Toward integrated tantalum pentoxide optical parametric oscillators

We present a hybrid waveguide-fiber optical parametric oscillator (OPO) exploiting degenerate four-wave mixing in tantalum pentoxide. The OPO, pumped with ultrashort pulses at 1.55 $\mu$m wavelength, generated tunable idler pulses with up to 4.1 pJ energy tunable between 1.63 $\mu$m and 1.68 $\mu$m center wavelength. An upper bound for the total tolerable cavity loss of 32 dB was found, rendering a chip-integrated OPO feasible as a compact and robust light source.Comment: 5 pages and 5 figures, submitted to Optics Letter

Entanglement of distant atoms by projective measurement: The role of detection efficiency

We assess proposals for entangling two distant atoms by measurement of emitted photons, analyzing how their performance depends on the photon detection efficiency. We consider schemes based on measurement of one or two photons and compare them in terms of the probability to obtain the detection event and of the conditional fidelity with which the desired entangled state is created. Based on an unravelling of the master equation, we quantify the parameter regimes in which one or the other scheme is more efficient, including the possible combination of the one-photon scheme with state purification. In general, protocols based on one-photon detection are more efficient in set-ups characterized by low photon detection efficiency, while at larger values two-photon protocols are preferable. We give numerical examples based on current experiments.Comment: 12 pages, 6 figure