共查询到20条相似文献,搜索用时 46 毫秒
1.
Strauf S Hennessy K Rakher MT Choi YS Badolato A Andreani LC Hu EL Petroff PM Bouwmeester D 《Physical review letters》2006,96(12):127404
We demonstrate that very few (2-4) quantum dots as a gain medium are sufficient to realize a photonic-crystal laser based on a high-quality nanocavity. Photon correlation measurements show a transition from a thermal to a coherent light state proving that lasing action occurs at ultralow thresholds. Observation of lasing is unexpected since the cavity mode is in general not resonant with the discrete quantum dot states and emission at those frequencies is suppressed. In this situation, the quasicontinuous quantum dot states become crucial since they provide an energy-transfer channel into the lasing mode, effectively leading to a self-tuned resonance for the gain medium. 相似文献
2.
《Physica E: Low-dimensional Systems and Nanostructures》2011,43(10):2489-2492
We demonstrate a photonic crystal nanocavity laser essentially driven by a self-assembled InAs/GaAs single quantum dot gain and its unique photon statistics. Gain tuning measurements and photon correlation measurements indicated that a single quantum dot plays a substantial role in the laser oscillation. Photon correlation measurements showed a distinct transition from anti-bunching to Poissonian via photon bunching around the threshold with the increase of the excitation power. Numerical simulations, including contributions of other light sources besides a single quantum dot, indicated that the photon bunching feature around the threshold can be enhanced by the interfusion of incoherent photons into the cavity mode. 相似文献
3.
Using a system of three distant cavities, we propose a method for constructing tripartite entangled coherent GHZ and W states which are robust due to the photon losses in the cavities. Each of cavities is doped with a semiconductor quantum dot. By the dynamics, the excitonic modes of quantum dots are enabled to exhibit entangled coherent GHZ and W states. Apart from the exciton losses, the master equation approach shows that when the populations of the field modes in the cavities are negligible the destruction of entanglement due to dissipation arises from photon losses, is effectively suppressed. 相似文献
4.
Gustavsson S Studer M Leturcq R Ihn T Ensslin K Driscoll DC Gossard AC 《Physical review letters》2007,99(20):206804
We use a double quantum dot as a frequency-tunable on-chip microwave detector to investigate the radiation from electron shot-noise in a near-by quantum point contact. The device is realized by monitoring the inelastic tunneling of electrons between the quantum dots due to photon absorption. The frequency of the absorbed radiation is set by the energy separation between the dots, which is easily tuned with gate voltages. Using time-resolved charge-detection techniques, we can directly relate the detection of a tunneling electron to the absorption of a single photon. 相似文献
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《Photonics and Nanostructures》2009,7(1):56-62
Quantum dots in photonic crystals are interesting both as a testbed for fundamental cavity quantum electrodynamics (QED) experiments and as a platform for quantum and classical information processing. We describe a technique to coherently access the QD-cavity system by resonant light scattering. Among other things, the coherent access enables a giant optical nonlinearity associated with the saturation of a single quantum dot strongly coupled to a photonic crystal cavity. We explore this nonlinearity to implement controlled phase and amplitude modulation between two modes of light at the single photon level—a nonlinearity observed so far only in atomic physics systems. We also measured the photon statistics of the reflected beam at various detunings with the QD/cavity system. These measurements reveal effects such as photon blockade and photon-induced tunneling, for the first time in solid state. These demonstrations lie at the core of a number of proposals for quantum information processing, and could also be employed to build novel devices, such as optical switches controlled at the single photon level. 相似文献
7.
Wu H George RE Wesenberg JH Mølmer K Schuster DI Schoelkopf RJ Itoh KM Ardavan A Morton JJ Briggs GA 《Physical review letters》2010,105(14):140503
Strong coupling between a microwave photon and electron spins, which could enable a long-lived quantum memory element for superconducting qubits, is possible using a large ensemble of spins. This represents an inefficient use of resources unless multiple photons, or qubits, can be orthogonally stored and retrieved. Here we employ holographic techniques to realize a coherent memory using a pulsed magnetic field gradient and demonstrate the storage and retrieval of up to 100 weak 10?GHz coherent excitations in collective states of an electron spin ensemble. We further show that such collective excitations in the electron spin can then be stored in nuclear spin states, which offer coherence times in excess of seconds. 相似文献
8.
