Abstract

In a quantum network, remote nodes containing stationary qubits have to be interconnected, e.g. by photonic flying qubits. For long-range transmission, photons at telecommunication wavelengths offer minimal loss in fibre links. The majority of atoms or ions serving as stationary qubits, however, do not offer optical transitions at telecom wavelengths. Hence techniques are necessary to bridge the gap between the near infrared and the telecom spectral regions. To this end we have developed a source of correlated photon pairs based on spontaneous parametric downconversion (SPDC) in a singly resonant optical parametric oscillator (OPO). The OPO is pumped below its oscillation threshold with a continuous wave laser at 532nm. The nonlinear crystal is made of periodically poled lithium tantalate offering six poling periods. This allows a tuning range of 806-954nm for the signal field and 1202-1564nm for the idler field, bridging the near infrared region with atomic transitions and the telecom bands. The OPO cavity tailors the SPDC spectrum to a comb of longitudinal modes, separated by 1GHz and with 7.2MHz linewidth each.

© 2015 IEEE