Simultaneous wavelength translation and amplitude modulation of single photons from a quantum dot

Hybrid quantum information devices that combine disparate physical systems interacting through photons offer the promise of combining low-loss telecommunications wavelength transmission with high fidelity visible wavelength storage and manipulation. The realization of such systems requires control over the waveform of single photons to achieve spectral and temporal matching. Here, we experimentally demonstrate the simultaneous wavelength translation and amplitude modulation of single photons generated by a quantum dot emitting near 1300 nm with an exponentially decaying waveform (lifetime ≈1.5 ns). Quasi-phase-matched sum-frequency generation with a pulsed 1550 nm laser creates single photons at 710 nm with a controlled amplitude modulation at 350 ps time scales.     

Erasing distinguishability using quantum frequency up-conversion

The frequency distinguishability of two single photons was successfully erased using single photon frequency up-conversion. A frequency nondegenerate photon pair generated via spontaneous four-wave mixing in a dispersion shifted fiber was used to emulate two telecom-band single photons that were in the same temporal mode but in different frequency modes. The frequencies of these photons were converted to the same frequency by using the sum-frequency generation process in periodically poled lithium niobate waveguides, while maintaining their temporal indistinguishability. As a result, the two converted photons exhibited a nonclassical dip in a Hong-Ou-Mandel quantum interference experiment. The present scheme will add flexibility to networking quantum information systems that use photons with various wavelengths.     

Shaping the waveform of entangled photons

We demonstrate experimentally tunable control of the joint spectrum, i.e., waveform and degree of frequency correlations, of paired photons generated in spontaneous parametric down-conversion. This control is mediated by the spatial shape of the pump beam in type-I noncollinear configurations.     

Single photon frequency up-conversion and its applications

Optical frequency up-conversion is a technique, based on sum frequency generation in a non-linear optical medium, in which signal light from one frequency (wavelength) is converted to another frequency. By using this technique, near infrared light can be converted to light in the visible or near visible range and therefore detected by commercially available visible detectors with high efficiency and low noise. The National Institute of Standards and Technology (NIST) has adapted the frequency up-conversion technique to develop highly efficient and sensitive single photon detectors and a spectrometer for use at telecommunication wavelengths. The NIST team used these single photon up-conversion detectors and spectrometer in a variety of pioneering research projects including the implementation of a quantum key distribution system; the demonstration of a detector with a temporal resolution beyond the jitter limitation of commercial single photon detectors; the characterization of an entangled photon pair source, including a direct spectrum measurement for photons generated in spontaneous parametric down-conversion; the characterization of single photons from quantum dots including the measurement of carrier lifetime with escalated high accuracy and the demonstration of the converted quantum dot photons preserving their non-classical features; the observation of 2nd, 3rd and 4th order temporal correlations of near infrared single photons from coherent and pseudo-thermal sources following frequency up-conversion; a study on the time-resolving measurement capability of the detectors using a short pulse pump and; evaluating the modulation of a single photon wave packet for better interfacing of independent sources. In this article, we will present an overview of the frequency up-conversion technique, introduce its applications in quantum information systems and discuss its unique features and prospects for the future.     

Transformation of single-photon wave packets in quantum storage with a tunable cavity

Optimal conditions for transformation of the waveform of single photons generated via cavity-enhanced spontaneous parametric down-conversion by means of optical quantum storage, in which an extended resonant medium in a tunable cavity is used as information carrier, are determined.     

Time-resolved single-photon detection by femtosecond upconversion

We demonstrate a time-resolved single-photon detection technique based on ultrafast sum-frequency generation, providing femtosecond measurement capability for single photons in photonic quantum information processing. Noncollinear broadband upconversion in periodically poled MgO-doped stoichiometric lithium tantalate with an ultrafast pump and detection with a Si single-photon counter enable efficient detection of IR photons and temporal resolution of ~150 fs. We utilize the timing resolution to map the generation efficiency profile along the propagation axis of a periodically poled KTiOPO(4) crystal, revealing its local grating quality with millimeter resolution. We also apply the technique to two-photon coincidence measurements and directly demonstrate time anticorrelation between coincident-frequency entangled photons that are parametrically generated under extended phase-matching conditions.     

Distinguishing N Photons in an Entangled State from N Separate Photons

We present a multimode model to describe an arbitrary N-photon state. In general, the N photons can be distinguished through their temporal modes. From this model, we can find the criterion for the N photons in an indistinguishable state of a single temporal mode. We find that simple multi-photon detection scheme cannot distinguish N photons in different temporal modes and only a multi-photon interference experiment can accomplish the goal. We apply the theory to the four-photon case in the process of parametric down-conversion. We will present the results for various four-photon interference schemes and identify a quantity to characterize how well the four photons are indistinguishable.     

