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Entangled photon pairs are an important resource for many types of quantum protocols. Semiconductor Bragg-reflection waveguides are a promising photon-pair source due to mature fabrication, integrability, large transparency window in the telecom wavelength range, integration capabilities for electro-optical devices as well as a high second-order nonlinear coefficient. To increase performance, we improved the fabrication of Bragg-reflection waveguides by employing fixed-beam-moving-stage optical lithography, low-pressure, and low chlorine concentration etching, and resist reflow. The reduction in sidewall roughness yields a low optical loss coefficient for telecom wavelength light of alpha reflow = 0.08 (6) mm-1. Owing to the decreased losses, we achieved a photon-pair production rate of 8800 (300) (mW center dot s center dot mm)-1, which is 15-fold higher than in previous samples. Published by Optica Publishing Group under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI., Optical Materials Express, 13 (5), ISSN:2159-3930

In the field of topological materials, the interaction between band topology and magnetism remains a current frontier for the advancement of new topological states and spintronic functionalities. D...

We fabricate low-loss AlGaAs Bragg-reflection waveguides for the creation of telecom wavelength photon pairs via parametric down-conversion. These photon pairs are used in a hybrid on-chip time-bin entanglement scheme.

Structural moir\'e superstructures arising from two competing lattices may lead to unexpected electronic behavior, such as superconductivity or Mottness. Most investigated moir\'e heterostructures are based on van der Waals (vdW) materials, as strong interface interactions typically lead to the formation of strained films or regular surface reconstructions. Here we successfully synthesize ultrathin Sb films, that are predicted to show thickness-dependent topological properties, on semi-insulating InSb(111)A. Despite the covalent nature of the substrate surface, we prove by scanning transmission electron microscopy (STEM) that already the first layer of Sb atoms grows completely unstrained, while azimuthally aligned. Rather than compensating the lattice mismatch of -6.4% by structural modifications, the Sb films form a pronounced moir\'e pattern as we evidence by scanning tunneling microscopy (STM) topography up to film thicknesses of several bilayers. Our model calculations based on density functional theory (DFT) assign the moir\'e pattern to a periodic surface corrugation. In agreement with DFT predictions, irrespective of the moir\'e modulation, the topological surface state known on thick Sb film is experimentally confirmed to persist down to low film thicknesses, and the Dirac point shifts towards lower binding energies with decreasing Sb thickness., Comment: 34 pages in total, 4 figures, 1 table and 1 TOC in the main text

The authors study, as a promising candidate for photovoltaic applications, the Mott insulator LaVO${}_{3}$, epitaxially grown as a thin film on SrTiO${}_{3}$. They elucidate the electronic properties by electrical transport and photoemission measurements. The origin of the conducting interface is identified to be electronic reconstruction due to the polar discontinuity between film and substrate. The authors find a potential gradient in the film and a downward band bending in the substrate, with the electrons residing in interfacial Ti states.

In this work, monolithic mode-locked GaSb-based lasers at 1.7 µm emission wavelength with heterodyne measurement of the frequency comb are presented. Mode-locking operation was confirmed by measuring the optical beatnote at the round-trip frequency of 9.56 GHz and analysing the frequency comb. Mode-locking operation occurred from 0.1 to 3.3 V reverse bias voltages at the absorber section and driving currents from 160 to 400 mA at the laser section with a minimum beatnote width of 6.6 kHz. The frequency comb spans over 13 nm with a mode spacing of 0.10 nm, measured by heterodyne-detection with a distributed feedback laser.

In this letter, we present evanescently coupled semiconductor laser arrays designed with a distributed Bragg reflector section for spectrally narrow emission and a combined waveguide section for high optical output powers. These devices were designed and fabricated in the AlGaAs material system with an InGaAsP quantum well providing emission in the 760–770 nm wavelength range. Measurements of the light-current characteristics reveal high optical output powers of 600 mW at 20 °C and 700 mW at 5 °C limited by thermal rollover without any signs of a catastrophic optical mirror damage or rapid power degradation. Spectrally narrow emission of 0.2 nm at −3 dB and a high wavelength stability with a small current tuning coefficient of 0.7 pm/mA were found. Far-field investigations reveal pre-dominant coupling of lowest order in-phase supermode emission without any sections for adjusting the phase of the electrical field vector for adjacent elements. Postprint

We demonstrate a deterministic Purcell-enhanced single photon source realized by integrating an atomically thin WSe