The shot noise of a parallel double quantum dot (DQD) system under the perturbation of microwave fields is investigated in the weak Kondo regime. Peak-valley structures exhibit in the differential conductance and shot noise, and side resonant peaks emerge around the Kondo peak due to the absorption and emission of photons. The shot noise is sensitively dependent on the adjusting approach through changing the gate voltages. Large resonant Fano factor accompanying photon-induced side peaks appear by simultaneously varying the two gate voltages. The photon suppression and enhancement of shot noise have been evaluated corresponding to the coherent and incoherent current correlation. The destructive interference causes the suppression of shot noise by changing the Aharonov–Bohm phase. 相似文献
9.
Vinck-Posada H Rodriguez BA Guimaraes PS Cabo A Gonzalez A 《Physical review letters》2007,98(16):167405
We show that the combined effect of photon emission and Coulomb interactions may drive an exciton-polariton system towards a dynamical coherent state, even without phonon thermalization or any other relaxation mechanism. Exact diagonalization results for a finite system (a multilevel quantum dot interacting with the lowest-energy photon mode of a microcavity) are presented in support of this statement. 相似文献
10.
We describe a mechanism for the production of polarization-entangled microwaves using intraband transitions in a pair of quantum dots. This proposal relies neither on spin-orbit coupling nor on control over electron-electron interactions. The quantum correlation of microwave polarizations is obtained from orbital degrees of freedom in an external magnetic field. We calculate the concurrence of emitted microwave photon pairs and show that a maximally entangled Bell pair is obtained in the limit of weak interdot coupling. 相似文献
11.
H.-K. Zhao J. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(3):513-524
The time-dependent transport through an ultrasmall quantum dot coupling to two electron reservoirs is investigated. The quantum
dot is perturbed by a quantum microwave field (QMF) through gate. The tunneling current formulae are obtained by taking expectation
values over coherent state (CS), and SU(1,1) CS. We derive the transport formulae at low temperature by employing the nonequilibrium
Green function technique. The currents exhibit coherent behaviors which are strongly associated with the applied QMF. The
time-dependent currents appear compound effects of resonant tunneling and time-oscillating evolution. The time-averaged current
and differential conductance are calculated, which manifest photon-assisted behaviors. Numerical calculations reveal the similar
properties as those in classical microwave field (CMF) perturbed system for the situations concerning CS and squeezed vacuum
SU(1,1) CS. But for other squeezed SU(1,1) CS, the tunneling behavior is quite different from the system perturbed by a single
CMF through gate. Due to the quantum signal perturbation, the measurable quantities fluctuate fiercely.
Received 28 May 1998 相似文献
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The detection of microwave states is complicated by strong thermal noise, which is inevitably introduced by linear amplifiers. We show how to extract from measured data normally or anti-normally ordered moments of photon creation and annihilation operators, the set of which contains complete information on the quantum state of an electromagnetic field. Equations for the evolution of the quantum state are derived in terms of moments. Using this approach, we consider in detail issues of decoherence and thermalization of microwave quantum states. Results are illustrated using the examples of Fock, coherent, squeezed, thermal, and even and odd coherent states (Schrödinger cat states). 相似文献
14.
We demonstrate single qubit density matrix tomography in a single semiconductor quantum dot system through consecutive phase sensitive rotations of the qubit via ultrafast coherent optical excitations. The result is important for quantifying gate operations in quantum information processing in the quantum dot systems as well as demonstrating consecutive arbitrary qubit rotations. 相似文献
15.
