Quantum Plasmonics for Low-Photon-Number Nonlinear Optics and Quantum Circuits

University Of Maryland, College Park, College Park MD

Investigators

Abstract

Title: Quantum Plasmonics for Low-Photon-Number Nonlinear Optics and Quantum Circuits Metallic nanostructures can confine light to nanometer length scales in the form of surface-plasmon polaritons, which are electromagnetic waves that propagate at the interface between metallic and dielectric surfaces. Surface plasmons can miniaturize optical devices to the nanoscale, and also generate extremely high electromagnetic intensities that create strong light-matter interactions. These properties open up the possibility for ultra-compact active optical devices such as optical switches, modulators, and wavelength converters, that operate at very high speeds and low energies. To achieve these capabilities, however, requires plasmonic nanostructures with a strong nonlinear optical response. Recent theoretical work has shown that when surface plasmons interact with single quantum emitters the two systems can hybridize to form new coupled modes of light and matter. In this hybridized regime, a single plasmon can produce a nonlinear optical response, paving the way for nonlinear plasmonic circuits operating at the fundamental quantum energy limit. To date, however, this hybridized regime remains elusive because quantum emitters typically suffer from large dephasing due to phonons and spectral wandering. In this program, we will investigate the interaction between metallic nanostructures and indium arsenide quantum dots to study the hybridized regime and develop ultra-fast nonlinear and quantum devices. Indium arsenide quantum dots exhibit a spectrally pure emission making them ideal for achieving hybridization. We will use these high quality quantum emitters to demonstrate hybridization, and explore its nonlinear and quantum optical properties. This program could ultimately pave the way towards nanoscale photonic devices with ultra-low energy dissipation, as well as compact quantum circuits that provide exponential computational speedup and unconditionally secure communication. The program will also support an outreach effort that provides research opportunities for undergraduate and high school students. Technical Description Plasmonic nanostructures can strongly enhance light-matter interactions by confining light to the nanoscale in the form of surface plasmon polaritons (or simply plasmons). Recently, it has been theoretically predicted that when a quantum emitter is placed in the high field region of a plasmonic nanostructure the two systems can hybridize. In this hybridized regime, the emitter and plasmon form new coupled modes that take on both atomic and photonic properties. These hybridized modes exhibit strong optical nonlinearities near the single photon level, making them a highly compelling system for developing opto-electronic and quantum devices with ultra-low power dissipation. Hybridization between single quantum emitters and plasmons has yet to be demonstrated because quantum emitters usually exhibit rapid dipole dephasing due to phonon scattering and spectral wandering. This dephasing destroys the quantum interference that creates the hybridized mode. We propose to overcome this problem using indium arsenide (InAs) quantum dots that exhibit a narrow and nearly transform limited optical emission, making them promising systems for attaining the hybridized regime. A key challenge to coupling these InAs quantum dots to metal nanostructures is that they are embedded in a gallium arsenide matrix and cannot be easily deposited onto plasmonic devices. We will address this challenge through a combination of device design and state-of-the-art nanofabrication techniques. We will characterize the linear and nonlinear properties of fabricated devices. We will then utilize the hybridized regime to demonstrate a nanophotonic optical transistor where a single absorbed control photon can switch many signal photons. We will also utilize the hybridized regime to create an interface between a single trapped spin in a quantum dot and a surface plasmon, which could serve as a fundamental building block for nanoscale quantum circuits. This program could ultimately pave the way towards nanoscale nonlinear photonic devices with ultra-low energy dissipation, and compact quantum circuits that provide exponential computational speedup and unconditionally secure communication.