2018/09/30 by Ileana-Cristina Benea-Chelmus, Francesca Fabiana Settembrini, Giacomo Scalari +1 · 1 citation
Engineering · Physics and Astronomy · #Atomic physics #Coherence (philosophical gambling strategy) #Computational physics #Electric field #Electromagnetic field #Electromagnetic radiation #Ground state #Mechanical and Optical Resonators #Optics #Photonic and Optical Devices #Physics #Quantum #Quantum Electrodynamics and Casimir Effect #Quantum fluctuation #Quantum mechanics #Terahertz radiation #Vacuum state #quant-ph
paper · pdf · doi:10.1038/s41586-019-1083-9
published as Nature 568, 202-206 (2019)
openalex publication_date 2019/04/10 · arxiv created 2020/09/03 · arxiv updated 2020/09/04 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Quantum mechanics ascribes to the ground state of the electromagnetic radiation zero-point electric field fluctuations that permeate empty space at all frequencies. No energy can be extracted from the ground state of a system and, therefore, these fluctuations cannot be measured directly with an intensity detector. The experimental proof of their existence came thus from more indirect evidence, such as the Lamb shift, the Casimir force between close conductors or spontaneous emission. A direct method to determine the spectral characteristics of vacuum field fluctuations has been missing so far. In this work, we perform a direct measurement of the field correlation on these fluctuations in the terahertz frequency range using electro-optic detection in a non-linear crystal placed in a cryogenic environment. We investigate their temporal and spatial coherence, which, at zero time delay and spatial distance, has a peak value of 6.2⋅ 10-2~V2/m2, corresponding to a fluctuating vacuum field of 0.25 V/m. With this measurement, we determine the spectral composition of the ground state of electromagnetic radiation which lies within the bandwidth of electro-optic detection.