Coupled Quantum Dot-cavity Research Articles

Controllable four-wave mixing based on quantum dot-cavity coupling system

We theoretically study the four-wave mixing (FWM) response in a quantum dot-cavity coupling system, where a two-level quantum dot (QD) is placed in an optical cavity while the cavity mode is coupled to the nanomechanical resonator via radiation pressure. The influences of the QD-cavity coupling strength, the Rabi coupling strength of the QD, and the power of the pump light on the FWM intensity are mainly considered. The numerical results show that the FWM intensity in this hybrid system can be significantly enhanced by increasing the QD-cavity coupling strength. In addition, the FWM intensity can be effectively modulated by the Rabi coupling strength and the pump power. Furthermore, the effects of the cavity decay rate and the cavity-pump detuning on the FWM signal are also explored. The obtained results may have potential applications in the fields of quantum optics and quantum information science.

Controllable bistable optical switch and normal mode splitting in hybrid optomechanical semiconductor microcavity containing single quantum dot driven by amplitude modulated field

We theoretically explore optical bistability for the possible signature of all-optical switching and their performance in a hybrid quantum optomechanical system comprising of two semiconductor microcavities coupled optically. One of the cavity is driven by an external amplitude-modulated pump laser while the second cavity, which contains a quantum dot (QD), is indirectly driven by light transmitted from the first cavity and a transverse optical field. The generated bistable behavior due to optomechanical nonlinearity shows a typical optical switching behavior and it can be controlled by changing the laser power, QD cavity coupling, modulating amplitude/frequency and the optomechanical coupling. A clear signature of energy exchange between the mechanical and optical modes is visible from the mechanical displacement spectrum. These results suggest that the present system can be used in sensitive optical switches and optical sensors.

Magnetically controllable photon blockade under a weak quantum-dot–cavity coupling condition

Quantum control of photons has become an area of great interest in the development of quantum technology. Here we explore how an external magnetic field can be exploited to control the statistical properties of photons in a bimodal cavity quantum electrodynamics (CQED) system. Our CQED system is composed of a bimodal micropillar Fabry-P\'erot cavity containing a single $V$-level quantum dot (QD) involving fine-structure-splitting neutral exciton transitions under the effect of the applied magnetic field in the presence of an incident pump laser field driving one cavity mode. With the introduction of the external magnetic field, not only is the conversion of polarization characteristics of photons achieved, but the statistics properties of photons are well engineered and the switching between photon bunching and antibunching is realized in the weak-coupling regime of CQED. The superiority of our system is manifested in the following aspects. (i) Using experimental parameters, we can manipulate the statistical properties of photons by appropriately tuning the strength of the magnetic field under the weak-coupling CQED condition, accompanied by either enhanced antibunching or a transition from antibunching to strong bunching of the light and vice versa. So we can arrive at selective photon statistics. (ii) The strong photon antibunching effect, under nonresonant scenarios but without the need to match the resonant or near-resonant conditions for the cavity and QD, can appear. Furthermore, we find that the multifrequency photon blockade can be generated in the present system, which is different from previous studies about photon blockade only for specific optical detuning. (iii) The high photon occupations or transmissions, simultaneously accompanied by strong photon antibunching in the system, are beneficial to the correlation measurement in practical experiments. This process works with a high quality of photon antibunching and bunching over a wide range of parameters and has potential applications in on-chip quantum information processing. It is hoped that the proposed scheme provides a possibility for the generation of tunable single-photon sources or controllable photon quantum gates.

Quantitative analysis of nonlinear dynamics of quantum light transmission in strongly coupled quantum dot-cavity systems

Abstract We compared transmission spectra of coupled high-Q cavity with quantum dot (QD) systems in the strong coupling regime with Input–Output Formalism (IOF) and Incoherent Pumping Mechanism (IPM) based on Lindblad master equation approach. The peak transmission of Dipole Induced Transparency (DIT) together with its full-width-half-maximum (FWHM) are enquired for detailed analysis. Both methods exhibit the same vacuum Rabi splitting in on-resonant case, in contrast, the peak of DIT is estimated smaller between 50% - 62.5% than experimentally observed value in off-resonant case. A key outcome of this comparison is that IPM seems to be unable to explain DIT phenomenon entirely in off-resonant case due to the imperfect capture of the emission of polariton’s atomic-like feature in the transmission spectrum.

