Dynamical Casimir effect in a Josephson metamaterial

By P. Lähteenmäki, G. Paraoanu, J. Hassel, P. Hakonen. Proceedings of the National Academy of Sciences of the United States of America, 2011

303 citations recorded by the source corpus.

The zero-point energy stored in the modes of an electromagnetic cavity has experimentally detectable effects, giving rise to an attractive interaction between the opposite walls, the static Casimir effect. A dynamical version of this effect was predicted to occur when the vacuum energy is changed either by moving the walls of the cavity or by changing the index of refraction, resulting in the conversion of vacuum fluctuations into real photons. Here, we demonstrate the dynamical Casimir effect using a Josephson metamaterial embedded in a microwave cavity at 5.4 GHz. We modulate the effective length of the cavity by flux-biasing the metamaterial based on superconducting quantum interference devices (SQUIDs), which results in variation of a few percentage points in the speed of light. We extract the full 4 × 4 covariance matrix of the emitted microwave radiation, demonstrating that photons at frequencies symmetrical with respect to half of the modulation frequency are generated in pairs. At large detunings of the cavity from half of the modulation frequency, we find power spectra that clearly show the theoretically predicted hallmark of the Casimir effect: a bimodal, “sparrow-tail” structure. The observed substantial photon flux cannot be assigned to parametric amplification of thermal fluctuations; its creation is a direct consequence of the noncommutativity structure of quantum field theory.

Subfields: Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/b5d6a5bd80dc788a2e0eb3237a57284bc05cec55

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Citations in the corpus

Progress in superconducting metamaterials (2014, background): “A number of authors are using a similar concept to investigate other effects like parametric amplification [100–102], impedance matching to a high-impedance source [103], the dynamical Casimir effect (DCE) [104] or an analogue of Hawking radiation [105].”
Colloquium: Stimulating uncertainty: Amplifying the quantum vacuum with superconducting circuits (2011, methodology): “As we have shown, superconducting circuits are very promising devices for experimental investigations of quantum vacuum amplification effects, and such circuits have already been used in the experimental demonstration of the DCE (Lähteenmäki et al., 2011; Wilson et al., 2011).”
The Quantum Vacuum (2014, methodology): “The other experiment employs an array of SQUIDs, effectively realizing a material with a fast-tunable index of refraction embedded in a cavity (Lähteenmäki et al., 2013).”
Quantum Simulation (2013, methodology): “such as the dynamical Casimir effect (Johansson et al., 2010; Lähteenmäki et al., 2013; Wilson et al., 2011).”