We study the excitonic dynamics of a driven quantum dot under influence phonon environment, going beyond weak exciton–phonon coupling approximation. By combining polaron transform and time-local projection operator techniques, we develop master equation that can be valid over much larger range strengths temperatures than in case standard weak-coupling approach. For experimentally relevant parameters considered here, find theories give very similar predictions for low (below 30 K), while at...

We develop a versatile master equation approach to describe the nonequilibrium dynamics of two-level system in contact with bosonic environment, which allows for exploration wide range parameter regimes within single formalism. As an experimentally relevant example, we apply this technique study excitonic Rabi rotations driven quantum dot, and compare its predictions numerical Feynman integral approach. find excellent agreement between two methods across generally difficult parameters. In...

We provide a self-contained review of master equation approaches to modelling phonon effects in optically driven self-assembled quantum dots. Coupling the (quasi) two-level excitonic system phonons leads dissipation and dephasing, rates which depend on excitation conditions, intrinsic properties QD sample, its temperature. describe several techniques, include weak-coupling equations that are perturbative exciton-phonon coupling, as well those based polaron transformation can remain valid for...

We investigate the energy transfer dynamics in a donor-acceptor model by developing time-local master equation technique based on variational transformation of underlying Hamiltonian. The allows minimisation Hamiltonian perturbation term dependent system parameters, and consequently results versatile valid over range system-bath coupling strengths, temperatures, environmental spectral densities. While our formalism reduces to well-known Redfield, Förster polaron forms appropriate limits,...

We investigate the temperature dependence of photon coherence properties through two interference (TPI) measurements from a single QD under resonant excitation. show that loss indistinguishability is only related to electron-phonon coupling without being affected by spectral diffusion. Through these measurements, and complementary microscopic theory, we identify independent separate decoherence processes each associated phonons. Below 10K, find relaxation vibrational lattice dominant...

We study the nature of energy transfer process within a pair coupled two-level systems (donor and acceptor) subject to interactions with surrounding environment. Going beyond standard weak-coupling approach, we derive master equation polaron representation that allows for investigation both weak strong system-bath couplings, as well reliable interpolation between these two limits. With this theory, are then able explore coherent incoherent regimes donor-acceptor pair. elucidate how degree...

We study the crucial role played by solid-state environment in determining photon emission characteristics of a driven quantum dot. For resonant driving, we predict phonon enhancement coherently emitted radiation field with increasing driving strength, stark contrast to conventional expectation rapidly decreasing fraction coherent stronger driving. This surprising behavior results from thermalization dot respect bath and leads nonstandard regime resonance fluorescence which significant...

We investigate temperature-dependent resonance fluorescence spectra obtained from a single self-assembled quantum dot. A decrease of the Mollow triplet sideband splitting is observed with increasing temperature, an effect we attribute to phonon-induced renormalization driven dot Rabi frequency. also present first evidence for nonperturbative regime phonon coupling, in which expected linear increase linewidth as function temperature canceled by corresponding reduction These results indicate...

We derive an extension to the quantum regression theorem which facilitates calculation of two-time correlation functions and emission spectra for systems undergoing non-Markovian evolution. The derivation exploits projection operator techniques, with we obtain explicit equations motion functions, making only a second-order expansion in system-environment coupling strength invoking Born approximation at fixed initial time. results are used investigate driven semiconductor dot coupled acoustic...

We present a joint experiment-theory analysis of the temperature-dependent emission spectra, zero-phonon linewidth, and second-order correlation function light emitted from single organic molecule. observe spectra with line together several additional sharp peaks, broad phonon sidebands, strongly temperature dependent homogeneous broadening. Our model includes both localized vibrational modes molecule thermal bath, which we include nonperturbatively, is able to capture all observed features....

Spectral filtering of resonance fluorescence is widely employed to improve single photon purity and indistinguishability by removing unwanted backgrounds. For filter bandwidths approaching the emitter linewidth, complex behaviour predicted due preferential transmission components with differing statistics. We probe this regime using a Purcell-enhanced quantum dot in both weak strong excitation limits, finding excellent agreement an extended sensor theory model. By changing only width,...

Unidirectional (chiral) emission of light from a circular dipole emitter into waveguide is only possible at points perfect polarization (C points), with elliptical polarizations yielding lower directional contrast. However, there no need to restrict engineered systems dipoles, and an appropriate choice unidirectional for any polarization. Using rather than circular, typically increases the size area suitable chiral interactions (in exemplary mode by factor ∼30), while simultaneously...

