Erik D. Kim

Integrated quantum optical networks based on quantum dots and photonic crystals

Single solid-state optical emitters have quantum mechanical properties that make them suitable for applications in information processing and sensing. Most of these quantum technologies rely on the capability to integrate the emitters in reliable solid-state optical networks. In this paper, we present integrated devices based on GaAs photonic crystals and InAs self-assembled quantum dots. These quantum networks are well suited to future optoelectronic devices operating at ultralow power levels, single-photon logic devices and quantum information processing.

Fast Spin Rotations by Optically Controlled Geometric Phases in a Charge-Tunable InAs Quantum Dot

We demonstrate optical control of the geometric phase acquired by one of the spin states of an electron confined in a charge-tunable InAs quantum dot via cyclic 2pi excitations of an optical transition in the dot. In the presence of a constant in-plane magnetic field, these optically induced geometric phases result in the effective rotation of the spin about the magnetic field axis and manifest as phase shifts in the spin quantum beat signal generated by two time-delayed circularly polarized optical pulses. The geometric phases generated in this manner more generally perform the role of a spin phase gate, proving potentially useful for quantum information applications.

Phonon mediated off-resonant quantum dot-cavity coupling under resonant excitation of the quantum dot

We propose a model for phonon-mediated off-resonant quantum dot‐cavity coupling and use it to successfully explain recently observed resonant quantum dot spectroscopic results. We explicitly incorporate the effect of phonons, which explains the role of temperature in the coupling mechanism and predicts an asymmetry in the coupling depending on whether the quantum dot is red or blue detuned with respect to the cavity. We show that the off-resonant coupling is enhanced by the cavity; in the absence of such enhancement, the coupling strength is greatly diminished at higher dot-cavity detunings. These results demonstrate that phonon-mediated processes effectively extend the detuning range in which off-resonant QD-cavity coupling may occur beyond that given by pure dephasing processes.

Linewidth broadening of a quantum dot coupled to an off-resonant cavity

We study the coupling between a photonic crystal cavity and an off-resonant quantum dot under resonant excitation of the cavity or the quantum dot. Linewidths of the quantum dot and the cavity as a function of the excitation laser power are measured. We show that the linewidth of the quantum dot, measured by observing the cavity emission, is significantly broadened compared to the theoretical estimate. This indicates additional incoherent coupling between the quantum dot and the cavity.

Single Charged Quantum Dot in a Strong Optical Field : Absorption, Gain, and the ac-Stark Effect

We investigate a singly charged quantum dot under a strong optical driving field by probing the system with a weak optical field. We observe all critical features predicted by Mollow for a strongly driven two-level atomic system in this solid state nanostructure, such as absorption, the ac-Stark effect, and optical gain. Our results demonstrate that even at high optical field strengths the electron in a single quantum dot with its dressed ground state and trion state behaves as a well-isolated two-level quantum system.

Proposed Coupling of an Electron Spin in a Semiconductor Quantum Dot to a Nanosize Optical Cavity

We propose a scheme to efficiently couple a single quantum dot electron spin to an optical nano-cavity, which enables us to simultaneously benefit from a cavity as an efficient photonic interface, as well as to perform high fidelity (nearly 100%) spin initialization and manipulation achievable in bulk semiconductors. Moreover, the presence of the cavity speeds up the spin initialization process beyond the GHz range.

Phonon-mediated coupling between quantum dots through an off-resonant microcavity

We present experimental results showing phonon-mediated coupling between two quantum dots embedded inside a photonic crystal microcavity. With only one of the dots being spectrally close to the cavity, we observe both frequency up-conversion and down-conversion of the pump light via a

Probing of single quantum dot dressed states via an off-resonant cavity

\sim1.2

Effect of photogenerated carriers on the spectral diffusion of a quantum dot coupled to a photonic crystal cavity

THz phonon. We demonstrate this process for both weak and strong regimes of dot-cavity coupling, and provide a simple theoretical model explaining our observations.

Picosecond optical spectroscopy of a single negatively charged self-assembled InAs quantum dot

Coherent interaction between a quantum dot and a resonant laser is observed through an incoherent read-out channel created by coupling to an off-resonant cavity. Under bichromatic driving of the quantum dot optical output collected from the off-resonant cavity exhibits two peaks, a signature of Rabi-side bands that matches closely with our theoretical model. The off-resonant cavity provides a convenient method for resonant quantum dot spectroscopy and quantum dot state readout.