Roberto Osellame’s research while affiliated with Italian National Research Council and other places

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Publications (697)


Adaptive boson sampling, tailored for quantum machine learning, via measurement post-selection
a The algorithm aims at solving a binary classification problem: in a 2D plane filled with different shapes, the goal is to classify the items according to the color feature. b Each point of the dataset is encoded in a quantum state ∣ψp⟩\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\vert {\psi }_{{{\boldsymbol{p}}}}\rangle$$\end{document}, according to the optical circuit output mode, with which such state is triggered. Actually, in the ABS theoretical scheme, the detection of a photon, exiting from U0, in one of the lower modes determines a specific adaptive transformation Up that cooperates in the generation of the state ∣ψp⟩\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\vert {\psi }_{{{\boldsymbol{p}}}}\rangle$$\end{document}. c The dataset is classified using a kernel method, specifically a Support Vector Machine. The kernel elements, defined as the overlap square moduli, can be directly derived from the sketched linear optical circuit, in which Vp is composed of U0 and Up. The square modulus of the overlap can be experimentally obtained through a measurement post-selection of the fraction of coincidences in which photons leave the circuit from the same modes as they entered. d Another way to evaluate the kernel arises from a post-selection reconstruction of the states with a tomography protocol, exploiting the projective unitary T that acts on the adaptive modes. This is the case of the experiment we implement here. After that, the kernel is provided to a classical hardware, which manages the binary classification task.
Experimental platforms
a Platform A. Such a platform used for 2-photon experiments in 6 modes, exploits a parametric down-conversion source that generates pairs of photons at 785 nm and a 6-mode universal programmable integrated optical circuit. The two photons are synchronized in time through delay lines. Polarization controllers and filters are employed to have fully indistinguishable photons. The operations of the chip are controlled via a power supply that applies currents to the heaters of the device. Finally, the time-to-digital converter processes the single-photon detector counts that are then analyzed for the experiment. b Platform B. In the second platform, we employ a semiconductor quantum dot source and an 8-mode universal programmable chip. The brightness of the source enables the implementation of up to 3-photon experiment. This time the photons emitted by the same quantum dot at different pump pulses are synchronized by a time-to-spatial demultiplexer in three different channels. Photon-detection has been performed by either avalanche photodiodes or by superconducting nanowire detectors. Photon number resolution in some of the experiments has been added by employing a probabilistic scheme based on mode-splitting via fiber beam-splitters. Legend: BBO (Beta-Barium Borate), F (frequency filter), HWP (half-wave plate), PBS (polarizing beam-splitter), PC (polarization compensation), APD (avalanche photodiode), TDC (time-to-digital converter), DMX (demultiplexing), SNSPD (superconducting nanowire single-photon detectors), BS (beam-splitter).
Two and three photons in ABS interferometers - platforms A and B1
a The experiment implements an ABS scheme [6, 2, 2, 3]. The circuit is encoded in a 6-mode universal programmable chip. In particular, we have a six-mode U0 and then three adaptive transformations Ui. The phase shifters ϕ (rectangles in the figure) and beam-splitter reflectivities θ (circles) are set to angles θ, ϕ = π/4 except for the θi of the Ui highlighted in red, orange and yellow that depends on the detection of one photon in the oj. Pairs of indistinguishable photons generated by parametric down-conversion evolve in such an interferometer and a qubit tomography conditioned on the detection oi is performed in the green part of the circuit. b Comparison between the numerically simulated kernel and the experimental one, the latter computed via the mutual state fidelity between the states reconstructed at the output of the programmable integrated optical circuit. c Experimental ρi\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\rho }_{i}$$\end{document} density