Analysis of a Quantum Nondemolition Measurement Scheme Based on Kerr Nonlinearity in Photonic Crystal Waveguides

We discuss the feasibility of a quantum nondemolition measurement (QND) of photon number based on cross phase modulation due to the Kerr effect in Photonic Crystal Waveguides (PCWs). In particular, we derive the equations for two modes propagating in PCWs and their coupling by a third order nonlinearity. The reduced group velocity and small cross-sectional area of the PCW lead to an enhancement of the interaction relative to bulk materials. We show that in principle, such experiments may be feasible with current photonic technologies, although they are limited by material properties. Our analysis of the propagation equations is sufficiently general to be applicable to the study of soliton formation, all-optical switching and can be extended to processes involving other orders of the nonlinearity

Coupling of PbS Quantum Dots to Photonic Crystal Cavities at Room Temperature

We demonstrate the coupling of PbS quantum dot emission to photonic crystal cavities at room temperature. The cavities are defined in 33% Al, AlGaAs membranes on top of oxidized AlAs. Quantum dots were dissolved in Poly-methyl-methacrylate (PMMA) and spun on top of the cavities. Quantum dot emission is shown to map out the structure resonances, and may prove to be viable sources for room temperature cavity coupled single photon generation for quantum information processing applications. These results also indicate that such commercially available quantum dots can be used for passive structure characterization. The deposition technique is versatile and allows layers with different dot densities and emission wavelengths to be re-deposited on the same chip.Comment: 9 pages, 3 figure

Coherent probing and saturation of a strongly coupled quantum dot

We coherently probe a quantum dot, strongly coupled to a photonic crystal nano-cavity, using a resonant laser beam. At higher pump power, the coupled systempsilas response becomes highly nonlinear. This coherent probing method has applications for classical and quantum information processing

Single photon nonlinear optics in photonic crystals

We coherently probe a quantum dot that is strongly coupled to a photonic crystal nano-cavity by scattering of a resonant laser beam. The coupled system's response is highly nonlinear as the quantum dot saturates with nearly one photon per cavity lifetime. This system enables large amplitude and phase shifts of a signal beam via a control beam, both at single photon levels. We demonstrate photon-photon interactions with short pulses in a system that is promising for ultra-low power switches and two-qubit quantum gates

Photon blockade in a photonic crystal cavity with a strongly coupled quantum dot

The strong coupling regime between a single emitter and the mode of an optical resonator allows for nonlinear optics phenomena at extremely low light intensities. Down to the single photon level, extreme nonlinearities can be observed, where the presence of a single photon inside the resonator either blocks or enhances the probability of subsequent photons entering the resonator. In this paper we experimentally show the existence of these phenomena, named photon blockade and photon induced tunneling, in a solid state system composed of a photonic crystal cavity with a strongly coupled quantum dot

Photonic crystal chips for optical communications and quantum information processing

We discuss recent our recent progress on functional photonic crystals devices and circuits for classical and quantum information processing. For classical applications, we have demonstrated a room-temperature-operated, low threshold, nanocavity laser with pulse width in the picosecond regime; and an all-optical switch controlled with 60 fJ pulses that shows switching time on the order of tens of picoseconds. For quantum information processing, we discuss the promise of quantum networks on multifunctional photonic crystals chips. We also discuss a new coherent probing technique of quantum dots coupled to photonic crystal nanocavities and demonstrate amplitude and phase nonlinearities realized with control beams at the single photon level

Efficient Photonic Crystal Cavity-Waveguide Couplers

Coupling of photonic crystal (PC) linear three-hole defect cavities (L3) to PC waveguides is theoretically and experimentally investigated. The systems are designed to increase the overlap between the evanescent cavity field and the waveguide mode, and to operate in the linear dispersion region of the waveguide. Our simulations indicate increased coupling when the cavity is tilted by 60 degrees with respect to the waveguide axis, which we have also confirmed by experiments. We obtained up to 90% coupling efficiency into the waveguide

Quantum dot-photonic crystal chips for quantum information processing

We have recently developed a technique for local, reversible tuning of individual quantum dots on a photonic crystal chip by up to 1.8nm, which overcomes the problem of large quantum dot inhomogeneous broadening - usually considered the main obstacle in employing such platform in practical quantum information processing systems. We have then used this technique to tune single quantum dots into strong coupling with a photonic crystal cavity, and observed strong coupling both in photoluminescence and in resonant light scattering from the system, as needed for several proposals for scalable quantum information networks and quantum computation

Photonic Crystal Microcavities for Classical and Quantum Information Processing

Photonic crystal (PC) cavities enable localization of light into volumes (V) below a cubic optical wavelength (smaller than any other types of optical resonators) with high quality (Q) factors. This permits a strong interaction of light and matter, which is relevant for construction of classical light sources with improved properties (e.g., low threshold lasers) and of nonclassical light sources (such as single and entangled photon sources), which are crucial pieces of hardware of quantum information processing systems. This talk will cover some of our recent experimental results on quantum and classical devices enabled by such interaction, as well as our work on designing such devices and circuits efficiently. We have demonstrated a spontaneous emission rate enhancement by a factor of 8 and suppression by a factor of 5 for a single self-assembled InAs/GaAs quantum dot (QD) embedded in a GaAs photonic crystal cavity and on- and off-resonance with the cavity mode, respectively. A strong localization of optical field in such a nanocavity (experimental Q-factor of 5000 and mode volume below a cubic optical wavelength) with a quantum dot embedded inside is of importance for building single photon sources with improved efficiency, photon indistinguishability, and repetition rate. We have demonstrated a single photon source on demand based on the pulsed excitation of a single quantum dot in such a nanocavity, with pulse duration between 200 ps and 8 ns and with a small multi-photon probability (as small as 5% compared to an attenuated laser of the same intensity). In addition, we have shown that colloidal PbS quantum dots coupled to AlGaAs photonic crystal cavities can be used as an alternative to self-assembled InAs/GaAs quantum dots for construction of cheap and reusable quantum and classical light emitters. We have also demonstrated an improved classical light source-laser, based on coupling of a large number (81) of photonic crystal nanocavities inside a two dimension- - al array. Such a laser exhibits a low lasing threshold (~2.5 mW), operates in a single mode, produces large output powers (greater than 12 muW, which two orders of magnitude larger than a single nanocavity laser), and can be directly modulated as speeds greater than 100 GHz. An inverse problem approach to designing photonic crystal cavities that we have developed enables their rapid optimization in a single step, thereby reducing the cavity optimization time from weeks to hours. We are also pursuing theoretical and experimental work on integration of a number of photonic crystal components (cavities and waveguides) into functional circuits for classical and quantum information processing, including nontrivial two-qubit quantum gates