Following the ultrafast optical excitation of an inhomogeneously broadened ensemble, the macroscopic optical polarization decays rapidly due to dephasing. This destructive interference is, however, reversible in photon echo experiments. Here, we propose a concept in which a control pulse slows down either the dephasing or the rephasing of the exciton ensemble during its presence. We analyze and visualize this optical freezing process by showing and discussing results for different single and multiple sequences of control pulses using a simple model of inhomogeneously broadened two-level systems. This idea has been realized in experiments performed on self-assembled (In,Ga)As quantum dots where it was possible to retard or advance the photon echo emission time by several picoseconds. The measurements are in very good agreement with numerical simulations for a more realistic model which, in particular, takes the spatial shape of the laser pulses into account.

The phase distributions of Anderson localized modes are measured in 2D disordered photonic crystals, using single-shot interferograms. The distribution closely follows the theoretical prediction.

We report the growth of CuMnSb thin films by molecular beam epitaxy on InAs (001) substrates. The CuMnSb layers are compressively strained (0.6 %) due to lattice mismatch. The thin films have a $\ensuremath{\omega}$ full width at half-maximum of 7.7 arcsec according to high resolution x-ray diffraction, and a root-mean-square roughness of 0.14 nm as determined by atomic force microscopy. Magnetic and electrical properties are found to be consistent with reported values from bulk samples. We find a N\'eel temperature of 62 K, a Curie-Weiss temperature of \ensuremath{-}65 K, and an effective moment of $5.9\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{B}/\mathrm{f}.\mathrm{u}.$ Transport measurements confirm the antiferromagnetic transition and show a residual resistivity at 4 K of $35\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}$\textohm{} cm.

D.W. acknowledges financial support by the Polish National Agency for Academic Exchange (NAWA) within the ULAM program (No. PPN/ULM/2019/1/00064). The Würzburg team acknowledges the support by the State of Bavaria and the Deutsche Forschungsgemeinschaft (DFG) within Project No. SCHN1376 5.1 / PR1749 1.1. The Jaynes-Cummings (JC) model represents one of the simplest ways in which single qubits can interact with single photon modes, leading to profound quantum phenomena like superpositions of light and matter states. One system, that can be described with the JC model, is a single quantum dot embedded in a micropillar cavity. In this joint experimental and theoretical study we investigate such a system using four-wave mixing (FWM) micro-spectroscopy. Special emphasis is laid on the dependence of the FWM signals on the number of photons injected into the microcavity. By comparing simulation and experiment, which are in excellent agreement with each other, we infer that up to ∼20 photons take part in the observed FWM dynamics. Thus we verify the validity of the JC model for the system under consideration in this non-trivial regime. We find that the inevitable coupling between the quantum dot exciton and longitudinal acoustic phonons of the host lattice influences the real time FWM dynamics and has to be taken into account for a sufficient description of the quantum dot-microcavity system. Performing additional simulations in an idealized dissipation-less regime, we observe that the FWM signal exhibits quasi-periodic dynamics, analog to the collapse and revival phenomenon of the JC model. In these simulations we also see that the FWM spectrum has a triplet structure, if a large number of photons is injected into the cavity. Postprint

A non-intuitive combination of near-Wigner Dyson spacing statistics and lognormal conductance distribution is measured in a two-dimensional finite-sized Anderson localizing system. Theoretical analysis uncovers a novel nonlinear connection between repulsion exponent and localization length.

Photon echo from trions and excitons in (In,Ga)As/GaAs quantum dots was studied theoretically and experimentally. Theoretical analysis allowed us to distinguish between photon echo signals from excitons and trions measured in the same range of wavelength using different polarization configurations of laser excitation. The theoretical predictions are in good agreement with the experimental data.

The G-protein-coupled receptor (GPCR) superfamily mediates cellular responses and communication across cellular membranes and is the largest known class of molecular targets with proven therapeutic value. For probing conformational changes of GPCRs and others in a live cell setting, fluorescence resonance energy transfer (FRET) is usually the method of choice. FRET probes often require careful labeling procedures, elaborate characterization, and assay optimization to provide both physiologically relevant probes with unaltered pharmacology and a sufficient dynamic range of the FRET changes. Here, we present an approach to optimize the energy transfer without changing the design of the FRET probe. We show that gold-coated glass coverslips reinforce the otherwise forbidden donor–acceptor energy transfer by virtual optimization of the dipole orientation. First, we confirm the resulting enhanced FRET efficiency on our nanocoatings for the inactive M1 muscarinic acetylcholine receptor (mAChR) labeled with a FRE...

