Quantum non-Gaussian multiphoton light

Abstract

We propose an experimental method of recognizing quantum non-Gaussian multiphoton states. This is a native quantum property of Fock states, the fundamental quantum states with a constant number of particles. Our method allows experimental development and characterization of higher Fock states of light, reaching even beyond the current technical limits of their generation. We experimentally demonstrate that it is capable of distinguishing realistic quantum non-Gaussian light with the mean number of photons up to five despite detection efficiency of 50%. We also provide evidence that our method can help to distinguish the number of single-photon emitters based only on their collective emission.

Criteria for single photon sources with variable nonclassicality threshold

“…They can only make results worse. This treatment of detector efficiency and dark counts saves the following criteria from systematic errors, as in previous works [22][23][24]. The interferometric network is adjustable; all beam splitters (BSs) and the phase shifts between them can be manipulated to reach the desired layout flexibly [25,26].…”

Multiphoton nonclassical light from clusters of single-photon emitters

“…Compared to the conditions on the 'click' statistics, an advantage of conditions (3) is that they are formulated in terms of normalized CFs, which are invariant to optical losses or detection inefficiency [13]. On the other hand, witnesses of nonclassicality [17] or quantum nonGaussianity [11] formulated in terms of multiphoton detection probabilities are more robust to noise than (3) [19].…”

“…For such a cluster, the number of photons will not significantly exceed the number of emitters, which suggests applications in quantum key distribution (QKD) [9] and quantum metrology [10], where a limit on the maximal number of the photons is highly relevant. Recently, it has been predicted that even a large number of realistic single-photon emitters can produce nonclassical light [8,11]. Importantly, this way of obtaining multiphoton quantum states does not require postselection or heralding, unlike methods based on nonlinear optical effects.…”

Sufficient condition for a quantum state to be genuinely quantum non-Gaussian

“…This technique was experimentally realized to demonstrate quantum non-Gaussianity of an imperfect single-photon state possessing even a positive Wigner function [12] and to study the resilience of quantum non-Gaussianity under dissipation [13]. Moreover, [14] introduced an experimental criterion to identify quantum non-Gaussianity of multi-photon states of light.…”