Quantum Frequency Conversion

To build a truly large scale long distance quantum network it is advantageous to connect quantum memories (QM) via photons in the telecommunication wavelength band because of their low loss through optical fibers. On the other hand, photons emitted by trapped ions are typically in the uv or visible range. Nonlinear media may be used to implement quantum frequency conversion (QFC) [1] of a trapped ion’s wavelength into either the IR or telecom band. It is well established that the QFC process preserves the quantum nature of the light. We are using periodically-poled lithium niobate (PPLN) to do QFC as a step toward demonstrating remote entanglement protocols and networking over optical fibers. Barium ions can emit single photons in the visible spectrum making engineering of the QFC material less challenging, making Ba+ a leading candidate for creating a photonic link between hybrid or distant quantum processors [2].


[1] "Quantum frequency conversion," Prem Kumar, Opt. Lett. 15, 1476-1478 (1990).

[2] "Ion-photon entanglement and quantum frequency conversion with trapped Ba+ ions" J.D. Siverns, X. Li, Q. Quraishi, Applied Optics, Vol. 56, Issue 3, pp. B222-B230, arxiv 1701.02783 (2017).

Fig. 1 Quantum frequency conversion block diagram showing difference frequency generation between pump and visible Ba+ photons.