matrices for the quantum states ρ1 (top) and ρ2 (bottom). We retrieved the density matrix by performing the qubit tomography with a tunable beam-splitter and phase-shifter. Uncertainties due to photon-counting statistics are smaller than the image scale. d 3-photon experiment in the 8-mode device. In this scenario we have r = 2 photons detected in 6 adaptive modes. We have a total amount of 15 transformations each of them triggered by the detection of two photons in a pair of the 6 outputs. The optical circuit is divided into an 8-mode unitary U0, and five transformations Ui, activated and combined according to the configurations of the r photons detected in the 6 output modes. The reflectivity values of the beam-splitters θi in red, orange, yellow, teal, and violet, depend on where the ancillary photons are detected, according to the formula displayed in the figure. e Comparison of the 15 × 15 kernels computed according to the theoretical modeling which assumes an imperfect single-photon source and the kernel reconstructed from the states measured at the output of the ABS scheme [8, 3, 2, 15]. Both experiments were carried out with APDs.
Three photons in an eight-mode adaptive Boson Sampling interferometer for generating Gaussian kernels
a The [8, 3, 2, 15] ABS scheme of platform B2. We synchronize n = 3 photons emitted from the quantum dot source and we process them in the m = 8 mode universal integrated circuit. The optical circuit is divided into an 8-mode randomly extracted unitary U0 and a 2-mode adaptive unitary Ui. Triggered by the detection of r = 2 photons in the 6 adaptive modes oj, the reflectivity value of the beam-splitter θi assumes 15 different values allowing for the reconstruction of 15 × 15 kernels. The green part of the circuit highlights the tomography station in which the dual rail qubit encoded in the remaining photon conditioned on the detection of the r photons in the other oj outputs is analyzed. On the right panel, we report the comparison between the 15 × 15 kernel simulated according to the theoretical model and the experimental one. b The [8, 3, 3, 15] scheme that encodes classical data in qutrit states (platform B3). The 8-mode U0 is followed by 3-mode adaptive Ui in which the reflectivity of two beam-splitters has been properly programmed in order to implement 15 different unitaries as before. Triggering on the detection of r = 2 photons in the 5 adaptive modes oj, considering both configurations in which photons are bunched in the same mode or are output from different modes, a 15 × 15 kernel has been reconstructed. The green part of the circuit is again the tomography station that analyzes the three-rail qutrit. The right panel reports the comparison between the 15 × 15 kernel simulated according to the theoretical model and the experimental one. c Experimental ρi density matrices for qutrits ρ1 and ρ2 to which correspond the following fidelity with the expected theoretical state, F1 = 0.995 ± 0.001 and F2 = 0.953 ± 0.010. The experimental density matrices are reconstructed by measuring in the tomography stage the generalized Pauli operators. Both experiments reported here were carried out with SNSPDs.
Classification of 1D and 2D datasets
a Example of classification of the 1D dataset performed by the SVM with the two quantum experimental kernels obtained from qubit states and qutrit states. The labels yi of the dataset are shown in the colors green and gray, while the symbols ‘o’ and ‘x’ indicate the training and test set, respectively. The background color represents the result of the classification. b–c Histograms of the average accuracy for classification with kernels collected in the experiment by choosing different assignments of the post-selected modes to the adaptive operation. For each kernel, the accuracy is averaged over 100 random partitions of data into training and test sets. In b results for qubits' kernels and in c the qutrits case. d–e Classification of a 2D dataset done with a preliminary clustering algorithm (K-means) followed by the application of a SVM with the two quantum experimental kernels obtained from d qubit states and e qutrit states. The correct label yi of the dataset is shown with the color (green/gray) of the symbols (‘o’: training set, ‘x’: test set). The background color represents the result of the classification.
Quantum machine learning with Adaptive Boson Sampling via post-selection
  • Article
  • Full-text available

