Analysis of a single-mode waveguide at sub-terahertz frequencies as a communication channel

TL;DR

This paper experimentally investigates the transmission properties of a single-mode waveguide at sub-terahertz frequencies, revealing frequency-dependent impedance effects and estimating the information capacity, with implications for quantum communication channels.

Contribution

It provides the first detailed experimental analysis of waveguide transmission at 160-300 GHz, highlighting impedance mismatch effects and their impact on information transfer.

Findings

Transmission varies strongly with frequency due to impedance mismatch.

High dynamic range measurements up to 80 dB were achieved.

Estimated information rate is about 1 bit per photon.

Abstract

We study experimentally the transmission of an electro-magnetic waveguide in the frequency range from 160 to 300 GHz. Photo-mixing is used to excite and detect the fundamental TE10 mode in a rectangular waveguide with two orders-of-magnitude lower impedance. The large impedance mismatch leads to a strong frequency dependence of the transmission, which we measure with a high-dynamic range of up to 80 dB, and with high frequency-resolution. The modified transmission function is directly related to the information rate of the waveguide, which we estimate to be about 1 bit per photon. We suggest that the results are applicable to a Josephson junction employed as a single-photon source and coupled to a superconducting waveguide to achieve a simple on-demand narrow-bandwidth free-space number-state channel.