An optical nanoantenna and adjacent atomic systems are strongly coupled when
an excitation is repeatedly exchanged between these subsystems prior to its
eventual dissipation into the environment. It remains challenging to reach the
strong coupling regime but it is equally rewarding. Once being achieved,
promising applications as signal processing at the nanoscale and at the single
photon level would immediately come into reach. Here, we study such hybrid
configuration from different perspectives. The configuration we consider
consists of two identical atomic systems, described in a two-level
approximation, which are strongly coupled to an optical nanoantenna. First, we
investigate when this hybrid system requires a fully quantum description and
provide a simple analytical criterion. Second, a design for a nanoantenna is
presented that enables the strong coupling regime. Besides a vivid time
evolution, the strong coupling is documented in experimentally accessible
quantities, such as the extinction spectra. The latter are shown to be strongly
modified if the hybrid system is weakly driven and operates in the quantum
regime. We find that the extinction spectra depend sensitively on the number of
atomic systems coupled to the nanoantenna.Comment: 14 pages, 7 figure
A novel scheme is proposed to generate a maximally entangled state between two qubits by means of a dissipation-driven process. To this end, we entangle the quantum states of qubits that are mutually coupled by a plasmonic nanoantenna. Upon enforcing a weak spectral asymmetry in the properties of the qubits, the steady-state probability to obtain a maximally entangled, subradiant state approaches unity. This occurs despite the high losses associated to the plasmonic nanoantenna that are usually considered as being detrimental. The entanglement scheme is shown to be quite robust against variations in the transition frequencies of the quantum dots and deviations in their prescribed position with respect to the nanoantenna. Our work paves the way for novel applications in the field of quantum computation in highly integrated optical circuits.
Unitary transformations are routinely modeled and implemented in the field of quantum optics. In contrast, nonunitary transformations that can involve loss and gain require a different approach. In this theory work, we present a universal method to deal with nonunitary networks. An input to the method is an arbitrary linear transformation matrix of optical modes that does not need to adhere to bosonic commutation relations. The method constructs a transformation that includes the network of interest and accounts for full quantum optical effects related to loss and gain. Furthermore, through a decomposition in terms of simple building blocks it provides a step-by-step implementation recipe, in a manner similar to the decomposition by Reck et al.[1] but applicable to nonunitary transformations. Applications of the method include the implementation of positive-operator-valued measures and the design of probabilistic optical quantum information protocols.
We propose to use nanoantennas (NAs) coupled to incoherently pumped quantum dots for ultrabright single photon emission. Besides fully quantum calculations, we analyze an analytical expression for the emitted photon rate. From these analytical considerations, it turns out that the Purcell factor and the pumping rate are the main quantities of interest. We also disclose a trade-off between the emitted photon rate and the nonclassical nature of the emitted light. This trade-off has to be considered while designing suitable NAs, which we also discuss in depth.
Spontaneous emission of quantum emitters can be modified by their optical environment, such as a resonant nanoantenna. This impact is usually evaluated under assumption that each molecular transition is dominated only by one multipolar channel, commonly the electric dipole. In this article, we go beyond the electric dipole approximation and take light-matter coupling through higher-order multipoles into account. We investigate a strong enhancement of the magnetic dipole and electric quadrupole emission channels of a molecule adjacent to a plasmonic nanoantenna. Additionally, we introduce a framework to study interference effects between various transition channels in molecules by rigorous quantum-chemical calculations of their multipolar moments and a consecutive investigation of the transition rate upon coupling to a nanoantenna. We predict interference effects between these transition channels, which allow in principle for a full suppression of radiation by exploiting destructive interference, waiving limitations imposed on the emitter’s coherence time by spontaneous emission.
Statistical properties of outgoing light pulses are studies after they have
been stored in a medium of atoms in the tripod configuration. A generalized
Hong-Ou-Mandel interference, storing of squeezed states and homodyne signal
analysis are discussed in the context of their dependence on the parameters of
the control fields used for light storage and release.Comment: 5 figure
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