Reconciling the eigenmode analysis with the Maxwell-Bloch equations approach to superradiance in the linear regime

The superradiance from a slab of inverted two-level atoms is theoretically analyzed in the linear regime from both the perspective of the expansion in eigenfunctions of the integral equation with the Lienard-Wiechert potential as kernel, and that of linearizing the Maxwell-Bloch equations. We show the equivalence of both approaches. We show that the so-called Reduced Maxwell-Bloch equations do not yield even approximately the correct solution when applied in the obvious way, but that they can be made to give the correct solution by adding a fictitious input field.     

The effects of the N atom collective Lamb shift on single photon superradiance

The problem of single photon collective spontaneous emission, a.k.a. superradiance, from N atoms prepared by a single photon pulse of wave vector k₀ has been the subject of recent interest. It has been shown that a single photon absorbed uniformly by the N atoms will be followed by spontaneous emission in the same direction [M. Scully, E. Fry, C.H.R. Ooi, K. Wodkiewicz, Phys. Rev. Lett. 96 (2006) 010501; M. Scully, Laser Phys. 17 (2007) 635]; and in extensions of this work we have found a new kind of cavity QED in which the atomic cloud acts as a cavity containing the photon [A.A. Svidzinsky, J.T. Chang, M.O. Scully, Phys. Rev. Lett. 100 (2008) 160504]. In most of our studies, we have neglected virtual photon (“Lamb shift”) contributions. However, in a recent interesting paper, Friedberg and Mannassah [R. Friedberg, J.T. Manassah, Phys. Lett. A 372 (2008) 2514] study the effect of virtual photons investigating ways in which such effects can modify the time dependence and angular distributions of collective single photon emission. In the present Letter, we show that such virtual transitions play no essential role in our problem. The conclusions of [M. Scully, E. Fry, C.H.R. Ooi, K. Wodkiewicz, Phys. Rev. Lett. 96 (2006) 010501; M. Scully, Laser Phys. 17 (2007) 635; A.A. Svidzinsky, J.T. Chang, M.O. Scully, Phys. Rev. Lett. 100 (2008) 160504] stand as published. However, the N atom Lamb shift is an interesting problem in its own right and we here extend previous work both analytically and numerically.     

The analysis of the integral gated mode single photon detector

This paper critically analyses and simulates the circuit configuration of the integral gated mode single photon detector which is proposed for eliminating the transient spikes problem of conventional gated mode single photon detector. The relationship between the values of the circuit elements and the effect of transient spikes cancellation has been obtained. With particular emphasis, the bias voltage of the avalanche photodiode and the output signal voltage of the integrator have been calculated. The obtained analysis results indicate that the output signal voltage of the integrator only relates to the total quantity of electricity of the avalanche charges by choosing the correct values of the circuit elements and integral time interval. These results can be used to optimize the performance of single photon detectors and provide guides for the design of single photon detectors.     

First-order photon interference of a single photon from a single quantum dot

Photon interference indicating wave-like nature of a single photon emitted from a single quantum dot is demonstrated. Photon state as a superposition of two orthogonal linear polarization modes is prepared inside a solid-state single photon source, which causes the first-order interference analogous to the Young’s double slit experiment. The lack of which-mode information is essential for observing the single photon interference.     

Evolution of collective N atom states in single photon superradiance: Effect of virtual Lamb shift processes

We present analytical solutions for the evolution of collective states of N atoms. On the one hand is a (timed) Dicke state prepared by the conditional absorption of a single photon and exhibiting superradiant decay. This is in strong contrast to the evolution of a symmetric Dicke state which is trapped for large atomic clouds. We show that virtual processes yield only a small effect on the evolution of the rapidly decaying timed Dicke state. However, they change the long time dynamics from exponential decay into a power-law behavior which can be observed experimentally. For trapped states virtual processes are much more important and provide new decay channels resulting in a slow decay of the otherwise trapped state.     

