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Register a new userTheory of non-Markovian decay of a cascade atom in high-Q cavities and photonic band-gap materials
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The dynamics of a three-level atom in a cascade configuration with both transitions coupled to a single structured reservoir of quantized field modes is treated using Laplace transform methods applied to the coupled amplitude equations. Results are also obtained from master equations by two different approaches, that is, involving either pseudomodes or quasimodes. Two different types of reservoir are considered, namely a high-Q cavity and a photonic band-gap system, in which the respective reservoir structure functions involve Lorentzians. Non-resonant transitions are included in the model. In all cases non-Markovian behaviour for the atomic system can be found, such as oscillatory decay for the high-Q cavity case and population trapping for the photonic band-gap case. In the master equation approaches, the atomic system is augmented by a small number of pseudomodes or quasimodes, which in the quasimode approach themselves undergo Markovian relaxation into a flat reservoir of continuum quasimodes. Results from these methods are found to be identical to those from the Laplace transform method including two-photon excitation of the reservoir with both emitting sequences. This shows that complicated non-Markovian decays of an atomic system into structured EM field reservoirs can be described by Markovian models for the atomic system coupled to a small number of pseudomodes or quasimodes.
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The spontaneous emission spectrum for a three level cascade configuration atom in a single mode high-Q cavity coupled to a zero temperature reservoir of continuum external modes is determined from the atom-cavity mode master equation using the quantum regression theorem. Initially the atom is in its upper state and the cavity mode empty of photons. Following Glauber, the spectrum is defined via the response of a detector atom. Spectra are calculated for the detector located inside the cavity (case A), outside the cavity end mirror (Case B-end emission), or placed for emission out the side of the cavity (Case C). The spectra for case A and case B are found to be essentially the same. In all the cases the predicted lineshapes are free of instrumental effects and only due to cavity decay. Spectra are presented for intermediate and strong coupling regime situations (where both atomic transitions are resonant with the cavity frequency), for cases of non-zero cavity detuning, and for cases where the two atomic transition frequencies differ. The spectral features for Cases B(A) and C are qualitatively similar, with six spectral peaks for resonance cases and eight for detuned cases. These general features of the spectra can be understood via the dressed atom model. However, Case B and C spectra differ in detail, with the latter exhibiting a deep spectral hole at the cavity frequency due to quantum interference effects.
Tailoring the interactions between quantum emitters and single photons constitutes one of the cornerstones of quantum optics. Coupling a quantum emitter to the band edge of a photonic crystal waveguide (PCW) provides a unique platform for tuning these interactions. In particular, the crossover from propagating fields $E(x) propto e^{pm ik_x x}$ outside the bandgap to localized fields $E(x) propto e^{-kappa_x |x|}$ within the bandgap should be accompanied by a transition from largely dissipative atom-atom interactions to a regime where dispersive atom-atom interactions are dominant. Here, we experimentally observe this transition for the first time by shifting the band edge frequency of the PCW relative to the $rm D_1$ line of atomic cesium for $bar{N}=3.0pm 0.5$ atoms trapped along the PCW. Our results are the initial demonstration of this new paradigm for coherent atom-atom interactions with low dissipation into the guided mode.
This paper presents feasible experimental schemes to realize controlled teleportation protocols via photonic Faraday rotations in low-Q cavities. The schemes deal with controlled teleportation of superposition states and two-particle entanglement of atomic states. The information is encoded in three-level atoms in a lambda configuration trapped inside coupled cavities by optical fibers. Also, we estimate the success probability and the current feasibility of the schemes.
Giant atoms have exhibited counterintuitive but interesting phenomena such as non-exponential decays which would benefit quantum information processing. However, recent experiments on electromagnetically induced transparency (EIT) of giant atoms observed standard spectra only. In this letter, we present a full quantum model for observing EIT in a single giant atom rather than a semi-classical one in recent works. With this model and a quantum transport theory in real space, a class of non-Markovian EIT can be observed which has not been witnessed before. This new phenomenon results from spatial non-locality of a multiple distant coupling structure in the giant atom, which physically forces propagating fields between the coupling points behaving as standing waves. We also show that the spatial non-locality induced non-Markovianity can be represented by a time-delayed master equation where widely-used Born approximation in the existing works breaks down.
We experimentally demonstrate high Quality factor dual-polarized TE-TM photonic crystal nanobeam cavities. The free-standing nanobeams are fabricated in a 500 nm thick silicon layer, and are probed using both tapered optical fiber and free-space resonant scattering set-ups. We measure Q-factors greater than 10^4 for both TM and TE modes, and observe large fiber transmission drops (0.3 -- 0.4) at the TM mode resonances.
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