A low-cost time-hopping impulse radio system for high data rate transmission

We present an efficient, low-cost implementation of time-hopping impulse radio that fulfills the spectral mask mandated by the FCC and is suitable for high-data-rate, short-range communications. Key features are: (i) all-baseband implementation that obviates the need for passband components, (ii) symbol-rate (not chip rate) sampling, A/D conversion, and digital signal processing, (iii) fast acquisition due to novel search algorithms, (iv) spectral shaping that can be adapted to accommodate different spectrum regulations and interference environments. Computer simulations show that this system can provide 110Mbit/s at 7-10m distance, as well as higher data rates at shorter distances under FCC emissions limits. Due to the spreading concept of time-hopping impulse radio, the system can sustain multiple simultaneous users, and can suppress narrowband interference effectively.Comment: To appear in EURASIP Journal on Applied Signal Processing (Special Issue on UWB - State of the Art

Frequency Multiplexing for Quasi-Deterministic Heralded Single-Photon Sources

Single-photon sources based on optical parametric processes have been used extensively for quantum information applications due to their flexibility, room-temperature operation and potential for photonic integration. However, the intrinsically probabilistic nature of these sources is a major limitation for realizing large-scale quantum networks. Active feedforward switching of photons from multiple probabilistic sources is a promising approach that can be used to build a deterministic source. However, previous implementations of this approach that utilize spatial and/or temporal multiplexing suffer from rapidly increasing switching losses when scaled to a large number of modes. Here, we break this limitation via frequency multiplexing in which the switching losses remain fixed irrespective of the number of modes. We use the third-order nonlinear process of Bragg scattering four-wave mixing as an efficient ultra-low noise frequency switch and demonstrate multiplexing of three frequency modes. We achieve a record generation rate of $4.6\times10^4$ multiplexed photons per second with an ultra-low $g^{2}(0)$ = 0.07, indicating high single-photon purity. Our scalable, all-fiber multiplexing system has a total loss of just 1.3 dB independent of the number of multiplexed modes, such that the 4.8 dB enhancement from multiplexing three frequency modes markedly overcomes switching loss. Our approach offers a highly promising path to creating a deterministic photon source that can be integrated on a chip-based platform.Comment: 28 pages, 9 figures. Comments welcom