Single photon emission from a single molecule

Photon emission from a single molecule at room temperature exhibits nonclassical features. Continuous wave fluorescence excitation provides antibunching in the emitted photons sequence as a signature of the property to only emit one photon at a time. A short pulsed excitation can then produce single photons on demand, with an overall quantum efficiency up to 4.5% in our experimental setup. Direct measurement of the Mandel parameter Q(T) for an observation period of duration T follows a subpoissonian statistics on short time scale and superpoissonian statistics on longer time scale. The latter is attributed to blinking in the fluorescence due to the occurence of a metastable molecular triplet state. To cite this article: F. Treussart et al., C. R. Physique 3 (2002) 501–508.     

The photon statistics of multiphoton lasers with single photon losses

We investigate the photon statistics of a single-modem-photon laser in a generalized Scully-Lamb laser model. The solution for the stationary state is obtained by recursion although detailed balance is not available form2. The threshold condition is gained from a discussion of the photon distribution in the stationary state. At threshold we find no amplitude stabilization and somewhat above it there is bistability form2 giving rise to enhanced fluctuations. Increasing the pumping the bistability more and more disappears and the photon statistics become similar to the ones of a usual laser.     

The counter-rotating terms in the superradiance

Summary It is pointed out that the counter-rotating terms play an important role in the superradiance of the first kind, in which the atomic system is initially in an uncorrelated state with maximal dipole moment. If the counter-rotating terms are added to the master equation for the Dicke model derived by Agarwal and Bonifacioet al., the numerical solutions for the atomic-population inversion and radiation rate show strong damped oscillations (damped recurrence effects) in their time behaviour. A new limiting relation for the cut-off frequency, which depends on the number of atoms, is also obtained for the treated model.

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Riassunto Si evidenzia che i termini controrotanti svolgono un importante ruolo nella superradianza del primo tipo, in cui il sistema atomico è inizialmente in uno stato incorrelato con impulso dipolare massimo. Se i termini controrotanti sono aggiunti all’equazione principale per il modello di Dicke derivato da Agarwal e Bonifacioet al., le soluzioni numeriche per l’inversione di popolazione atomica e il valore di radiazione mostrano forti oscillazioni smorzate (effetti di ricorrenza smorzati) nel loro comportamento nel tempo. Si ottiene anche una nuova relazione per la frequenza di taglio per il modello trattato che dipende dal numero di atomi.

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Резюме Отмечается, что члены с противоположным вращением играют важную роль в суперсветимости первого рода, где атомная система первоначально находится в некоррелированном состоянии с максимальным дипольным моментом. Если члены с противоположным вращением добавляются в ?управляющие? уравнение для модели Дикка, которое было получено Агарвалом, Ъонифачио и др., то численные решения для инверсии атомной заселенности и интенсивности излучения обнаруживают сильные затухающиее осцилляции (затухаюцие рекуррентные эффекты), в их временном поведении. Для рассматриваемой модели получено новое предельное соотношение для частоты обрезания, которая зависит от числа атомов.

     

单光子计数器的校验方法研究

单光子计数器的校验标定分为两个步骤:验证仪器的计数与其接受的光能量之间的线性关系,即采用光照度平方反比定律、发光二极管发光强度与其电流的关系逐一进行校验,其中后一种方法能更方便也能更准确地进行测量;标定单光子计数器。使用恒流源控制发光二极管电流来制成弱光标准光源,利用大动态范围的光子计数器,结合弱光辐照计标定光子计数器。实验结果表明,由于光子计数器的核心器件光电倍增管及其高压电源不很稳定,光子计数器需要经常校验和标定。使用发光二极管制成标准光源来进行校验和标定光子计数器是一种较好的解决方法。     

The strange eigenmode in Lagrangian coordinates

For a distribution advected by a simple chaotic map with diffusion, the "strange eigenmode" is investigated from the Lagrangian (material) viewpoint and compared to its Eulerian (spatial) counterpart. The eigenmode embodies the balance between diffusion and exponential stretching by a chaotic flow. It is not strictly an eigenmode in Lagrangian coordinates, because its spectrum is rescaled exponentially rapidly.     

