Photon Emission Statistics Research Articles

Photon-emission statistics for single nitrogen-vacancy centers

Photon-emission statistics for single nitrogen-vacancy centers

Engineering quantum dots for improved single photon emission statistics.

High fidelity single photon sources are required for the implementation of quantum information processing and communications protocols. Although colloidal quantum dots (CQDs) are single photon sources, their efficacy is limited by their tendency to show finite multiphoton emission at higher excitation powers. Here, we show that wave function engineering of CQDs enables the realization of emitters with significantly improved single photon emission performance. We study the ZnS/CdSe/CdS system. It is shown that this system offers significantly improved probabilities of single photon emission. While conventional CQDs such as CdSe/CdS exhibit a g2(0) > 0.5 ± 0.02 at ⟨N⟩ = 2.17, ZnS/CdSe/CdS show a greatly improved g2(0) ≈ 0.04 ± 0.01. Improved single photon emission performance encourages the use of colloidal materials as quantum light sources in emerging quantum devices.

Photon emission statistics of a driven microwave cavity

Photon emission statistics of a driven microwave cavity

Sub-to-super-Poissonian photon statistics in cathodoluminescence of color center ensembles in isolated diamond crystals.

Impurity-vacancy centers in diamond offer a new class of robust photon sources with versatile quantum properties. While individual color centers commonly act as single-photon sources, their ensembles have been theoretically predicted to have tunable photon-emission statistics. Importantly, the particular type of excitation affects the emission properties of a color center ensemble within a diamond crystal. While optical excitation favors non-synchronized excitation of color centers within an ensemble, electron-beam excitation can synchronize the emitters excitation and thereby provides a control of the second-order correlation function g 2(0). In this letter, we demonstrate experimentally that the photon stream from an ensemble of color centers can exhibit g 2(0) both above and below unity, thereby confirming long standing theoretical predictions by Meuret etal. [S. Meuret, L. H. G. Tizei, T. Cazimajou, etal., "Photon bunching in cathodoluminescence," Phys. Rev. Lett., vol. 114, no. 19, p. 197401, 2015.]. Such a photon source based on an ensemble of few color centers in a diamond crystal provides a highly tunable platform for informational technologies operating at room temperature.

High-Yield Deterministic Focused Ion Beam Implantation of Quantum Defects Enabled by In Situ Photoluminescence Feedback.

Focused ion beam implantation is ideally suited for placing defect centers in wide bandgap semiconductors with nanometer spatial resolution. However, the fact that only a few percent of implanted defects can be activated to become efficient single photon emitters prevents this powerful capability to reach its full potential in photonic/electronic integration of quantum defects. Here an industry adaptive scalable technique is demonstrated to deterministically create single defects in commercial grade silicon carbide by performing repeated low ion number implantation and in situ photoluminescence evaluation after each round of implantation. An array of 9 single defects in 13 targeted locations is successfully created-a ≈70% yield which is more than an order of magnitude higher than achieved in a typical single pass ion implantation. The remaining emitters exhibit non-classical photon emission statistics corresponding to the existence of at most two emitters. This approach can be further integrated with other advanced techniques such as in situ annealing and cryogenic operations to extend to other material platforms for various quantum information technologies.

In Situ Ion Counting for Improved Implanted Ion Error Rate and Silicon Vacancy Yield Uncertainty.

An in situ counted ion implantation experiment improving the error on the number of ions required to form a single optically active silicon vacancy (SiV) defect in diamond 7-fold compared to timed implantation is presented. Traditional timed implantation relies on a beam current measurement followed by implantation with a preset pulse duration. It is dominated by Poisson statistics, resulting in large errors for low ion numbers. Instead, our in situ detection, measuring the ion number arriving at the substrate, results in a 2-fold improvement of the error on the ion number required to generate a single SiV compared to timed implantation. Through postimplantation analysis, the error is improved 7-fold compared to timed implantation. SiVs are detected by photoluminescence spectroscopy, and the yield of 2.98% is calculated through the photoluminescence count rate. Hanbury-Brown-Twiss interferometry is performed on locations potentially hosting single-photon emitters, confirming that 82% of the locations exhibit single photon emission statistics.