January 2025

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55 Reads

Francesco Hoch

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Eugenio Caruccio

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Giovanni Rodari

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[...]

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The implementation of large-scale universal quantum computation represents a challenging and ambitious task on the road to quantum processing of information. In recent years, an intermediate approach has been pursued to demonstrate quantum computational advantage via non-universal computational models. A relevant example for photonic platforms has been provided by the Boson Sampling paradigm and its variants, which are known to be computationally hard while requiring at the same time only the manipulation of the generated photonic resources via linear optics and detection. Beside quantum computational advantage demonstrations, a promising direction towards possibly useful applications can be found in the field of quantum machine learning, considering the currently almost unexplored intermediate scenario between non-adaptive linear optics and universal photonic quantum computation. Here, we report the experimental implementation of quantum machine learning protocols by adding adaptivity via post-selection to a Boson Sampling platform based on universal programmable photonic circuits fabricated via femtosecond laser writing. Our experimental results demonstrate that Adaptive Boson Sampling is a viable route towards dimension-enhanced quantum machine learning with linear optical devices.

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High dioptric power micro-lenses fabricated by two-photon polymerization

December 2024

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27 Reads

Specimen-induced aberrations limit the penetration depth of standard optical imaging techniques in vivo, mainly due to the propagation of high NA beams in a non-homogenous medium. Overcoming these limitations requires complex optical imaging systems and techniques. Implantable high NA micro-optics can be a solution to tissue induced spherical aberrations, but in order to be implanted, they need to have reduced complexity, offering a lower surface to the host immune reaction. Here, we design, fabricate, and test a single micro-optical element with high dioptric power and high NA (up to 1.25 in water). The sag function is inspired by the classical metalens phase and improved to reduce the spherical aberrations arising from the refractive origin of the phase delay at the lens periphery. We successfully fabricated these high-NA quasi-parabolic aspheric microlenses with varying focal lengths by two-photon polymerization in biocompatible photoresist SZ2080. The entire process is optimized to minimize fabrication time while maintaining the structures’ robustness: the smoothness reaches optical ( λ20\frac{\lambda }{{20}} ) quality. The dioptric power and magnification of the microlenses were quantified over a 200 × 200 µm aberration-free field of view. Our results indicate that these microlenses can be used for wide-field imaging under linear excitation and have the optical quality to be utilized for nonlinear excitation imaging. Moreover, being made of biocompatible photoresist, they can be implanted close to the observation volume and help to reduce the spherical aberration of laser beams penetrating living tissues.


Implantable Micro-optics for label-free non-linear imaging

October 2024

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50 Reads

The European Physical Journal Conferences

Non-linear excitation microscopy offers superior in-vivo imaging but faces challenges in deep tissue. High numerical aperture beams suffer spherical aberrations, while tissue scattering impacts image quality. To address this, we propose implantable microlenses for precise focusing below the skin in lab animals. By using low numerical aperture lasers, we avoid spherical aberrations induced by high NA objectives. Our study presents various microlens designs differing in size, shape, and fabrication methods, all on glass or organo-hybrid ceramic substrates. This approach shows promise for enhancing deep tissue imaging, facilitating better understanding of biological processes in vivo.


Development of a Microfluidic Device for Blood Cells Extraction in Liquid Biopsy

October 2024

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75 Reads

The European Physical Journal Conferences

This project aims to produce a microfluidic device capable of separating 6 μm and 20 μm diameters particles by inertial sorting. This Lab-on-Chip (LoC) was designed with a trapezoidal cross-section for better fluid control and effective particle manipulation at the microscopic level, as demonstrated by COMSOL simulations. The device was manufactured on a substrate of Polymethyl Methacrylate (PMMA) by femtosecond laser technology and then assembled using an innovative geometry-preserving Isopropyl alcohol-based procedure. The LoC was test with spherical plastic microparticles of two diameters (6 μm and 20 μm) suspended in distilled water. The separation efficiencies were (98.2 ± 1.6) % for 20 μm diameter particles and (70.0 ± 1.8) % for 6 μm diameter particles in good agreement with the simulation results. Finally, after a microfluidic channels’ acetone vapors treatment, the device demonstrated a good ability to separate biological particles (Red Blood Cells) at different concentrations (20%, 30%, 40%, 50%) in a PBS buffer.


