Twiss Measurements Research Articles

Generation of single photon emitters at a SiO2/SiC interface by high-temperature oxidation and reoxidation at lower temperatures

We report on an approach to produce single photon emitters at the SiO2/SiC interface. We form a high-quality SiO2/SiC interface by high-temperature oxidation and subsequently perform oxidation at lower temperatures (200 °C–1000 °C) to generate the emitters. After reoxidation at 800 °C, we confirmed the formation of emitters with a bright luminescence (>50 kcps). Through Hambury-Brown and Twiss measurements, single photon characteristics were confirmed. Thus, the proposed approach is effective in generating highly bright single photon emitters at the SiO2/SiC interface.

Tight nonclassicality criteria for unbalanced Hanbury Brown–Twiss measurement scheme with click detectors

Tight nonclassicality criteria for unbalanced Hanbury Brown–Twiss measurement scheme with click detectors

Localising two sub-diffraction emitters in 3D using quantum correlation microscopy

The localisation of fluorophores is an important aspect of determining the biological function of cellular systems. Quantum correlation microscopy (QCM) is a promising technique for providing diffraction unlimited emitter localisation that can be used with either confocal or widefield modalities. However, so far, QCM has not been applied to three dimensional localisation problems. Here we show that QCM provides diffraction-unlimited three-dimensional localisation for two emitters within a single diffraction-limited spot. By introducing a two-stage maximum likelihood estimator, our modelling shows that the localisation precision scales as 1/t where t is the total detection time. Diffraction unlimited localisation is achieved using both intensity and photon correlation from Hanbury Brown and Twiss measurements at as few as four measurement locations. We also compare the results of (MC) simulations with the Cramér–Rao lower bound.

Spin-Polarization-Induced Chiral Polariton Lasing at Room Temperature

Exciton-polaritons are hybrid bosons that define the peculiar interaction between the semiconductor and the optical cavity. The ultra-low effective mass of polariton inherited from its photon fraction benefits the efficient Bose–Einstein condensation process. Due to the unique superfluidity of polariton condensate, the persistent angular momentum of the system will facilitate plenty of chiral phenomena, such as the spin precession, the spin–orbit coupling, and the emergence of quantum vortices. Here, we report a chiral polariton laser via robust spin-polarization of polariton condensation at room temperature. The self-formed chirality of the microcavity breaks the spatial inversion symmetry and lifts the energy degeneracy of polariton spin doublets by a considerable value of 11 meV, which can be demonstrated by the angle-resolved spectra recorded after a Wollaston prism. The bosonic condensation only occurs in the low-energy spin-up polaritons, resulting in polariton lasing with stable right-circular (σ+) polarization. The second-order coherence of a polariton chiral laser is determined by performing the Hanbury Brown–Twiss measurement, which indicates the quantum phase transition during the condensation process. Moreover, the robustness of the chirality of polariton lasing is demonstrated, and the basic physical mechanisms of the system are illustrated by the generalized Gross–Pitaevskii (G–P) equation. The results set solid building blocks for the development of chiral quantum photonics and spin polaritonics.

Correcting the BA coalescence factor at energies relevant for the GSI-HADES experiment and the RHIC Beam Energy Scan

We investigate the coalescence factors ${B}_{2}$ and ${B}_{3}$ at low collision energies ($\sqrt{{s}_{\mathrm{NN}}}<6$ GeV) with special focus on the HADES and RHIC-Beam Energy Scan (BES) experiments. It is shown that, in order to properly interpret the coalescence factors ${B}_{A}$, two important corrections are necessary: (I) ${B}_{2}$ has to be calculated using the proton $\ifmmode\times\else\texttimes\fi{}$ neutron yields in the denominator, instead of the square of the proton yield, and (II) the primordial proton (neutron) densities have to be used for the normalization and not the final-state (free) protons (neutrons). Both effects lead to a drastic reduction of ${B}_{2}$ and ${B}_{3}$ at low energies. This reduction decreases the discrepancy between the volumes extracted from Hanbury Brown--Twiss measurements and the volumes extracted from the coalescence factor ($V\ensuremath{\propto}1/{B}_{2}$). While at HADES and low RHIC-BES energies these corrections are substantial, they become irrelevant above $\sqrt{{s}_{\mathrm{NN}}}>6$ GeV. The proposed correction method is model independent and is only based on the measurement of protons, clusters, and charged pions.