Photon-emission statistics induced by electron tunneling in plasmonic nanojunctions

We investigate the statistics of photons emitted by tunneling electrons in a single electronic level plasmonic nanojunction. We compute the waiting-time distribution of successive emitted photons $w(\tau)$. When the cavity damping rate $\kappa$ is larger than the electronic tunneling rate $\Gamma$, we show that in the photon-antibunching regime, $w(\tau)$ indicates that the average delay-time between two successive photon emission events is given by $1/\Gamma$. This is in contrast with the usually considered second-order correlation function of emitted photons, $g^{(2)}(\tau)$, which displays the single time scale $1/\kappa$. Our analysis shows a relevant example for which $w(\tau)$ gives independent information on the photon-emission statistics with respect to $g^{(2)}(\tau)$, leading to a physical insight on the problem. We discuss how this information can be extracted from experiments even in presence of a non-perfect photon detection yield.

Chaotic spin-photonic quantum states in an open periodically modulated cavity.

When applied to dynamical systems, both classical and quantum, time periodic modulations can produce complex non-equilibrium states which are often termed "chaotic." Being well understood within the unitary Hamiltonian framework, this phenomenon is less explored in open quantum systems. Here, we consider quantum chaotic states emerging in a leaky cavity when the intracavity photonic mode is coherently pumped with the pumping intensity varying periodically in time. We show that a single spin when placed inside the cavity and coupled to the mode can moderate transitions between regular and chaotic regimes-that are identified by using quantum Lyapunov exponents or features of photon emission statistics-and thus can be used to control the degree of chaos.

Photon Correlation Spectroscopy of Luminescent Quantum Defects in Carbon Nanotubes.

Defect-decorated single-wall carbon nanotubes have shown rapid growing potential for imaging, sensing, and the development of room-temperature single-photon sources. The key to the highly nonclassical emission statistics is the discrete energy spectrum of defect-localized excitons. However, variations in defect configurations give rise to distinct spectral bands that may compromise single-photon efficiency and purity in practical devices, and experimentally it has been challenging to study the exciton population distribution among the various defect-specific states. Here, we performed photon correlation spectroscopy on hexyl-decorated single-wall carbon nanotubes to unravel the dynamics and competition between neutral and charged exciton populations. With autocorrelation measurements at the single-tube level, we prove the nonclassical photon emission statistics of defect-specific exciton and trion photoluminescence and identify their mutual exclusiveness in photoemissive events with cross-correlation spectroscopy. Moreover, our study reveals the presence of a dark state with population-shelving time scales between 10 and 100 ns. These new insights will guide further development of chemically tailored carbon nanotube states for quantum photonics applications.

(Invited) Correlations in Photon Emission from Neutral and Charged Exciton States in Functionalized Carbon Nanotubes

Covalently functionalized carbon nanotubes support localized excitons with a discrete photoluminescence spectrum and single photon emission statistics [1,2]. The spectrum of hexyl-modified nanotubes features two distinct photoluminescence bands attributed to neutral and charged configurations of exciton-localizing sp3-defects [3]. Here we report correlations in photon emission events by the respective states of neutral and charged defect-trapped excitons, and explain the observations in the framework of different exciton manifolds that compete for the photogenerated population. [1] X. Ma, N. F. Hartmann, J. K. S. Baldwin, S. K. Doorn, and H. Htoon, Nat. Nanotechnol.10, 671 (2015).[2] X. He, N. F. Hartmann, X. Ma, Y. Kim, R. Ihly, J. L. Blackburn, W. Gao, J. Kono, Y. Yomogida, A. Hirano, T. Tanaka, H. Kataura, H. Htoon, and S. K. Doorn, Nat. Photon. 11, 577 (2017).[3] H. Kwon, M. Kim, M. Nutz, N. F. Hartmann, V. Perrin, B. Meany, M. S. Hofmann, C. W. Clark, S. K. Doorn, A. Högele, and Y. Wang, submitted.

Quantum electrodynamics at room temperature coupling a single vibrating molecule with a plasmonic nanocavity

Interactions between a single emitter and cavity provide the archetypical system for fundamental quantum electrodynamics. Here we show that a single molecule of Atto647 aligned using DNA origami interacts coherently with a sub-wavelength plasmonic nanocavity, approaching the cooperative regime even at room temperature. Power-dependent pulsed excitation reveals Rabi oscillations, arising from the coupling of the oscillating electric field between the ground and excited states. The observed single-molecule fluorescent emission is split into two modes resulting from anti-crossing with the plasmonic mode, indicating the molecule is strongly coupled to the cavity. The second-order correlation function of the photon emission statistics is found to be pump wavelength dependent, varying from g(2)(0) = 0.4 to 1.45, highlighting the influence of vibrational relaxation on the Jaynes-Cummings ladder. Our results show that cavity quantum electrodynamic effects can be observed in molecular systems at ambient conditions, opening significant potential for device applications.