(a) Schematic of the fabricated MZIs. The DCs have been fabricated by concatenating different arches of circumference of radius R = 35 mm, which bring the two waveguides of the DC at a minimum interaction distance d = 4.65 µm. Waveguide separation D before and after the DCs is 100 µm. Waveguides distance p from the top surface is 50 µm. Three different MZIs have been fabricated with different lengths L of the interferometric arms (1 mm, 5 mm and 10 mm). The inset shows a microscope picture of the waveguide cross section, together with a near-field intensity image of the guided mode, identical for TE and TM polarizations. (b) Schematic of the geometry of the 3D undercuts. For all MZIs: b = 30 µm, W = 70 µm, h1 = 75 µm and h2 = 120 µm. The length of the MZI arms differ for the values of Lu, which are 1 mm, 4 mm and 8 mm. (c) Schematic of the metal film patterning. Laser ablation is used to narrow the lateral width of the resistive heaters to the value of t = 15 µm and to isolate large pads for electrical connections. In the inset we show a white-light microscope image of one of the bridge coated with gold, after the ablation of the resistor edges and the definition of the electrical pads. (d) Photograph of the device at the end of the fabrication process.
(a) Sketch of the experimental setup used for the PIC characterization. The lenses used for in- and out-coupling of the light in the chip have a focal length of 10 cm. (b) Photograph of the PIC mounted on the cold finger, before the closure of the cryostat.
(a)–(c) Experimental characterization of TBAR at room (red dots) and cryogenic (blue diamonds) temperature. The three plots (a)–(c) correspond to MZI 1, 2 and 3 (see table 1), respectively. The solid red line is best fit function of room temperature data, according to equations (1) and (2). Red and blue arrows indicate the value of dissipated power needed to attain a 2π phase shift in the two cases. Error bars are smaller than data point markers. (d)–(f) Computed trends of the TOPS efficiencies at room (red dots) and cryogenic (blue diamonds) temperatures as a function of dissipated power, according to equation (4). The solid red line is a plot of α+βP, according to best fit parameters listed in table 1.
(a) Mean temperature variation ΔTM along the bridge of the three MZIs as a function of the power dissipation P. Straight segments connect the simulated data points for eye guiding. (b) 2D map of the temperature variation ΔT calculated on the waveguides plane parallel to the sample top surface, with P=P2πA for all MZIs. Dashed black lines indicate the cutlines used for the plots shown in panel (c). White contour lines indicate where temperature increases by 0.5 K. Dark blue rectangles indicate the trenches around the TOPS bridge. (c) Plot of ΔT as a function of the position along the waveguides of the MZIs when P=P2πA (see cutlines in panel (b)). Dashed lines mark the mean temperature variation ΔTM2π. The simulations in all panels consider room temperature and high vacuum starting conditions.
Integrated thermo-optic phase shifters for laser-written photonic circuits operating at cryogenic temperatures

October 2024

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45 Reads

Integrated photonics offers compact and stable manipulation of optical signals in miniaturized chips, with the possibility of changing dynamically their functionality by means of integrated phase shifters. Cryogenic operation of these devices is becoming essential for advancing photonic quantum technologies, accommodating components like quantum light sources, single photon detectors and quantum memories operating at liquid helium temperatures. In this work, we report on a programmable glass photonic integrated circuit (PIC) fabricated through femtosecond laser waveguide writing (FLW) and controlled by thermo-optic phase shifters both in a room-temperature and in a cryogenic setting. By taking advantage of a femtosecond laser microstructuring process, we achieved reliable PIC operation with minimal power consumption and confined temperature gradients in both conditions. This advancement marks the first cryogenically-compatible programmable FLW PIC, paving the way for fully integrated quantum architectures realized on a laser-written photonic chip.


Experimental observation of counter-intuitive features of photonic bunching

October 2024

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28 Reads

Bosonic bunching is a term used to describe the well-known tendency of bosons to bunch together, and which differentiates their behaviour from that of fermions or classical particles. However, in some situations perfectly indistinguishable bosons may counter-intuitively bunch less than classical, distinguishable particles. Here we report two such counter-intuitive multiphoton bunching effects observed with three photons in a three-mode balanced photonic Fourier interferometer. In this setting, we show indistinguishable photons actually minimize the probability of bunching. We also show that any non-trivial value of the three-photon collective photonic phase leads to a decreased probability of all photons ending up in the same mode, even as we increase pairwise indistinguishability. Our experiments feature engineering of partial indistinguishability scenarios using both the time and the polarization photonic degrees of freedom, and a polarization-transparent 8-mode tunable interferometer with a quantum-dot source of single photons. Besides the foundational understanding, the observation of these counter-intuitive phenomena open news perspective in devising more efficient ways of routing photons for advantage in metrology and quantum computation.


