We report on the observation of the strong coupling regime between a single GaAs quantum dot and a microdisk optical mode. Photoluminescence is performed at various temperatures to tune the quantum dot exciton with respect to the optical mode. At resonance, we observe an anticrossing, signature of the strong coupling regime with a well resolved doublet. The Vacuum Rabi splitting amounts to 400 μeV and is twice as large as the individual linewidths.
We study the hybrid exciton-polaritons in a bad microcavity containing the organic and inorganic quantum wells. The corresponding polariton states are given. The analytical solution and the numerical result of the stationary spectrum for the cavity field are finished
We investigate exciton emission of quantum well embedded in a semiconductor microcavity. The analytical expressions of the light intensity for the cases of excitonic number state and coherent state are presented by using secular approximation. Our results show that the effective exciton-exciton interaction leads to the appearance of collapse and revival of the light intensity. The revival time is twice compared the coherent state case with that of the number state. The dissipation of the exciton-polariton lowers the revival amplitude but does not alter the revival time. The influences of the d…
We present a detailed analysis of exciton-photon interaction in a microcavity made out of a photonic crystal slab. Here we have analyzed a disk-like quantum dot where an exciton is formed. Excitonic eigen-functions in addition to their eigen-energies are found through direct matrix diagonalization, while wave functions corresponding to unbound electron and hole are chosen as the basis set for this procedure. In order to evaluate these wave functions precisely, we have used Luttinger Hamiltonian in the case of hole while ignoring bands adjacent to conduction band for electron states. After anal…
We analyze the entanglement between two matter modes in a hybrid quantum system consists of a microcavity, a quantum well, and a mechanical oscillator. Although the exciton mode in the quantum well and the mechanical oscillator are initially uncoupled, their interaction through the microcavity field results in an indirect exciton-mode--mechanical-mode coupling. We show that this coupling is a Fano-Agarwal-type coupling induced by the decay of the exciton and the mechanical modes caused by the leakage of photons through the microcavity to the environment. Using experimental parameters and for s…
Controlled non-local energy and coherence transfer enables light harvesting in photosynthesis and non-local logical operations in quantum computing. The most relevant mechanism of coherent coupling of distant qubits is coupling via the electromagnetic field. Here, we demonstrate the controlled coherent coupling of spatially separated excitonic qubits via the photon mode of a solid state microresonator. This is revealed by two-dimensional spectroscopy of the sample's coherent response, a sensitive and selective probe of the coherent coupling. The experimental results are quantitatively describe…
We have demonstrated efficient production of triggered single photons by coupling a single semiconductor quantum dot to a three-dimensionally confined optical mode in a micropost microcavity. The efficiency of emitting single photons into a single-mode travelling wave is approximately 38%, which is nearly two orders of magnitude higher than for a quantum dot in bulk semiconductor material. At the same time, the probability of having more than one photon in a given pulse is reduced by a factor of seven as compared to light with Poissonian photon statistics.
