Scalability Of Parametric Down-Conversion For Generating Higher-Order Fock States

Spontaneous parametric down-conversion (SPDC) is the most widely used method to generate higher-order Fock states (n >= 2). Yet, a consistent performance analysis from fundamental principles is missing. Here, we address this problem by introducing a framework for state fidelity and generation probability under the consideration of losses and multimode emission. With this analysis we show the fundamental limitations of this process as well as a trade-off between state fidelity and generation rate intrinsic to the probabilistic nature of the process. This identifies the parameter space for which SPDC is useful when generating higher-order Fock states for quantum applications. We experimentally investigate the multiphoton regime of SPDC and demonstrate heralded Fock states up to vertical bar n > = 4.