Fast quantum computing with semiconductor quantum dots in a microcavity

嵌入光子微腔中的两个量子点内的协同双光子激射

Cooperative two-photon lasing in two Quantum Dots embedded inside Photonic microcavity

本文提出在耦合单模光子晶体腔的两个量子点中实现协同双光子激射，利用极化子变换主方程和量子激光理论分析单光子与双光子过量发射，并指出通过调节泵浦强度可抑制单光子发射。

Fast Two-Qubit Gates in Semiconductor Quantum Dots using a Photonic Microcavity

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…

Optomechanical control of mode conversion in a hybrid semiconductor microcavity containing a quantum dot

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…

Externally mode-matched cavity quantum electrodynamics with charge-tunable quantum dots

We present coherent reflection spectroscopy on a charge and DC Stark tunable quantum dot embedded in a high-quality and externally mode-matched microcavity. The addition of an exciton to a single-electron charged quantum dot forms a trion that interacts with the microcavity just below strong coupling regime of cavity quantum electrodynamics. Such an integrated, monolithic system is a crucial step towards the implementation of scalable hybrid quantum information schemes that are based on an efficient interaction between a single photon and a confined electron spin.

Controllable Normal mode splitting and Switching performance in hybrid optomechanical semiconductor microcavity containing single quantum dot

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…

High-Rate Entanglement Source via Two-Photon Emission from Semiconductor Quantum Wells

We propose a compact high-intensity room-temperature source of entangled photons based on the efficient second-order process of two-photon spontaneous emission from electrically-pumped semiconductor quantum wells in a photonic microcavity. Two-photon emission rate in room-temperature semiconductor devices is determined solely by the carrier density, regardless of the residual one-photon emission. The microcavity selects two-photon emission for a specific signal and idler wavelengths and at a preferred direction without modifying the overall rate. Pair-generation rate in GaAs/AlGaAs quantum wel…

Nonlinear optical response properties of a quantum dot embedded in a semiconductor microcavity : possible applications in quantum communication platforms

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…

Polariton linewidth and the reservoir temperature dynamics in a semiconductor microcavity

A method of determining the temperature of the nonradiative reservoir in a microcavity exciton-polariton system is developed. A general relation for the homogeneous polariton linewidth is theoretically derived and experimentally used in the method. In experiments with a GaAs microcavity under nonresonant pulsed excitation, the reservoir temperature dynamics is extracted from the polariton linewidth. Within the first nanosecond the reservoir temperature greatly exceeds the lattice temperature and determines the dynamics of the major processes in the system. It is shown that, for nonresonant pul…

Entangling photons using a charged quantum dot in a microcavity

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…

半导体微腔中的压缩光

Squeezed light in a semiconductor microcavity

本文通过半导体微腔中的强激子-声子非线性相互作用，实现宽频带内的高频率光学压缩，展示了压缩光在量子信息处理和传感中的应用潜力。

Conditional phase shift from a quantum dot in a pillar microcavity

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…

Acoustic control of the lasing threshold in QDs ensemble coupled to an optical microcavity

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.

Tuning the mode-splitting of a semiconductor microcavity with uniaxial stress

A splitting of the fundamental optical modes in micro/nano-cavities comprising semiconductor heterostructures is commonly observed. Given that this splitting plays an important role for the light-matter interaction and hence quantum technology applications, a method for controlling the mode-splitting is important. In this work we use an open microcavity composed of a "bottom" semiconductor distributed Bragg reflector (DBR) incorporating an n-i-p heterostructure, paired with a "top" curved dielectric DBR. We measure the mode-splitting as a function of wavelength across the stopband. We demonstr…

Spin-based quantum information processing with semiconductor quantum dots and cavity QED

A quantum information processing scheme is proposed with semiconductor quantum dots located in a high-Q single mode QED cavity. The spin degrees of freedom of one excess conduction electron of the quantum dots are employed as qubits. Excitonic states, which can be produced ultrafastly with optical operation, are used as auxiliary states in the realization of quantum gates. We show how properly tailored ultrafast laser pulses and Pauli-blocking effects, can be used to achieve a universal encoded quantum computing.

