Summary form only given. We investigate electromagnetically induced transparency (EIT) in the non-perturbative regime as a way to achieve maximal photon-photon interactions. In this new regime we discuss single versus multi-atom systems and conditional quantum logic operations.
Quantum limit of dissipation-free photon-photon interactions at the few photon level is studied in the context of giant Kerr nonlinearities in cavity electromagneti cally induced transparency (EIT). It is shown that photon-photon interaction is largest when the cavity contains a sing le atom. In contrast to conventional nonlinearities, increasing the number of atoms cannot in crease the interaction strength but will in general degrade the performance by enhancing di spersion. In the non-perturbative regime, the single-atom photon-photon interaction can be limited by lossy states excited from long-lived EIT states. Asymptotically, in the strong coupling limit, photon-photon interaction is determined by the single photon-atom coupling strength. Photon blockade occurs for single atoms but only partial blockade can occur for low dispersion and not at all in the high-dispersion limit of the multi-atom case.
Dissipation-free photon-photon interaction at the single-photon level is studied in the context of cavity electromagnetically induced transparency (EIT). For a single multilevel atom exhibiting EIT in the strong cavity-coupling regime, the anharmonicity of the atom-cavity system has an upper bound determined by single atom-photon coupling strength. A photon blockade effect is inferred to occur for both single- and multiatom cases from the behavior of transition rates between dressed states of the system. Numerical calculations of the second-order coherence function indicate that photon antibunching in both single- and two-atom cases are strong and comparable.
Quantum memory (QM) enables quantum state mapping between flying and stationary quantum states and is the building block of quantum information science, which enables to achieve a plethora of quantum information protocols, such as quantum state transfer across remote quantum nodes, distributed quantum logic gate, and quantum precession measurement network. Great progresses of quantum memories have been achieved, and electromagnetically induced transparency (EIT) is one of the well-understood approaches of QM. Quantum states of light are the essential quantum resources for implementing quantum enhanced task, and thus it is a long-standing goal to store and release non-classical states of light. This paper presents an up-to-date review on recent developments in EIT-based QM: EIT quantum memories have been realized in warm atomic cell, cold atoms and solid system, respectively; and EIT mechanism has been applied to store and release single photon, squeezed state, entangled photon pairs and multipartite entangled states of optical modes.
Electromagnetically induced transparency is a promising approach to implement quantumcommunication in quantum system. In this study, quantum coherence and interference in theexcitation pathways of a three-level Λ atomic system leads to the formation of new states of matter(i.e. the dark state). This state decouples itself from the excitation beams leading to phenomenasuch as coherent population trapping (CPT), electromagnetically induced transparency (EIT).Taking into account quantum coherence and interference in an optically dense electromagneticallyinducedtransparent medium, we investigate the non-destructive storage and retrieval of singlephotonquantum states in the dark state of this dense ensemble of gas phase medium. The storageand retrieval process is based on the intracavity electromagnetically induced transparency by whichproperties of a cavity filled with three-level Λ-type atoms are manipulated by an external control field.We demonstrate the peculiar case for the storage and retrieval of time-entangled periodic input pulses(a soliton train) in the dark state by adiabatic photon transfer under conditions of dynamicalimpedance matching. These multiplexed photon states are expected to allow sharing quantuminformation among many users, and are currently of very high demand for applications in longdistanceand multiplexed quantum communication.
Electromagnetically induced transparency is a promising approach to implement quantumcommunication in quantum system. In this study, quantum coherence and interference in theexcitation pathways of a three-level Λ atomic system leads to the formation of new states of matter(i.e. the dark state). This state decouples itself from the excitation beams leading to phenomenasuch as coherent population trapping (CPT), electromagnetically induced transparency (EIT).Taking into account quantum coherence and interference in an optically dense electromagneticallyinducedtransparent medium, we investigate the non-destructive storage and retrieval of singlephotonquantum states in the dark state of this dense ensemble of gas phase medium. The storageand retrieval process is based on the intracavity electromagnetically induced transparency by whichproperties of a cavity filled with three-level Λ-type atoms are manipulated by an external control field.We demonstrate the peculiar case for the storage and retrieval of time-entangled periodic input pulses(a soliton train) in the dark state by adiabatic photon transfer under conditions of dynamicalimpedance matching. These multiplexed photon states are expected to allow sharing quantuminformation among many users, and are currently of very high demand for applications in longdistanceand multiplexed quantum communication.