Quantum entanglement concentration for photonic polarization state assisted by electron spin

In order to assure the security of the long-distance quantum communication, the maximum entangled state is necessary. However, the decoherence of the entanglement is inevitable because of the channel noise and the interference of the environment. Quantum entanglement concentration can be used to convert a non-maximum entangled state into a maximum one. In previous entanglement concentration proposals, we need the initial coefficients of non-maximum entangled state or repeat the entanglement concentration process to improve the possibility of success, which reduces the efficiency of the entanglement concentration. A more efficient entanglement concentration for phontonic polarization state is proposed in this paper, which is based on the interaction between circularly polarized light and quantum dot-cavity system. An auxiliary photon is introduced to connect two distant participants. To overcome the channel noise, the auxiliary photon transmits though two channels between the two participants. The photons interact with coupled quantum dot-cavity before and after the auxiliary photon transmission. Then the states of spins and auxiliary photon are measured, and the maximum phontonic polarization entangled state is obtained by single-photon operations according to the measurement results. The success possibility of the proposed scheme is 1 in ideal conditions, that is, the concentration can be realized deterministically. However, the cavity leakage is unavoidable, so the fidelity of the entanglement concentration is calculated by taking one of the measurement results for example. The results show that the influences of the initial coefficients of non-maximum entangled state on the fidelity can be ignored in most cases, which saves a mass of photons used to measure the initial coefficients of the non-maximum entangled state. The fidelities with varying coupling strengths and cavity leakages are also shown in the paper. In the case of weak coupling, the fidelity is low and varies sharply with cavity leakage. Fortunately, the fidelity will plateau in a strong coupling case, and reaches 99.8% with a coupling strength 0.7 for diverse cavity leakages. Much progress has been made in the study of the strong coupling between quantum dot and optical cavity, which can satisfy the requirement of our entanglement concentration. So the proposed scheme is feasible in the current experimental conditions. In general, our proposal still maintains high fidelity even considering the cavity leakage, and the initial information about partially entangled state and the repetition of the entanglement concentration process are not required. This not only improves the security of the quantum entanglement concentration, but also contributes to efficient quantum information processing with less quantum resources. These characteristics increase the universality and efficiency of the entanglement concentration, thus assuring the quality of the long-distance quantum entanglement.

Complete Coherent Control of a Quantum Dot Strongly Coupled to a Nanocavity.

Strongly coupled quantum dot-cavity systems provide a non-linear configuration of hybridized light-matter states with promising quantum-optical applications. Here, we investigate the coherent interaction between strong laser pulses and quantum dot-cavity polaritons. Resonant excitation of polaritonic states and their interaction with phonons allow us to observe coherent Rabi oscillations and Ramsey fringes. Furthermore, we demonstrate complete coherent control of a quantum dot-photonic crystal cavity based quantum-bit. By controlling the excitation power and phase in a two-pulse excitation scheme we achieve access to the full Bloch sphere. Quantum-optical simulations are in good agreement with our experiments and provide insight into the decoherence mechanisms.

Quantum interference induced photon blockade in a coupled single quantum dot-cavity system.

We propose an experimental scheme to implement a strong photon blockade with a single quantum dot coupled to a nanocavity. The photon blockade effect can be tremendously enhanced by driving the cavity and the quantum dot simultaneously with two classical laser fields. This enhancement of photon blockade is ascribed to the quantum interference effect to avoid two-photon excitation of the cavity field. Comparing with Jaynes-Cummings model, the second-order correlation function at zero time delay g(2)(0) in our scheme can be reduced by two orders of magnitude and the system sustains a large intracavity photon number. A red (blue) cavity-light detuning asymmetry for photon quantum statistics with bunching or antibunching characteristics is also observed. The photon blockade effect has a controllable flexibility by tuning the relative phase between the two pumping laser fields and the Rabi coupling strength between the quantum dot and the pumping field. Moreover, the photon blockade scheme based on quantum interference mechanism does not require a strong coupling strength between the cavity and the quantum dot, even with the pure dephasing of the system. This simple proposal provides an effective way for potential applications in solid state quantum computation and quantum information processing.

Auger Processes Mediating the Nonresonant Optical Emission from a Semiconductor Quantum Dot Embedded Inside an Optical Cavity

We show that Auger processes involving wetting layer transitions mediate emission from a cavity that is detuned from a quantum dot by even tens of meV. The wetting layer thus acts as a reservoir, which by Coulomb scattering can supply or absorb the energy difference between emitter and cavity. We perform microscopic calculations of the effect treating the wetting layer as a non-Markovian reservoir interacting with the coupled quantum dot-cavity system through Coulomb interactions. Experimentally, cavity feeding has been observed in the asymmetric detuning range of -10 to +45 meV. We show that this asymmetry arises naturally from the quasiequilibrium properties of the wetting layer reservoir. Furthermore, we present numerical calculations of both photoluminescence spectra and photon correlations, demonstrating good qualitative agreement with experiments.