Nonclassical light from an incoherently pumped quantum dot in a microcavity

Semiconductor microcavities with artificial single-photon emitters have become one of the backbones of semiconductor quantum optics. In many cases however, technical and physical issues limit the study of optical fields to incoherently excited systems. We analyze the model of a two-level system in a single-mode cavity, where the former is incoherently driven. The specific structure of the applied master equation yields a recurrence relation for the steady-state values of correlations of the intracavity field and the emitter. We provide boundary conditions, that permit a systematical, easy to i…

Quantum optical phenomena in semiconductor quantum dots

Quantum optical phenomena are explored in artificial atoms well known as semiconductor quantum dots, in the presence of excitons and biexcitons. The analytical results are obtained using the conventional time-dependent perturbation technique. Numerical estimations are made for arealistic sample of CdS quantum dots in a high-Q cavity. Quantum optical phenomena such as quantum Rabi oscillations, photon statistics and collapse and revival of population inversion in exciton and biexciton states are observed. In the presence of biexcitons the collapse and revival phenomenon becomes faster due to th…

Dynamics of spatial coherence and momentum distribution of polaritons in a semiconductor microcavity under conditions of Bose-Einstein condensation

The dynamics of spatial coherence and momentum distribution of polaritons in the regime of Bose-Einstein condensation are investigated in a GaAs microcavity with embedded quantum wells under nonresonant excitation with picosecond laser pulses. It is shown that the onset of the condensate first order sparial coherence is accompanied by narrowing of the polariton momentum distribution. At the same time, at sufficiently high excitation densities, there is significant qualitative discrepancy between the dynamic behavior of the width of the polariton momentum distribution determined from direct mea…

Suppression of surface-related loss in a gated semiconductor microcavity

We present a surface passivation method that reduces surface-related losses by almost two orders of magnitude in a highly miniaturized GaAs open microcavity. The microcavity consists of a curved dielectric distributed Bragg reflector (DBR) with radius $\sim 10$ $μ$m paired with a GaAs-based heterostructure. The heterostructure consists of a semiconductor DBR followed by an n-i-p diode with a layer of quantum dots in the intrinsic region. Free-carrier absorption in the highly doped n- and p-layers is minimized by positioning them close to a node of the vacuum electromagnetic-field. The surface,…

Exploiting exciton-exciton interactions in semiconductor quantum dots for quantum-information processing

We propose an all-optical implementation of quantum-information processing in semiconductor quantum dots, where electron-hole excitations (excitons) serve as the computational degrees of freedom (qubits). We show that the strong dot confinement leads to an overall enhancement of Coulomb correlations and to a strong renormalization of the excitonic states, which can be exploited for performing conditional and unconditional qubit operations.

Generation of non-classical light using semiconductor quantum dots

Sources of non-classical light are of paramount importance for future applications in quantum science and technology such as quantum communication, quantum computation and simulation, quantum sensing and quantum metrology. In this review we discuss the fundamentals and recent progress in the generation of single photons, entangled photon pairs and photonic cluster states using semiconductor quantum dots. Specific fundamentals which are discussed are a detailed quantum description of light, properties of semiconductor quantum dots and light-matter interactions. This includes a framework for the…

Spin-based quantum gating with semiconductor quantum dots by bichromatic radiation method

A potential scheme is proposed for realizing a two-qubit quantum gate in semiconductor quantum dots. Information is encoded in the spin degrees of freedom of one excess conduction electron of each quantum dot. We propose to use two lasers, radiation two neighboring QDs, and tuned to blue detuning with respect to the resonant frequencies of individual excitons. The two-qubit phase gate can be achieved by means of both Pauli-blocking effect and dipole-dipole coupling between intermediate excitonic states.