We consider a semiconductor quantum well in a microcavity driven by coherent light and coupled to a squeezed vacuum reservoir. By systematically solving the pertinent quantum Langevin equations in the strong coupling and low excitation regimes, we study the effect of exciton-photon detuning, external coherent light, and the squeezed vacuum reservoir on vacuum Rabi splitting and on quantum statistical properties of the light emitted by the quantum well. We show that the exciton-photon detuning leads to a shift in polariton resonance frequencies and a decrease in fluorescence intensity. We also …
We observe antibunching in the photons emitted from a strongly-coupled single quantum dot and pillar microcavity in resonance. When the quantum dot was spectrally detuned from the cavity mode, the cavity emission remained antibunched, and also anticorrelated from the quantum dot emission. Resonant pumping of the selected quantum dot via an excited state enabled these observations by eliminating the background emitters that are usually coupled to the cavity. This device demonstrates an on-demand single photon source operating in the strong coupling regime, with a Purcell factor of 61 and quantu…
A novel, optimized numerical method of modeling of an exciton-polariton superfluid in a semiconductor microcavity was proposed. Exciton-polaritons are spin-carrying quasiparticles formed from photons strongly coupled to excitons. They possess unique properties, interesting from the point of view of fundamental research as well as numerous potential applications. However, their numerical modeling is challenging due to the structure of nonlinear differential equations describing their evolution. In this paper, we propose to solve the equations with a modified Runge--Kutta method of 4th order, fu…
Large conditional phase shifts from coupled atom-cavity systems are a key requirement for building a spin photon interface. This in turn would allow the realisation of hybrid quantum information schemes using spin and photonic qubits. Here we perform high resolution reflection spectroscopy of a quantum dot resonantly coupled to a pillar microcavity. We show both the change in reflectivity as the quantum dot is tuned through the cavity resonance, and measure the conditional phase shift induced by the quantum dot using an ultra stable interferometer. These techniques could be extended to the stu…
We show theoretically that entangled photon pairs can be produced on demand through the biexciton decay of a quantum dot strongly coupled to the modes of a photonic crystal. The strong coupling allows to tune the energy of the mixed exciton-photon (polariton) eigenmodes, and to overcome the natural splitting existing between the exciton states coupled with different linear polarizations of light. Polariton states are moreover well protected against dephasing due to their lifetime ten to hundred times shorter than that of a bare exciton. Our analysis shows that the scheme proposed can be achiev…
Bell's inequality in three coupled quantum dots (QDs) within cavity QED, including Forster and exciton-phonon interactions, is investigated theoretically. For an initially entangled state, Bell's inequality is valid for certain times and violated for some other times. It is shown that the system moves from a product state to a entangled state and back again during it's time evolution.
It is usually assumed that when performing a photoluminescence experiment on a microcavity containing an inhomogeneously broadened quantum dots ensemble, the cavity mode appears as a positive peak with a linewidth that reflects the mode quality factor Q. We show in this article that this conclusion is in general not true, and that the measured mode linewidth depends strongly on the excitation power for microcavities having large Purcell factors. We analyze theoretically this effect in the case of the micropillar cavity and we show that the same microcavity can give rise to a large variety of p…
We present two novel schemes to generate photon polarization entanglement via single electron spins confined in charged quantum dots inside microcavities. One scheme is via entangled remote electron spins followed by negatively-charged exciton emissions, and another scheme is via a single electron spin followed by the spin state measurement. Both schemes are based on giant circular birefringence and giant Faraday rotation induced by a single electron spin in a microcavity. Our schemes are deterministic and can generate an arbitrary amount of multi-photon entanglement. Following similar procedu…
We investigate the possibility to achieve scalable photonic quantum computing by the giant optical circular birefringence induced by a quantum-dot spin in a double-sided optical microcavity as a result of cavity quantum electrodynamics. We construct a deterministic controlled-not gate on two photonic qubits by two single-photon input-output processes and the readout on an electron-medium spin confined in an optical resonant microcavity. This idea could be applied to multi-qubit gates on photonic qubits and we give the quantum circuit for a three-photon Toffoli gate. High fidelities and high ef…
