Quantum entanglement is a powerful resource that revolutionizes information science, opens new horizons in communication technologies, and pushes the frontiers of sensing and imaging. Whether or not the methods of quantum entanglement can be extended to life-science imaging is far from clear. Live biological systems are eluding quantum-optical probes, proving, time and time again, too lossy, too noisy, too warm, and too wet to be meaningfully studied by quantum states of light. The central difficulty that puts the main roadblock on the path toward entanglement-enhanced nonlinear bioimaging is that the two-photon absorption (TPA) of entangled photons can exceed the TPA of uncorrelated photons only at the level of incident photon flux densities as low as one photon per entanglement area per entanglement time. This fundamental limitation has long been believed to rule out even a thinnest chance for a success of bioimaging with entangled photons. Here, we show that new approaches in nonlinear and quantum optics, combined with the latest achievements in biotechnologies, open the routes toward efficient photon-entanglement-based strategies in TPA microscopy that can help confront long-standing challenges in life-science imaging. Unleashing the full potential of this approach will require, however, high throughputs of virus-construct delivery, high expression efficiencies of genetically encodable fluorescent markers, high-brightness sources of entangled photons, as well as a thoughtful entanglement engineering in time, space, pulse, and polarization modes. We demonstrate that suitably tailored nonlinear optical fibers can deliver entangled photon pairs confined to entanglement volumes many orders of magnitude smaller than the entanglement volumes attainable through spontaneous parametric down-conversion. These ultracompact modes of entangled photons are shown to enable a radical enhancement of the TPA of entangled photons, opening new avenues for quantum entanglement in life-science imaging.

中文翻译：

---

生命科学成像的光子纠缠：重新思考可能的极限

量子纠缠是一种强大的资源，可以彻底改变信息科学，开辟通信技术的新视野，并推动传感和成像的前沿。量子纠缠的方法是否可以扩展到生命科学成像还远未明确。活的生物系统正在躲避量子光学探测器，一次又一次地证明，太有损、太嘈杂、太温暖、太潮湿，无法通过光的量子态进行有意义的研究。阻碍纠缠增强非线性生物成像的主要障碍是纠缠光子的双光子吸收 (TPA) 只有在入射光子通量密度低至 1 的水平上才能超过不相关光子的 TPA每个纠缠时间每个纠缠区域的光子。长期以来，人们一直认为这种基本限制甚至排除了使用纠缠光子进行生物成像成功的最微弱的机会。在这里，我们展示了非线性和量子光学的新方法，结合生物技术的最新成就，为 TPA 显微镜中基于光子纠缠的有效策略开辟了道路，有助于应对生命科学成像中长期存在的挑战。然而，释放这种方法的全部潜力将需要病毒构建体的高通量、可遗传编码的荧光标记的高表达效率、纠缠光子的高亮度源，以及在时间、空间、脉冲方面进行深思熟虑的纠缠工程, 和偏振模式。我们证明了适当定制的非线性光纤可以提供纠缠光子对，纠缠体积比通过自发参数下转换可获得的纠缠体积小许多数量级。这些纠缠光子的超紧凑模式可以彻底增强纠缠光子的 TPA，为生命科学成像中的量子纠缠开辟新途径。