On the spectroscopy of quantum dots in microcavities

At the occasion of the OECS conference in Madrid, we give a succinct account of some recent predictions in the spectroscopy of a quantum dot in a microcavity that remain to be observed experimentally, sometimes within the reach of the current state of the art.Comment: OECS11 Conference proceedings, in editor style. 4 pages, 1 figure. Animations provided separatel

Multimode Fock states with large photon number: effective descriptions and applications in quantum metrology

We develop general tools to characterise and efficiently compute relevant observables of multimode $N$-photon states generated in non-linear decays in one-dimensional waveguides. We then consider optical interferometry in a Mach-Zender interferometer where a $d$-mode photonic state enters in each arm of the interferometer. We derive a simple expression for the Quantum Fisher Information in terms of the average photon number in each mode, and show that it can be saturated by number-resolved photon measurements that do not distinguish between the different $d$ modes.Comment: 18 pages, 11 figures. V2: Minor change

Non-reciprocal few-photon devices based on chiral waveguide-emitter couplings

We demonstrate the possibility of designing efficient, non reciprocal few-photon devices by exploiting the chiral coupling between two waveguide modes and a single quantum emitter. We show how this system can induce non-reciprocal photon transport at the single-photon level and act as an optical diode. Afterwards, we also show how the same system shows a transistor-like behaviour for a two-photon input. The efficiency in both cases is shown to be large for feasible experimental implementations. Our results illustrate the potential of chiral waveguide-emitter couplings for applications in quantum circuitry.Comment: Mathematica notebook attached for calculation of detection probabilitie

Optimization of photon correlations by frequency filtering

Photon correlations are a cornerstone of Quantum Optics. Recent works [NJP 15 025019, 033036 (2013), PRA 90 052111 (2014)] have shown that by keeping track of the frequency of the photons, rich landscapes of correlations are revealed. Stronger correlations are usually found where the system emission is weak. Here, we characterize both the strength and signal of such correlations, through the introduction of the 'frequency resolved Mandel parameter'. We study a plethora of nonlinear quantum systems, showing how one can substantially optimize correlations by combining parameters such as pumping, filtering windows and time delay.Comment: Small updates to take into account the recent experimental observation of the physics here analyze

Plasmon-polariton emission from a coherently p-excited quantum dot near a metal interface

We study the emission of surface plasmon polaritons by the decay of the lowest excited state of a quantum emitter when the system is excited by a laser in resonance with a higher excited state (p-shell excitation). By solving a master equation and by using the quantum-regression theorem, we show how the emission is enhanced by the Purcell effect due to the weak coupling between the emitter and the structured spectral density of plasmon-polariton states of a metal surface. Measurable magnitudes, as the spectrum and the second-order coherence function, are extremely affected by the coherent p-shell excitation. In many cases, such coherent excitation completely masks the physical features of the emission under study. The coexistence between coherent p-shell excitation in the first step of the process and weak coupling in the final step is very important and completely general for any structured reservoir of final states. The advantage of our system is that, just by changing the distance from the quantum emitter to the metal surface, one can access a very rich set of regimes as purely dissipative direct photon emission or emission of plasmon polaritonsThis work was supported by the Spanish MICINN under Contracts No. MAT2008-01555 and No. MAT2011-22997and by CAM under Contract No. S-2009/ESP-1503. C.S.-M. acknowledges a grant from the Universidad Autonoma de Madrid. A.G.-T. acknowledges an FPU Grant No. AP2008-00101 from the Spanish Ministry of Educatio

Two-photon spectra of quantum emitters

We apply our recently developed theory of frequency-filtered and time-resolved N-photon correlations to study the two-photon spectra of a variety of systems of increasing complexity: single mode emitters with two limiting statistics (one harmonic oscillator or a two-level system) and the various combinations that arise from their coupling. We consider both the linear and nonlinear regimes under incoherent excitation. We find that even the simplest systems display a rich dynamics of emission, not accessible by simple single photon spectroscopy. In the strong coupling regime, novel two-photon emission processes involving virtual states are revealed. Furthermore, two general results are unraveled by two-photon correlations with narrow linewidth detectors: i) filtering induced bunching and ii) breakdown of the semi-classical theory. We show how to overcome this shortcoming in a fully-quantized picture.Comment: 27 pages, 8 figure

Linear and nonlinear coupling of quantum dots in microcavities

We discuss the topical and fundamental problem of strong-coupling between a quantum dot an the single mode of a microcavity. We report seminal quantitative descriptions of experimental data, both in the linear and in the nonlinear regimes, based on a theoretical model that includes pumping and quantum statistics.Comment: Proceedings of the symposium Nanostructures: Physics and Technology 2010 (http://www.ioffe.ru/NANO2010), 2 pages in proceedings styl

Entanglement of two qubits mediated by one-dimensional plasmonic waveguides

We investigate qubit-qubit entanglement mediated by plasmons supported by one-dimensional waveguides. We explore both the situation of spontaneous formation of entanglement from an unentangled state and the emergence of driven steady-state entanglement under continuous pumping. In both cases, we show that large values for the concurrence are attainable for qubit-qubit distances larger than the operating wavelength by using plasmonic waveguides that are currently available.Comment: 4 pages, 4 figures. Minor Changes. Journal Reference added. Highlighted in Physic