We demonstrate a single-photon source based on a quantum dot in a micropost microcavity that exhibits a large Purcell factor together with a small multi-photon probability. For a quantum dot on resonance with the cavity, the spontaneous emission rate is increased by a factor of five, while the probability to emit two or more photons in the same pulse is reduced to 2% compared to a Poisson-distributed source of the same intensity. In addition to the small multi-photon probability, such a strong Purcell effect is important in a single-photon source for improving the photon outcoupling efficiency…
We propose a deterministic and scalable scheme to construct a two-qubit controlled-NOT (CNOT) gate and realize entanglement swapping between photonic qubits using a quantum-dot (QD) spin in a double-sided optical microcavity. The scheme is based on spin selective photon reflection from the cavity and can be achieved in a nondestructive and heralded way. We assess the feasibility of the scheme and show that the scheme can work in both the weak coupling and the strong coupling regimes. The scheme opens promising perspectives for long-distance photonic quantum communication and distributed quantu…
We investigate the possibility of creating X-waves, or localized wave packets, in resonantly excited exciton-polariton superfluids. We demonstrate the existence of X-wave traveling solutions in the coupled exciton-photon system past the inflection point, where the effective mass of lower polaritons is negative in the direction perpendicular to the wavevector of the pumping beam. Contrary to the case of bright solitons, X-waves do not require nonlinearity for sustaining their shape. Nevertheless, we show that nonlinearity is important for their dynamics, as it allows for their spontaneous forma…
We demonstrate purely resonant continuous-wave optical laser excitation to coherently prepare an excitonic state of a single semiconductor quantum dot (QDs) inside a high quality pillar microcavity. As a direct proof of QD resonance fluorescence, the evolution from a single emission line to the characteristic Mollow triplet10 is observed under increasing pump power. By controlled utilization of weak coupling between the emitter and the fundamental cavity mode through Purcell-enhancement of the radiative decay, a strong suppression of pure dephasing is achieved, which reflects in close to Fouri…
We propose an entanglement beam splitter (EBS) using a quantum-dot spin in a double-sided optical microcavity. In contrast to the conventional optical beam splitter, the EBS can directly split a photon-spin product state into two constituent entangled states via transmission and reflection with high fidelity and high efficiency (up to 100 percent). This device is based on giant optical circular birefringence induced by a single spin as a result of cavity quantum electrodynamics and the spin selection rule of trion transition (Pauli blocking). The EBS is robust and it is immune to the fine stru…
Semiconductor quantum dots (known as artificial atoms) hold great promise for solid-state quantum networks and quantum computers. To realize a quantum network, it is crucial to achieve light-matter entanglement and coherent quantum-state transfer between light and matter. Here we present a robust photon-spin entangling gate with high fidelity and high efficiency (up to 50 percent) using a charged quantum dot in a double-sided microcavity. This gate is based on giant circular birefringence induced by a single electron spin, and functions as an optical circular polariser which allows only one ci…
We present experimental results showing phonon-mediated coupling between two quantum dots embedded inside a photonic crystal microcavity. With only one of the dots being spectrally close to the cavity, we observe both frequency up-conversion and down-conversion of the pump light via a $\sim1.2$ THz phonon. We demonstrate this process for both weak and strong regimes of dot-cavity coupling, and provide a simple theoretical model explaining our observations.
Up to now, all the works about constructing quantum logic gates, an essential part in quantum computing, are focused on operating on one degree of freedom (DOF) of quantum systems. Here, we investigate the possibility to achieve a scalable photonic quantum computing based on two DOFs of quantum systems and construct a deterministic hyper-controlled-not (hyper-CNOT) gate operating on both spatial-mode and polarization DOFs of a photon pair simultaneously, by using the giant optical Faraday rotation induced by a single-electron spin in a quantum dot inside a one-side optical microcavity as a res…
We propose a scheme for the quantum nondemolition (QND) measurement of a single electron spin in a single quantum dot (QD). Analytical expressions are obtained for the optical Faraday effect between a quantum dot exciton and microcavity field. The feasibility of the QND measurement of a single electron spin is discussed for a GaAs/AlAs microcavity with an InAs QD.
We analyze the impact of both an incoherent and a coherent continuous excitation on our proposal to generate a two-photon state from a quantum dot in a microcavity [New J. Phys. 13, 113014 (2011)]. A comparison between exact numerical results and analytical formulas provides the conditions to efficiently generate indistinguishable and simultaneous pairs of photons under both types of excitation.