We describe the wet-chemical synthesis of high-aspect-ratio single-crystalline gold platelets with thicknesses down to 20 nm and edge lengths up to 0.2 mm. By employing statistical analysis of a large number of platelets, we investigate the effect of temperature on the growth velocities of the top and side facets for constant concentrations of the three common ingredients: ethylene glycol, chloroauric acid, and water. We further show that by varying the chemical environment during growth, the ratio between the growth velocities can be adjusted, and thus thickness and lateral size can be tuned independently. Very large but ultrathin single-crystalline gold platelets represent an important starting material for top-down nanofabrication and may also find applications as transparent conducting substrates as well as substrates for high-end scanning probe and electron microscopy.

This work was supported by the National Natural Science Foundation of China, the Chinese Academy of Sciences, the National Fundamental Research Program, and the State of Bavaria. Boson sampling is considered as a strong candidate to demonstrate ‘quantum computational supremacy’ over classical computers. However, previous proof-of-principle experiments suffered from small photon number and low sampling rates owing to the inefficiencies of the single-photon sources and multiport optical interferometers. Here, we develop two central components for high-performance boson sampling: robust multiphoton interferometers with 99% transmission rate and actively demultiplexed single-photon sources based on a quantum dot–micropillar with simultaneously high efficiency, purity and indistinguishability. We implement and validate three-, four- and five-photon boson sampling, and achieve sampling rates of 4.96 kHz, 151 Hz and 4 Hz, respectively, which are over 24,000 times faster than previous experiments. Our architecture can be scaled up for a larger number of photons and with higher sampling rates to compete with classical computers, and might provide experimental evidence against the extended Church–Turing thesis. Postprint Postprint Postprint

The work was supported by the Elite Network of Bavaria (K-NW-2013-247), the DFG priority program SPP1666, the Volkswagen Stiftung Program, the State of Bavaria and the German Research Foundation (Ka2318/4-1). S.A.T. acknowledges support from the RFBR (projects 14-22-02102 and 16-02-00375). We report on the observation of photogalvanic effects induced by terahertz radiation in type-II GaSb/InAs quantum wells with inverted band order. Photocurrents are excited at oblique incidence of radiation and consists of several contributions varying differently with the change of the radiation polarization state; the one driven by the helicity and the other one driven by the linearly polarization of radiation are of comparable magnitudes. Experimental and theoretical analyses reveal that the photocurrent is dominated by the circular and linear photogalvanic effects in a system with a dominant structure inversion asymmetry. A microscopic theory developed in the framework of the Boltzmann equation of motion considers both photogalvanic effects and describes well all the experimental findings. Postprint

A biochemical sensor based on the combination of a complex coupled distributed feedback laser with a sensing waveguide is presented. The sensing waveguide was realized by etching a deep trench into the middle of a ridge waveguide to increase the analyte overlap. These devices were investigated with respect to their sensitivity to refractive index changes of a surrounding analyte. A wavelength shift of about 12nm was observed applying an index change of $\Delta n= {{0.48}}$ . The analyte overlap was calculated to be 5.6. Using this kind of monolithic, active, and single-frequency device could be an easy approach to sensitive affinity arrays.

We experimentally investigate spectral statistics in Anderson localization in two-dimensional amorphous disordered media. Intensity distributions captured over an ultrabroad wavelength range of $\sim 600$~nm and averaged over numerous configurations provided the Ioffe-Regel parameter to be $\sim2.5$ over the investigated wavelength range. The spectra of the disordered structures provided access to several quasimodes, whose widths and separations allowed to directly estimate the optical Thouless conductance $g_{Th}$, consistently observed to be below unity. The probability distribution of $g_{Th}$ was measured to be a log-normal. Despite being in the Anderson localization regime, the spacings of energy levels of the system was seen to follow a near Wigner-Dyson function. Theoretical calculations based on the tight-binding model, modified to include coupling to a bath, yielded results that were in excellent agreement with experiments. From the model, the level-spacing behavior was attributed to the degree of localization obtained in the optical disordered system., Comment: 6 pages, 7 figures in main manuscript, and 3 pages, 5 figures in Supplementary Document

Anderson localization (AL) of light[1], one of the most exotic mesoscopic phenomena, can be realized at two limits of disorder, namely, near-periodic disorder[2] or strong disorder[3]. AL can be characterized by sub-unity conductance. A critical parameter of interest is the fluctuations of conductance which reveals the statistical behaviour of the system and offers a more complete description of the underlying physics. However, the conventional technique of quantifying conductance precludes the measurement of the fluctuations thereof. In this work, we achieve Anderson localization of light in Gallium Arsenide membranes at both near-periodic disorder and strong disorder. We measure the generalized conductance fluctuations using the intensity distribution of light, and reveal hitherto unknown features of transport under the two approaches of localization.

