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Register a new userDark state with counter-rotating dissipative channels
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Dark state as a consequence of interference between different quantum states has great importance in the fields of chip-scale atomic clock and quantum information. For the $Lambda$-type three-level system, this dark state is generally regarded as being dissipation-free because it is a superposition of two lowest states without dipole transition between them. However, previous studies are based on the rotating-wave approximation (RWA) by neglecting the counter-rotating terms in the system-environment interaction. In this work, we study non-Markovian quantum dynamics of the dark state in a $Lambda$-type three-level system coupled to two bosonic baths and reveal the effect of counter-rotating terms on the dark state. In contrast to the dark state within the RWA, leakage of the dark state occurs even at zero temperature, as a result of these counter-rotating terms. Also, we present a method to restore the quantum coherence of the dark state by applying a leakage elimination operator to the system.
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Recent experiments have pushed the studies on atom-photon interactions to the ultrastrong regime, which motivates the exploration of physics beyond the rotation wave approximation. Here we study the single-photon scattering on a system composed by a coupling cavity array with a two-level atom in the center cavity, which, by varying two outside coupling parameters, corresponds to a model from a supercavity QED to a waveguide QED with counter-rotating wave (CRW) interaction. By applying a time-independent scattering theory based on the bound states in the scattering region, we find that the CRW interaction obviously changes the transmission valley even in the weak atom-cavity coupling regime; In particular, the CRW interaction leads to an inelastic scattering process and a Fano-type resonance, which is directly observed in the crossover from the supercavity QED case to the waveguide QED case. Predictably, our findings provide the potential of manipulating the CRW effects in realistic systems.
Recently, the studies on the light-matter interaction have been pushed into the ultrastrong coupling regime, which motivates the exploration of applications of the counter rotating wave (CRW) interaction. Even in the ultrastrong coupling regime, however, few photons can be generated from the vacuum by switching on the CRW interaction. Here we propose a scheme to enhance the photon generation from the vacuum by a bang-bang (switching on/off) control of the CRW interaction. By developing a pruning greedy algorithm to search the optimal control sequence, we find that the maximum photon number obtained for a given time period in our scheme can be dramatically increased up to several orders than that from switching on the CRW interaction.
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We first derive for the general form of the fidelity for various bosonic channels. Thereby we give the fidelity of different quantum bosonic channel, possibly with product input and entangled input respectively, as examples. The properties of the fidelity are carefully examined.
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