Fig. 3. Shape and surface characterization employing SEM and 3D optical profilometer. (a), (b), and (c) SEM images of a single parabolic microlens with diameter Ø = 600 µm, and fn = 350 µm. Close up of the central region on the top plane of the lens of (a) highlights the improved smoothness obtained in our fabrication process. (d) 2D optical profiles over a topographic area = 229 × 172 μm 2 of top of the lens in panel (b). (e) 3D optical profiles over a topographic volume = 229 × 172 × 60 μm 3 , covering the central region on the top dome of the lens in panel (b). (f) The scan length was 101 μm, and the 2D line profile was acquired over a distance of 165 μm along the x-axis and 31.15 μm along the z-axis, starting from the top of the lens and moving downwards. The average line roughness of í µí± ≈ 24.0 ± 4 í µí±›í µí±š was obtained.
Figure 5. (a) off-axis DHM setup used for the measurement of the microlens phase. A laser diode emitting at í µí¼† = 635 í µí±›í µí±š nm is expanded by a first beam expander (AL+L0 lenses). On the upper (reference) path, the beam is further expanded 2 times (L1+L2 lenses) onto the mirror M1. A third telescope composed of the lenses L3 and L4 conjugates M1 onto the CMOS camera (IDS, UI-3240CP-M-GL). By tilting M1 along one axis, the reference beam impinges centered on the CMOS camera with a twofold angular demagnification. The lower (sample) path conjugates the sample plane (here the exit pupil of the microlens) onto the CMOS camera by means of the tube lens (TL) on the bottom path. The light field from the sample is superimposed with the reference beam on the camera. (b) results of the analysis of the phase profile for the í µí±“ = 350 í µí¼‡í µí±š microlens over an area of 120 × 120 í µí¼‡í µí±š. The top images are the experimental phase computed from the DHM interferogram with a spatial resolution of 1.72 í µí¼‡í µí±š (left) and the best fit phase (right). The bottom plots are cross sections along the rows and the columns of the experimental (red dotted lines) and the best fit (green solid lines) of the phase images.
Geometrical parameters of parabolic microlenses with variable nominal focal lengths.
The microlenses magnification evaluated on wide-field images of the USAF 1951 target.
High dioptric power micro-lenses fabricated by two-photon polymerization

October 2024

·

58 Reads

Specimen-induced aberrations limit the penetration depth of standard optical imaging techniques in vivo, mainly due to the propagation of high NA beams in a non-homogenous medium. Overcoming these limitations requires complex optical imaging systems and techniques. Implantable high NA micro-optics can be a solution to tissue induced spherical aberrations but in order to be implanted they need to have reduced complexity, offering reduced surface to the host immune reaction. Here, we design, fabricate and test a single micro-optical element with high dioptric power and high NA (up to 1.4 in air). The sag function is inspired to the classical metalens phase and improved to reduce the spherical aberrations arising from the refractive origin of the phase delay at the lens periphery. We successfully fabricated these high-NA quasi-parabolic aspheric microlenses with varying focal lengths by two-photon polymerization in biocompatible photoresist SZ2080. The entire process is optimized to minimize fabrication time while maintaining the structures' robustness: the smoothness reaches optical (λ/20) quality. The dioptric power and magnification of the microlenses were quantified over a 200×200 μm aberration-free field of view. Our results indicate that these microlenses can be used for wide-field imaging under linear excitation and have the optical quality to be utilized for nonlinear excitation imaging. Moreover, being made of biocompatible photoresist, they can be implanted close to the observation volume and help to reduce the spherical aberration of laser beams penetrating in living tissues.


