Abstract Controllable single-photon scattering in a one-dimensional waveguide coupled to a Jaynes–Cummings structure containing a time-modulated two-level atom interacting with a single-mode cavity is investigated. The photon transmission and reflection amplitudes are calculated by using an effective Floquet Hamiltonian in real space. The results show that the coupling between the atom and the cavity mode can dynamically be tuned via periodically modulating the atomic transition frequency. As a consequence, the scattering behaviors of the waveguide photons can be actively manipulated, and a controllable single-photon switch with high on-off ratio could be realized. More interestingly, the switch works well within a wide frequency region, i.e., the transmission of both resonant and off-resonant waveguide photons can be effectively switched on or off with appropriate system parameters. Furthermore, the proposed dynamically tunable switching scheme is robust against atomic dissipation associated with the help of atom-cavity coupling mismatch. Such single-photon device can be used as an elementary unit for various quantum information processing.
Abstract Controllable single-photon scattering in a one-dimensional waveguide coupled to a Jaynes–Cummings structure containing a time-modulated two-level atom interacting with a single-mode cavity is investigated. The photon transmission and reflection amplitudes are calculated by using an effective Floquet Hamiltonian in real space. The results show that the coupling between the atom and the cavity mode can dynamically be tuned via periodically modulating the atomic transition frequency. As a consequence, the scattering behaviors of the waveguide photons can be actively manipulated, and a controllable single-photon switch with high on-off ratio could be realized. More interestingly, the switch works well within a wide frequency region, i.e., the transmission of both resonant and off-resonant waveguide photons can be effectively switched on or off with appropriate system parameters. Furthermore, the proposed dynamically tunable switching scheme is robust against atomic dissipation associated with the help of atom-cavity coupling mismatch. Such single-photon device can be used as an elementary unit for various quantum information processing.
The dynamical control of single-photon scattering in a one-dimensional waveguide coupled to a Floquet atom-cavity system with time-modulated coupling constants is investigated. The analytical expressions for determining the scattering properties are obtained by using an effective Floquet Hamiltonian in real space. The photon transport is extremely sensitive to the time-modulated atom-cavity coupling strengths. Two cases, i.e., the effective Floquet Hamiltonian either includes or excludes a static coupling term, are discussed in detail. The results show that, with such Floquet atom-cavity configuration, an active photonic switch with nearly ideal switching contrast could be implemented. The transmission of the waveguide photons with different frequencies can dynamically be switched on or off via adjusting the modulated amplitude or relative modulated phase no matter whether the static coupling between the atom and the two cavity modes is considered or not. The application of the dynamic modulated atom-cavity coupling strengths instead of a purely static one makes our photonic switch more tunable. These results are expected to be applicable in quantum information processing and in active quantum device design involving dynamical modulation.
The dynamic control of single-photon scattering in a pair of one-dimensional waveguides mediated by a time-modulated atom–cavity system is investigated. Two cases, where the waveguides are coupled symmetrically or asymmetrically to the atom–cavity system, are discussed in detail. The results show that such time-modulated atom–cavity configuration can behave as a dynamical tunable directional single-photon router. The photons with different frequencies can dynamically be routed from the incident waveguide into any ports of the other with a 100% probability via adjusting the modulated amplitude or phases of the time-modulated atom–cavity coupling strengths, associate with the help of the asymmetrical waveguide–cavity couplings. Furthermore, the influence of dissipation on the routing capability is investigated. It is shown that the present single-photon router is robust against the dissipative process of the system, especially the atomic dissipation. These results are expected to be applicable in quantum information processing and design quantum devices with dynamical modulation.
Single-photon routing between two one-dimensional waveguides mediated by a single-mode cavity embedded with a time-modulated two-level atom is investigated. Two configurations, where the single photon is incident from an infinite or semi-infinite waveguide, are considered. Using the analytical expressions of the single-photon scattering amplitudes, the transmission behaviors in the two waveguides are discussed. The results show that the time modulation of the atomic frequency enables a dynamically tunable quantum router. A single photon with different frequencies can be routed dynamically from the incident waveguide to the other by properly manipulating the amplitude-to-frequency ratio of the atom. The routing efficiency can be improved to approach 100% by terminating the incident waveguide. In the semi-waveguide configuration, the routing behaviors controlled by the quantum coherent feedback are also investigated. The influence of the phase shifts introduced by the terminated waveguide on the routing capability and the conditions for perfect single-photon routing are discussed in detail. A frequency tunable targeted single-photon router can even be realized with the help of chiral coupling. These results may be beneficial to the photon control in a quantum network based on time-modulated quantum nodes.
