Analogue cosmological particle creation in an ultracold quantum fluid of light
Steinhauer, Jeff and Abuzarli, Murad and Aladjidi, Tangui and Bienaimé, Tom and Piekarski, Clara and Liu, Wei and Giacobino, Elisabeth and Bramati, Alberto and Glorieux, Quentin

Nature Communications 13, 1--7 (2022)

Nature Communications 13, 1--7  (2022)

The rapid expansion of the early universe resulted in the spontaneous production of cos- mological particles from vacuum fluctuations, some of which are observable today in the cosmic microwave background anisotropy. The analogue of cosmological particle creation in a quantum fluid was proposed, but the quantum, spontaneous effect due to vacuum fluc- tuations has not yet been observed. Here we report the spontaneous creation of analogue cosmological particles in the laboratory, using a quenched 3-dimensional quantum fluid of light. We observe acoustic peaks in the density power spectrum, in close quantitative agreement with the quantum-field theoretical prediction. We find that the long-wavelength particles provide a window to early times. This work introduces the quantum fluid of light, as cold as an atomic Bose-Einstein condensate