Dark-state photonic entanglement filters

Abstract

Preserving entanglement in the presence of decoherence remains a major challenge for quantum technologies. Recent proposals [M.A. Selim et al., Science 387, 1424 (2025)] have employed photonic filters based on anti-parity-time symmetry to recover certain entangled states, but these approaches require intricate, symmetry-constrained waveguide architectures and precise bath engineering. In this work, we show that such strict non-Hermitian symmetry constraints are not necessary for entanglement filtering. Instead, we identify post-selection and the emergence of dark states -- arising naturally through destructive interference in simple photonic settings -- as the essential mechanisms. By avoiding the need for special bath engineering or non-Hermitian symmetries, our approach significantly simplifies the design and architecture, enhances universality, and extends applicability beyond previously studied dimer configurations. We demonstrate this concept using minimal waveguide network designs, offering a broadly accessible route to robust entanglement filtering.

to appear in Optics letters. This work builds upon and extends the results of M.A. Selim et al. [Science 387, 1424 (2025)] by showing that anti-parity-time symmetry and environment engineering are not necessary for entanglement filtering. We demonstrate a more general approach based on post-selection and interference in simpler photonic networks

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Cited by in corpus (3)

• Phase Transitions and Virtual Exceptional Points in Quantum Emitters Coupled to Dissipative Baths
• Exact dynamics and bound states of a cavity coupled to a two-dimensional reservoir
• Non-Hermiticity induced thermal entanglement phase transition