Anderson localization is a striking phenomenon wherein transport of light is arrested due to the formation of disorder-induced resonances. Hitherto, Anderson localization has been demonstrated separately in two limits of disorder, namely, amorphous disorder and nearly-periodic disorder. However, transport properties in the two limits are yet unstudied, particularly in a statistically consistent manner. Here, we experimentally measure light transport across two-dimensional open mesoscopic structures, wherein the disorder systematically ranges from nearly-periodic to amorphous. We measure the generalized conductance, which quantifies the transport probability in the sample. Although localization was identified in both the limits, statistical measurements revealed a discrepant behavior in the generalized conductance fluctuations in the two disorder regimes. Under amorphous disorder, the generalized conductance remains below unity for any configuration of the disorder, attesting to the arrested nature of transport. Contrarily, at near-periodic disorder, the distribution of generalized conductance is heavy-tailed towards large conductance values, indicating that the overall transport is delocalized. Theoretical results from a model based on the tight-binding approximation, augmented to include open boundaries, are in excellent agreement with experiments, and also endorse the results over much larger ensembles. These results quantify the differences in the two disorder regimes, and advance the studies of disordered systems into actual consequences of Anderson localization in light transport., Comment: 27 pages, 15 figures, including Supplementary Information

Compared to traditional non-linear optical crystals, like BaB2O4, KTiOPO4 or LiNbO3, semiconductor integrated sources of photon pairs may operate at pump wavelengths much closer to the bandgap of the materials. This is also the case for Bragg-reflection waveguides (BRWs) targeting parametric down-conversion (PDC) to the telecom C-band. The large non-linear coefficient of the AlGaAs alloy and the strong confinement of the light enable extremely bright integrated photon pair sources. However, under certain circumstances, a significant amount of detrimental broadband photoluminescence has been observed in BRWs. We show that this is mainly a result of linear absorption near the core and subsequent radiative recombination of electron–hole pairs at deep impurity levels in the semiconductor. For PDC with BRWs, we conclude that devices operating near the long wavelength end of the S-band or the short C-band require temporal filtering shorter than 1 ns. We predict that shifting the operating wavelengths to the L-band reduces the amount of photoluminescence by 70% and making small adjustments in the material composition results in its total reduction of 90%. Such measures enable us to increase the average pump power and/or the repetition rate, which makes integrated photon pair sources with on-chip multi-gigahertz pair rates feasible for future devices.

The recent progress in integrated quantum optics has set the stage for the development of an integrated platform for quantum information processing with photons, with potential applications in quantum simulation. Among the different material platforms being investigated, direct-bandgap semiconductors and particularly gallium arsenide (GaAs) offer the widest range of functionalities, including single- and entangled-photon generation by radiative recombination, low-loss routing, electro-optic modulation and single-photon detection. This paper reviews the recent progress in the development of the key building blocks for GaAs quantum photonics and the perspectives for their full integration in a fully-functional and densely integrated quantum photonic circuit.

The layered van der Waals compounds ( MnBi 2 Te 4)( Bi 2 Te 3) were recently established as the first intrinsic magnetic topological insulators. We report a study on the epitaxial growth of ( MnBi 2 Te 4 ) m ( Bi 2 Te 3 ) n films based on the co-deposition of MnTe and Bi 2 Te 3 on BaF 2 (111) substrates. X-ray diffraction and scanning transmission electron microscopy evidence the formation of multilayers of stacked MnBi 2 Te 4 septuple layers and Bi 2 Te 3 quintuple layers with a predominance of MnBi 2 Te 4. The elemental composition and morphology of the films is further characterized by x-ray photoemission spectroscopy and atomic force microscopy. X-ray magnetic circular and linear dichroism spectra are comparable to those obtained for MnBi 2 Te 4 single crystals and confirm antiferromagnetic order in the films.

