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Antibunching of microwave-frequency photons observed in correlation measurements using linear detectors


At optical frequencies the radiation produced by a source, such as a laser, a black body or a single-photon emitter, is frequently characterized by analysing the temporal correlations of emitted photons using single-photon counters. At microwave frequencies, however, there are no efficient single-photon counters yet. Instead, well-developed linear amplifiers allow for efficient measurement of the amplitude of an electromagnetic field. Here, we demonstrate first- and second-order correlation function measurements of a pulsed microwave-frequency single-photon source integrated on the same chip with a 50/50 beam splitter followed by linear amplifiers and quadrature amplitude detectors. We clearly observe single-photon coherence in first-order and photon antibunching in second-order correlation function measurements of the propagating fields.

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Figure 1: Sample and schematic of the experimental set-up.
Figure 2: Quadrature amplitude and cross-power measurements.
Figure 3: Correlation function measurements.

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We thank T. Frey and G. Littich for their contributions at the early stages of the project. We also thank C. M. Caves, D. Esteve and especially K. W. Lehnert for very fruitful discussions and J. Blatter for comments on the manuscript. This work was supported by the European Research Council (ERC) through a Starting Grant and by ETHZ. M.P.d.S. was supported by a NSERC postdoctoral fellowship. A.B. was supported by NSERC, CIFAR and the Alfred P. Sloan Foundation.

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D.B., C.L. and L.S. carried out the experiments. D.B. and C.L. analysed the data and developed hardware data processing. J.M.F. and L.S. designed and fabricated the sample. Experiments were carried out at ETH Zurich; all authors in Zurich contributed to setting up and maintaining the cryogenic set-up, and developing measurement software. M.P.d.S. and A.B. contributed to the theoretical interpretation. A.W. and D.B. wrote the manuscript. All authors commented on the manuscript. A.W. supervised the project.

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Correspondence to A. Wallraff.

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Bozyigit, D., Lang, C., Steffen, L. et al. Antibunching of microwave-frequency photons observed in correlation measurements using linear detectors. Nature Phys 7, 154–158 (2011).

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