We consider a set of observers who live near the boundary of global AdS, and are allowed to act only with simple low-energy unitaries and make measurements in a small interval of time. The observers are not allowed to leave the near-boundary region. We describe a physical protocol that nevertheless allows these observers to obtain detailed information about the bulk state. This protocol utilizes the leading gravitational back-reaction of a bulk excitation on the metric, and also relies on the entanglement-structure of the vacuum. For low-energy states, we show how the near-boundary observers can use this protocol to completely identify the bulk state. We explain why the protocol fails completely in theories without gravity, including non-gravitational gauge theories. This provides perturbative evidence for the claim that one of the signatures of holography --- the fact that information about the bulk is also available near the boundary --- is already visible in the low-energy theory of gravity.

中文翻译：

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靠近边界的观察者获取量子引力的大量信息的物理协议

我们考虑一组居住在全球AdS边界附近的观察员，这些观察员只能与简单的低能耗unit行动，并在很小的时间间隔内进行测量。不允许观察员离开近边界区域。我们描述了一种物理协议，但是该协议允许这些观察者获得有关体状态的详细信息。该协议利用公制激励的领先重力反作用，也依赖于真空的纠缠结构。对于低能态，我们展示了近边界观察者如何使用此协议来完全识别体态。我们解释了为什么该协议在没有引力的理论（包括非引力计理论）中完全失败。