Basic features of coherent radiation generated by relativistic charge bunches

Abstract

Radiation generated by relativistic charges can be analyzed and described in exquisite detail. One reason that such detailed analysis is possible is because the phases of radiated photons often are determined completely by the initial conditions of the relativistic charges and the radiating system. The phase relationships between the initial charges and the radiated photons represent coherence in the emitted radiation. A previous paper decribed how this coherence could affect the spatial and spectral distributions of radiation generated by a single charge in a periodic radiator. The present paper discusses a complementary issue; namely, how the temporal shape of a relativistic charge bunch can emphasize specific features of the radiation generated at a single interaction site.     

Narrowband photon pair generation and waveform reshaping

In this article, we review on narrowband photon pairs producedin nonlinear crystals, and especially in atomic ensembles. In atomicensembles, “write-read” process in pulse mode andspontaneous four-wave mixing process (SFWM) in continuous mode aretwo popular photon pair generation schemes. We specifically discussthe experimental works with continuous SFWM scheme in cold atomicensembles. Photon pairs produced in these systems are characteristicof controllable long coherence time, and therefore are accessiblewith direct temporal modulation. We elaborate on the recent techniqueson modulation and waveform reshaping of narrow-band paired photons.     

单光子调制频谱用于量子点荧光寿命动力学的研究

本文开展了基于单光子调制频谱测量量子点荧光寿命动力学特性的研究.在脉冲激光激发下,对探测到的量子点单光子荧光信号进行频谱分析以获得荧光调制频谱,研究发现特征频谱信号幅值与荧光寿命之间存在确定的非线性对应关系.这种单光子调制频谱方法能有效消除背景噪声和单光子探测器暗计数的影响,用于分析量子点荧光寿命动力学特性时在准确度以及时间分辨率方面都较目前普遍采用的荧光衰减曲线寿命拟合方法呈现出明显优势:当涨落误差为5%时,寿命测量准确度提高了一个数量级;当涨落误差和偏离误差均为5%时,对动力学测量效率以及时间分辨率提高了四倍以上.因此单光子调制频谱可以作为获取量子点在短时间尺度内激发态动力学信息的一种有效技术手段.     

Complete deterministic linear optics Bell state analysis

We show how hyperentanglement allows us to deterministically distinguish between all four polarization Bell states of two photons. In this proof-of-principle experiment, we employ the intrinsic time-energy correlation of photon pairs generated with high temporal definition in addition to the polarization entanglement obtained from parametric down-conversion. For the identification, no nonlinear optical elements or auxiliary photons are needed. The new possibilities this complete Bell measurement offers are demonstrated by realizing an optimal dense coding protocol.     

All optical arbitrary waveform generation by optical frequency comb based on cascading intensity modulation

We propose and experimentally demonstrate an all optical arbitrary waveform generation by optical frequency comb (OFC) based on cascading intensity modulation. By selecting spectral lines of interest from OFC through optical filters, 10 GHz, 20 GHz, and 60 GHz sinusoidal signals with low phase noise and more complex waveforms, including ultra-short pulse, half-wave cosine, and single frequency modulated MMW signals, are generated easily.     

Ultrafast optical frequency comb synthesizer and analyzer

We propose an ultrafast optical arbitrary waveform synthesizing/analyzing technique demonstrated with 2 Tbit/s waveforms. An ultrafast waveform was generated by manipulating the amplitude and phase of a 400?GHz optical frequency comb using a newly developed colorless optical synthesizer. The 400?GHz optical frequency comb was generated from a 25?GHz optical frequency comb using a colorless arrayed waveguide grating. This waveform was then analyzed on the frequency axis using a custom heterodyne-detection technique based on the dual-heterodyne mixing method. The phase and amplitude spectra can be observed in parallel using another optical frequency comb as a reference combined with an arrayed waveguide grating. This optical system, named the ultrafast optical frequency comb synthesizer and analyzer, can synthesize and analyze an arbitrary waveform in the THz frequency region.     

The role of the envelope in processing iterated rippled noise.