Assisted with linear optical manipulation, single photon, entangled photon pairs, photon measurement, and classical communication, a scheme for two-spin qubits phase gate and teleportation of a CNOT gate between two electron spins from acting on local qubits to acting on remote qubits using quantum dots in optical microcavities is proposed. The scheme is based on spin selective photon reflection from the cavity and is achieved in a deterministic way by the sequential detection of photons and the single-qubit rotations of a single electron spin in a self-assembled GaAs/InAs quantum dot. The fea…
Narrow dark resonances associated with electromagnetically induced transparency play a key role in enhancing photon-photon interactions. The schemes realized to date relied on the existence of long-lived atomic states with strong van der Waals interactions. Here, we show that by placing an atomically thin semiconductor with ultra-fast radiative decay rate inside a \textcolor{black}{0D} cavity, it is possible to obtain narrow dark or bright resonances in transmission whose width could be much smaller than that of the cavity and bare exciton decay rates. While breaking of translational invarianc…
In this paper we introduce and analyze a new system design for quantum-dot-based qubits that simultaneously supports scalable one-qubit and two-qubit gates, and single-shot qubit measurement. All three key processes (one-qubit gates, two-qubit gates, and qubit measurement) rely on the interaction between the electron in each quantum dot and exciton-polaritons formed in a quantum well situated near the quantum dots. A key novel feature of our proposed system is the use of polariton traps, which we show enhances the quantum-dot--quantum-well interaction by a factor of 10 and consequently results…
We show that it is possible to realize quantum superpositions of switched-on and -off strong light-matter interaction in a single quantum dot- semiconductor microcavity system. Such superpositions enable the observation of counterintuitive quantum conditional dynamics effects. Situations are possible where cavity photons as well as the emitter luminescence display exponential decay but their joint detection probability exhibits vacuum Rabi oscillations. Remarkably, these quantum correlations are also present in the nonequilibrium steady state spectra of such coherently driven dissipative quant…
In this work we have studied the quantum statistical properties of the photon emitted from a driven microcavity embedded with a single armchair-edged graphene nanoribbon (GNR). The system is coherently pumped with weak laser amplitude. Analytical expressions are derived in both strong and weak coupling regimes and the nonclassical proprieties of the emitted field have been investigated. Furthermore, it is concluded that this excitonic system presents several statistical similarities to the atomic system, in particular for the bad-cavity and good-cavity limits in the weak laser amplitude regime…
We investigate theoretically two-photon processes in a microcavity containing one quantum dot in the strong coupling regime. The cavity mode can be tuned to resonantly drive the two-photon transition between the ground and the biexciton states, while the exciton states are far-off resonance due to the biexciton binding energy. We study the steady state of the quantum dot and cavity field in presence of a continuous incoherent pumping. We identify the regime where the system acts as two-photon emitter and discuss the feasibility and performance of realistic single quantum dot devices for two-ph…
We study the photon emission from a quantum dot embedded in a microcavity. Incoherent pumping of its excitons and biexciton provokes the emission of leaky and cavity modes. By solving a master equation we obtain the correlation functions required to compute the spectrum and the relative efficiency among the emission of pairs and single photons. A quantum regime appears for low pumping and large rate of emission. By means of a post-selection process, a two beams experiment with different linear polarizations could be performed producing a large polarization entanglement visibility precisely in …
We present experimental observations of a non-resonant dynamic Stark shift in strongly coupled microcavity quantum well exciton-polaritons - a system which provides a rich variety of solid-state collective phenomena. The Stark effect is demonstrated in a GaAs/AlGaAs system at 10K by femtosecond pump-probe measurements, with the blue shift approaching the meV scale for a pump fluence of 2 mJcm^-2 and 50 meV red detuning, in good agreement with theory. The energy level structure of the strongly coupled polariton Rabi-doublet remains unaffected by the blue shift. The demonstrated effect should al…
Implementations for quantum computing require fast single- and multi-qubit quantum gate operations. In the case of optically controlled quantum dot qubits theoretical designs for long-range two- or multi-qubit operations satisfying all the requirements in quantum computing are not yet available. We have developed a design for a fast, long-range two-qubit gate mediated by a photonic microcavity mode using excited states of the quantum dot-cavity system that addresses these needs. This design does not require identical qubits, it is compatible with available optically induced single qubit operat…
We investigate the strong coupling regime of a self-assembled quantum dot in a tunable microcavity with dark-field laser spectroscopy. The high quality of the spectra allows the lineshapes to be analyzed revealing subtle quantum interferences. Agreement with a model calculation is achieved only by including exciton dephasing which reduces the cooperativity from a bare value of 9.0 to the time-averaged value 5.5. In the pursuit of high cooperativity, besides a high-Q and low mode-volume cavity, we demonstrate that equal efforts need to be taken towards lifetime-limited emitter linewidths.