Complete eigenmode analysis of a ladder-type multiple-gap resonant cavity

A theoretical model is developed for calculating the eigenmodes of the multi-gap resonant cavity. The structure of concern is a kind of ladder-type circuit, offering the advantages of easy fabrication, high characteristic impedance(R/Q),and thermal capacity in the millimeter wave to THz regime. The eigenfunction expansion method is used to establish the field expressions for the gaps and the coupling region. Then, the match conditions at the interface are employed, which leads to a group of complicate boundary equations in the form of an infinite series. To facilitate the mathematical treatments and perform a highly efficient calculation, these boundary equations are transformed into the algebraic forms through the matrix representations. Finally, the concise dispersion equation is obtained. The roots of the dispersion equation include both the axial modes in the gaps, which include the fundamental and the high-order modes, and the cavity modes in the coupling region. Extensive numerical results are presented and the behaviors of the multi-gap resonant cavity are examined.     

基于偏振纠缠光子对的单光子源

提出了一种基于参量下转换纠缠光子对获得单光子源的实验方案,并对实验的光路、数据采集方面做了详细介绍.实验结果显示,由此方案获得的单光子源的品质要优于弱相干光式的单光子源两个数量级,即多光子光脉冲出现的概率降低了100倍.实验结果表明此方案有望得到实际应用. 关键词： 单光子源 参量下转换 反符合测量     

Statistical analysis of the temporal single-photon response of superconducting nanowire single photon detection

A new method to study the transient detection efficiency(DE) and pulse amplitude of superconducting nanowire single photon detectors(SNSPD) during the current recovery process is proposed — statistically analyzing the single photon response under photon illumination with a high repetition rate.The transient DE results match well with the DEs deduced from the static current dependence of DE combined with the waveform of a single-photon detection event.This proves that static measurement results can be used to analyze the transient current recovery process after a detection event.The results are relevant for understanding the current recovery process of SNSPDs after a detection event and for determining the counting rate of SNSPDs.     

Nanoscale solid-state single photon router

A novel scheme for a solid-state single-photon router based on a single quantum dot (QD) coupled to a nanomechanical resonator (NR) is proposed and analyzed theoretically. It relies on the coherent coupling between the quantum dot and the NR. We demonstrate that when a single-photon signal is tuned on resonance with the exciton in the QD, one can use a strong pump field to choose to what output port of this signal field is delivered, which is based on the analogue of electromagnetically induced transparency (EIT) effect which we refer it as phonon induced transparency (PIT) in this coupled system. The path between the reflection output port and the transmission output port can be achieved by simply turning off and on the pump field. The numerical results also indicate that this router can operate efficiently in the optical regime and at ultralow pump power as well as short switching time (～ns). This nanoscale router presented here will offer potential applications in scalable solid-state quantum networks and quantum information.     

Decoding the dynamics of a single trapped atom from photon correlations

Received: 4 September 1998     

Time correlated single photon mie scattering from a sonoluminescing bubble

Application of time correlated single photon counting to pulsed Mie scattering enables one to resolve changes in light scattering to better than 50 ps. This technique is applied to the highly nonlinear motion of a sonoluminescing bubble. Physical processes, such as outgoing shock wave emission, that limit the interpretation of the data are measured with a streak camera and microscopy. Shock speeds about 6 km/s have been observed.     

Creating single time-bin-entangled photon pairs

When a single emitter is excited by two phase-coherent pulses with a time delay, each of the pulses can lead to the emission of a photon pair, thus creating a "time-bin-entangled" state. Double pair emission can be avoided by initially preparing the emitter in a metastable state. We show how photons from separate emissions can be made indistinguishable, permitting their use for multiphoton interference. Possible realizations are discussed. The method might also allow the direct creation of n-photon entangled states (n > 2).     

Direct measurement of the photon statistics of a triggered single photon source

We studied intensity fluctuations of a single photon source relying on the pulsed excitation of the fluorescence of a single molecule at room temperature. We directly measured the Mandel parameter Q(T) over 4 orders of magnitude of observation time scale T by recording every photocount. On time scale of a few excitation periods, sub-Poissonian statistics is clearly observed and the probablility of two-photons events is 10 times smaller than Poissonian pulses. On longer times, blinking in the fluorescence, due to the molecular triplet state, produces an excess of noise.