Coherence and multimode correlations from vacuum fluctuations in a microwave superconducting cavity

Pasi Lähteenmäki (Corresponding Author), Gheorghe Sorin Paraoanu, Juha Hassel, Pertti J. Hakonen (Corresponding Author)

    Research output: Contribution to journalArticleScientificpeer-review

    44 Citations (Scopus)


    The existence of vacuum fluctuations is one of the most important predictions of modern quantum field theory. In the vacuum state, fluctuations occurring at different frequencies are uncorrelated. However, if a parameter in the Lagrangian of the field is modulated by an external pump, vacuum fluctuations stimulate spontaneous downconversion processes, creating squeezing between modes symmetric with respect to half of the frequency of the pump. Here we show that by double parametric pumping of a superconducting microwave cavity, it is possible to generate another type of correlation, namely coherence between photons in separate frequency modes. The coherence correlations are tunable by the phases of the pumps and are established by a quantum fluctuation that stimulates the simultaneous creation of two photon pairs. Our analysis indicates that the origin of this vacuum-induced coherence is the absence of which-way information in the frequency space.
    Original languageEnglish
    Article number12548
    Number of pages7
    JournalNature Communications
    Publication statusPublished - 2016
    MoE publication typeA1 Journal article-refereed


    • Applied physics
    • Quantum mechanics
    • Single photons and quantum effects


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