An often-overlooked property of transition metal oxide thin films is their microscopic surface structure and its effect on the electronic properties in the ultrathin limit. Contrary to the expected conservation of the perovskite stacking order in the (001) direction, heteroepitaxially grown SrIrO3 films on TiO2-terminated SrTiO3 are found to exhibit a terminating SrO surface layer. The proposed mechanism for the self-organized conversion involves the adsorption of excess oxygen ions at the apical sites of the IrO2-terminated surface and the subsequent decomposition of the IrO6 octahedra into gaseous molecular IrO3 and the remaining SrO-terminated surface. Whereas the ab initio calculated electronic structure of SrO-terminated SrIrO3 in the monolayer limit exhibits a striking similarity to bulk Sr2IrO4, the broken octahedral symmetry at the IrO2-terminated surface would mix the otherwise crystal field split e(g) and t(2g) states, resulting in distinctly different low-energy electronic states. Published under license by AIP Publishing.

The electronic structures of BaBiO3 (BBO) thin films grown on SrTiO3 substrates are found to be thickness dependent. The origin of this behavior remains under debate and has been suggested to be attributed to the structural and compositional modifications at the BBO/SrTiO3 interface during the first stage of film growth. Though a wetting layer with thickness of ≈1 nm has been experimentally identified at the interface, details on the microstructures of such a layer and their effect on the subsequent film growth are lacking so far, particularly at the atomic scale. Herein, atomic‐resolution scanning transmission electron microscopy is used to study the interface structure of a 30 nm‐thick BBO film grown on an Nb‐doped SrTiO3 (STO) substrate through domain matching epitaxy. An interfacial δ‐Bi2O3 (BO)‐like phase with fluorite structure is identified, showing a layer‐by‐layer spacing of ≈3.2 Å along the growth direction. The orientation relationship between the BO‐like phase and surrounding perovskites (P) is found to be BO||P and BO||P. The presence of the BO‐like phase results in two types of interfaces, i.e., a coherent BO/STO and a semicoherent BBO/BO interface. Thickness variations are observed in the BO‐like layer, resulting in the formation of antiphase domains in the BBO films.

We present passive mode locking of a GaSb-based monolithic diode laser emitting at 2.2 μm with a fundamental repetition rate around 9.57 GHz. A pulse width of ∼2.4 ps is reconstructed by shifted wave intermode beat Fourier transform spectroscopy-measurements, yielding a time-bandwidth product of 1.8. Mode-locking is observed for a range of reverse bias voltages from 1.3 to 3.3 V and driving currents from 110 to 300 mA. The continuous wave output power is ∼17.5 mW with the absorber segment left floating and ∼4.5 mW at a reverse bias of 3.1 V in the mode-locked regime. The full-width-half-maximum of the radio frequency signal is measured for all operation conditions, with a minimum of 8.4 kHz.

Molecule and gas sensing is a key technology that is applied in multiple environmental, industrial and medical fields. In particular optical detection technologies enable contactless, nondestructive, highly sensitive and fast detection of even smallest concentrations of trace gases and molecules. During the past years, an increasing demand for mid-infrared (MIR) light sources suitable for, e.g. molecule or gas sensing applications, has driven the development and optimization of novel MIR lasers and light sources, such as quantum cascade lasers (QCL) or interband cascade lasers (ICL). Despite the progress on MIR light sources, there is still a lack in appropriate MIR detectors. Here, we present and discuss two promising and novel GaSb/InAs-based detector concepts. First, resonant tunneling diode (RTD) photodetectors as an alternative to avalanche photodetectors. In RTDs, amplification of photogenerated minority charge carriers is based on modulation of a majority charge carrier resonant tunneling current. Second, interband cascade photodetectors (ICD), in which a cascading scheme allows for fast carrier extraction and a compensation of the diffusion length limitation.

Funding: European Research Council under the European Union’s Seventh Framework Program (ERC Grant Agreement No. 615613); German Research Foundation (CRC 787, GRK1558); project EMPIR 14IND05 MIQC2 co-financed by the Participating States and from the European Union’s Horizon 2020 research and innovation program. Microlasers are ideal candidates to bring the fascinating variety of nonlinear complex dynamics found in delay-coupled systems to the realm of quantum optics. Particularly attractive is the possibility of tailoring the devices’ emission properties via non-invasive delayed optical coupling. However, until now scarce research has been done in this direction. Here, we experimentally and theoretically investigate the effects of delayed optical feedback on the mode-switching dynamics of an electrically driven bimodal quantum-dot micropillar laser, characterizing its impact on the micropillar’s output power, optical spectrum and photon statistics. Feedback is found to influence the switching dynamics and its characteristics time scales. In addition, stochastic switching is reduced with the subsequent impact on the microlaser photon statistics. Our results contribute to the comprehension of feedback-induced phenomena in micropillar lasers and pave the way towards the external control and tailoring of the properties of these key systems for the nanophotonics community. Publisher PDF

