Quantum Frequency Translation of Single-Photon States in a Photonic Crystal Fiber

We experimentally demonstrate frequency translation of a nonclassical optical field via four-wave mixing (Bragg-scattering process) in a photonic crystal fiber (PCF). The high nonlinearity and the ability to control dispersion in PCF enable efficient translation between nearby photon channels within the visible to-near-infrared spectral range, useful in quantum networks. Heralded single photons at 683 nm were translated to 659 nm with an efficiency of $28.6\pm 2.2$ percent. Second-order correlation measurements on the 683- and 659-nm fields yielded $g_{683}^{(2)}(0)=0.21\pm 0.02$ and $g_{659}^{(2)}(0)=0.19\pm 0.05$, respectively, showing the nonclassical nature of both fields.

Figure 1

(a) The modulation interaction process. Two photons from pump 1 are annihilated while two sideband photons (signal and idler), equally spaced in frequency from the pump by $\Delta {\omega }_{\mathrm{MI}}$, are created. Up (down) arrows indicate creation (destruction). (b) The Bragg-scattering quantum frequency translation process. Photons from pump 1 and the $S1$ mode are annihilated while photons in pump 2 and the $S2$ mode are created. The frequency separation between the pumps $\Delta {\omega }_{\mathrm{BS}}$ is equal to the separation $S1$ and $S2$.

Figure 2

(a) Scanning electron microscope (SEM) cross-sectional image of fiber 1. (b) Cross-sectional SEM image of fiber 2. The two large cladding holes near the core help to induce birefringence in the fiber.

Figure 3

Setup used to create and frequency translate single-photon states. Both pumps $P1$ and $P2$ are 100 ps Ti-sapphire lasers. A single photon is created in fiber 1 at 683-nm, heralded, and combined with $P1$ and $P2$ to be translated to 659-nm in fiber 2. Five detectors measure $g^{(2)}(0)$ of both 683- and 659-nm channels, with the 989-nm channel detector acting as the herald. Opaque rectangles represent either long-pass or bandpass filters and transparent rectangles signify dichroic mirrors.