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Quantum Science and Technology

Phase-modulated single-photon nonreciprocal transport and directional router in a waveguide–cavity–emitter system beyond the chiral coupling

Xin Wang, Wen‐Xing Yang, Aixi Chen, Ling Li, Tao Shui, Xiyun Li, Zhen Yu Wu

Published Dec 17, 2021• 34 citations
Publisher

Abstract

Abstract We propose a potentially practical scheme for the controllable single-photon transport via waveguides which are coupled to a microcavity–emitter system. The microcavity–emitter system consists of a V-type three-level emitter and two or one single-mode microcavity. A driving field is used to drive a hyperfine transition between two upper excited states of the V-type three-level emitter. Beyond chiral coupling between waveguides and microcavity–emitter system, we show that the perfectly nonreciprocal single-photon transport in a single waveguide and the single-photon router with 100% routing probability in two waveguides can be achieved. Interesting enough, whether the nonreciprocal single-photon transport or the single-photon router can be switched periodically by adjusting the phase associated with microcavity–emitter coupling strength and the driving field. The complete physical explanation of the underlying mechanism is presented.

DOI
10.1088/2058-9565/ac4425

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Abstract We propose a potentially practical scheme for the controllable single-photon transport via waveguides which are coupled to a microcavity–emitter system. The microcavity–emitter system consists of a V-type three-level emitter and two or one single-mode microcavity. A driving field is used to drive a hyperfine transition between two upper excited states of the V-type three-level emitter. Beyond chiral coupling between waveguides and microcavity–emitter system, we show that the perfectly nonreciprocal single-photon transport in a single waveguide and the single-photon router with 100% routing probability in two waveguides can be achieved. Interesting enough, whether the nonreciprocal single-photon transport or the single-photon router can be switched periodically by adjusting the phase associated with microcavity–emitter coupling strength and the driving field. The complete physical explanation of the underlying mechanism is presented.
We study the controllable single-photon scattering via a one-dimensional waveguide which is coupled to a two-level emitter and a single-mode cavity simultaneously. The emitter and the cavity are also coupled to each other and form a three-level system with cyclic transitions within the zero- and single-excitation subspaces. As a result, the phase of emitter-cavity coupling strength serves as a sensitive control parameter. When the emitter and cavity locate at the same point of the waveguide, we demonstrate the Rabi splitting and quasidark-state-induced perfect transmission for the incident photons. More interestingly, when they locate at different points of the waveguide, a controllable nonreciprocal transmission can be realized and the nonreciprocity is robust to the weak coupling between the system and environment. Furthermore, we demonstrate that our theoretical model is experimentally feasible with currently available technologies.
The implementation of quantum routers is an important and desired task in quantum information science, since quantum routers are important components of quantum networks. Here, we propose a scheme for implementing single-photon routers in a waveguide-QED system, which consists of two coupled two-level atoms coupled to two waveguides to form a four-port quantum device. We obtain the exact analytical expressions of the single-photon scattering amplitudes using the real-space method. By taking the propagating time of photons between two coupling points into account or not, we consider the system working in the Markovian and non-Markovian regimes, respectively. In addition, we introduce the chiral coupling, which breaks the symmetry of the waveguide model, to manipulate the transmission of single photons. We find that when the system works in the non-Markovian regime, the single photon can be transmitted on demand by adjusting the asymmetry coefficient. More interestingly, the complete single-photon routing in this device does not require an ideal chiral coupling, loosening the photon transport conditions. This work will motivate the studies concerning the nonreciprocal and chiral quantum devices in the waveguide-QED platform.
Abstract We present a theoretical study of controlled single-photon routing in a cavity-quantum electrodynamics system coupled to dual waveguides, where each cavity embedding with a two-level atom mediates photon transport between two channels. The proposed system achieves enhanced routing performance through tailored phase-dependent cavity–waveguide couplings that generate optimized quantum interference patterns. Using a real-space formalism, we derive analytical expressions for single-photon scattering amplitudes and identify optimal conditions for maximum routing efficiency. Our analysis shows that targeted routing with near-unity efficiency can be realized by precisely manipulating both the accumulated phase and differential phase shift, while the atom–cavity coupling strength enables frequency-selective tunability. Furthermore, we demonstrate engineered nonreciprocal transmission and chiral scattering, enabling deterministic control over photonic propagation direction. This phase-tunable protocol establishes a scalable platform for quantum network implementation and enables novel functionalities in photonic quantum information processing.
Abstract The photon router plays an essential role in the optical quantum network. However, conventional routers generally couple photons chirally into waveguides to achieve complete transmission from the input port to the required port. Here, we use non-chiral photon-atom interactions for targeted routing. The system consists of two V-type three-level atoms and two parallel waveguides. In addition, the two atoms are driven by external coherent fields, respectively. With a real-space Hamiltonian, the probability of photon transmitted to four ports can be obtained. The study shows that a single photon input from the left port of the waveguide-a can be deterministically transferred to any of the four ports of the two waveguides by adjusting the detuning of the atom and the driving field on the atom, as well as the distance between the two atoms.
Abstract We propose a potentially practical scheme for constructing a quantum network based on a system where three waveguides are coupled to two two-level atoms. In the case of chiral couplings between the waveguides and atoms, we realize a directed single-photon router and the efficiency of single-photon routing reaches 100%. In addition, in this network, the photon input from one port of the channel can be fully routed to any outport of the other two channels by modulating the coupling strength of the waveguides and atoms and the frequency of the incident photon. Thus, a quantum network can be constructed based on our scheme. The influence of the ratio of chiral coupling strength on the properties of the single-photon router is also shown. We also show how the efficiency of routing is affected by system dissipation.
We investigate the controllable single-photon transport via a microresonator coupled to two meandering waveguides at multiple coupling points. Using the analytical expressions of the single-photon scattering amplitudes obtained by the real-space Hamiltonian, the transport characteristics in the waveguide system are demonstrated. These results show that the perfectly nonreciprocal transmission in a single waveguide and the directional routing approaching the unity probability in two waveguides can be achieved by adjusting the resonator-waveguide coupling related to the phase parameter, arising from the phase-dependent interference effect of the multiple point couplings of the resonator. Our proposal may have wide potentials in quantum information processing.