2013/01/18 by C. Lang, C. B. Lang, C. Eichler +8 · 2 citations
Computer Science · Physics and Astronomy · #Mechanical and Optical Resonators #Quantum Information and Cryptography #Quantum optics and atomic interactions #cond-mat.mes-hall #cond-mat.supr-con #quant-ph
paper · pdf · doi:10.1038/nphys2612
published as Nature Physics 9, 345-348 (2013)
arxiv created 2013/01/18 · openalex publication_date 2013/05/03 · crossref created 2013/05/03 · crossref issued 2013/05/05 · crossref published 2013/05/05 · crossref published-online 2013/05/05 · crossref published-print 2013/06/01 · arxiv updated 2013/06/21 · openalex created_date 2016/06/24 · crossref deposited 2025/04/11 · crossref indexed 2026/06/04 · openalex updated_date 2026/08/04
Interference at a beam splitter reveals both classical and quantum properties of electromagnetic radiation. When two indistinguishable single photons impinge at the two inputs of a beam splitter they coalesce into a pair of photons appearing in either one of its two outputs. This effect is due to the bosonic nature of photons and was first experimentally observed by Hong, Ou, and Mandel (HOM) [1]. Here, we present the observation of the HOM effect with two independent single-photon sources in the microwave frequency domain. We probe the indistinguishability of single photons, created with a controllable delay, in time-resolved second-order cross- and auto-correlation function measurements. Using quadrature amplitude detection we are able to resolve different photon numbers and detect coherence in and between the output arms. This measurement scheme allows us to observe the HOM effect and, in addition, to fully characterize the two-mode entanglement of the spatially separated beam splitter output modes. Our experiments constitute a first step towards using two-photon interference at microwave frequencies for quantum communication and information processing, e.g. for distributing entanglement between nodes of a quantum network [2, 3] and for linear optics quantum computation [4, 5].