Iterated rippled noise (IRN) is generated by a cascade of delay and add (the gain after the delay is 1.0) or delay and subtract (the gain is -1.0) operations. The delay and add/subtract operations impart a spectral ripple and a temporal regularity to the noise. The waveform fine structure is different in these two conditions, but the envelope can be extremely similar. Four experiments were used to determine conditions in which the processing of IRN stimuli might be mediated by the waveform fine structure or by the envelope. In experiments 1 and 3 listeners discriminated among three stimuli in a single-interval task: IRN stimuli generated with the delay and add operations (g = 1.0), IRN stimuli generated using the delay and subtract operations (g = -1.0), and a flat-spectrum noise stimulus. In experiment 2 the listeners were presented two IRN stimuli that differed in delay (4 vs 6 ms) and a flat-spectrum noise stimulus that was not an IRN stimulus. In experiments 1 and 2 both the envelope and waveform fine structure contained the spectral ripple and temporal regularity. In experiment 3 only the envelope had this spectral and temporal structure. In all experiments discrimination was determined as a function of high-pass filtering the stimuli, and listeners could discriminate between the two IRN stimuli up to frequency regions as high as 4000-6000 Hz. Listeners could discriminate the IRN stimuli from the flat-spectrum noise stimulus at even higher frequencies (as high as 8000 Hz), but these discriminations did not appear to depend on the pitch of the IRN stimuli. A control experiment (fourth experiment) suggests that IRN discriminations in high-frequency regions are probably not due entirely to low-frequency nonlinear distortion products. The results of the paper imply that pitch processing of IRN stimuli is based on the waveform fine structure.     

A novel multi-optical/quantum memory and encoding system using multi-photon generation

We propose a novel system of an optical/quantum memory generation, which can be used for multi-optical/quantum memory applications. The large bandwidth of a single pulse is generated using a soliton pulse in a Kerr-type nonlinear medium, i.e. a nonlinear waveguide. The generation of the localized temporal and spatial soliton pulses within the nano-waveguide is achieved. The free spectrum range enhancement of the generated multi-soliton signals can be formed and achieved using the nano-waveguide incorporating the Mach Zhender Interferometer (MZI). The different light path of the soliton pulses is introduced by the delayed lines of the interferometer. This improves the wavelength free spectrum range, where the different entangled photon pairs can also obtained. Furthermore, the generated photons can be filtered and stored within a system, where the storage of single or multi-photons using the proposed system can be achieved, which in turn can be used for multi-optical/quantum memory applications.     

A photonic scheme for the generation of dual linear chirp microwave waveform based on the external modulation technique and its airborne application

Due to high frequency and large time bandwidth product; photonic generation and processing of arbitrary microwave waveforms has been an interesting topic in recent time. Here, a relatively new photonic technique has been proposed for the generation of a dual linear chirp microwave waveform in Ku-band. In this method two single drive Mach–Zehnder Modulators are cascaded at minimum transmission point and in push–pull mode. Theoretical analysis and simulation are developed by giving a complete mathematical model. As the result of this methodology, a dual linear chirp microwave waveform in Ku-band with relatively large bandwidth is generated. Comparative analysis is done in the present cascading technique with dual parallel Mach–Zehnder Modulator (DPMZM) technique. Range-Doppler coupling of the radar system has been investigated with the help of an ambiguity function diagram of the generated waveform. Results have analyzed through MATLAB simulation and verified by experimental results.     

Generation of subpicosecond electrical pulses by optical rectification

We describe the generation of subpicosecond electrical pulses by optical rectification of ultrashort optical pulses. The electrical pulses are generated by the second-order nonlinear response of a LiTaO(3) crystal bonded to a coplanar transmission line. A bipolar temporal waveform with a width of 875 fs was measured after a propagation distance of 175mum . This pulse width was limited by the response time of the photoconductive sampler. We observed both broadening and amplitude reduction in the temporal waveform owing to propagation.     

Detectability of dissipative motion in quantum vacuum via superradiance

We propose an experiment for generating and detecting vacuum-induced dissipative motion. A high frequency mechanical resonator driven in resonance is expected to dissipate mechanical energy in quantum vacuum via photon emission. The photons are stored in a high quality electromagnetic cavity and detected through their interaction with ultracold alkali-metal atoms prepared in an inverted population of hyperfine states. Superradiant amplification of the generated photons results in a detectable radio-frequency signal temporally distinguishable from the expected background.     

Source linewidth effects in temporal imaging of Gaussian Schell-model pulses

A transform-limited Gaussian pulse generated from an externally modulated stationary source is launched within a temporal imaging system composed of a second-order dispersion followed by a time lens and a subsequent quadratic dispersion. We consider the effect of the statistical properties of the emitted light for temporal imaging. In particular, it is shown that the design parameters that ensure a received signal with the minimum root-mean-square (rms) width achievable, which is called the temporal image of the incident pulse, are strongly dependent on the coherence properties of the input waveform. Finally, limitations on the temporal resolution of the setup are highlighted and a realistic numerical example is provided.     

Tunable control of the frequency correlations of entangled photons

We experimentally demonstrate a new technique to control the type of frequency correlations of entangled photon pairs generated by spontaneous parametric downconversion. Frequency-correlated and frequency-anticorrelated photons are produced when a broadband pulse is used as a pump. The method is based on the control of the group velocities of the interacting waves and can be applied in any nonlinear medium and frequency band of interest.