Cavity quantum electrodynamics with charge-controlled quantum dots coupled to a fiber Fabry–Perot cavity

We demonstrate non-perturbative coupling between a single self-assembled InGaAs quantum dot and an external fiber-mirror-based microcavity. Our results extend the previous realizations of tunable microcavities while ensuring spatial and spectral overlap between the cavity mode and the emitter by simultaneously allowing for deterministic charge control of the quantum dots. Using resonant spectroscopy, we show that the coupled quantum dot cavity system is at the onset of strong coupling, with a cooperativity parameter of C ≈ 2.0 ± 1.3. Our results constitute a milestone in the progress toward the realization of a high-efficiency solid-state spin–photon interface.

Proposed Quenching of Phonon-Induced Processes in Photoexcited Quantum Dots due to Electron-Hole Asymmetries

Differences in the confinement of electrons and holes in quantum dots are shown to profoundly impact the magnitude of scattering with acoustic phonons. Using an extensive model that includes the non-Markovian nature of the phonon reservoir, we show how the effect may be addressed by photoluminescence excitation spectroscopy of a single quantum dot. We also investigate the implications for cavity QED, i.e., a coupled quantum dot-cavity system, and demonstrate that the phonon scattering may be strongly quenched. The quenching is explained by a balancing between the deformation potential interaction strengths and the carrier confinement and depends on the quantum dot shape. Numerical examples suggest a route towards engineering the phonon scattering.

Erratum: Phonon mediated off-resonant quantum dot–cavity coupling under resonant excitation of the quantum dot [Phys. Rev. B84, 085309 (2011)

where ρdos(ν) is the density of states of phonons at frequency ν and other parameters are explained in the original paper. The values of γr used in the paper were based on the experimental results. Therefore, the error in Eq. (A26) does not affect any conclusions and results of the paper. The derivation of this expression follows Carmichael (Ref. 1, Chap. 1.3). Starting with the equations for correlation functions [(A24) and (A25)] from the paper, the summation over reservoir oscillators can be replaced with integration over the reservoir by introducing a density of states of phonons at a frequency ω as ρdos(ω) [such that ρdos(ω)dω gives the total number of oscillators, i.e., phonons with frequencies in the intervals ω and ω + dω], and transforming g 23 → g23(ω). We note that, by such definition, ρdos(ω) has a dimension of inverse frequency. This leads to the following expressions for the correlation functions (where τ = t ′ − t): 〈 †(t + τ ) (t)〉R = ∫ ∞

Fast Purcell-enhanced single photon source in 1,550-nm telecom band from a resonant quantum dot-cavity coupling

High-bit-rate nanocavity-based single photon sources in the 1,550-nm telecom band are challenges facing the development of fibre-based long-haul quantum communication networks. Here we report a very fast single photon source in the 1,550-nm telecom band, which is achieved by a large Purcell enhancement that results from the coupling of a single InAs quantum dot and an InP photonic crystal nanocavity. At a resonance, the spontaneous emission rate was enhanced by a factor of 5 resulting a record fast emission lifetime of 0.2 ns at 1,550 nm. We also demonstrate that this emission exhibits an enhanced anti-bunching dip. This is the first realization of nanocavity-enhanced single photon emitters in the 1,550-nm telecom band. This coupled quantum dot cavity system in the telecom band thus provides a bright high-bit-rate non-classical single photon source that offers appealing novel opportunities for the development of a long-haul quantum telecommunication system via optical fibres.

Ultrafast Photon-Photon Interaction in a Strongly Coupled Quantum Dot-Cavity System

We study dynamics of the interaction between two weak light beams mediated by a strongly coupled quantum dot-photonic crystal cavity system. First, we perform all-optical switching of a weak continuous-wave signal with a pulsed control beam, and then perform switching between two weak pulsed beams (40 ps pulses). Our results show that the quantum dot-nanocavity system enables fast, controllable optical switching at the single-photon level.

Microcavity enhanced single photon emission from an electrically driven site-controlled quantum dot

In this work we report on the integration of single site-controlled quantum dots (SCQDs) into electrically driven micropillar cavities. The electroluminescence of these devices features emission of single SCQDs with inhomogeneous broadenings down to 170 µeV. The enhancement of electroluminescence by quantum dot-cavity coupling is demonstrated by temperature dependent investigations. Single photon emission from a spatially and spectrally coupled SCQD-resonator system is confirmed by photon autocorrelation measurements under electrical excitation yielding a g(2)(0) value of 0.42.