We propose a ground-state ansatz for the Ohmic spin-boson model that improves upon variational treatment of Silbey and Harris biased systems in scaling limit. In particular, it correctly captures smooth crossover behaviour expected magnetisation when moving between delocalised localised regimes model, feature is unable to properly reproduce, while also provides lower energy estimate region. further demonstrate validity our intuitive by showing leads predictions excellent agreement with those...

Unitary transformations can allow one to study open quantum systems in situations for which standard, weak-coupling type approximations are not valid. We develop here an extension of the variational (polaron) transformation approach system dynamics, applies arbitrarily large exciton transport networks with local environments. After deriving a time-local master equation transformed frame, we go on compare population dynamics predicted using our technique other established equations. The frame...

We develop a wavefunction approach to describe the scattering of two photons on quantum emitter embedded in one-dimensional waveguide. Our method allows us calculate exact dynamics complete system at all times, as well transmission properties emitter. show that nonlinearity with respect incoming depends strongly excitation and spectral shape pulses, resulting which crucially their separation width. In addition, for counter-propagating we analyze induced level correlations scattered state,...

Coherent scattering of light by a single quantum emitter is fundamental process at the heart many proposed technologies. Unlike atomic systems, solid-state emitters couple to their host lattice phonons. Using dot in an optical nanocavity, we resolve these interactions both time and frequency domains, going beyond picture develop comprehensive model from emitters. We find that even presence cavity, phonon coupling leads sideband completely insensitive excitation conditions, non-monotonic...

We investigate how two spatially separated qubits coupled to a common heat bath can be entangled by purely dissipative dynamics. identify dynamical time scale associated with the lifetime of dissipatively generated entanglement and show that it much longer than either typical single-qubit decoherence or on which direct exchange interaction entangle qubits. give an approximate analytical expression for long-time evolution qubit concurrence propose ion trap scheme in such dynamics should observable.

We demonstrate the emission of highly indistinguishable photons from a quasi-resonantly pumped coupled quantum dot--microcavity system operating in regime cavity electrodynamics. Changing sample temperature allows us to vary dot--cavity detuning and, on spectral resonance, we observe threefold improvement Hong-Ou-Mandel interference visibility, reaching values excess 80%. Our measurements off-resonance allow investigate varying Purcell enhancements, and probe dephasing environment at...

The desire to produce high-quality single photons for applications in quantum information science has lead renewed interest exploring solid-state emitters the weak excitation regime. Under these conditions it is expected that are coherently scattered, and so benefit from a substantial suppression of detrimental interactions between source its surrounding environment. Nevertheless, we demonstrate here this reasoning incomplete, as phonon continue play crucial role determining emission...

Using a variational approach we investigate the delocalized to localized crossover in ground state of an Ohmic two-impurity spin-boson model, describing two otherwise non-interacting spins coupled common bosonic environment. We show that competition between environment-induced Ising spin interaction and externally applied fields leads variations system-bath coupling strength, $\alpha_c$, at which delocalized-localized occurs. Specifically, regime lies $\alpha_c=0.5$ $\alpha_c=1$ depending...

We present the design of a tapered nanocavity, obtained by sandwiching photonic wire section between planar gold reflector and few-period Bragg mirror integrated into wire. Thanks to its ultrasmall mode volume (0.71 λ3/n3), this hybrid nanocavity largely enhances spontaneous emission rate an embedded quantum dot (Purcell factor: 6), while offering wide operation bandwidth (full-width half-maximum: 20 nm). In addition, top shapes cavity far-field very directive output beam, with Gaussian...

Resonant excitation of solid state quantum emitters has the potential to deterministically excite a localized exciton while ensuring maximally coherent emission. In this work, we demonstrate coupling an in lithographically positioned, site-controlled semiconductor dot external resonant laser field. For strong continuous-wave driving observe characteristic Mollow triplet and analyze Rabi splitting sideband widths as function strength temperature. The increase linearly with temperature square...

The indistinguishability of successively generated photons from a single quantum emitter is most commonly measured using two-photon interference at beam splitter. Whilst for sources excited in the pulsed regime bunching reflects full wave-packet emitted photons, continuous wave (cw) excitation, inevitable dependence on detector timing resolution and driving strength obscures underlying photon process. Here we derive method to extract cw measurements by considering relevant correlation...

We report a joint experimental and theoretical study of the interference properties single-photon source based on In(Ga)As quantum dot embedded in quasiplanar GaAs microcavity. Using resonant laser excitation with pulse separation 2 ns, we find near-perfect emitted photons, corresponding indistinguishability $\mathcal{I}=(99.6{\phantom{\rule{0.16em}{0ex}}}_{\ensuremath{-}\phantom{\rule{0.16em}{0ex}}1.4}^{+\phantom{\rule{0.16em}{0ex}}0.4})%$. For larger separations, quasiresonant conditions,...