Optical decay into CROW waveguides  an exact solution
MarcAndré Dupertuis
LASPE and LPN, Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH1015 Lausanne
M.A.Dupertuis is Maître d'Enseignement et de Recherche at EPF Lausanne, Switzerland. His post doctoral stay was in Helsinki, Finland, with Stig Stenholm. Fundamental and applied topics ranging from plasma and condensed matter physics to quantum optics interest him, using as much analytics than numerics. Semiconductor nanostructures, in particular symmetry effects on with multiexcitons in quantum dots have been in recent focus. With Monique Combescot he investigated novel ways to approach composite bosons like polaritons. Present interest is on practical schemes for entangled photon generation in diverse material systems and configurations, and on teaching quantum information with IBM quantum experience.
Abstract
Photonic quantum processing is a promising route towards largescale quantum computation and communication, with a need for fully integrated devices. Recently we have proposed a microsystem (MS) made of two emitters strongly... [ view full abstract ]
Photonic quantum processing is a promising route towards largescale quantum computation and communication, with a need for fully integrated devices. Recently we have proposed a microsystem (MS) made of two emitters strongly coupled to a twomode cavity (Fig.1) as a source of directionallyentangled photons. Such a MS is potentially a solid state on demand electrically pumped source, ultrabright and integrable in a 2D photonic band gap circuit.
The MS principle relies on a fundamental symmetry plane (Fig.1), and an engineered degeneracy of the intermediate dressed states of the cascade from “twoquanta dressed states”. The photon pairs must be collected by narrowband waveguides, indicating use of coupledresonator optical waveguides (CROW) whose minibands selecting the photon pairs.
Here we explore the decay of a single MS transition into periodic CROW waveguide with a WeisskopfWigner approach. We have found a new closed form solution for the probability to remain in the excited state P (Fig.2), and even for the final emitted quantum state, valid for all parameter values. In Fig.2 the contours of P are displayed as a function of the coupling and the detuning. We clearly see that the parameter space is divided into three regions of fundamentally different behaviour. First, in the white region the asymptotic decay is always complete, and becomes faster (and progressively nonexponential) as coupling increases. Second, in the region hatched region P is not defined since the probability to stay in the excited state oscillates forever between two values: this is the strong coupling region with the CROW. Third, in the remaining area the asymptotic decay is never complete (P > 0), nor is it completely inhibited (P) < 1.
These results may seem surprising, in particular the possibility of partial decay when the transition frequency is outside the channel bandwidth where the coupling constant vanishes, but constitutes a beautiful exact model for qualitative behaviour previously discussed in [1].
[1] A.G.Kofman et al., J. Mod. Opt. 41, p.353 (1994); P.R.Berman et al., Adv. At. Mol. and Opt. Phys. 59, p.175 (2010)
Authors

MarcAndré Dupertuis
(LASPE and LPN, Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH1015 Lausanne)
Topic Areas
Fundamental science for quantum technologies , Quantum optics and nonclassical light sources , Solid states and hybrid systems
Session
PS3 » Poster Session (13:30  Friday, 7th September, Hall)
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