370 research outputs found
Coupling quasi-phase matching: entanglement buildup in nonlinear waveguide arrays
Wavevector quasi-phase matching was devised in the 1960s as a way to boost
nonlinear interactions with efficient quantum noise squeezing as one
outstanding outcome. In the era of quantum technologies, we propose a new
coupling quasi-phase matching for efficient generation of multimode
downconverted quantum light in nonlinear waveguide arrays. We highlight this
technique achieving multimode quantum entanglement and Einstein-Podolsky-Rosen
steering buildup. We discuss the feasibility of this method with current
technology and demonstrate its competitiveness as a resource for continuous
variables quantum information.Comment: 9 pages, 5 figures, v2 closer to published versio
Zero supermode-based multipartite entanglement in nonlinear waveguides arrays
We show that arrays of nonlinear waveguides in the second
harmonic generation regime are a promising source of continuous-variable
entanglement. We indeed demonstrate analytically that optical arrays with odd
number of waveguides injected with the zero-eigenvalue fundamental supermode
entangle this fundamental supermode with a collective harmonic field. Moreover
the fundamental individual modes are multipartite entangled and their
entanglement grows with propagation length. The device is scalable, robust to
losses, does not rely on specific values of nonlinearity and coupling and is
easily realized with current technology. It thus stands as an unprecedented
candidate for generation of multipartite continuous-variable entanglement for
optical quantum information processing.Comment: Main text: 7 pages, 6 figures. Supplemental material: 5 pages, 2
figure. v2 closer to published versio
Spatial Propagation and Characterization of Quantum States of Light in Integrated Photonic Devices
In this dissertation we introduce a quantum theory of propagation of
light in integrated photonic devices. The necessity of this theory is justi ed
due to the conceptual and formal inconsistencies the Hamiltonian theory
presents when dealing with propagation problems. Taking into account the
orthonormalization property and the modal norms, we carry out a canonical
quantization of the
ux of Momentum and derive Heisenberg equations. We
apply it to coupling devices with di erent features of the refractive index:
inhomogeneities, nonlinear response and losses; like N N linear and nonli-
near directional couplers and spontaneous parametric down conversion and
spontaneous four wave mixing-based nonlinear inhomogeneous waveguides.
Likewise, we introduce the optical eld-strength space and the amplitude
probability distributions in this representation, and by means of a spatial-
type Lagrangian theory we derive by path integration propagators in this
space for di erent-media based devices. In this way we solve the propagation
for discrete and continuous variables.
Next, we present a new method of characterization of quantum states
introducing a generalized quantum polarization, based on the con nement in
particular regions of the optical eld space of the probability distributions
of quantum states. Likewise, we propose a consistent polarization degree,
a gure which measures how di erent a state is from a full unpolarized
one, showing its application to the characterization of various examples of
stationary and dynamic quantum states.
The last aim of this dissertation is to measure quantum states of light
propagating in integrated photonic devices. We designe a versatile and relia-
ble electro-optic integrated device to accomplish this goal. This device allows
carrying out any SU(2) unitary transformation and is able to be nested as
well, allowing its extension to SU(N) transformations. Likewise, it outper-
forms other current schemes based on pasive directional couplers due to its
ability to reduce the e ect produced by fabrication errors, a very important
fact when complex circuits are involved. We perform simulations and show
possible applications.
In summary, in this thesis we develop tools to design and simulate the
performance of photonic devices, as well as propose a characterization me-
thod for quantum states propagating within, with interest in the conti-
nuously growing eld of integrated quantum photonics
Continuous-variable entanglement of two bright coherent states that never interacted
We study continuous-variable entanglement of bright quantum states in a pair
of evanescently coupled nonlinear waveguides operating in the
regime of degenerate down-conversion. We consider the case where only the
energy of the nonlinearly generated fields is exchanged between the waveguides
while the pump fields stay independently guided in each original waveguide. We
show that this device, when operated in the depletion regime, entangles the two
non-interacting bright pump modes due to a nonlinear cascade effect. It is also
shown that two-colour quadripartite entanglement can be produced when certain
system parameters are appropriately set. This device works in the
traveling-wave configuration, such that the generated quantum light shows a
broad spectrum. The proposed device can be easily realized with current
technology and therefore stands as a good candidate for a source of bipartite
or multipartite entangled states for the emerging field of optical
continuous-variable quantum information processing.Comment: 10 pages, 12 figure
Artificial Rheotaxis
Motility is a basic feature of living microorganisms, and how it works is
often determined by environmental cues. Recent efforts have focused on develop-
ing artificial systems that can mimic microorganisms, and in particular their
self-propulsion. Here, we report on the design and characterization of syn-
thetic self-propelled particles that migrate upstream, known as positive rheo-
taxis. This phenomenon results from a purely physical mechanism involving the
interplay between the polarity of the particles and their alignment by a
viscous torque. We show quantitative agreement between experimental data and a
simple model of an overdamped Brownian pendulum. The model no- tably predicts
the existence of a stagnation point in a diverging flow. We take advantage of
this property to demonstrate that our active particles can sense and
predictably organize in an imposed flow. Our colloidal system represents an
important step towards the realization of biomimetic micro-systems withthe
ability to sense and respond to environmental changesComment: Published in Science Advances [Open access journal of Science
Magazine
Hierarchy of Genuine Tripartite Non-Gaussian Entanglement
Triple-photon states generated by three-mode spontaneous parametric
down-conversion are the paradigm of unconditional non-Gaussian states,
essential assets for quantum advantage. How to fully characterize their
non-Gaussian entanglement remains however elusive. We propose here a hierarchy
of sufficient and necessary conditions for separability of the broad family of
spontaneously-generated three-mode non-Gaussian states. We further derive
state-of-the-art conditions for genuine tripartite non-Gaussian entanglement,
the strongest class of entanglement. We apply our criteria to triple-photon
states revealing that they are fully inseparable and genuinely entangled in
moments of order 3n. Our results establish a systematic framework for
characterizing the entanglement of triple-photon states and thus fostering
their application in quantum information protocols
Symmetry-based analytical solutions to the \chi^{(2)} nonlinear directional coupler
In general the ubiquitous \chi^{(2)} nonlinear directional coupler, where
nonlinearity and evanescent coupling are intertwined, is nonintegrable. We
rigorously demonstrate that matching excitation to the even or odd fundamental
supermodes yields dynamical analytical solutions for any phase matching in a
symmetric coupler. We analyze second harmonic generation and optical parametric
amplification regimes and study the influence of fundamental fields parity and
power on the operation of the device. These fundamental solutions are useful to
develop applications in classical and quantum fields such as all-optical
modulation of light and quantum-states engineering.Comment: 7 pages, 6 figure
- …