Magnetic-field-dependent quantum emission in hexagonal boron nitride at room temperature

Optically addressable spins associated with defects in wide-bandgap semiconductors are versatile platforms for quantum information processing and nanoscale sensing, where spin-dependent inter-system crossing transitions facilitate optical spin initialization and readout. Recently, the van der Waals material hexagonal boron nitride (h-BN) has emerged as a robust host for quantum emitters, promising efficient photon extraction and atom-scale engineering, but observations of spin-related effects have remained thus far elusive. Here, we report room-temperature observations of strongly anisotropic photoluminescence patterns as a function of applied magnetic field for select quantum emitters in h-BN. Field-dependent variations in the steady-state photoluminescence and photon emission statistics are consistent with an electronic model featuring a spin-dependent inter-system crossing between triplet and singlet manifolds, indicating that optically-addressable spin defects are present in h-BN.

Tunneling blockade and single-photon emission in GaAs double quantum wells

We report on the selective excitation of single impurity-bound exciton states in a GaAs double quantum well (DQW). The structure consists of two quantum wells (QWs) coupled by a thin tunnel barrier. The DQW is subject to a transverse electric field to create spatially indirect inter-QW excitons with electrons and holes located in different QWs. We show that the presence of intra-QW charged excitons (trions) blocks carrier tunneling across the barrier to form indirect excitons, thus opening a gap in their emission spectrum. This behavior is attributed to the low binding energy of the trions. Within the tunneling blockade regime, emission becomes dominated by processes involving excitons bound to single shallow impurities, which behave as two-level centers activated by resonant tunneling. The quantum nature of the emission is confirmed by the antibunched photon emission statistics. The narrow distribution of emission energies ($\ensuremath{\sim}10$ meV) and the electrical connection to the QWs make these single-exciton centers interesting candidates for applications in single-photon sources.

Enhanced Single-Photon Emission from Carbon-Nanotube Dopant States Coupled to Silicon Microcavities.

Single-walled carbon nanotubes are a promising material as quantum light sources at room temperature and as nanoscale light sources for integrated photonic circuits on silicon. Here, we show that the integration of dopant states in carbon nanotubes and silicon microcavities can provide bright and high-purity single-photon emitters on a silicon photonics platform at room temperature. We perform photoluminescence spectroscopy and observe the enhancement of emission from the dopant states by a factor of ∼50, and cavity-enhanced radiative decay is confirmed using time-resolved measurements, in which a ∼30% decrease of emission lifetime is observed. The statistics of photons emitted from the cavity-coupled dopant states are investigated by photon-correlation measurements, and high-purity single photon generation is observed. The excitation power dependence of photon emission statistics shows that the degree of photon antibunching can be kept high even when the excitation power increases, while the single-photon emission rate can be increased to ∼1.7 × 107 Hz.

Counting statistics of photon emissions detected in non-Markovian environment

In this work we present a large-deviation analysis for the counting statistics of atomic spontaneous emissions continuously detected in finite-bandwidth non-Markovian environment. We show that the statistics of the spontaneous emissions depends on the time interval (τ) of successive detections, which can result in big differences such as dynamical phase transition. This feature excludes the idea of regarding the spontaneous emissions as detection-free objective events. Possible experiment is briefly discussed in connection with the state-of-the-art optical cavity set-up.

Excitation wavelength dependent photon anti-bunching/bunching from single quantum dots near gold nanostructures.