The authors acknowledge financial support from the State of Bavaria, as well as from the DFG within the Project Schn1376/3.1: Polariton based single-photon sources, and from the Danish Research Council for Technology and Production (Sapere Aude LOQIT, DFF4005-00370). The development of high quality factor solid-state microcavities with low mode volumes has paved the way towards on-chip cavity quantum electrodynamics experiments and the development of high-performance nanophotonic devices. Here, we report on the implementation of a new kind of solid-state vertical microcavity, which allows for confinement of the electromagnetic field in the lateral direction without deep etching. The confinement originates from a local elongation of the cavity layer imprinted in a shallow etch and epitaxial overgrowth technique. We show that it is possible to improve the quality factor of such microcavities by a specific in-plane bullseye geometry consisting of a set of concentric rings with sub wavelength dimensions. This design results in a smooth effective lateral photonic potential and therefore in a reduction of lateral scattering losses, which makes it highly appealing for experiments in the framework of exciton-polariton physics demanding tight spatial confinement. Postprint

The development and physical understanding of high-beta nanolasers operating in regime of cavity-quantum-electrodynamics (cQED) is a highly interdisciplinary field of research, involving important aspects of nanotechnology, quantum optics, and semiconductor physics. Of particular interest is the quantum limit of operation, in which a few or even a single emitter act as gain material. The regime of strong light-matter coupling is typically associated with weak excitation. With current realizations of cQED systems, strong coupling may persevere even at elevated excitation levels sufficient to cross the threshold to lasing. In the presence of stimulated emission, the vacuum-Rabi doublet in the emission spectrum is modified and the established criterion for strong coupling no longer applies. Based on an analytic approach, we provide a generalized criterion for strong coupling and the corresponding emission spectrum that includes the influence of higher Jaynes-Cummings states. The applicability is demonstrated in a theory-experiment comparison of a state-of-the-art few-emitter quantum-dot (QD)–micropillar laser as a particular realization of the driven dissipative Jaynes-Cummings model [1]. Furthermore, we address the question if and for which parameters true single-emitter lasing can be achieved. By using a master-equation approach for up to 8 QDs coupled to the mode, we provide evidence for the coexistence of strong coupling and lasing in our system in the presence of background emitter contributions by identifying signatures in the mean-photon number, the photon-autocorrelation function, and the emission linewidth. [1] C. Gies et al., accepted for publication in PRA, arxiv:1606.05591

Boson sampling is a well-defined task that is strongly believed to be intractable for classical computers, but can be efficiently solved by a specific quantum simulator. However, an outstanding problem for large-scale experimental boson sampling is the scalability. Here we report an experiment on boson sampling with photon loss, and demonstrate that boson sampling with a few photons lost can increase the sampling rate. Our experiment uses a quantum-dot-micropillar single-photon source demultiplexed into up to seven input ports of a 16*16 mode ultra-low-loss photonic circuit, and we detect three-, four- and five-fold coincidence counts. We implement and validate lossy boson sampling with one and two photons lost, and obtain sampling rates of 187 kHz, 13.6 kHz, and 0.78 kHz for five-, six- and seven-photon boson sampling with two photons lost, which is 9.4, 13.9, and 18.0 times faster than the standard boson sampling, respectively. Our experiment shows an approach to significantly enhance the sampling rate of multiphoton boson sampling., Comment: 10 pages, 12 figures, submitted

We present a novel compact nanophotonic device consisting of a nonclassical light source excited by a monolithically integrated and electrically driven quantum dot (QD) microlaser. Our device concept is based on self-assembled InAs QDs embedded in micropillar cavities and has many potential applications in the fields of quantum communication and quantum optics-based information processing. Electrically driven micropillars act as whispering gallery mode microlasers operable in both continuous and pulsed mode, with narrow pulse widths of 520 ps and decay constants as low as 160 ps observed. These microlasers are used as on-chip excitation sources to laterally excite individual QDs in nearby micropillars, which in turn act as vertically emitting nonclassical light sources. Our compact solid-state platform utilizes cavity-quantum electrodynamic effects to create antibunched light in continuous and pulsed operation with g(2)CW (0) = 0.76 ± 0.03 and g(2)Pulsed (0)= 0.78±0.11, demonstrating its potential for the generation of triggered single photons in a highly integrated chip. Postprint

