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Applied Physics Letters

Controllable nonreciprocal single-photon frequency converter via a four-level system

Ya Jun Yang, Jing Lu, Lan Zhou

Published Apr 1, 2024• 5 citations
Publisher

Abstract

We propose an efficient, nonreciprocal single-photon device that achieves single-photon routing and frequency conversion through chiral coupling of two one-dimensional waveguides with a four-level atom. Photons incoming from one port can be definitely directed to another port. However, the photon frequency conversion has been achieved only when the single photons are transferred from one waveguide to the other, and its probability can reach unity. Applied the on-demand classical field to drive an atom, the transmission quantum tunneling path can be turned off and on by exploiting the Autler–Townes splitting mechanism. Our results illustrate the potential of our device for applications in a quantum network.

DOI
10.1063/5.0197437

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We propose an efficient, nonreciprocal single-photon device that achieves single-photon routing and frequency conversion through chiral coupling of two one-dimensional waveguides with a four-level atom. Photons incoming from one port can be definitely directed to another port. However, the photon frequency conversion has been achieved only when the single photons are transferred from one waveguide to the other, and its probability can reach unity. Applied the on-demand classical field to drive an atom, the transmission quantum tunneling path can be turned off and on by exploiting the Autler–Townes splitting mechanism. Our results illustrate the potential of our device for applications in a quantum network.
We propose a single-photon frequency converter via a one-dimensional waveguide coupled to a three-level VVV-type atom. An on-demand classical driving field is used to couple to the atom, allowing it to absorb a photon with a given frequency and then emit a photon with a different carried frequency. We study such a single-photon frequency conversion mechanism in two kinds of realistic physical systems: the system of coupled-resonator waveguide with cosine dispersion relation and the one of waveguide with linear dispersion relation. To demonstrate the single-photon transfer efficiency, we introduce the concept of scattering flows via the calculation of group velocities and find that the driving field prefers to be weak in the coupled-resonator waveguide but arbitrarily strong in the linear waveguide to achieve an optimal transfer efficiency. Furthermore, we demonstrate that our theoretical model is experimentally feasible with currently available technologies.
Abstract Single-photon frequency conversion in the system composed of a Λ -type three-level giant atom chiral couples to a one-dimensional waveguide is investigated. Two configurations, i.e. one of the atomic transitions couples to the waveguide at two separated points while the other one either directly or indirectly couples to the waveguide at a single point, are considered. The scattering amplitudes for representing the frequency conversion in the two kinds of coupling schematics are obtained analytically with the real-space approach. The results show that perfect nonreciprocal transmission with preserving frequency and ideal directional frequency conversion can be realized due to the time-reversal symmetry broken induced by the chiral coupling as well as the self-interference comes from the giant atom. In particular, in the indirect coupling configuration, the scattering spectra exhibit two directional frequency conversion windows due to the atom-cavity coupling, which enables the present system suitable for the simultaneous manipulation of incident photons with different frequencies. These results may have potential applications in various quantum information processing and quantum network engineering.
We demonstrate the possibility of designing efficient, nonreciprocal few-photon devices by exploiting the chiral coupling between two waveguide modes and a single quantum emitter. We show how this system can show nonreciprocal photon transport at the single-photon level by exploiting a single-photon routing mechanism. Afterwards, we also demonstrate how the fundamentally different two-photon response makes the system show a transistorlike behavior, where a first photon can open a transmission channel for a second incoming photon. The efficiency in both cases is shown to be large for feasible experimental implementations. Our results illustrate the potential of chiral waveguide-emitter couplings for applications in quantum circuitry.
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.
We propose to construct a nonreciprocal single-photon frequency converter via multiple semi-infinite coupled-resonator waveguides (CRWs). We first demonstrate that the frequency of a single photon can be converted nonreciprocally through two CRWs, which are coupled indirectly by optomechanical interactions with two nondegenerate mechanical modes. Based on this nonreciprocity, two different single-photon circulators are proposed in the T\mathsf{T}T-shaped waveguides consisting of three semi-infinite CRWs, which are coupled pairwise by optomechanical interactions. One circulator is proposed by using two nondegenerate mechanical modes and the other one is proposed by using three nondegenerate mechanical modes. Nonreciprocal single-photon frequency conversion is induced by breaking the time-reversal symmetry, and the optimal conditions for nonreciprocal frequency conversion are obtained. These proposals can be used to realize nonreciprocal frequency conversion of single photons in any two distinctive waveguides with different frequencies and they can allow for dynamic control of the direction of frequency conversion by tuning the phases of external driving lasers, which may have versatile applications in hybrid quantum networks.
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.