Yuan Zhou Dong-Yan Lü Guang-Hui Wang Yan-Hua Fu Ming-Yao He Hong-Tao Ren 《理论物理通讯》2021,73(6):65101
It remains a great challenge to realize direct manipulation of a nitrogen-vacancy(NV) spin at the single-quantum level with a microwave(MW) cavity. As an alternative, a hybrid system with the spin–phonon–photon triple interactions mediated by a squeezed cantilever-type harmonic resonator is proposed. According to the general mechanical parametric amplification of this in-between phonon mode, the direct spin–phonon and photon–phonon couplings are both exponentially enhanced, which can even further improve the coherent manipulation of a single NV spin and MW photon with a higher efficiency. In view of this triple system with enhanced couplings and the additional sideband adjustable designs, this scheme may provide a more efficient phonon-mediated platform to bridge or manipulate the MW quantum and a single electron spin coherently. It is also hoped to evoke wider applications in the areas of quantum state transfer and preparation,ultrasensitive detection and quantum nondestructive measurement, etc. 相似文献
16.
Nonlinear susceptibility of a quantum dot (QD) embedded in a two-sided cavity, is studied theoretically from a weak-coupling to a strong-coupling regime. In the relevance of a quantum logic gate, the corresponding nonlinear phase shifts (Kerr effect) are estimated for coherent wavepackets including one photon on average. In the weak-coupling regime, the phase shift enhances strongly as a function of a coupling constant between the cavity photon and QD, and eventually saturates in the strong-coupling regime. We also show transmission spectra to evaluate the efficiency of the phase shift. Although the efficiency decreases monotonically in the weak-coupling regime, it rises in the strong-coupling regime. 相似文献
17.
M. Pelton C. Santori G.S. Solomon O. Benson Y. Yamamoto 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(2):179-190
Current quantum cryptography systems are limited by the attenuated coherent pulses they use as light sources: a security loophole
is opened up by the possibility of multiple-photon pulses. By replacing the source with a single-photon emitter, transmission
rates of secure information can be improved. We have investigated the use of single self-assembled InAs/GaAs quantum dots
as such single-photon sources, and have seen a tenfold reduction in the multi-photon probability as compared to Poissonian
pulses. An extension of our experiment should also allow for the generation of triggered, polarization-entangled photon pairs.
The utility of these light sources is currently limited by the low efficiency with which photons are collected. However, by
fabricating an optical microcavity containing a single quantum dot, the spontaneous emission rate into a single mode can be
enhanced. Using this method, we have seen 78% coupling of single-dot radiation into a single cavity resonance. The enhanced
spontaneous decay should also allow for higher photon pulse rates, up to about 3 GHz.
Received 8 July 2001 and Received in final form 25 August 2001 相似文献
18.
Stievater TH Li X Steel DG Gammon D Katzer DS Park D Piermarocchi C Sham LJ 《Physical review letters》2001,87(13):133603
Transient nonlinear optical spectroscopy, performed on excitons confined to single GaAs quantum dots, shows oscillations that are analogous to Rabi oscillations in two-level atomic systems. This demonstration corresponds to a one-qubit rotation in a single quantum dot which is important for proposals using quantum dot excitons for quantum computing. The dipole moment inferred from the data is consistent with that directly obtained from linear absorption studies. The measurement extends the artificial atom model of quantum dot excitonic transitions into the strong-field limit, and makes possible full coherent optical control of the quantum state of single excitons using optical pi pulses. 相似文献
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Xiaodong Xu Bo Sun P.R. Berman Duncan G. Steel Daniel Gammon L.J. Sham 《Solid State Communications》2009,149(35-36):1479-1484
We review the investigation of a single quantum dot driven by a strong optical field. By coherent pump-probe spectroscopy, we demonstrate the Autler–Townes splitting and Mollow absorption spectrum in a single neutral quantum dot. Furthermore, we also show the typical Mollow absorption spectrum by driving a singly charged quantum dot in a strong optical coupling regime. Our results show all the typical features of an isolated atomic system driven by a strong optical field, such as the AC stark effect, Rabi side bands and optical gain effect, which indicate that both neutral and charged quantum dots maintain the discrete energy level states even at high optical field strengths. 相似文献