{ "cells": [ { "cell_type": "markdown", "metadata": {}, "source": [ "## Steady-state superradiance, lasing and cooperative resonance fluorescence\n", "\n", "Notebook author: Nathan Shammah (nathan.shammah at gmail.com)\n", "\n", "\n", "We consider a system of $N$ two-level systems (TLSs) with identical frequency $\\omega_{0}$, incoherently pumped at a rate $\\gamma_\\text{P}$ and de-excitating at a collective emission rate $\\gamma_\\text{CE}$,\n", "\n", "\\begin{eqnarray}\n", "\\dot{\\rho} &=&-i\\lbrack \\omega_{0}J_z,\\rho \\rbrack\n", "+\\frac{\\gamma_\\text {CE}}{2}\\mathcal{L}_{J_{-}}[\\rho]\n", "+\\frac{\\gamma_\\text{P}}{2}\\sum_{n=1}^{N}\\mathcal{L}_{J_{+,n}}[\\rho]\n", "\\end{eqnarray}\n", "This system can sustain superradiant light emission and line narrowing [1-3], whose peak intensity scales proportionally to $N^2$.\n", "\n", "It is then natural to ask the question of whether the system sustains a superradiant light emission steady state also when local losses are included, just like for the transient superfluorescent light emission [4]. We thus study also\n", "\\begin{eqnarray}\n", "\\dot{\\rho} &=&-i\\lbrack \\omega_{0}J_z,\\rho \\rbrack\n", "+\\frac{\\gamma_\\text {CE}}{2}\\mathcal{L}_{J_{-}}[\\rho]\n", "+\\sum_{n=1}^{N}\\left(\\frac{\\gamma_\\text{P}}{2}\\mathcal{L}_{J_{+,n}}[\\rho]+\n", "\\frac{\\gamma_\\text{E}}{2}\\mathcal{L}_{J_{-,n}}[\\rho]\\right)\n", "\\end{eqnarray}\n", "and apply the detailed balance condition to the local emission and pumping rates. This study has relevance to the application of superradiance in light-harvesting devices. \n", "\n", "We will also assess the possibility of coherently driving the system $\\propto J_x$ in the Hamiltonian, which leads to cooperative resonance fluorescence. \n", "\n", "See Refs. [1-12] for more information. Simulations performed with QuTiP [13] and PIQS [8], imported as $\\texttt{qutip.piqs}$. " ] }, { "cell_type": "code", "execution_count": 1, "metadata": {}, "outputs": [], "source": [ "import matplotlib.pyplot as plt\n", "from qutip import *\n", "from qutip.piqs import *\n", "import numpy as np\n", "from scipy import constants" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## 1) Time evolution\n", "\n", "We study the system of Eq. (1) by using the $\\texttt{qutip.piqs}$ module to build the Liouvillian of the system. Using QuTiP's $\\texttt{mesolve}()$ we can calculate operators expectation values in time as well as higher order correlation functions. " ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "### System properties\n", "We initialize an object of the $\\texttt{Dicke}$ class using $\\texttt{qutip.piqs}$. The attributes of this object are used to define the rates of the Liouvillian superoperator. The Hamiltonian is constructed using the $\\texttt{jspin}$ functions in the Dicke basis. The collective and local dissipation rates are defined according to a list of keywords:\n", "\n", "
Keyword | \n", "Rate $\\gamma_j$ | \n", "Lindbladian $\\mathcal{L}[\\rho]$ | \n", "
$\\texttt{emission}$ | \n", "$\\gamma_\\text{E}$ | \n", "\\begin{eqnarray}\\mathcal{L}[\\rho]&=&\\sum_n^N \\left(J_{-,n}\\rho J_{+,n} - \\frac{1}{2}J_{+,n}J_{-,n}\\rho - \\frac{1}{2}\\rho J_{+,n}J_{-,n} \\right)\\end{eqnarray} | \n", "
$\\texttt{pumping}$ | \n", "$\\gamma_\\text{P}$ | \n", "\\begin{eqnarray}\\mathcal{L}[\\rho]&=&\\sum_n^N \\left(J_{+,n}\\rho J_{-,n} - \\frac{1}{2}J_{-,n}J_{+,n}\\rho - \\frac{1}{2}\\rho J_{-,n}J_{+,n} \\right)\\end{eqnarray} | \n", "
$\\texttt{dephasing}$ | \n", "$\\gamma_\\text{D}$ | \n", "\\begin{eqnarray}\\mathcal{L}[\\rho]&=&\\sum_n^N \\left(J_{z,n}\\rho J_{z,n} - \\frac{1}{2}J_{z,n}J_{z,n}\\rho - \\frac{1}{2}\\rho J_{z,n}J_{z,n} \\right)\\end{eqnarray} | \n", "
$\\texttt{collective}\\_\\texttt{emission}$ | \n", "$\\gamma_\\text{CE}$ | \n", "\\begin{eqnarray}\\mathcal{L}[\\rho]&=& J_{-}\\rho J_{+} - \\frac{1}{2}J_{+}J_{-}\\rho - \\frac{1}{2}\\rho J_{+}J_{-} \\end{eqnarray} | \n", "
$\\texttt{collective}\\_\\texttt{pumping}$ | \n", "$\\gamma_\\text{CP}$ | \n", "\\begin{eqnarray}\\mathcal{L}[\\rho]&=& J_{+}\\rho J_{-} - \\frac{1}{2}J_{-}J_{+}\\rho - \\frac{1}{2}\\rho J_{-}J_{+} \\end{eqnarray} | \n", "
$\\texttt{collective}\\_\\texttt{dephasing}$ | \n", "$\\gamma_\\text{CD}$ | \n", "\\begin{eqnarray}\\mathcal{L}[\\rho]&=& J_{z}\\rho J_{z} - \\frac{1}{2}J_{z}^2\\rho - \\frac{1}{2}\\rho J_{z}^2 \\end{eqnarray} | \n", "