IQIM Virtual Seminar, November 6, 2020 - Chaitali Joshi

Speaker: Chaitali Joshi, AWS Quantum Postdoctoral Scholar, Mirhosseini Group
Title: Quantum photonics with color qubits
Abstract: Optical photons are excellent flying qubits for long-distance quantum networks due to negligible thermal noise and decoherence at room temperature. In this talk, I will discuss how frequency encoding can be combined with nonlinear optics and fiber and integrated photonic technologies to address challenges in scaling future photonic quantum networks. Frequency multiplexing has had a profound impact on classical telecommunication networks, creating low loss and inexpensive hardware that can be exploited for quantum applications. I will describe quantum photonic applications where frequency encoding provides a distinct advantage in terms of scaling losses and resource overhead compared to polarization, spatial or temporal mode encoding.
Coherent manipulation of light in the frequency domain at the single-photon level requires a strong, noise-free nonlinear process. I will discuss our implementation of four-wave mixing (FWM) in a commercial dispersion-shifted fiber to achieve quantum frequency conversion with near-unity efficiency and low noise. I will discuss how we used this process as an active "frequency switch" to realize a low-loss multiplexed single-photon source that can be scaled to the deterministic regime. Next, I will discuss how we used this process as a frequency beam-splitter to demonstrate two-photon Hong-Ou-Mandel type interference between entangled photons of different colors- a hallmark of quantum indistinguishability. Finally, I will discuss our realization of a FWM-based "time lens" for the generation and detection of single-photon waveforms with picosecond resolution. Based on Joshi et al., Nat. Comm. 9, 847 (2018), Joshi et al. Phys. Rev. Lett. 124, 143601(2020)