Subcycle quantum electrodynamics

• Published in: Nature (London) 2017-01, Vol.541 (7637), p.376-379
• Main Authors: Riek, C., Sulzer, P., Seeger, M., Moskalenko, A. S., Burkard, G., Seletskiy, D. V., Leitenstorfer, A.
• Format: Article
• Language: English
• Subjects: 639/624/400/482; 639/766/400/584; 639/766/483; Analysis; Asymmetry; Electric fields; Electromagnetic radiation; Fluctuations; Humanities and Social Sciences; letter; multidisciplinary; Noise; Noise levels; Optics; Quantum electrodynamics; Quantum theory; Science; Spacetime
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature21024

Few-femtosecond laser pulses are used to generate squeezed mid-infrared light transients and to detect distorted quantum fluctuations of the electric field directly in the time domain. Squeezed light in the mid-infrared An essential technique in the field of quantum optics is the production of squeezed light, which has fluctuations below the vacuum limit, at least, in either the amplitude or phase of the light field. Fluctuations in one of these variables can be reduced at the expense of the other, conforming to Heisenberg's uncertainty limit. Such squeezed states of light are of considerable importance in quantum information systems and precision metrology, including gravitational-wave detectors. In this paper, Leitenstorfer and colleagues open up an exciting direction in this area by generating squeezed light in transient mid-infrared light fields and detecting quantum fluctuations directly in the time domain with few-femtosecond laser pulses. They succeed in observing squeezed and increased quantum fluctuations in adjacent time regions. In contrast to existing quantum detection techniques, the quantum properties can be characterized without the need to amplify or change them. Squeezed states 1 , 2 , 3 , 4 of electromagnetic radiation have quantum fluctuations below those of the vacuum field. They offer a unique resource for quantum information systems 5 and precision metrology 6 , including gravitational wave detectors, which require unprecedented sensitivity 7 . Since the first experiments on this non-classical form of light 8 , 9 , quantum analysis has been based on homodyning techniques and photon correlation measurements 10 , 11 . These methods currently function in the visible to near-infrared and microwave 12 spectral ranges. They require a well-defined carrier frequency, and photons contained in a quantum state need to be absorbed or amplified. Quantum non-demolition experiments 13 , 14 may be performed to avoid the influence of a measurement in one quadrature, but this procedure comes at the expense of increased uncertainty in another quadrature. Here we generate mid-infrared time-locked patterns of squeezed vacuum noise. After propagation through free space, the quantum fluctuations of the electric field are studied in the time domain using electro-optic sampling with few-femtosecond laser pulses 15 , 16 . We directly compare the local noise amplitude to that of bare (that is, unperturbed) vacuum. Our nonlinear approach operates off resonance a