Phonon mediated off-resonant quantum dot–cavity coupling under resonant excitation of the quantum dot

A theoretical model for the phonon-mediated off-resonant coupling between a quantum dot and a cavity, under resonant excitation of the quantum dot, is presented. We show that the coupling is caused by electron-phonon interaction in the quantum dot and is enhanced by the cavity. We analyze recently observed resonant quantum dot spectroscopic data by our theoretical model.

Influences of pure dephasing and incoherent pumping in a coupled quantum dot–cavity system and its application

The influences of pure dephasing and incoherent pumping on the spectra from a coupled target quantum dot–cavity system are systematically investigated. We find that incoherent pumping has a similar effect on the spectra as pure dephasing does. The results of off-resonance study indicate that a frequency-stabilized single photon source can be achieved by controlling either pure dephasing rate or incoherent pumping rate. Furthermore, we investigate the strategies to optimize the efficiency of a single photon source. The obtained results offer appealing perspectives in developing an efficient frequency-stabilized solid-state single photon source.

量子点腔非谐振耦合系统纯退相干的特性及应用

The quantum dot-cavity system was investigated using a quantum master equation that took incoherent pumping,stimulated emission and pure dephasing into consideration,and analytical emission spectra at cavity and dot were presented.The theoretical analysis results show that the pure dephasing shifts the emission intensity towards the cavity frequency in non-resonant coupling system and thus can be a very good explanation of the non-resonantly coupled cavity effective emission effect.In order to further study the application of pure dephasing in the quantum dot-cavity coupled systems,the effective quantum dot-cavity coupling rate and the efficiency of the single photon source for detuned systems were introduced,and good cavity and bad ragime were able to be defined through comparing the effective quantum dot-cavity coupling rate and the cavity decay rate.Influence of the pure dephasing on the efective coupling rate and the efficiency of the single photon source were investigated in resonance and detuning selected two set of theoretical parameters according to the experimental data.The results show that the pure dephasing can increase the efftive quantum dot-cavity coupling and the efficiency of single photon source for detuned system and thus may make a transition from bad cavity to good cavity ragime;a set of parameters having larger coupling efficiency in a certain range can meet good cavity ragime that its single photon sources efficiency is obviously better than the other set.Compared with bad cavity regime laser in non-resonant coupling system,the good cavity regime is a necessary condition to achieve single quantum dot lasers;the Fano function shows no evidence of a maximum in the non-resonant coupling system and thus there is no laser threshold in this system.

Non-Markovian Model of Photon-Assisted Dephasing by Electron-Phonon Interactions in a Coupled Quantum-Dot–Cavity System

We investigate the influence of electron-phonon interactions on the dynamical properties of a quantum-dot-cavity QED system. We show that non-markovian effects in the phonon reservoir lead to strong changes in the dynamics, arising from photon-assisted dephasing processes, not present in markovian treatments. A pronounced consequence is the emergence of a phonon induced spectral asymmetry when detuning the cavity from the quantum-dot resonance. The asymmetry can only be explained when considering the polaritonic quasiparticle nature of the quantum-dot-cavity system. Furthermore, a temperature induced reduction of the light-matter coupling strength is found to be relevant in interpreting experimental data, especially in the strong coupling regime.

Nonlinear photoluminescence spectra from a quantum-dot–cavity system: Interplay of pump-induced stimulated emission and anharmonic cavity QED

We investigate the power-dependent photoluminescence spectra from a strongly coupled quantum dot-cavity system using a quantum master equation technique that accounts for incoherent pumping, pure dephasing, and fermion or boson statistics. Analytical spectra at the one-photon correlation level and the numerically exact multi-photon spectra for fermions are presented. We compare to recent experiments on a quantum dot-micropiller cavity system and show that an excellent fit to the data can be obtained by varying only the incoherent pump rates in direct correspondence with the experiments. Our theory and experiments together show a clear and systematic way of studying stimulated-emission induced broadening and anharmonic cavity-QED.

Origin of the Optical Emission within the Cavity Mode of Coupled Quantum Dot-Cavity Systems

The origin of the emission within the optical mode of a coupled quantum dot-micropillar system is investigated. Time-resolved photoluminescence is performed on a large number of deterministically coupled devices in a wide range of temperature and detuning. The emission within the cavity mode is found to exhibit the same dynamics as the spectrally closest quantum dot state. Our observations indicate that fast dephasing of the quantum dot state is responsible for the emission within the cavity mode. An explanation for recent photon correlation measurements reported on similar systems is proposed.