technique proved accurate when compared with fluorescence-based measurements.

The research, supported by India’s National Quantum Mission, may help advance quantum technologies that rely on precise knowledge of atom density.