In this study, we aim to investigate the change in photon emission statistics of single CdSe/CdS core/shell quantum dots (QDs) on dielectric modified gold nanoparticle (NP) substrates as a function of the excitation wavelength. Photons emitted from single QDs are typically "anti-bunched" and are independent of the excitation wavelength. However, when QDs are coupled to plasmonic substrates, even at the low excitation power regime, we observed a significant change in photoluminescence emission behavior of single QDs; i.e. the emission transformed from incomplete photon anti-bunched to bunched when the excitation was changed from "off" to "on" plasmon resonance. Theoretical studies based on electrodynamics modeling suggested that for the QD-Au NP system, the quantum yield of single excitons decreases while that of biexcitons increases. In addition, when excited at the "on" resonance condition, the absorption is highly enhanced, resulting in an increased population of higher order excitons of the QDs. The higher order exciton emission was directly observed as an additional peak appeared at the blue side of the exciton peak of single QDs. The combined effect of the change in quantum yield and the increase in the absorption cross-section switches the photons emitted by single QDs from anti-bunched to bunched. These results provided direct evidence that not only the plasmonic nanostructures but also the excitation wavelength can effectively control the photon emission statistics of single QDs in the hybrid metal-semiconductor system. Manipulating the multiexciton-plasmon interaction in a hybrid complex like this could possibly open up new doors for applications such as entangled photon pair generation and plasmon-enhanced optoelectronic devices.

Temperature dependence of the single photon emission from interface-fluctuation GaN quantum dots

The temperature dependent single photon emission statistics of interface-fluctuation GaN quantum dots are reported. Quantum light emission is confirmed at temperatures up to ~77 K, by which point the background emission degrades the emission purity and results in a measured g(2) (0) in excess of 0.5. A discussion on the extent of the background contamination is also given through comparison to extensive data taken under various ambient and experimental conditions, revealing that the quantum dots themselves are emitting single photons with high purity.

Size-Dependent Biexciton Quantum Yields and Carrier Dynamics of Quasi-Two-Dimensional Core/Shell Nanoplatelets.

Quasi-two-dimensional nanoplatelets (NPLs) possess fundamentally different excitonic properties from zero-dimensional quantum dots. We study lateral size-dependent photon emission statistics and carrier dynamics of individual NPLs using second-order photon correlation (g(2)(τ)) spectroscopy and photoluminescence (PL) intensity-dependent lifetime analysis. Room-temperature radiative lifetimes of NPLs can be derived from maximum PL intensity periods in PL time traces. It first decreases with NPL lateral size and then stays constant, deviating from the electric dipole approximation. Analysis of the PL time traces further reveals that the single exciton quantum yield in NPLs decreases with NPL lateral size and increases with protecting shell thickness, indicating the importance of surface passivation on NPL emission quality. Second-order photon correlation (g(2)(τ)) studies of single NPLs show that the biexciton quantum yield is strongly dependent on the lateral size and single exciton quantum yield of the NPLs. In large NPLs with unity single exciton quantum yield, the corresponding biexciton quantum yield can reach unity. These findings reveal that by careful growth control and core-shell material engineering, NPLs can be of great potential for light amplification and integrated quantum photonic applications.

Cavity assisted emission of single, paired and heralded photons from a single quantum dot device.

The photon emission into different spatial directions of a quantum dot in a micropillar cavity is theoretically analyzed. We propose two types of photon emission statistics from a single quantum light device: (i) single photon emission into the axial, strong coupling direction and a two-photon emission into the lateral, weak coupling direction, as well as (ii) the simultaneous use of both emission directions for the temporally ordered generation of two photons within a defined time-bin constituting a heralded single photon source. Our results open up exciting perspectives for solid state based quantum light sources, which can be generalized to any quantum emitter-microcavity system featuring spatially distinct emission channels between the resonator and unconfined modes.

Photocount statistics of ultra-weak photon emission from germinating mung bean

Ultra-weak photon emission (UPE) is an endogenous bioluminescence phenomenon present in all biological samples with an active oxidative metabolism, even without an external pre-illumination. To verify the potential of UPE for non-invasive monitoring of metabolism and growth in germinating plants, the aim of this study was to investigate the UPE from a model system - germinating mung bean seedlings (Vigna radiata) - and analyze the statistical properties of UPE during the growth in two different conditions of imbibition (pure water and 1% sucrose). We found that in all days and in both conditions, photocount distributions of UPE time series follow the negative binomial distribution whose parameters changed during the growth due to the increasing ratio of signal-to-detector dark count. Correspondingly for both groups, the mean values of UPE increased during the seedlings growth, while the values of Fano factor show a decreasing trend towards 1 during the 6day period. While our results do not show any significant difference in hypocotyl length and weight gain between the two groups of mung seedlings, there is an indication of a tiny suppressing effect of sucrose on UPE intensity. We believe that UPE can be exploited for a sensitive non-invasive analysis of oxidative metabolism during the plant development and growth with potential applications in agricultural research.