Latent Quantum Resources

Abstract

Optical nonclassicality [1] is a convex quantum resource describing the property that a light mode in a given quantum state requires eld quantization for a correct description of measurements performed on it. Technically, this means that such quantum states cannot be expressed as statistical mixtures of coherent states. However, the informational incompleteness of measurements such as photocounting can lead to situations where the measurement statistics of nonclassical states can still be simulated using a classical mixture of coherent states. In this case, the quantum resource becomes latent: the state remains resourceful, but its nonclassicality is not directly visible in the measurement statistics. Using optical nonclassicality as an example, we demonstrate that information about a quantum resource can still be revealed without requiring additional measurement data. This can be achieved through conditional state preparation. Suppose two parties, Alice and Bob, share two light modes. Alice performs a measurement on her mode, thereby preparing quantum states on Bob's side. We assume that Bob's direct measurements cannot reveal the nonclassicality of these states. However, by employing the steering of latent nonclassicality technique, we can conclude that at least one of Bob's states must be nonclassical [2].