Frequency-to-Time Mapping Technique for Direct Spectral Characterization of Biphoton States From Pulsed Spontaneous Parametric Processes

The well-established frequency-to-time mapping technique is employed as a convenient and time-efficient method to directly characterize the spectral correlations of biphoton states from a pulsed-excited spontaneous parametric down-conversion process. We were enabled by this technique to implement for the first time, the spectral Hanbury-Brown and Twiss measurement, revealing directly the single frequency-mode bandwidth of the biphoton state.

High-order photon correlations through double Hanbury Brown–Twiss measurements

We present an experimental technique that can accurately measure the high-order photon correlations of various light fields based on double Hanbury Brown–Twiss scheme. The system consists of four conventional binary response single-photon counting modules which are non-photon-number-resolving detectors. We theoretically analyze the effects of the experimental conditions on the high-order photon correlations of coherent, chaotic thermal, Fock and squeezed vacuum states with considering the overall efficiency and background noise. In experiment, we determine the proper resolution time from 29 = 512 ns to 211 = 2048 ns and counting rate from 10 kc s−1 to 100 kc s−1 for characterizing the exact second-, third- and fourth-order photon correlations of chaotic thermal state. At complete time delays, we also observe the third- and fourth-order photon correlations of chaotic thermal state, with the maximum high-order correlation values of 5.99 ± 0.02 and 23.9 ± 0.2 respectively, which are in good agreement with the theoretical values of 6 and 24. The demonstrated experimental technique with high accuracy is a promising tool for investigating quantum optical coherence and ghost imaging.

Enhanced Spontaneous Emission Rates for Single Isoelectronic Luminescence Centers in Photonic Crystal Cavities

Purcell effect enhancement of spontaneous emission rates is demonstrated for isoelectronic trap single-photon emitters. Two-dimensional photonic crystal slabs with L3 defects were fabricated in nitrogen delta-doped GaAs. Photoluminescence spectra of each photonic crystal cavity had a series of sharp and bright lines arising from individual nitrogen luminescence centers, which was confirmed by Hanbury-Brown and Twiss measurements. The emission rates of these lines depended on cavity detuning, indicating a resonant character of the enhancement. The observed emission lifetime in the cavity was 400 ps, which would be the shortest lifetime reported so far for luminescence centers in GaAs.

Quantum multilateration: Subdiffraction emitter pair localization via three spatially separate Hanbury Brown and Twiss measurements

Typically, optical microscopy uses the wavelike properties of light to image a scene. However, photon arrival times provide more information about emitter properties than the classical intensity alone. Here we show that the Hanbury Brown and Twiss experiment (second-order correlation function) measures the relative brightness of two single-photon emitters. By combining the total number of detected photons with the zero-lag value of the correlation function, the positions and relative brightness of two emitters in two dimensions can be resolved from only three measurement positions: trilateration. This result is impossible to achieve on the basis of classical intensity measurements alone and represents a minimal demonstration of the advantage gained using quantum measurements over conventional classical microscopy. The effective point-spread function for imaging scales approximately as the inverse square root of the acquisition time.

Hybrid Integration of Solid-State Quantum Emitters on a Silicon Photonic Chip.

Scalable quantum photonic systems require efficient single photon sources coupled to integrated photonic devices. Solid-state quantum emitters can generate single photons with high efficiency, while silicon photonic circuits can manipulate them in an integrated device structure. Combining these two material platforms could, therefore, significantly increase the complexity of integrated quantum photonic devices. Here, we demonstrate hybrid integration of solid-state quantum emitters to a silicon photonic device. We develop a pick-and-place technique that can position epitaxially grown InAs/InP quantum dots emitting at telecom wavelengths on a silicon photonic chip deterministically with nanoscale precision. We employ an adiabatic tapering approach to transfer the emission from the quantum dots to the waveguide with high efficiency. We also incorporate an on-chip silicon-photonic beamsplitter to perform a Hanbury-Brown and Twiss measurement. Our approach could enable integration of precharacterized III-V quantum photonic devices into large-scale photonic structures to enable complex devices composed of many emitters and photons.

Hanbury Brown and Twiss measurements in curved space

Hanbury Brown and Twiss measurements on speckle patterns propagating along curved surfaces improve understanding of spatial coherence. When Hanbury Brown and Twiss (HBT) proposed their technique of intensity correlation measurements1,2,3 to examine the angular size of stars in the visible range, they challenged the common conception of quantum mechanics and kicked off a discussion that led to the establishment of quantum optics4,5,6. In this Letter we revisit this fundamental technique and study its implications in the presence of space curvature. To this end we theoretically and experimentally investigate the evolution of speckle patterns propagating along two-dimensional surfaces of constant positive and negative Gaussian curvature, defying the notion that light always gains spatial coherence during free-space propagation. We also discuss the measurability of the traversed space's curvature utilizing HBT from an inhabitant's point of view. Through their symmetry, surfaces with constant Gaussian curvature act as analogue models for universes possessing non-vanishing cosmological constants.

