Figure 2: Experimental set-up for the entanglement verification and quantum teleportation.

Femtosecond laser pulses from a Ti–sapphire laser (coherent), with a repetition frequency of 76 MHz, a carrier wavelength of 706.5 nm and a polarization along the direction, are split by a birefringent calcite into two coherent paths with equal amplitudes. After rotation of the pulse polarization to equal superposition of and with a half-wave plate (HWP1) set at 22.5°, we introduce a time delay of 388 fs to the two polarization components H and V, with a birefringent beta barium borate (BBO) crystal. We use the lead pulse of H polarization as the write beam and the lagged pulse of V polarization as the read beam. After semicircle HWPs set at 0° and 45°, respectively, at the upper and lower paths, the polarization states of the pump beams are shown in the figure before the diamond sample. The write beam is focused by the lens L1 on the diamond sample and generates a Stokes photon in one of the paths, and an excitation in the corresponding optical phonon modes of the diamond. The Stokes photon, at the wavelength of 780 nm, is transmitted by the dichromatic mirror DM1 after the collection lens L2, with its two paths recombined by the calcite C2. The lens L3 and L4 are used to adjust the distance between the two optical paths, so that they can be combined at the calcite C2. The single-photon detector APD2, together with rotation of the polarizer P2, detects the two path (or polarization) components of the Stokes photon in different bases. To read out the state of the phonon modes, the read pulse converts the phonon to the anti-Stokes photon in the corresponding paths. The anti-Stokes photon, at a shorter wavelength of 645 nm, is reflected by both of the dichromatic mirrors DM1 and DM2, with its two paths recombined through the calcite C3. The photon coincidence counts are registered through a FPGA (Field-Programmable Gate Array) board with a 5 nm coincidence window.