Accidental coincidences in camera-based high-dimensional entanglement certification

TL;DR

This paper investigates how accidental coincidences affect high-dimensional entanglement certification using camera-based methods, showing that current camera technologies can certify entanglement without subtracting accidentals under certain conditions.

Contribution

It analyzes the impact of accidental coincidences on entanglement certification with camera-based systems and demonstrates conditions under which certification is possible without accidental subtraction.

Findings

Accidental coincidences critically impact entanglement certification.

Current camera technologies can certify entanglement without accidental subtraction with Gaussian approximation.

The role of camera temporal characteristics is crucial in certification accuracy.

Abstract

High-dimensional entangled states, such as spatially-entangled photon pairs produced by Spontaneous Parametric Down-Conversion (SPDC), are a key resource for quantum technologies. In recent years, camera-based coincidence counting approaches have considerably improved the ability to characterize them in terms of speed and dimensionality. However, these methods have limitations, including in most of them the necessity to subtract accidental coincidences. Here, we study the role of these accidentals in entanglement certification for a single-photon avalanche diode (SPAD) array and an intensified time-stamping (Tpx3Cam) camera. Using both Einstein-Podolsky-Rosen (EPR) and entropy-based criteria, we show that the level of accidental coincidences - determined by the temporal characteristics of the camera - and whether they are subtracted critically impact entanglement certification. In particular, we demonstrate that current single-photon camera technologies enable entanglement certification without accidental subtraction only if a Gaussian approximation is applied to the measured two-photon state. Our work is important for developing quantum-optics application in adversarial scenarios, such as high-dimensional quantum key distribution (HD-QKD), and also for loophole-free experimental testing of quantum foundations.