7,395 research outputs found
Integrated sources of entangled photons at telecom wavelength in femtosecond-laser-written circuits
Photon entanglement is an important state of light that is at the basis of
many protocols in photonic quantum technologies, from quantum computing, to
simulation and sensing. The capability to generate entangled photons in
integrated waveguide sources is particularly advantageous due to the enhanced
stability and more efficient light-crystal interaction. Here we realize an
integrated optical source of entangled degenerate photons at telecom
wavelength, based on the hybrid interfacing of photonic circuits in different
materials, all inscribed by femtosecond laser pulses. We show that our source,
based on spontaneous parametric down-conversion, gives access to different
classes of output states, allowing to switch from path-entangled to
polarization-entangled states with net visibilities above 0.92 for all selected
combinations of integrated devices
An integrated cryogenic optical modulator
Integrated electrical and photonic circuits (PIC) operating at cryogenic
temperatures are fundamental building blocks required to achieve scalable
quantum computing, and cryogenic computing technologies. Optical interconnects
offer better performance and thermal insulation than electrical wires and are
imperative for true quantum communication. Silicon PICs have matured for room
temperature applications but their cryogenic performance is limited by the
absence of efficient low temperature electro-optic (EO) modulation. While
detectors and lasers perform better at low temperature, cryogenic optical
switching remains an unsolved challenge. Here we demonstrate EO switching and
modulation from room temperature down to 4 K by using the Pockels effect in
integrated barium titanate (BaTiO3)-based devices. We report the nonlinear
optical (NLO) properties of BaTiO3 in a temperature range which has previously
not been explored, showing an effective Pockels coefficient of 200 pm/V at 4 K.
We demonstrate the largest EO bandwidth (30 GHz) of any cryogenic switch to
date, ultra-low-power tuning which is 10^9 times more efficient than thermal
tuning, and high-speed data modulation at 20 Gbps. Our results demonstrate a
missing component for cryogenic PICs. It removes major roadblocks for the
realisation of novel cryogenic-compatible systems in the field of quantum
computing and supercomputing, and for interfacing those systems with the real
world at room-temperature
Hybrid integration methods for on-chip quantum photonics
The goal of integrated quantum photonics is to combine components for the generation, manipulation, and detection of nonclassical light in a phase-stable and efficient platform. Solid-state quantum emitters have recently reached outstanding performance as single-photon sources. In parallel, photonic integrated circuits have been advanced to the point that thousands of components can be controlled on a chip with high efficiency and phase stability. Consequently, researchers are now beginning to combine these leading quantum emitters and photonic integrated circuit platforms to realize the best properties of each technology. In this paper, we review recent advances in integrated quantum photonics based on such hybrid systems. Although hybrid integration solves many limitations of individual platforms, it also introduces new challenges that arise from interfacing different materials. We review various issues in solid-state quantum emitters and photonic integrated circuits, the hybrid integration techniques that bridge these two systems, and methods for chip-based manipulation of photons and emitters. Finally, we discuss the remaining challenges and future prospects of on-chip quantum photonics with integrated quantum emitters. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen
Polarization entangled state measurement on a chip
The emerging strategy to overcome the limitations of bulk quantum optics
consists of taking advantage of the robustness and compactness achievable by
the integrated waveguide technology. Here we report the realization of a
directional coupler, fabricated by femtosecond laser waveguide writing, acting
as an integrated beam splitter able to support polarization encoded qubits.
This maskless and single step technique allows to realize circular transverse
waveguide profiles able to support the propagation of Gaussian modes with any
polarization state. Using this device, we demonstrate the quantum interference
with polarization entangled states and singlet state projection.Comment: Revtex, 5+2 pages (with supplementary information), 4+1 figure
Integrated photonic quantum gates for polarization qubits
Integrated photonic circuits have a strong potential to perform quantum
information processing. Indeed, the ability to manipulate quantum states of
light by integrated devices may open new perspectives both for fundamental
tests of quantum mechanics and for novel technological applications. However,
the technology for handling polarization encoded qubits, the most commonly
adopted approach, is still missing in quantum optical circuits. Here we
demonstrate the first integrated photonic Controlled-NOT (CNOT) gate for
polarization encoded qubits. This result has been enabled by the integration,
based on femtosecond laser waveguide writing, of partially polarizing beam
splitters on a glass chip. We characterize the logical truth table of the
quantum gate demonstrating its high fidelity to the expected one. In addition,
we show the ability of this gate to transform separable states into entangled
ones and vice versa. Finally, the full accessibility of our device is exploited
to carry out a complete characterization of the CNOT gate through a quantum
process tomography.Comment: 6 pages, 4 figure
Progress towards on-chip single photon sources based on colloidal quantum dots in silicon nitride devices
New results on integration of colloidal quantum dots (QDs) into SiN microstructures are reported, including QD positioning with nanometric accuracy and the efficient coupling of their emission to waveguides and cavities. The results are relevant to on-chip quantum optics and information processing
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