New Sensor Measures Light Particles Nondestructively

Researchers at the University of Innsbruck have demonstrated a method for measuring visible light particles nondestructively. The method could be used to investigate the quantum properties of light.

The team placed an ionized calcium atom between two hollow mirrors, creating a cavity through which visible laser light was guided. “The ion has only a weak influence on the light,” said professor Tracy Northup. The researchers took quantum measurements of the ion. Based on these measurements, they were able to make statistical predictions about the number of light particles in the chamber. They used the measurements first to obtain the ion-cavity interaction strength. Then they reconstructed the cavity photon-number distribution for coherent states and for a state with mixed thermal-coherent statistics, finding overlaps above 99% with the calibrated states.

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