Limits of the time-multiplexed photon-counting method

TL;DR

This paper investigates the scalability limits of time-multiplexed photon-counting detectors in quantum optics, considering fiber dispersion and losses, and identifies optimal detector size for realistic efficiencies.

Contribution

It provides a detailed analysis of how fiber dispersion and losses affect the scalability of time-multiplexed detectors, revealing the optimal detector size under realistic conditions.

Findings

Optimal detector size is 256 bins at 85% efficiency.

Fiber dispersion and losses limit the distinguishability of Fock states.

Scalability is constrained by physical effects in realistic setups.

Abstract

The progress in building large quantum states and networks requires sophisticated detection techniques to verify the desired operation. To achieve this aim, a cost- and resource-efficient detection method is the time multiplexing of photonic states. This design is assumed to be efficiently scalable; however, it is restricted by inevitable losses and limited detection efficiencies. Here, we investigate the scalability of time-multiplexed detectors under the effects of fiber dispersion and losses. We use the distinguishability of Fock states up to $n=20$ after passing the time-multiplexed detector as our figure of merit and find that, for realistic setup efficiencies of $\eta=0.85$, the optimal size for time-multiplexed detectors is 256 bins.