Compact non-degenerate entangled-photon source and near-infrared-to-telecom quantum teleportation

Abstract

The polarization-entangled photon source (PEPS) at non-degenerated wavelengths is pivotal to connect quantum systems working at different wavelengths, with the assistance of quantum teleportation. Here, a compact Sagnac-type photon source is designed and demonstrated, in which two photons with wavelengths at 810 and 1550~nm are highly entangled in polarization degree of freedom. The two photons are generated from a periodically poled lithium niobate crystal pumped with a 532~nm continuous-wave laser, via type-0 nondegenerate spontaneous parametric down-conversion. The polarization of three lights is rotated by a single periscope, which makes the Sagnac interferometer compact and stable. The generated two photons are with high brightness of $3\times10^4$ pairs/s/mW, which are highly entangled with fidelity of $0.985\pm0.002$. The entanglement is verified by violating the Clauser-Horne-Shimony-Holt inequality with $\mathcal S =2.756\pm0.007$. Finally, teleportation is demonstrated with this nondegenerate source, in which photonic states at 810~nm is teleported to 1550~nm with fidelity of $0.955\pm0.003$.

Figures (5)

• Figure 1: The schematic drawing of experimental setup. a) The setup of Sagnac-type nondegenerate PEPS. b) The compact periscope. The blue-marked surface corresponds to anti-reflection coating, while the one yellow-marked surface corresponds to reflection coating. The six prisms are bonded together using a high-transmittance optical adhesive. c) The setup to perform teleportation. d) Symbols used in (a) and (c). PBS: polarizing beam splitter; HWP: half-wave plate; QWP: quarter-wave plate; BD: beam displacer; DM: dichroic mirror; CG: compensation glass; SMF: single-mode fiber.
• Figure 2: a) The counts rate of signal photon $N_s$ (orange dots), idler photon $N_i$ (red squares) and two-photon coincidence $C$ (purple triangles) at different pump powers. b) The collection efficiency of signal photon $\eta_s$ (orange dots) and idler photon $\eta_i$ (red squares) at different pump powers. c) The photon pair generation rate (PGR) at different pump powers. All the data are collected in the computational basis. The statistic errors are too small compared to the size of data points.
• Figure 3: a) Real part of the reconstructed $\rho_\text{exp}$. b) Imaginary part of the reconstructed $\rho_\text{exp}$. c) Polarization correlation between signal and idler photons. The red, blue, purple and green dots represent the results by fixing $\theta_s$ at $0^\circ$, $45^\circ$, $90^\circ$ and $135^\circ$, respectively.
• Figure 4: Experimental results of state fidelities after teleportation. The red, orange, green and purple bars represents the fidelity with BSM outcomes of $\ket{\Phi^+}$, $\ket{\Phi^-}$, $\ket{\Psi^+}$ and $\ket{\Psi^-}$, respectively.
• Figure 5: The schematic drawing of experimental setups to generate non-degenerate entangled photon sources with (a) type-I and (b) type-II SPDC.