L. C. Loredo, M. A. Broome, P. Hilaire, O. Gazzano, I. Sagnes, A. Lemaitre, M. P. Almeida, P. Senellart, A. G. White.
A BosonSampling device is a quantum machine expected to perform tasks intractable for a classical computer, yet requiring minimal non-classical resources as compared to full-scale quantum computers. Photonic implementations to date employed sources based on inefficient processes that only simulate heralded single-photon statistics when strongly reducing emission probabilities. BosonSampling with only single-photon input has thus never been realised. Here, we report on a BosonSampling device operated with a bright solid-state source of highly-pure single-photon Fock states: the emission from an efficient and deterministic quantum dot-micropillar system is demultiplexed into three partially-indistinguishable single-photons, with purity 1−g (2)(0) of 0.990 ± 0.001, interfering in a 6×6 linear optics network. Our demultiplexed source is orders-of-magnitude brighter than current heralded multi-photon sources based on spontaneous parametric down-conversion, allowing us to complete the BosonSampling experiment 100 times faster than previous equivalent implementations. This intrinsic source superiority places BosonSampling with larger photon numbers within near reach.
Figure: a) Second-order autocorrelation function in log scale. An ideal single-photon Fock state has a g2(0) = 0, here the authors measure g2(0) = 0.010. b) Experimental setup of BosonSampling with a solid-state single photon source. Laser pulses centred at 905 nm excite a quantum-dot embedded in a micropillar cavity, which itself is housed in an optically accessable cryostat (Cryo) system at 13 K. A dichroic mirror (DM), and band-pass filter (BP) with 0.85 nm FWHM are used to isolate the emitted single-photons at 932 nm collected in a single-mode fibre (SMF). A passive demultiplexer composed of beam-splitters with tunable transmittances—half-wave plates (HWP), and polarising beam-splitters (PBS)—and compensating delay lines of 12.5 ns probabilistically converts three consecutive single photons into separate spatial modes, where they are directed into the BosonSampling circuit. The scattering linear network is composed of polarisers (Pol), half-wave plates, a 3×3 non-polarising fibre beam-splitter (FBS), and polarising fibre beam-splitters (PFBS), which in combination form a 6×6 mode network. Six avalanche photo-diodes (APDs) are used at the output to detect up to 3-fold coincidence events.