Dissipative multilevel giant atoms with waveguide coupling open new avenues for investigating quantum interference and scattering phenomena. Here, we systematically study single-photon scattering in the pair of dissipative three-level giant atoms coupled to a one-dimensional waveguide. We find that destructive interference can suppress frequency conversion while stabilizing the transmission and reflection. And we can obtain the frequency-independent perfect transmission under specific detuning and phase. On the one hand, we present the conditions for realizing destructive interference and frequency-independent perfect transmission. On the other hand, by further considering dissipation, we find that increasing the dissipation rate enhances transmission and reduces reflection. Notably, we find that the system has the ability of maintain stable scattering even under high-loss conditions. Our results suggest that a pair of dissipative three-level giant atoms can provide valuable reference for the design of scalable multi-atom quantum devices.
Dissipative multilevel giant atoms with waveguide coupling open new avenues for investigating quantum interference and scattering phenomena. Here, we systematically study single-photon scattering in the pair of dissipative three-level giant atoms coupled to a one-dimensional waveguide. We find that destructive interference can suppress frequency conversion while stabilizing the transmission and reflection. And we can obtain the frequency-independent perfect transmission under specific detuning and phase. On the one hand, we present the conditions for realizing destructive interference and frequency-independent perfect transmission. On the other hand, by further considering dissipation, we find that increasing the dissipation rate enhances transmission and reduces reflection. Notably, we find that the system has the ability of maintain stable scattering even under high-loss conditions. Our results suggest that a pair of dissipative three-level giant atoms can provide valuable reference for the design of scalable multi-atom quantum devices.
The coupling of three-level giant atoms with one-dimensional waveguides can show interesting phenomena of transmission and reflection. Since the non-waveguide mode can cause the dissipation of external atoms, we consider the effect of the dissipation rate on the scattering of single photons in the system with giant atom–waveguide coupling. We find that as the dissipation rate of giant atoms increases, the transmission rate of a single photon increases and the reflection rate decreases. In addition, by varying the phase difference and decay rate, the giant atoms are able to achieve perfect transmission and total reflection over the entire frequency range. We also find and show the conditions for the conversion of the optimal frequency. When the cumulative phase of photons reaches a certain value, the system can achieve perfect transmission, which is independent of frequency. This model of coupling giant atoms with waveguides has a promising application in quantum communication and quantum information processing.
Abstract We theoretically investigate single-photon scattering and nonreciprocal transmission in a coupled resonator waveguide which is coupled to a driven three-level giant atom via two distant sites. In our system, the local coupling phases are introduced to induce intriguing interference effects. As a result, the phase difference can serve as a sensitive controller for the photon scattering. It is found that the photon scattering properties can be effectively tailored by the size of the giant atom, the driving field and the phase difference. Intriguingly, by carefully tuning the parameters such as the atomic dissipation and the phase difference, a perfect nonreciprocal single-photon transmission can be realized. Additionally, the photon frequency can be adjusted by modulating Rabi frequency of the driving field. These results have significant potential for the development of nonreciprocal optical devices using the giant-atom configuration.
Abstract The single-photon frequency conversion in a one-dimensional waveguide coupled to a giant three-level atom is investigated. The analytical expressions of the single-photon scattering spectra are derived via the real-space Hamiltonian. Numerical results show that high-efficiency frequency conversion of single photons can be achieved by controlling the atom-waveguide coupling due to the phase-dependent interference effect of the multiple point couplings of the giant atom, and the conversion efficiency can ideally reach unity. The conversion spectra in both the Markovian and non-Markovian regimes show that multiple staggered peaks and dips emerge due to the non-Markovian retardation effect, in contrast to a single peak and dip in the Markovian regime. The influence of dissipation on the fidelity of frequency conversion is also displayed, and it shows that the fidelity is not sensitive to dissipation.
Abstract A waveguide-QED with giant atoms, which is capable of accessing various limits of a small one, provides a new paradigm to study photon scatterings. Thus, how to achieve nonreciprocal photon transmissions via such a giant atom setup is highly desirable. In this study, the nonreciprocal single-photon scattering characteristics of a double-driven Λ-type three-level giant atom, where one of the transition couples to a 1D waveguide at two separate points, and the other is driven by two coherent driving fields, are investigated. It is found that a frequency-tunable single-photon diode with an ideal contrast ratio can be achieved by properly manipulating the local coupling phases between the giant atom and the waveguide, the accumulation phase between the two waveguide coupling points, the Rabi frequencies and phase difference of the two driven fields. Compared to the previous single driving schemes, on the one hand, the presence of the second driving field can provide more tunable parameters to manipulate the nonreciprocal single-photon scattering behavior. On the other hand, here perfect nonreciprocal transmission for photons with arbitrary frequencies is achievable by tuning the driving phases while the two driving fields keep on turning, which provides an alternative way to control the nonreciprocal single-photon scattering. Furthermore, the results reveal that both the location and width of each optimal nonreciprocal transmission window is also sensitive to the driving detuning, and a single-photon diode with wide or narrow bandwidth can be realized based on demand. These results may be beneficial for designing nonreciprocal single-photon devices based on a double-driven giant atom setup.
Abstract We explore the scattering and nonreciprocal transmission of single photons in an array of N coherently coupled two-level atoms, with only the two end atoms interacting with a waveguide at distinct spatial points. The chain serves as a giant-atom-like scatterer with internal collective modes. Using the real-space approach, analytical expressions for the scattering amplitudes are obtained. For the ideal case without atomic loss, the transmission is reciprocal and can be modulated by the relative local coupling phase, the accumulated propagation phase, the interatomic hopping strength, and the photon–atom detuning. We further observe that the oscillatory behavior of the transmission spectrum becomes more pronounced as the number of atoms increases. When atomic loss into nonguided modes is included, phase-dependent interference gives rise to dissipation-assisted nonreciprocal transmission. By appropriately tuning the phase factors, the atomic loss rate, and the hopping strength, one can achieve maximal nonreciprocity, corresponding to complete suppression of transmission for one incident direction. These results establish a flexible platform for engineering directional single-photon transport in guided-wave quantum electrodynamics.
The nonlocal emitter-waveguide coupling, which gives birth to the so called giant atom, represents a new paradigm in the field of quantum optics and waveguide QED. In this paper, we investigate the single-photon scattering in a one-dimensional waveguide on a two-level or three-level giant atom. Thanks to the natural interference induced by the back and forth photon transmitted/reflected at the atom-waveguide coupling points, the photon transmission can be dynamically controlled by the periodic phase modulation via adjusting the size of the giant atom. For the two-level giant-atom setup, we demonstrate the energy shift which is dependent on the atomic size. For the driven three-level giant-atom setup, it is of great interest that, the interference effect between different atomic transition paths, can lead to a complete transmission window, analogous to the electromagnetically induced transparency and beyond the two-photon resonance mechanism, and the width of the transmission valleys (reflection range) is tunable in terms of the atomic size. Our investigation will be beneficial to the photon or phonon control in quantum network based on mesoscopical or even macroscopical quantum nodes involving the giant atom.