Robust Measurement for the Discrimination of Binary Coherent States

Departmental News

Prof. Elohim Becerra, CQulC, UNM

Posted: July 25, 2018

Robust measurements at low powers by counting photons

Optical communication uses light to encode and transmit information over long distances, such as in optical fibers with losses, and requires reliable detection schemes to read out information from low levels of light. However, noise and imperfections in real-world devices and detectors severely affect the measurement fidelity and ultimately limits the amount of information that we can communicate.  Recent work in the quantum-optics group led by Elohim Becerra at UNM demonstrated an optimized measurement capable of overcoming these imperfections by counting the number of photons in pulses of light carrying information in their optical phase. This measurement reads off the information contained in the light by first combining the light pulse with a reference pulse to compare their relative phase, and then counting the number of photons in the combined pulse. Previous work in ultra-sensitive measurements has focused instead on detecting no light vs. any amount of light in the combined pulse, and their sensitivities have been limited by noise and imperfections. This novel measurement scheme allows for a high degree of robustness to these imperfections while reaching high measurement sensitivities. Moreover, due to its simplicity, this measurement is inherently compatible with high-bandwidth communication technologies to accommodate the high rates of information transfer in today’s optical communication networks. 

This work was published in the July 2 issue of Physical Review Letters: 

Robust Measurement for the Discrimination of Binary Coherent States

M. T. DiMario and F. E. Becerra

Phys. Rev. Lett. 121, 023603 (2018)