Restoring polarization entanglement from solid-state photon sources by time-dependent photonic control

TL;DR

This paper presents a photonic control method that compensates for emitter-induced phase evolution, restoring polarization entanglement in solid-state photon sources without needing to modify the emitter.

Contribution

The authors introduce a time-dependent photonic control protocol that reverses phase evolution, enabling robust entanglement recovery in solid-state quantum emitters.

Findings

Restores polarization entanglement without temporal post-selection.

Uses dynamic phase modulation to counteract emitter-induced phase shifts.

Achieves entanglement recovery independently of detector timing resolution.

Abstract

Quantum states of light are central resources for quantum communication, networking, and photonic information processing. In many quantum emitters, coherent internal dynamics arising from intrinsic or field-induced level splittings imprint a deterministic, time-dependent phase on the emitted light. When emission times are stochastic and detector timing resolution is finite, this phase evolution becomes effectively unresolved, suppressing observable entanglement. Here, we demonstrate a photonic-compensation protocol that removes this emitter-induced phase evolution directly in the photonic domain. Rather than modifying the emitter, we apply synchronized, time-dependent coherent operations to the emitted photons that reverse the accumulated phase independently of the emission time. Using exciton fine-structure splitting in a semiconductor quantum dot as a model system, we implement dynamic phase modulation and perform time-resolved two-photon polarization tomography. We show that this restores a stationary two-photon polarization state and recovers polarization entanglement without temporal post-selection and independently of detector timing resolution. Our approach provides a scalable route to robust solid-state entangled-photon sources and, more broadly, establishes a strategy for removing the imprint of coherent emitter dynamics on photonic entanglement in integrated platforms.