在开关光学微腔中由量子点产生超短（约10ps）自发辐射脉冲

Generation of ultrashort (~10ps) spontaneous emission pulses by quantum dots in a switched optical microcavity

本研究通过自由载流子脉冲注入开关 GaAs/AlAs 微柱腔，利用量子点集合体作为内部光源，实现了 6 至 300 皮秒的超短自发辐射脉冲，为超快成像和量子光子学提供了关键资源。

Electric Field effects on quantum correlations in semiconductor quantum dots

We study the effect of external electric bias on the quantum correlations in the array of optically excited coupled semiconductor quantum dots. The correlations are characterized by the quantum discord and concurrence and are observed using excitonic qubits. We employ the lower bound of concurrence for thermal density matrix at different temperatures. The effect of the Förster interaction on correlations will be studied. Our theoretical model detects nonvanishing quantum discord when the electric field is on while concurrence dies, ensuring the existence of nonclassical correlations as measure…

Spatial light modulation based on coherent population oscillation in semiconductor quantum dots

Due to coherent population oscillation (CPO) effect, we theoretically examine the generation and manipulation of Laguerre-Gaussian beams in terms of phase and amplitude modulation respectively in semiconductor quantum dots (SQDs). The results indicate that both phase modulation with low absorption of probe field and amplitude modulation with high efficiency can be achieved. Thus the practical way demonstrates that the SQDs system can function as effective optically addressed spatial light modulator with which the transverse spatial properties of probe fields can be artificially modulated.

Quantum computation in semiconductor quantum dots of electron-spin asymmetric anisotropic exchange

The universal quantum computation is obtained when there exists asymmetric anisotropic exchange between electron spins in coupled semiconductor quantum dots. The asymmetric Heisenberg model can be transformed into the isotropic model through the control of two local unitary rotations for the realization of essential quantum gates. The rotations on each qubit are symmetrical and depend on the strength and orientation of asymmetric exchange. The implementation of the axially symmetric local magnetic fields can assist the construction of quantum logic gates in anisotropic coupled quantum dots. Th…

On the coupling of two quantum dots through a cavity mode

The effective coupling of two distant quantum dots through virtual photon exchange in a semiconductor microcavity is studied. The experimental conditions for strong coupling and its manifestation in the spectra of emission are analyzed.

Quantum statistics of photon from a semiconductor microcavity embedded with a graphene nanoribbon

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…

Effective cavity pumping from weakly coupled quantum dots

We derive the effective cavity pumping and decay rates for the master equation of a quantum dot-microcavity system in presence of $N$ weakly coupled dots. We show that the in-flow of photons is not linked to the out-flow by thermal equilibrium relationships.

Hidden Vacuum Rabi oscillations: Dynamical Quantum Superpositions of On/Off Interaction between a Single Quantum Dot and a Microcavity

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…

Entangling spin and charge degrees of freedom in semiconductor quantum dots

In this theoretical manuscript I propose a scheme for entangling a single electron semiconductor spin qubit with a single electron semiconductor charge qubit in a triangular triple quantum dot configuration. Two out of three quantum dots are used to define a single electron semiconductor charge qubit. Furthermore, the spin qubit is embedded in the Zeeman sub-levels of the third quantum dot. Combining single qubit gates with entangling CNOT gates allows one to construct a SWAP gate, and therefore to use the semiconductor spin qubit as a long-lived memory for the semiconductor charge qubit.

