Abstract We investigate a T -shaped single-photon router constructed by two waveguides connected via a giant Λ-type three-level atom. Under a real-space approach, the analytical expressions of the single-photon transmission and reflection amplitudes are obtained. It is shown that a high transfer-rate routing between two waveguides can be effectively achieved by modulating the phase difference, the accumulated phase and the atom-waveguide coupling strengths, and its frequencies can be tuned with a classical driving field. Interestingly, chiral scattering and a single-photon targeted router with direction selectivity have been realized by the ideally equivalent atom-waveguide interaction. We believe that our results have potential applications in constructing optical quantum devices and designing the single-photon quantum routing using the giant-atom setup.
Abstract We investigate a T -shaped single-photon router constructed by two waveguides connected via a giant Λ-type three-level atom. Under a real-space approach, the analytical expressions of the single-photon transmission and reflection amplitudes are obtained. It is shown that a high transfer-rate routing between two waveguides can be effectively achieved by modulating the phase difference, the accumulated phase and the atom-waveguide coupling strengths, and its frequencies can be tuned with a classical driving field. Interestingly, chiral scattering and a single-photon targeted router with direction selectivity have been realized by the ideally equivalent atom-waveguide interaction. We believe that our results have potential applications in constructing optical quantum devices and designing the single-photon quantum routing using the giant-atom setup.
Abstract We investigate a π-shaped single-photon router composed of an infinite waveguide and two semi-infinite waveguides coupled through double two-level giant atoms, where each giant atom is further coupled to a single-mode cavity. Using the real-space approach, analytical expressions of the single-photon scattering amplitudes are derived. The numerical results show that optimal routing with unit efficiency can be achieved by precisely adjusting frequency detunings between the incident photon and the atomic as well as cavity resonances, the accumulated phase, local coupling phases and coupling strengths between atoms, waveguides and cavities. Additionally, chiral single-photon scattering is observed, demonstrating a strong direction-dependence in the scattering properties, with perfect chiral scattering achieved under specific phase-matching conditions. We believe that our research has considerable potential applications for designing advanced optical quantum devices and implementing efficient single-photon quantum routing based on giant atom architectures.
We investigate the single-photon quantum routing composed of two infinite waveguides coupled to two giant two-level atoms. The exact expressions of the single-photon transmission and reflection amplitudes are derived with the real-space approach. It is found that the single photon scattering behavior is strongly dependent on the phase difference between the two adjacent atom-waveguide coupling points, the frequency detuning, the coupling strength between the two giant atoms, and the interaction strengths between the giant atoms and the waveguides. Our studies show that an ideal single photon router with unit efficiency can be realised by designing the size of the giant atom, and the frequency detuning or adjusting the interaction strengths between the atoms and the waveguides. The results suggest the potential to effectively control the single-photon quantum routing based on the giant-atom setup.
Abstract We investigate the single-photon scattering properties of a driven three-level giant atom chirally coupled to two waveguides simultaneously in both the Markovian and the non-Markovian regimes. It is shown that under the Markovian limit, the chiral photon-atom interactions enable nonreciprocal scattering in a single waveguide and targeted photon routing with a probability of 100% in two waveguides, while the presence of the driving field and the giant atom structure introduce a more tunable parameter to manipulate the single-photon scattering behaviors. We also examine how the non-reciprocity and routing capability are influenced by the imperfect chirality and the atomic dissipation. In the non-Markovian regime, we show that the scattering behaviors are more complicated. The non-Markovicity induced non-reciprocity and photon routing are demonstrated in this paper. We believe that those results have potential applications in quantum network engineering.
This work is to investigate the single-photon scattering in a waveguide quantum electrodynamics system consisting of two dipole-coupled giant atoms, each interacting with a separate one-dimensional infinite waveguide at two distinct coupling points. Our primary objective is to establish a theoretical framework for manipulating photon propagation paths via quantum interference induced by multiple coupling points and local phase engineering. Unlike traditional chiral coupling schemes, an innovative method, in which the coupling phases are designed locally at each atom-waveguide interface, is used to achieve effective chiral coupling, thereby introducing novel quantum interference mechanisms. Using a real-space approach, we derive analytical expressions for four-port scattering amplitudes. We establish the conditions for achieving perfect directional routing to any output port and demonstrate the coherent control mechanisms implemented by geometric and local coupled phases. Continuous frequency tunability is primarily achieved through dipole-dipole interaction, and finely tuned through the accumulated phase and local coupling phases. Local phase differences precisely regulate port-specific probability distributions within the waveguides while preserving total routing efficiency. Furthermore, we elucidate the mechanisms of nonreciprocal transport and chiral scattering. The analysis reveals different governing principles: perfect nonreciprocity arises from the interplay of the accumulated phase, local coupling phases, photon-atom detuning, and dipole-dipole interaction. In contrast, perfect chiral scattering depends entirely on the accumulated phase and local coupling phases, and is independent of detuning. Notably, under the phase-matching conditions, the system achieves both perfect chiral and directional routing, and realizes frequency-selective path-asymmetric photon control. These findings provide a comprehensive framework for manipulating quantum interference in multi-atom waveguide systems, highlighting applications in quantum information processing, including tunable single-photon routers, isolators, and chiral quantum nodes. By implementing superconducting circuits, the local phase can be dynamically adjusted, thus proving the feasibility of the experiment.
Abstract We investigate single-photon quantum routing composed of double two-level atoms coupled to two infinite waveguides. By introducing local coupling phases at atom-waveguide connecting points, we engineer asymmetric atom-waveguide interactions, which enables the directional control of photon propagation for achieving high-efficiency quantum routing. Using the real-space approach, we derived exact expressions of the single-photon scattering amplitudes, allowing for a comprehensive analysis of the routing dynamics. For both identical and non-identical atomic configurations, we systematically explored the conditions for achieving perfect photon transfer. Our results demonstrate that complete photon transfer can be realized by precisely tuning the coupling phases, the accumulated phase and atomic frequencies. This work provides a theoretical foundation for developing high-efficiency quantum routers with potential applications in quantum networks and photonic quantum information processing.
In this paper, we propose a single-photon routing scheme using a hybrid system, where a two-level giant atom is coupled to a pair of one-dimensional coupled-resonator waveguides. Using the discrete-coordinate scattering approach, exact expressions of the four scattering coefficients are obtained, and the single-photon routing properties are studied. We find that the single-photon routing properties are closely related to the size of the giant atom, the coupling strength between the giant atom and waveguides, and the phase difference between two coupled channels of the atom-upper (lower) waveguide. Without considering the effect of phases of the atom-waveguide coupling coefficients, the probability for a single-photon routing from one waveguide to the other does not exceed 50. However, by properly selecting coupling points between the giant atom and two waveguides, and the phase difference between two atom-upper (lower) waveguide coupling coefficients, a single photon can be transferred from the input port to an arbitrarily selected output port deterministically, i.e., with 100 probability. It is also found that chiral and nonreciprocal single-photon scattering can be realized in our model by properly adjusting the phase difference between two atom-upper (lower) waveguide coupled channels. Our paper offers a promising route towards achieving tunable single-photon routing and constructing optical scalable quantum networks.