ABSTRACT
In the context of emerging quantum technologies, this work marks an important progress towards practical quantum optical systems in the continuous variable regime. It shows the feasibility of experiments where non-Gaussian state generation entirely relies on plug-and-play components from guided-wave optics technologies. This strategy is successfully demonstrated with the heralded preparation of low amplitude Schrödinger cat states via single-photon subtraction from a squeezed vacuum. All stages of the experiment are based on off-the-shelf fiber components. This leads to a stable, compact, and easily re-configurable realization, fully compatible with existing fiber networks and, more in general, with future out-of-the-laboratory applications.
ABSTRACT
We demonstrate supermode-based second harmonic generation in an integrated nonlinear interferometer made of linear and nonlinear directional couplers. We use a fully-fibered pump shaper to demonstrate second harmonic generation pumped by the symmetric or anti-symmetric fundamental spatial modes. The selection of the pumping mode and thus of a specific SHG spectral profile is achieved through the selection of the fundamental wavelength and via a robust phase setting scheme. We use two methods: either post-selecting or actively setting the pumping mode. Such modal phase matching paves the way for classical and quantum applications of coupled nonlinear photonic circuits, where multimode excitation, encoding and detection are a route for multiplexing and scaling up light-processing.
ABSTRACT
In this Letter, we present a universal approach enabling the full characterization of the quantum properties of a multimode optical system in terms of squeezing and morphing supermodes. These are modes undergoing a continuous evolution that allow uncoupling the system dynamics in terms of statistically independent physical observables. This dynamical feature, never considered so far, enables the description and investigation of an extremely broad variety of key resources for experimental quantum optics, ranging from optical parametric oscillators to silicon-based microring resonators, as well as optomechanical systems.
ABSTRACT
Single-photon entangled states, i.e., states describing two optical paths sharing a single photon, constitute the simplest form of entanglement. Yet they provide a valuable resource in quantum information science. Specifically, they lie at the heart of quantum networks, as they can be used for quantum teleportation, swapped, and purified with linear optics. The main drawback of such entanglement is the difficulty in measuring it. Here, we present and experimentally test an entanglement witness allowing one to say whether a given state is path entangled and also that entanglement lies in the subspace, where the optical paths are each filled with one photon at most, i.e., refers to single-photon entanglement. It uses local homodyning only and relies on no assumption about the Hilbert space dimension of the measured system. Our work provides a simple and trustworthy method for verifying the proper functioning of future quantum networks.
ABSTRACT
Using a continuous-wave Type II optical parametric oscillator below threshold, we have demonstrated a novel source of heralded single photons with high fidelity. The generated state is characterized by homodyne detection and exhibits a 79% fidelity with a single-photon Fock state (91% after correction of detection loss). The low admixture of vacuum and the well-defined spatiotemporal mode are critical requirements for their subsequent use in quantum information processing.
ABSTRACT
Pattern function quantum homodyne tomography (QHT) has been used for characterizing the output of a degenerate below-threshold type-I OPO. The recovered photon number distributions deviated from those relative to Gaussian thermal states. The Kurtosis of the homodyne data confirmed these deviations, thus proving the power of QHT to highlight unexpected features of quantum states.
