An optical receiver for the Lunar Laser Communication Demonstration based on photon-counting superconducting nanowires

Abstract

The Lunar Laser Communication Demonstration (LLCD) successfully demonstrated for the first time duplex laser communications between a lunar-orbiting satellite and ground stations on Earth with error-free downlink data rates up to 622 Mb/s utilizing an optical receiver based on photon-counting superconducting nanowires and operating near 1550 nm.

Superconducting nanowire single-photon detector with integrated impedance-matching taper

“…1,2 With exceptional performance, [3][4][5][6][7] it has played an essential role in various applications, especially quantum information science 8,9 and deep-space optical communication. 10 A common problem with SNSPDs is their low output voltage and signal-to-noise ratio (SNR), which has been a limiting factor in detector timing jitter. 11 A simple lumped-circuit model dictates that the output voltage from the nanowire cannot exceed I B × Z load , where I B is the bias current and Z load is the load impedance.…”

Space QUEST mission proposal: experimentally testing decoherence due to gravity

“…The gravitational timedilation is the difference, Δ t =t d −τ, between the propagation times of the photons sent to the ISS as measured by local observers along the path, τ, and a global observer situated far from the gravitating body t d . We find where r e is Earth radius, h is the ISS height, m is the mass of the Earth expressed in units of length 38…”

“…Typically in QM a measurement is considered finished when the measurement has been stored as classical information that the quantum system can no longer affect 40 . This process takes a certain amount of time, 38 When working in natural units and in the context of gravitational physics or relativity it is common practice to express mass of a spherical body in terms of its Schwarzschild radius. 39 We assume that, provided we are able to keep track of all degrees of freedom of the local environment (including the observers) then from some 'higher vantage point' the overall state can still be described as being a pure entangled state globally.…”

“…In principle single-photon detector arrays like Si APD arrays with ⪆ 200 pixels or nanowire arrays with ≈16-32 pixels could be built which would be ideal candidates. For example, the lunar laser communication demonstration used 4 arrays of 4 nanowire detectors [38] and APD arrays are commercially available [39]. Such systems can be adapted/combined for use in the OGS.…”

Toward optimum efficiency in a quantum receiver for coded ppm

“…In parallel, technology has advanced to where noiseless photon counters can be used to achieve quite good performance ( [4]). We show here that, when an end-to-end error correction code is added, in fact such a system can out-perform the "optimum" MPE system at low signal powers.…”