We report the efficient coherent photon scattering from a semiconductor quantum dot embedded in a pillar microcavity. We show that a surface acoustic wave can periodically modulate the energy levels of the quantum dot, but has a negligible effect on the cavity mode. The scattered narrow-band laser is converted to a pulsed single-photon stream, displaying an anti-bunching dip characteristic of single-photon emission. Multiple phonon sidebands are resolved in the emission spectrum, due to the absorption and emission of vibrational quanta in each scattering event.
We demonstrate the emission of highly indistinguishable photons from a quasi-resonantly pumped coupled quantum dot--microcavity system operating in the regime of cavity quantum electrodynamics. Changing the sample temperature allows us to vary the quantum dot--cavity detuning, and on spectral resonance we observe a three-fold improvement in the Hong--Ou--Mandel interference visibility, reaching values in excess of 80\%. Our measurements off-resonance allow us to investigate varying Purcell enhancements, and to probe the dephasing environment at different temperatures and energy scales. By comp…
We propose and characterize a two-photon emitter in a highly polarised, monochromatic and directional beam, realized by means of a quantum dot embedded in a linearly polarized cavity. In our scheme, the cavity frequency is tuned to half the frequency of the biexciton (two excitons with opposite spins) and largely detuned from the excitons thanks to the large biexciton binding energy. We show how the emission can be Purcell enhanced by several orders of magnitude into the two-photon channel for available experimental systems.
The future of quantum communication systems and quantum networks heavily rely on the ability to fabricate and coherently control the conversion of photons between different modes based on a solid-state plateform. In this work, we propose and theoretically investigate a scheme to optomechanically control coherent mode conversion of optical photons by utilizing two optically coupled hybrid semiconductor microcavities containing a quantum dot (QD). One of the microcavity is pumped by an external laser and the second cavity is driven by light emitted by the QD that is embedded in the interface sep…
We exploit the nonlinearity arising from the spin-photon interaction in an InAs quantum dot to demonstrate phase shifts of scattered light pulses at the single-photon level. Photon phase shifts of close to 90 degrees are achieved using a charged quantum dot in a micropillar cavity. We also demonstrate a photon phase switch by using a spin-pumping mechanism through Raman transitions in an in-plane magnetic field. The experimental findings are supported by a theoretical model which explores the dynamics of the system. Our results demonstrate the potential of quantum dot-induced nonlinearities fo…
The Jaynes-Cummings model, describing the interaction between a single two-level system and a photonic mode, has been used to describe a large variety of systems, ranging from cavity quantum electrodynamics, trapped ions, to superconducting qubits coupled to resonators. Recently there has been renewed interest in studying the quantum strong-coupling (QSC) regime, where states with photon number greater than one are excited. This regime has been recently achieved in semiconductor nanostructures, where a quantum dot is trapped in a planar microcavity. Here we study the quantum strong-coupling re…
We theoretically explore optical bistability for possible signature of all optical switching and their performance in a hybrid quantum optomechanical system comprising of two semiconductor microcavity coupled optically. One of the cavity is driven by an external optical pump laser while the second cavity which contains a quantum dot is indirectly driven by light transmitted from the first cavity. 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, rocking paramete…
We theoretically investigate optical bistability, mechanically induced absorption (MIA) and Fano resonance of a hybrid system comprising of a single quantum dot (QD) embedded in a solid state microcavity interacting with the quantized cavity mode and the deformation potential associated with the lattice vibration. We find that the bistability can be tuned by the QD-cavity mode coupling. We further show that the normalized power transmission displays anomalous dispersion indicating that the system can be used to generate slow light. We also demonstrate the possibility of using the system as all…
We demonstrate a technique for achieving spectral resonance between a polarization-degenerate micropillar cavity mode and an embedded quantum dot transition. Our approach is based on a combination of isotropic and anisotropic tensile strain effected by laser-induced surface defects, thereby providing permanent tuning. Such a technique is a prerequisite for the implementation of scalable quantum information schemes based on solid-state cavity quantum electrodynamics.