Nonreciprocal single-photon scattering in a one-dimensional waveguide coupled to a giant two-level atom assisted with a time-modulated single-mode cavity is investigated. The analytic expressions of the single-photon scattering amplitudes are derived by using an effective Floquet Hamiltonian in real space. The scattering characteristics are discussed detail in both the Markovian and the non-Markovian regimes, and the corresponding conditions for achieving perfect nonreciprocal single-photon transmission are obtained. In the Markovian regime, a frequency-tunable single-photon diode with an ideal transmission contrast ratio can be realized by adjusting the frequency of the cavity mode, the local coupling phase difference, and the accumulated phase between the two coupling points. Furthermore, the influence of the intrinsic energy dissipations on the photon transport is discussed in detail. It is found that the dissipations of the cavity and the giant atom affect discriminatively the nonreciprocal single-photon scattering process. In the non-Markovian regime, the influence of the non-Markovian retarded effect induced by the time delay on the nonreciprocal single-photon scattering is discussed in detail. The results reveal that, although the retarded effect leads to a complex nonreciprocal scattering spectrum, dynamic tunable perfect nonreciprocal transmission with more abundant physical phenomena suitable for photons with different frequencies within a larger range can also be achieved. Such a nonreciprocal single-photon device can be used as an elementary unit for various quantum information processing and may have potential applications in quantum network engineering.
We study the transmission and reflection properties of a single-photon pulse in a one-dimensional waveguide side coupled with a Jaynes-Cummings system, namely, a multi-cavity with an embedded Rydberg atom. A Single-photon pulse is applied to tune the atoms energy spectrum, and varying it can bring the atomic qubit transition on or off-resonance for the cavity. The transmission and reflection behavior are systematically explored by a real-space model Hamiltonian and we find that the coupling strength between the waveguide and the side optical cavity exerts a tremendous impact on it. The influence of cavity and atomic dissipations and the incident pulse width on the transport properties of the single-photon is also investigated simultaneously. Based on these phenomena, we point out the possibility of utilizing this system as a single-photon transport in practice and has potential applications in quantum information.
In recent years, it has been a hot research topic to study the interaction between atomic ensemble and cavities, and many researches have been done in this regard. In such a system, some atoms are trapped in the cavity, which can be used to study their dynamic characteristics, e.g., the evolution of photon numbers and photon transition. The Jaynes-Cummings model is an important model for studying the dynamic characteristics of the cavity-atom system, which is based on the interaction between a single two-level atom and the cavity field. Recently, coherent photon control in cavity under specific conditions has become an important part of quantum computing and communication. It is worth noting that the tunable photon transmission and all-optical switches based on the cavity have already aroused much interest and have been used in many areas. The quantum information and networks are mostly rooted in complex optical devices, which may show nonreciprocal or asymmetric photon transport. In this paper, we demonstrate that by using an optical closed-loop system the unconventional photon transport can be realized with two mutually perpendicular cavities coupled through external fiber and a two-level atom placed on the intersection. This three-mode system supports two orthogonal propagation directions, that is to say, and the interactions among probe fields are mutually perpendicular. Without ignoring the spontaneous decay of the natural atom, the complex and controllable quantum interference induced by the efficient hybrid interaction of the light, cavity modes, and the atom in such a closed-loop structure can result in a few interesting symmetric and asymmetric photon transport behaviors, i.e. coherent perfect synthesis and coherent perfect reflection. Aside from these compelling properties, the group velocity can also be modulated, i.e., fast and slow light effect. All of these processes can be dynamically controlled by using the probe field phase difference, the tunneling coupling between two cavities and the coupling between the cavity and the atom. Importantly, due to so many advantages, such a tunable scheme can be readily extended to some optical devices, e.g., the switch and the router that is challenging to conventional optical devices.