arXiv subjects

Jörn P. Epping

Publications and source records attributed to Jörn P. Epping.

9 recordsLinked to original sources

arXiv2023

20-Mode Universal Quantum Photonic Processor

Integrated photonics is an essential technology for optical quantum computing. Universal, phase-stable, reconfigurable multimode interferometers (quantum photonic processors) enable manipulation of photonic quantum states and are one of the main components of photonic quantum computers in various architectures. In this paper, we report the realization of the largest quantum photonic processor to date. The processor enables arbitrary unitary transformations on its 20 input modes with an amplitude fidelity of $F_{\text{Haar}} = 97.4\%$ and $F_{\text{Perm}} = 99.5\%$ for Haar-random and permutation matrices, respectively, an optical loss of 2.9 dB averaged over all modes, and high-visibility quantum interference with $V_{\text{HOM}}=98\%$. The processor is realized in $\mathrm{Si_3N_4}$ waveguides and is actively cooled by a Peltier element.

quant-ph↗

arXiv2022

Fully on-chip photonic turnkey quantum source for entangled qubit/qudit state generation

Integrated photonics has recently become a leading platform for the realization and processing of optical entangled quantum states in compact, robust and scalable chip formats with applications in long-distance quantum-secured communication, quantum-accelerated information processing and non-classical metrology. However, the quantum light sources developed so far have relied on external bulky excitation lasers making them impractical, not reproducible prototype devices, hindering scalability and the transfer out of the lab into real-world applications. Here we demonstrate a fully integrated quantum light source, which overcomes these challenges through the combined integration of a laser cavity, a highly efficient tunable noise suppression filter ($> 55$ dB) exploiting the Vernier effect and a nonlinear microring for entangled photon pair generation through spontaneous four-wave mixing. The hybrid quantum source employs an electrically-pumped InP gain section and a Si$_3$N$_4$ low-loss microring filter system, and demonstrates high performance parameters, i.e., a pair emission over four resonant modes in the telecom band (bandwidth $\sim 1$ THz), and a remarkable pair detection rate of $\sim 620$ Hz at a high coincidence-to-accidental ratio of $\sim 80$. The source directly creates high-dimensional frequency-bin entangled quantum states (qubits/qudits), verified by quantum interference measurements with visibilities up to $96\%$ (violating Bell-inequality) and by density matrix reconstruction through state tomography showing fidelities of up to $99\%$. Our approach, leveraging a hybrid photonic platform, enables commercial-viable, low-cost, compact, light-weight, and field-deployable entangled quantum sources, quintessential for practical, out-of-lab applications, e.g., in quantum processors and quantum satellite communications systems.

physics.optics↗

arXiv2022

High Fidelity 12-Mode Quantum Photonic Processor Operating at InGaAs Quantum Dot Wavelength

Reconfigurable quantum photonic processors are an essential technology for photonic quantum computing. Although most large-scale reconfigurable quantum photonic processors were demonstrated at the telecommunications C band around 1550 nm, high-performance single photon light sources utilizing quantum dots that are well-suited for photonic quantum computing operate at a variety of wavelengths. Thus, a demand exists for the compatibility of quantum photonic processors with a larger wavelength range. Silicon nitride (SiN) has a high confinement and wide transparency window, enabling compact, low-loss quantum photonic processors at wavelengths outside the C band. Here, we report a SiN universal 12-mode quantum photonic processor with optimal operation at a wavelength of 940 nm, which is compatible with InGaAs quantum dot light sources that emit light in the 900 nm to 970 nm wavelength range. The processor can implement arbitrary unitary transformations on its 12 input modes with a fidelity of 98.6 %, with a mean optical loss of 3.4 dB/mode.

quant-ph↗

arXiv2020

A 12-mode Universal Photonic Processor for Quantum Information Processing

Photonic processors are pivotal for both quantum and classical information processing tasks using light. In particular, linear optical quantum information processing requires both largescale and low-loss programmable photonic processors. In this paper, we report the demonstration of the largest universal quantum photonic processor to date: a low-loss, 12-mode fully tunable linear interferometer with all-to-all coupling based on stoichiometric silicon nitride waveguides.

quant-ph↗

arXiv2019

Hybrid integrated semiconductor lasers with silicon nitride feedback circuits

Hybrid integrated semiconductor laser sources offering extremely narrow spectral linewidth as well as compatibility for embedding into integrated photonic circuits are of high importance for a wide range of applications. We present an overview on our recently developed hybrid-integrated diode lasers with feedback from low-loss silicon nitride (Si3N4 in SiO2) circuits, to provide sub-100-Hz-level intrinsic linewidths, up to 120 nm spectral coverage around 1.55 um wavelength, and an output power above 100 mW. We show dual-wavelength operation, dual-gain operation, laser frequency comb generation, and present work towards realizing a visible-light hybrid integrated diode laser.

