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Science  07 Dec 2007:
Vol. 318, Issue 5856, pp. 1527
DOI: 10.1126/science.318.5856.1527a

The ability to detect single photons makes it possible to investigate the quantum properties of light and to implement strategies for quantum cryptography and quantum communications with single photons as the information carriers. To date, photon detectors have come in two guises: They can be designed either for sensitivity at a single energy or over a broad range of energies, but neither option has offered on-chip tunability of the detected wavelength. Gustavsson et al. now describe a frequency-tunable single-photon detector for the microwave regime using a double quantum dot structure. They are able to shift the discrete energy levels of one dot with respect to the other by application of appropriate gate voltages. Using time-resolved charge detection techniques, they can then directly relate the detection of a tunneling electron to the absorption of a single photon, the energy of which corresponds to the tuned energy-level separation between the two dots. — ISO

Phys. Rev. Lett. 99, 206804 (2007).

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