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Conventional entangled photon sources are not heralded. The desired quality of quantum light sources is heralding, to confirm the generation of the quantum state without measuring it. This problem can be solved either by spectral filtering using optical cavities 22 or by using very narrow bandpass filters, but typically at the price of reducing the number of photon pairs generated (thus further reducing the overall efficiency 15). Moreover, the SPDC process has a broad emission spectrum, which decreases the coherence length of the emitted photons and limits their usefulness for long-distance quantum communication 21. For example, even though SPDC sources are considered better in efficiency and emission rate relative to other mechanisms, they are still limited by the low nonlinear coefficient ( ∼10 −5 pairs per one pump photon) 19, 20. The photon sources based on nonlinear process has several limitations. In SPDC, pump photons interact with the quantum vacuum field inside a medium and down convert into photon pairs. The most common approach to generate entangled photons is via spontaneous parametric down-conversion (SPDC) in nonlinear χ (2) crystals 17. Currently, such schemes are promising for compact footprint relative to other technologies, but at the cost of lower emission rates. In particular, the spontaneous four-wave mixing process has promising prospects since it is accessible in integrated platforms 15, 16. The need to create entangled photons motivated the study of quantum optics in different physical systems, such as hot vapor 8, 9, cold atoms 10, semiconductors 11, 12, quantum dots 13, nitrogen-vacancy centers in diamond 14 and more 15, 16, 17, 18. All these applications require efficient entangled photon sources, which are especially desirable in the telecommunications wavelengths, where photon propagation losses are low. Quantum hyper-dense coding protocols enable breaking the classical limit for information transfer and sharing more than one bit of information on a single qubit 7.

In other areas of quantum optics, entangled photons have been used to demonstrate quantum teleportation over a long distance 4, 5, 6. In recent years, entangled multi-particle cluster states were used in quantum computation 1, 2, 3. We characterize the photon comb states by analyzing the Hong-Ou-Mandel interference and propose proof-of-concept experiments.Įntanglement is a unique feature of quantum mechanics that enables new possibilities in the fields of quantum information and quantum optics. The resulting high-dimensionally entangled photons are entangled in more than one degree of freedom: in all of their spectral components, in addition to the polarization-forming a hyper-entangled state, which is particularly interesting in high information capacity quantum communication. The TPE rate is significantly enhanced by a designed photonic cavity, whose many resonances also translate into high-dimensional entanglement. A Rydberg blockade helps to excite a single Rydberg excitation while the input light field is more efficiently collectively absorbed by all the atoms. The entangled photons are produced by exciting a rubidium atom to a Rydberg state, from where the atom decays via two-photon emission (TPE). The heralding of the process enables non-destructive detection of the photon pairs. We propose a scheme to demonstrate the mechanism and quantify its expected performance. Here we present a mechanism for the generation of heralded entangled photons from Rydberg atom cavity quantum electrodynamics (cavity QED). This motivates the exploration of physical mechanisms for entangled photon generation, with a special interest in mechanisms that can be heralded, preferably at telecommunications wavelengths.

Current state-of-the-art sources are based on nonlinear processes that are limited in their efficiency and wavelength tunability. Entangled photon pairs are a fundamental component for testing the foundations of quantum mechanics, and for modern quantum technologies such as teleportation and secured communication.