physics.optics↗

arXiv2017

Photo-induced second-order nonlinearity in stoichiometric silicon nitride waveguides

We report the observation of second-harmonic generation in stoichiometric silicon nitride waveguides grown via low-pressure chemical vapour deposition. Quasi-rectangular waveguides with a large cross section were used, with a height of 1 μm and various different widths, from 0.6 to 1.2 μm, and with various lengths from 22 to 74 mm. Using a mode-locked laser delivering 6-ps pulses at 1064 nm wavelength with a repetition rate of 20 MHz, 15% of the incoming power was coupled through the waveguide, making maximum average powers of up to 15 mW available in the waveguide. Second-harmonic output was observed with a delay of minutes to several hours after the initial turn-on of pump radiation, showing a fast growth rate between 10$^{-4}$ to 10$^{-2}$ s$^{-1}$, with the shortest delay and highest growth rate at the highest input power. After this first, initial build-up, the second-harmonic became generated instantly with each new turn-on of the pump laser power. Phase matching was found to be present independent of the used waveguide width, although the latter changes the fundamental and second-harmonic phase velocities. We address the presence of a second-order nonlinearity and phase matching, involving an initial, power-dependent build-up, to the coherent photogalvanic effect. The effect, via the third-order nonlinearity and multiphoton absorption leads to a spatially patterned charge separation, which generates a spatially periodic, semi-permanent, DC-field-induced second-order susceptibility with a period that is appropriate for quasi-phase matching. The maximum measured second-harmonic conversion efficiency amounts to 0.4% in a waveguide with 0.9 x 1 μm$^2$ cross section and 36 mm length, corresponding to 53 μW at 532 nm with 13 mW of IR input coupled into the waveguide. The according $χ^{(2)}$ amounts to 3.7 pm/V, as retrieved from the measured conversion efficiency.

physics.optics↗

arXiv2015

Ultrafast, low-power, all-optical switching via birefringent phase-matched transverse mode conversion in integrated waveguides

We demonstrate the potential of birefringence-based, all-optical, ultrafast conversion between the transverse modes in integrated optical waveguides by modelling the conversion process by numerically solving the multi-mode coupled nonlinear Schroedinger equations. The observed conversion is induced by a control beam and due to the Kerr effect, resulting in a transient index grating which coherently scatters probe light from one transverse waveguide mode into another. We introduce birefringent phase matching to enable efficient all-optically induced mode conversion at different wavelengths of the control and probe beam. It is shown that tailoring the waveguide geometry can be exploited to explicitly minimize intermodal group delay as well as to maximize the nonlinear coefficient, under the constraint of a phase matching condition. The waveguide geometries investigated here, allow for mode conversion with over two orders of magnitude reduced control pulse energy compared to previous schemes and thereby promise nonlinear mode switching exceeding efficiencies of 90% at switching energies below 1 nJ.

physics.optics↗

arXiv2015

High confinement, high yield Si3N4 waveguides for nonlinear optical application

In this paper we present a novel fabrication technique for silicon nitride (Si3N4) waveguides with a thickness of up to 900 nm, which are suitable for nonlinear optical applications. The fabrication method is based on etching trenches in thermally oxidized silicon and filling the trenches with Si3N4. Using this technique no stress-induced cracks in the Si3N4 layer were observed resulting in a high yield of devices on the wafer. The propagation losses of the obtained waveguides were measured to be as low as 0.4 dB/cm at a wavelength of around 1550 nm.

physics.optics↗

arXiv2013

Integrated CARS Source based on Seeded Four-wave Mixing in Silicon Nitride

We present a theoretical investigation of an integrated nonlinear light source for coherent anti-Stokes Raman scattering (CARS) based on silicon nitride waveguides. Wavelength tunable and temporally synchronized signal and idler pulses are obtained by using seeded four-wave mixing. We find that the calculated input pump power needed for nonlinear wavelength generation is more than one order of magnitude lower than in previously reported approaches based on optical fibers. The tuning range of the wavelength conversion was calculated to be 1418 nm to 1518 nm (idler) and 788 nm to 857 nm (signal), which corresponds to a coverage of vibrational transitions from 2350 cm$^{-1}$ to 2810 cm$^{-1}$. A maximum conversion efficiency of 19.1% at a peak pump power of 300 W was obtained.

physics.optics↗