Abstract
True on-demand high-repetition-rate single-photon sources are highly sought after for quantum information processing applications. However, any coherently driven two-level quantum system suffers from a finite re-excitation probability under pulsed excitation, causing undesirable multi-photon emission. Here, we present a solid-state source of on-demand single photons yielding a raw second-order coherence of g(2)(0)=(7.5±1.6)×10−5 without any background subtraction or data processing. To this date, this is the lowest value of g(2)(0) reported for any single-photon source even compared to the previously reported best background subtracted values. We achieve this result on GaAs/AlGaAs quantum dots embedded in a low-Q planar cavity by employing (i) a two-photon excitation process and (ii) a filtering and detection setup featuring two superconducting single-photon detectors with ultralow dark-count rates of (0.0056±0.0007) s−1 and (0.017±0.001) s−1, respectively. Re-excitation processes are dramatically suppressed by (i), while (ii) removes false coincidences resulting in a negligibly low noise floor.
Highlights
We present a solid-state source of on-demand single photons yielding a raw second-order coherence of gð2Þð0Þ 1⁄4 ð7:561:6Þ Â 10À5 without any background subtraction or data processing. This is the lowest value of gð2Þð0Þ reported for any single-photon source even compared to the previously reported best background subtracted values. We achieve this result on GaAs/AlGaAs quantum dots embedded in a low-Q planar cavity by employing (i) a two-photon excitation process and (ii) a filtering and detection setup featuring two superconducting singlephoton detectors with ultralow dark-count rates of ð0:005660:0007Þ sÀ1 and ð0:01760:001Þ sÀ1, respectively
We use an aspheric lens with a working distance of 4.93 mm to focus the excitation laser under a slight angle through a solid immersion lens in the Weierstraß geometry and onto the QD under investigation. 90% of the confocally collected photoluminescence passes the non-polarizing beam splitter we use to couple in the pulse-stretched excitation laser with a repetition rate of 80.028 MHz
We use tunable notch filters (FWHM 1⁄4 0.4 nm; extinction ratio $30 dB) mounted on stepper motors to selectively block laser light before we couple into an optical fiber
Summary
We present a solid-state source of on-demand single photons yielding a raw second-order coherence of gð2Þð0Þ 1⁄4 ð7:561:6Þ Â 10À5 without any background subtraction or data processing. We achieve this result on GaAs/AlGaAs quantum dots embedded in a low-Q planar cavity by employing (i) a two-photon excitation process and (ii) a filtering and detection setup featuring two superconducting singlephoton detectors with ultralow dark-count rates of ð0:005660:0007Þ sÀ1 and ð0:01760:001Þ sÀ1, respectively.
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