High dioptric power micro-lenses fabricated by two-photon polymerization

October 2024

·

17 Reads

Specimen-induced aberrations limit the penetration depth of standard optical imaging techniques in vivo, mainly due to the propagation of high NA beams in a non-homogenous medium. Overcoming these limitations requires complex optical imaging systems and techniques. Implantable high NA micro-optics can be a solution to tissue induced spherical aberrations but in order to be implanted they need to have reduced complexity, offering reduced surface to the host immune reaction. Here, we design, fabricate and test a single micro-optical element with high dioptric power and high NA (up to 1.4 in air). The sag function is inspired to the classical metalens phase and improved to reduce the spherical aberrations arising from the refractive origin of the phase delay at the lens periphery. We successfully fabricated these high-NA quasi-parabolic aspheric microlenses with varying focal lengths by two-photon polymerization in biocompatible photoresist SZ2080. The entire process is optimized to minimize fabrication time while maintaining the structures' robustness: the smoothness reaches optical (λ/20) quality. The dioptric power and magnification of the microlenses were quantified over a 200×200 μm aberration-free field of view. Our results indicate that these microlenses can be used for wide-field imaging under linear excitation and have the optical quality to be utilized for nonlinear excitation imaging. Moreover, being made of biocompatible photoresist, they can be implanted close to the observation volume and help to reduce the spherical aberration of laser beams penetrating in living tissues.


High dioptric power micro-lenses fabricated by two-photon polymerization

October 2024

·

39 Reads

Specimen-induced aberrations limit the penetration depth of standard optical imaging techniques in vivo, mainly due to the propagation of high NA beams in a non-homogenous medium. Overcoming these limitations requires complex optical imaging systems and techniques. Implantable high NA micro-optics can be a solution to tissue induced spherical aberrations but in order to be implanted they need to have reduced complexity, offering reduced surface to the host immune reaction. Here, we design, fabricate and test a single micro-optical element with high dioptric power and high NA (up to 1.4 in air). The sag function is inspired to the classical metalens phase and improved to reduce the spherical aberrations arising from the refractive origin of the phase delay at the lens periphery. We successfully fabricated these high-NA quasi-parabolic aspheric microlenses with varying focal lengths by two-photon polymerization in biocompatible photoresist SZ2080. The entire process is optimized to minimize fabrication time while maintaining the structures' robustness: the smoothness reaches optical (λ/20) quality. The dioptric power and magnification of the microlenses were quantified over a 200×200 μm aberration-free field of view. Our results indicate that these microlenses can be used for wide-field imaging under linear excitation and have the optical quality to be utilized for nonlinear excitation imaging. Moreover, being made of biocompatible photoresist, they can be implanted close to the observation volume and help to reduce the spherical aberration of laser beams penetrating in living tissues.


Citations (31)


... Spiral microfluidic channels exhibit significant potential for particle sorting, mixing and manipulation in biomedical engineering due to their unique hydrodynamic properties [1,2]. Through the centrifugal effect of fluids and flow gradients, spiral flow channels can efficiently focus, disperse and sort particles, providing an ideal platform for single-cell analysis, particle capture and biochemical reactions [3]. ...

Reference:

Picosecond Laser Etching of Glass Spiral Microfluidic Channel for Microparticles Dispersion and Sorting
Lab-on-Chip Systems for Cell Sorting: Main Features and Advantages of Inertial Focusing in Spiral Microchannels

Micromachines

... The latter aspect is particularly relevant when using femtosecond pulses, which opens up the possibility for detailed time-dependent studies. Developments [24] in time-resolved X-ray spectroscopy are aimed at tracking ultra-fast chemical rearrangements and charge transfers in molecules and materials, [25,26] and to determine the reaction kinetics. [23,27] The K-shell absorption edge of Mg in solution is located around 1.3 keV. ...

A flexible beamline combining XUV attosecond pulses with few-femtosecond UV and near-infrared pulses for time-resolved experiments

... The re-calibration procedure is adapted from methods used for single-phase actuator calibration in applicationspecific integrated circuits (ASPICs). 25,[34][35][36] This method relies on the construction of a temporary interferometer using single PUCs. In the ASPIC approach, this structure, also known as a META-MZI, is built using two PUCs configured as 50:50 couplers with all internal PUCs set to the bar state. ...