We have developed a microcavity single-photon source based on a single quantum dot within a planar cavity in which wet-oxidation of a high-aluminium content layer provides lateral confinement of both the photonic mode and the injection current. Lateral confinement of the optical mode in optically pumped structures produces a strong enhancement of the radiative decay rate. Using microcavity structures with doped contact layers, we demonstrate a single-photon emitting diode where current may be injected into a single dot.
Semiconductor quantum-dot cavity systems are promising sources for solid-state based on-demand generation of single photons for quantum communication. Commonly, the spectral characteristics of the emitted single photon are fixed by system properties such as electronic transition energies and spectral properties of the cavity. In the present work we study single-photon generation from the quantum-dot biexciton through a partly stimulated non-degenerate two-photon emission. We show that frequency and linewidth of the single photon can be fully controlled by the stimulating laser pulse, ultimatel…
We present a scheme for efficient state teleportation and entanglement swapping using a single quantum-dot spin in an optical microcavity based on giant circular birefringence. State teleportation or entanglement swapping is heralded by the sequential detection of two photons, and is finished after the spin measurement. The spin-cavity unit works as a complete Bell-state analyzer with a built-in spin memory allowing loss-resistant repeater operation. This device can work in both the weak coupling and the strong coupling regime, but high efficiencies and high fidelities are only achievable when…
We propose a scheme to realize a highly efficient solid state source of photon pairs using cavity-assisted stimulated Raman adiabatic passage (STIRAP) in a single quantum dot, where a single photon from pump pulse and two stokes photons from cavity mode drives the Raman transition. The Autler-Townes doublet, generated by using a resonant continuous wave laser between biexciton and exciton states, and two-photon-resonant transition through strongly coupled cavity mode are utilized to facilitate (1+2)type Raman transition in the quantum dot. We show in the case of weak pump although the probabil…
Entanglement generation in microcavity exciton-polaritons is an interesting application of the peculiar properties of these half-light/half-matter quasiparticles. In this paper we theoretically investigate their luminescence dynamics and entanglement formation in single, double, and triple cavities. We derive general expressions and selection rules for polariton-polariton scattering. We evaluate a number of possible parametric scattering schemes in terms of entanglement, and identify the ones that are experimentally most promising.
Exciton-polariton solitons are strongly nonlinear quasiparticles composed of coupled exciton-photon states due to the interaction of light with matter. In semiconductor microcavity systems such as semiconductor micro and nanowires, polaritons are characterized by a negative mass which when combined with the repulsive nonlinear exciton-exciton interaction, leads to the generation of bright polariton solitons. In this work we investigate the dynamics of bright exciton-polariton solitons in a finite-size microcavity waveguide, for which radiative losses are assumed balanced by the external pumpin…
We propose a theoretical model which describes the coupling between quantum dots ensemble and optical microcavity. By this model we simulate the interaction of the system with the strain pulse which can strongly modify the lasing of QDs.
Two-photon absorption (TPA) allows accessing dark states of matter otherwise inaccessible to light, which serve as important building blocks for quantum information processing. In a semiconductor microcavity, TPA driven condensation of strongly-coupled light-matter exciton-polaritons can enable new solid-state quantum simulations of dark state-condensate interactions, and was predicted to stimulate THz emission. Here, we report the first observation of two-photon pumped polariton condensation, demonstrated by angle-resolved photoluminescence in a GaAs-based microcavity. TPA is evidenced in the…
