4 research outputs found
Continuous variable entanglement on a chip
Encoding quantum information in continuous variables (CV)---as the quadrature
of electromagnetic fields---is a powerful approach to quantum information
science and technology. CV entanglement---light beams in
Einstein-Podolsky-Rosen (EPR) states---is a key resource for quantum
information protocols; and enables hybridisation between CV and single photon
discrete variable (DV) qubit systems. However, CV systems are currently limited
by their implementation in free-space optical networks: increased complexity,
low loss, high-precision alignment and stability, as well as hybridisation,
demand an alternative approach. Here we show an integrated photonic
implementation of the key capabilities for CV quantum technologies---generation
and characterisation of EPR beams in a photonic chip. Combined with integrated
squeezing and non-Gaussian operation, these results open the way to universal
quantum information processing with light
Efficient generation of highly squeezed light and second harmonic wave with periodically poled MgO:LiNbO_3
We report on effective generation of continuous-wave squeezed light and
second harmonics with a periodically poled MgO:LiNbO (PPMgLN)
crystal which enables us to utilize the large nonlinear optical coefficient
. We achieved the squeezing level of dB at 860
nm by utilizing a subthreshol optical parametric oscillator with a PPMgLN
crystal. We also generated 400 mW of second harmonics at 430 nm from 570 mW of
fundamental waves with 70% of conversion efficiency by using a PPMgLN crystal
inside an external cavity.Comment: 4 pages, 3 figure
On-chip continuous-variable quantum entanglement
Entanglement is an essential feature of quantum theory and the core of the majority of quantum information science and technologies. Quantum computing is one of the most important fruits of quantum entanglement and requires not only a bipartite entangled state but also more complicated multipartite entanglement. In previous experimental works to demonstrate various entanglement-based quantum information processing, light has been extensively used. Experiments utilizing such a complicated state need highly complex optical circuits to propagate optical beams and a high level of spatial interference between different light beams to generate quantum entanglement or to efficiently perform balanced homodyne measurement. Current experiments have been performed in conventional free-space optics with large numbers of optical components and a relatively large-sized optical setup. Therefore, they are limited in stability and scalability. Integrated photonics offer new tools and additional capabilities for manipulating light in quantum information technology. Owing to integrated waveguide circuits, it is possible to stabilize and miniaturize complex optical circuits and achieve high interference of light beams. The integrated circuits have been firstly developed for discrete-variable systems and then applied to continuous-variable systems. In this article, we review the currently developed scheme for generation and verification of continuous-variable quantum entanglement such as Einstein-Podolsky-Rosen beams using a photonic chip where waveguide circuits are integrated. This includes balanced homodyne measurement of a squeezed state of light. As a simple example, we also review an experiment for generating discrete-variable quantum entanglement using integrated waveguide circuits