Researchers demonstrate an electrically driven nanoscale transmitter based on the broadband quantum shot noise of electrons tunnelling across a feed gap. Unlike radiowave antennas, so far optical nanoantennas cannot be fed by electrical generators. Instead, they are driven by light1 or indirectly via excited discrete states in active materials2,3 in their vicinity. Here we demonstrate the direct electrical driving of an in-plane optical antenna by the broadband quantum-shot noise of electrons tunnelling across its feed gap. The spectrum of the emitted photons is determined by the antenna geometry and can be tuned via the applied voltage. Moreover, the direction and polarization of the light emission are controlled by the antenna resonance, which also improves the external quantum efficiency by up to two orders of magnitude. The one-material planar design offers facile integration of electrical and optical circuits and thus represents a new paradigm for interfacing electrons and photons at the nanometre scale, for example for on-chip wireless communication and highly configurable electrically driven subwavelength photon sources.

The authors are grateful for financial support by the BMBF via national project EIPHRIK (FKZ: 13N10710), the European Union (FPVII (2007-2013) under grant agreement No. 256959 NANOPOWER and No. 318287 LANDAUER), and the Brazilian Agencies FAPESP (2013/24253-5, 2012/13052-6, and 2012/51415-3), CNPq and CAPES. Sensor miniaturization together with broadening temperature sensing range are fundamental challenges in nanothermometry. By exploiting a large temperature-dependent screening effect observed in a resonant tunneling diode in sequence with a GaInNAs/GaAs quantum well, we present a low dimensional, wide range, and high sensitive nanothermometer. This sensor shows a large threshold voltage shift of the bistable switching of more than 4.5 V for a temperature raise from 4.5 to 295 K, with a linear voltage-temperature response of 19.2 mV K-1, and a temperature uncertainty in the millikelvin (mK) range. Also, when we monitor the electroluminescence emission spectrum, an optical read-out control of the thermometer is provided. The combination of electrical and optical read-outs together with the sensor architecture excel the device as a thermometer with the capability of noninvasive temperature sensing, high local resolution, and sensitivity. Postprint

The dynamics of spatial coherence and momentum distribution of polaritons in the regime of Bose-Einstein condensation are investigated in a GaAs microcavity with embedded quantum wells under nonresonant excitation with picosecond laser pulses. It is shown that the onset of the condensate first order sparial coherence is accompanied by narrowing of the polariton momentum distribution. At the same time, at sufficiently high excitation densities, there is significant qualitative discrepancy between the dynamic behavior of the width of the polariton momentum distribution determined from direct measurements and that calculated from the coherence spatial distribution. This discrepancy is observed at the fast initial stage of the polariton system kinetics and, apparently, results from the strong spatial nonuniformity of the phase of the condensate wave function, which equilibrates on a much longer time scale., Comment: 5 pages, 4 figures

We acknowledge the financial support by the European Research Council (ERC) Starting Grant PICSEN (grant no. 306387) The exact optical response of quantum few-level systems depends crucially on the exact choice of the incoming pulse areas. We use four-wave mixing (FWM) spectroscopy to infer the coherent response and dynamics of single InAs quantum dots (QDs) and study their pulse area dependence. By combining atomic force microscopy with FWM hyperspectral imaging, we show that the retrieved FWM signals originate from individual QDs enclosed in natural photonic defects. The optimized light-matter coupling in these defects allows us to perform our studies in a wide range of driving field amplitudes. When varying the pulse areas of the exciting laser pulses Rabi rotations of microscopic interband coherences can be resolved by the two-pulse FWM technique. We investigate these Rabi coherence rotations within two- and three-level systems, both theoretically and experimentally, and explain their damping by the coupling to acoustic phonons. To highlight the importance of the pulse area in uence, we show that the phonon-induced dephasing of QD excitons depends on the pulse intensity. Postprint

We present antimonide-based resonant tunneling photodetectors with GaSb/AlAsSb double barrier structures and pseudomorphically grown prewell emitter structures comprising the ternary compound semiconductors GaInSb and GaAsSb. Due to the incorporation of GaInSb and GaAsSb prewell emitters, room temperature resonant tunneling with peak-to-valley current ratios of up to 2.4 are shown. The room temperature operation is attributed to the enhanced Γ-Lvalley energy separation and consequently a re-population of the Γ-conduction band of the ternary compound emitter prewell with respect to bulk GaSb. By integration of a quaternary absorption layer, RTDs photodetectors with cut-off wavelengths up to 3 μm have been realized.