Zeno Quantum Gates in Semiconductor Quantum Dots

We propose a scheme for a two-qubit conditional phase gate by quantum Zeno effect with semiconductor quantum dots. The system consists of two charged dots and one ancillary dot that can perform Rabi oscillations under a resonant laser pulse. The quantum Zeno effect is induced by phonon-assisted exciton relaxation between the ancillary dot and the charged dots, which is equivalent to a continuous measurement. We solve analytically the master equation and simulate the dynamics of the system using a realistic set of parameters. In contrast to standard schemes, larger phonon relaxation rates incre…

Non-adiabatic geometrical quantum gates in semiconductor quantum dots

In this paper we study the implementation of non-adiabatic geometrical quantum gates with in semiconductor quantum dots. Different quantum information enconding/manipulation schemes exploiting excitonic degrees of freedom are discussed. By means of the Aharanov-Anandan geometrical phase one can avoid the limitations of adiabatic schemes relying on adiabatic Berry phase; fast geometrical quantum gates can be in principle implemented

Coherent population transfer in coupled semiconductor quantum dots

We propose a solid-state implementation of stimulated Raman adiabatic passage in two coupled semiconductor quantum dots. Proper combination of two pulsed laser fields allows the coherent carrier transfer between the two nanostructures without suffering significant losses due to environment coupling. By use of a general solution scheme for the carrier states in the double-dot structure, we identify the pertinent dot and laser parameters.

Wavelength-tunable open double-microcavity to enhance two closely spaced optical transitions

Microcavities have long been recognized as indispensable elements in quantum photonic research due to their usefulness for enhanced light extraction and light-matter interaction. A conventional high-Q cavity structure typically allows only a single optical transition to be tuned into resonance with a specific mode. The transition to a more advanced double-cavity structure, however, introduces new and interesting possibilities such as enhancing two spectrally close optical transitions at the same time with two distinct cavity modes. Here, we investigate a cavity structure composed of a monolith…

Optical-fiber based measurement of an ultra-small volume high-Q photonic crystal microcavity

A two-dimensional photonic crystal semiconductor microcavity with a quality factor Q ~ 40,000 and a modal volume Veff ~ 0.9 cubic wavelengths is demonstrated. A micron-scale optical fiber taper is used as a means to probe both the spectral and spatial properties of the cavity modes, allowing not only measurement of modal loss, but also the ability to ascertain the in-plane localization of the cavity modes. This simultaneous demonstration of high-Q and ultra-small Veff in an optical microcavity is of potential interest in quantum optics, nonlinear optics, and optoelectronics. In particular, the…

Optimizing photon indistinguishability in the emission from incoherently-excited semiconductor quantum dots

Most optical quantum devices require deterministic single-photon emitters. Schemes so far demonstrated in the solid state imply an energy relaxation which tends to spoil the coherent nature of the time evolution, and with it the photon indistinguishability. We focus our theoretical investigation on semiconductor quantum dots embedded in microcavities. Simple and general relations are identified between the photon indistinguishability and the collection efficiency. The identification of the key parameters and of their interplay provides clear indications for the device optimization.

Optical RKKY Interaction between Charged Semiconductor Quantum Dots

We show how a spin interaction between electrons localized in neighboring quantum dots can be induced and controlled optically. The coupling is generated via virtual excitation of delocalized excitons and provides an efficient coherent control of the spins. This quantum manipulation can be realized in the adiabatic limit and is robust against decoherence by spontaneous emission. Applications to the realization of quantum gates, scalable quantum computers, and to the control of magnetization in an array of charged dots are proposed.

Quantum state preparation in semiconductor dots by adiabatic rapid passage

Preparation of a specific quantum state is a required step for a variety of proposed practical uses of quantum dynamics. We report an experimental demonstration of optical quantum state preparation in a semiconductor quantum dot with electrical readout, which contrasts with earlier work based on Rabi flopping in that the method is robust with respect to variation in the optical coupling. We use adiabatic rapid passage, which is capable of inverting single dots to a specified upper level. We demonstrate that when the pulse power exceeds a threshold for inversion, the final state is independent …

Giant Stark effect in the emission of single semiconductor quantum dots

We study the quantum-confined Stark effect in single InAs/GaAs quantum dots embedded within a AlGaAs/GaAs/AlGaAs quantum well. By significantly increasing the barrier height we can observe emission from a dot at electric fields of -500 kV/cm, leading to Stark shifts of up to 25 meV. Our results suggest this technique may enable future applications that require self-assembled dots with transitions at the same energy.