[Paper Review] Quantum statistics of polariton parametric interactions

M. Sassermann, Z. Vörös+3 more|arXiv (Cornell University)|Aug 3, 2018

Strong Light-Matter Interactions1 references3 citations

TL;DR

This study investigates quantum statistics in polariton parametric scattering using a GaAs planar microcavity, demonstrating that signal-signal and idler-idler correlations exceed signal-idler correlations due to uncorrelated background light. By applying spectral and temporal filtering, the authors suppress background and observe a shift toward non-classical photon statistics, though values remain in the classical regime, indicating that improved time resolution is key to observing non-classicality.

ABSTRACT

Using a high-quality GaAs planar microcavity, we optically generate polariton pairs, and verify their correlations by means of time-resolved single-photon detection. We find that correlations between the different modes are consistently lower than identical mode correlations, which is attributed to the presence of uncorrelated background. We discuss a model to quantify the effects of such a background on the observed correlations. Using spectral and temporal filtering, the background can be suppressed and a change in photon statistics towards non-classical correlations is observed. These results improve our understanding of the statistics of polariton-polariton scattering and background mechanisms, and pave the way to the generation of entangled polariton pairs.

Motivation & Objective

• To understand the quantum statistics of polariton-polariton scattering in a planar microcavity under parametric excitation.
• To identify and quantify the role of uncorrelated background light in degrading quantum correlations between signal and idler modes.
• To explore how spectral and temporal filtering can suppress background and enhance non-classical photon statistics.
• To assess the feasibility of observing non-classical behavior, such as anti-bunching, in polariton-based quantum systems.
• To evaluate improvements in detection time resolution and microcavity design for enabling observable quantum correlations.

Proposed method

• Optically excite a high-quality GaAs planar microcavity to generate polariton pairs via parametric scattering on the lower polariton branch.
• Use time-resolved single-photon detection to measure intensity correlations between signal, idler, and pump modes.
• Apply spectral and temporal filtering to suppress uncorrelated background light and isolate parametrically generated polariton pairs.
• Model the background contribution as resonant absorption and re-emission by donors, affecting correlation measurements.
• Calculate non-classicality witnesses (e.g., ΔW) and conditional coherence to quantify the distance to non-classical regimes.
• Extrapolate the effect of improved time resolution using Gaussian detector response functions, estimating performance with 10 ps FWHM jitter.

Experimental results

Research questions

• RQ1 Why are signal-signal and idler-idler correlations higher than signal-idler correlations in polariton parametric scattering?
• RQ2 To what extent does uncorrelated background light from donor recombination distort measured quantum correlations?
• RQ3 How effective is spectral and temporal filtering in suppressing background and enhancing non-classical photon statistics?
• RQ4 What level of detection time resolution is required to observe non-classical anti-bunching in polariton systems?
• RQ5 Can improvements in microcavity design, such as increased Rabi splitting and narrower linewidths, significantly reduce background and enhance quantum signatures?

Key findings

• Signal-signal and idler-idler correlations consistently exceed signal-idler correlations due to the presence of uncorrelated background light.
• The background is attributed to donors resonantly absorbing and re-emitting free excitons in the same phase-space region as the parametrically generated modes.
• Spectral and temporal filtering reduce background and shift the system closer to non-classical character, decreasing the distance to non-classicality (ΔW) by approximately 2.6 standard deviations at the smallest coincidence window.
• Despite filtering, the measured photon statistics remain in the classical regime, with conditional coherence values indicating classical behavior.
• Extrapolation shows that a detection system with 10 ps FWHM timing jitter could increase cross-correlation to gH(0) ≈ 0.88, approaching non-classical anti-bunching.
• Improving detector time resolution is identified as the most effective path forward, with a 3× improvement potentially enabling observation of non-classical statistics.