We study the time evolution of the Optical Spin Hall Effect (OSHE), which occurs when exciton-polaritons undergo resonant Rayleigh scattering. The resulting spin pattern in momentum space is quantified by calculating the degree of circular polarization of the momentum space image for each point in time. We find the degree of circular polarization performing oscillations, which can be described within the framework of the pseudospin model by Kavokin et al. (Ref. 1)., 6 pages, 4 figures

We employ two-dimensional (2D) coherent, nonlinear spectroscopy to investigate couplings within\ud individual InAs quantum dots (QD) and QD molecules. Swapping pulse ordering in a two-beam\ud sequence permits to distinguish between rephasing and non-rephasing four-wave mixing (FWM)\ud configurations. We emphasize the non-rephasing case, allowing to monitor two-photon coherence\ud dynamics. Respective Fourier transform yields a double quantum 2D FWM map, which is corroborated\ud with its single quantum counterpart, originating from the rephasing sequence. We introduce\ud referencing of the FWM phase with the one carried by the driving pulses, overcoming the necessity\ud of its active-stabilization, as required in 2D spectroscopy. Combining single and double quantum\ud 2D FWM, provides a pertinent tool in detecting and ascertaining coherent coupling mechanisms\ud between individual quantum systems, as exemplified experimentally.

We report on a theoretical and experimental study performed on AlAs/GaAs micropillar cavities containing InGaAs quantum dots as active medium. The devices have the interesting property of having almost all emission (spontaneous and stimulated) channelled into one cavity mode. They are excellent experimental platforms for studying laser physics because their emission behaviours question our understanding of lasing action. Analysis of spectrally-resolved photoluminescence and photon autocorrelation will be discussed and a physically definitive criterion for lasing applicable to all systems will be presented.

Quantum photonics holds great promise for future technologies such as secure communication, quantum computation, quantum simulation, and quantum metrology. An outstanding challenge for quantum photonics is to develop scalable miniature circuits that integrate single-photon sources, linear optical components, and detectors on a chip. Plasmonic nanocircuits will play essential roles in such developments. However, for quantum plasmonic circuits, integration of stable, bright, and narrow-band single photon sources in the structure has so far not been reported. Here we present a plasmonic nanocircuit driven by a self-assembled GaAs quantum dot. Through a planar dielectric-plasmonic hybrid waveguide, the quantum dot efficiently excites narrow-band single plasmons that are guided in a two-wire transmission line until they are converted into single photons by an optical antenna. Our work demonstrates the feasibility of fully on-chip plasmonic nanocircuits for quantum optical applications.

Quantum photonics holds great promise for future technologies such as secure communication, quantum computation, quantum simulation, and quantum metrology. An outstanding challenge for quantum photonics is to develop scalable miniature circuits that integrate single-photon sources, linear optical components, and detectors on a chip. Plasmonic nanocircuits will play essential roles in such developments. Plasmonic components feature ultracompact geometries and can be controlled more flexibly and more energy-efficiently compared to conventional dielectric components due to strong field confinement and enhancement. Moreover, plasmonic components are compatible with electronic circuits, thanks to their deep subwavelength sizes as well as their electrically conducting materials. However, for quantum plasmonic circuits, integration of stable, bright, and narrow-band single photon sources in the structure has so far not been reported. Here we present a quantum plasmonic nanocircuit driven by a self-assembled GaAs quantum dot. The quantum dot efficiently excites narrow-band single plasmons that are guided in a two-wire transmission line until they are converted into single photons by an optical antenna. Our work demonstrates the feasibility of fully on-chip plasmonic nanocircuits for quantum optical applications.

Quantum dots (QDs) can be incorporated into solid state photonic devices such as cavities or waveguides that enhance the light-matter interaction. A near unit efficiency light-matter interaction is essential for deterministic, scalable quantum information devices [1]. In this limit, a single photon input into the device will undergo a large rotation of the polarization of the light field due to the strong interaction with the QD. In the past preliminary results have indicated that a low quality-factor (Q∼290) pillar microcavity possesses a high s-factor and that the instantaneous interactions should be deterministic and with high fidelity [2].