High-fidelity and polarization-insensitive universal photonic processors fabricated by femtosecond laser writing

... Femtosecond laser microstructuring has been studied extensively due to its versatile, contactless processing, outstanding precision, and structure quality on a wide range of materials, which have been proven experimentally [1][2][3][4] and well supported by femtosecond ablation modeling [5][6][7]. Femtosecond lasers are employed due to a wide range of advantages over other laser sources, such as low residual heating of materials and low thermal damage [8], and are thus suitable for sensitive thin film removal [9] and micro- [10,11] and nanodevice manufacturing [12][13][14], but also as enablers of specific structuring techniques, e.g., inducing periodic surface structures [15,16], polarization effects [17], surface wear resistance improvement [18][19][20], and nonlinear absorption mechanisms [10]. Some drawbacks are present over longer pulsed laser sources, namely lower process efficiency [21] and complicated laser sources [22]. ...

Femtosecond Laser Nanomachining of High‐Aspect‐Ratio Channels in Bulk Fused Silica

... Moreover, multipartite entanglement is a potential asset in several applications, such as conference key agreement [3], measurement-based quantum computing [4,5], quantum codes [6], and quantum metrology [7] to name a few. The Greenberger-Horne-Zeilinger (GHZ) state [8] is a maximally entangled multipartite state that has been already realized at different platforms, including photons [9][10][11], trapped ions [12], semiconducting qubits [13], and superconducting qubits [14]. Because of the non-perfect generation and, in the case of communication, noisy transmission, it may be necessary to purify or distill these states before their application [15,16]. ...

High-fidelity four-photon GHZ states on chip

npj Quantum Information

... use low-loss bulk optics and fiber optics [39][40][41][42][43][44] or stateof-the-art silicon photonics [45][46][47], where the total IL is ∼ 3 -3.5 dB. Recently, borosilicate glass-based FLW chips with lower IL of ∼ 2 -3 dB have been developed [48][49][50][51], where the PL of 0.13 dB/cm [48,51] and the CL of 0.2 dB/facet [51] were achieved in the NIR range of wavelengths. ...

Universal photonic processors fabricated by direct femtosecond-laser writing
  • Citing Conference Paper
  • March 2024

... DDS demonstrates its ability to enhance performance even under such computationally demanding conditions. Additionally, the integration of DDS with current efficient VQA algorithms [38][39][40][41][42][43][44] can create a synergistic effect, further improving and accelerating the practical applicability of VQA algorithms. ...

Variational quantum algorithm for experimental photonic multiparameter estimation

npj Quantum Information

... with A being the baseline, B the amplitude and φ 2ω the phase of the oscillation at 2ω, and τ R = φ 2ω /(2ω) the RABITT delay. All of these quantities can be expressed using twophoton or higher-order dipole matrix elements between the initial neutral state and the final photoelectron state [31]. The information on the ionization time delay is stored within this RABITT delay, which is also affected by the dressing field. ...

Anisotropy Parameters for Two-Color Photoionization Phases in Randomly Oriented Molecules: Theory and Experiment in Methane and Deuteromethane
  • Citing Article
  • February 2024

The Journal of Physical Chemistry A

... Nevertheless, shorter UV pulses are required to induce a sudden electronic excitation before any significant structural rearrangement can take place. So far, this scheme remains unexplored due to the challenges in producing and utilizing few-femtosecond UV pulses for time-resolved measurements, which have been surmounted only very recently [15][16][17][18][19] . ...

Ultraviolet supercontinuum generation using a differentially-pumped integrated glass chip

... Comparing with large varieties of conventional twodimensional implementations, integrated photonics through FLDW technique exhibit great prospect in the fields of optical communication [5], three-dimensional (3D) integrated photonics [6], 3D optical topology [7,8] and astro-photonics [9]. Furthermore, the exemplified fascinating applications enabled by the technique of FLDW include beam rotators [10], broadband directional coupler [11], adiabatic mode converters [12,13], multichannel interconnectors [14], attenuators [15], birefringent retarders [16], wave-plates [17,18] and optical modulators [19][20][21]. For the waveguide manufactured by FLDW, it is commonly deeply buried beneath the surface to prevent the structure from ablation damage. ...

Micro-opto-mechanical glass interferometer for megahertz modulation of optical signals