Hanbury–Brown–Twiss measurements at large rapidity separations, or can we measure the proton radius in p-A collisions?

We point out that current calculations of inclusive two-particle correlations in p-A collisions based on the Color Glass Condensate approach exhibit a contribution from Hanbury–Brown–Twiss correlations. These HBT correlations are quite distinct from the standard ones, in that they are apparent for particles widely separated in rapidity. The transverse size of the emitter which is reflected in these correlations is the gluonic size of the proton. This raises an interesting possibility of measuring the proton size directly by the HBT effect of particle pairs produced in p-A collisions.

Quantum photonics hybrid integration platform

Fundamental to integrated photonic quantum computing is an on-chip method for routing and modulating quantum light emission. We demonstrate a hybrid integration platform consisting of arbitrarily designed waveguide circuits and single-photon sources. InAs quantum dots (QD) embedded in GaAs are bonded to a SiON waveguide chip such that the QD emission is coupled to the waveguide mode. The waveguides are SiON core embedded in a SiO2 cladding. A tuneable Mach Zehnder interferometer (MZI) modulates the emission between two output ports and can act as a path-encoded qubit preparation device. The single-photon nature of the emission was verified using the on-chip MZI as a beamsplitter in a Hanbury Brown and Twiss measurement.

Single photon emission from impurity centers in AlGaAs epilayers on Ge and Si substrates

We show that the epitaxial growth of thin layers of AlGaAs on Ge and Si substrates allows to obtain single photon sources by exploiting the sparse and unintentional contamination with acceptors of the AlGaAs. Very bright and sharp single photoluminescence lines are observed in confocal microscopy. These lines behave very much as single excitons in quantum dots, but their implementation is by far much easier, since it does not require 3D nucleation. The photon antibunching is demonstrated by time resolved Hanbury Brown and Twiss measurements.

Optical properties of a single-colour centre in diamond with a green zero-phonon line

We report the photoluminescence characteristics of a colour centre in diamond grown by plasma-assisted chemical vapour deposition. The colour centre emits with a sharp zero-phonon line at 2.330 eV (λ=532 nm) and a lifetime of 3.3 ns, thus offering potential for a high-speed single-photon source with green emission. It displays a vibronic emission spectrum with a Huang–Rhys parameter of 2.48 at 77 K. Hanbury–Brown and Twiss measurements reveal that the electronic level structure of the defect includes a metastable state that can be populated from the optically excited state.

Recent HBT results in Au+Au and p+ p collisions from PHENIX

We present Hanbury-Brown Twiss measurements from the PHENIX experiment at RHIC for final results for charged kaon pairs from s N N = 200 GeV Au+Au collisions and preliminary results for charged pion pairs from s = 200 GeV p+ p collisions. We find that for kaon pairs from Au+Au, each traditional 3D Gaussian radius shows approximately the same linear increase as a function of N part 1 / 3 . An imaging analysis reveals a significant non-Gaussian tail for r ≳ 10 fm . The presence of a tail for kaon pairs demonstrates that similar non-Gaussian tails observed in earlier pion measurements cannot be fully explained by decays of long-lived resonances. The preliminary analysis of pions from s = 200 GeV p+p minimum biased collisions show correlations which are well suited to traditional 3D HBT radii extraction via the Bowler-Sinyukov method, and we present R out , R side , and R long as a function of mean transverse pair mass.

Why a long-lived fireball can be compatible with Hanbury-Brown–Twiss measurements

The common interpretation of HBT data measured at top SPS energies leads to apparent source lifetimes of 6-8 fm/c and emission duration of approximately 2-3 fm/c. We investigate a scenario with continuous pion emission from a long-lived (~17 fm/c) thermalized source in order to show that it is not excluded by the data. Starting from a description of the source's spacetime expansion based on gross thermodynamical properties of hot matter (which is able to describe a number of experimental observables), we introduce the pion emission function with a contribution from continuous emission during the source's lifetime and another contribution from the final breakup and proceed by calculating the HBT parameters R_out and R_side. The results are compared with experimental data measured at SPS for 158 AGeV central Pb-Pb collisions. We achieve agreement with data, provided that some minor modifications of the fireball evolution scenario are made and find that the parameter R_out is not sensitive to the fireball lifetime, but only to the duration of the final breakup, in spite of the fact that emission takes place throughout the whole lifetime. We explicitly demonstrate that those findings do not alter previous results obtained within this model.