We obtain a general result for the Lamb shift of excited states of multi-level atoms in inhomogeneous electromagnetic structures and apply it to study atomic hydrogen in inverse-opal photonic crystals. We find that the photonic-crystal environment can lead to very large values of the Lamb shift, as compared to the case of vacuum. We also predict that the position-dependent Lamb shift should extend from a single level to a mini-band for an assemble of atoms with random distribution in space, similar to the velocity-dependent Doppler effect in atomic/molecular gases.
Spontaneous emission of an excited atom in a featureless continuum of electromagnetic modes is a fundamental process in quantum electrodynamics associated with an exponential decay of the quantum emitter to its ground state accompanied by an irreversible emission of a photon. However, such a simple scenario is deeply modified when considering a $^{\prime}$giant$^{\prime}$ atom, i.e an atom whose dimension is larger than the wavelength of the emitted photon. In such an unconventional regime, non-Markovian effects and strong deviations from an exponential decay are observed owing to interference…
Photonic state engineering via energy-level crossing by giant atoms in topological waveguide QED setup
School of Physics Science and Technology, Shenyang Normal University（沈阳师范大学物理科学与技术学院）；School of Physical Science and Technology, Soochow University（苏州大学物理科学与技术学院）；Center for Quantum Sciences and School of Physics, Northeast Normal University（东北师范大学量子科学中心与物理学院）
Optical non-linearities usually appear for large intensities, but discrete transitions allow for giant non-linearities operating at the single photon level. This has been demonstrated in the last decade for a single optical mode with cold atomic gases, or single two-level systems coupled to light via a tailored photonic environment. Here we demonstrate a two-modes giant non-linearity by using a three-level structure in a single semiconductor quantum dot (QD) embedded in a photonic wire antenna. The large coupling efficiency and the broad operation bandwidth of the photonic wire enable us to ha…
Giant Purcell broadening and Lamb shift for DNA-assembled near-infrared quantum emitters
Ecole Polytechnique Fédérale de Lausanne (EPFL)（洛桑联邦理工学院）；University of Fribourg（弗里堡大学）；Materials Physics Center CSIC-UPV/EHU（CSIC-巴斯克国立自治大学材料物理中心）；Donostia International Physics Center (DIPC)（圣塞巴斯蒂安国际物理中心）；Ikerbasque, Basque Foundation for Science（伊克拉巴斯科，巴斯克科学基金会）；University of the Basque Country (UPV/EHU)（巴斯克国立自治大学）
Nanyang Technological University（南洋理工大学）；MajuLab, International Joint Research Unit UMI 3654, CNRS, Université Côte d’Azur, Sorbonne Université, National University of Singapore, Nanyang Technological University, Singapore（MajuLab，国际联合研究单位UMI 3654，法国国家科学研究中心，蔚蓝海岸大学，索邦大学，新加坡国立大学，南洋理工大学）；Centre for Disruptive Photonic Technologies（颠覆性光子技术中心）
Atomic Quantum Memory for Photonic Qubits via Scattering in Cavity QED
研究了一种在腔QED中存储光子量子比特的原子量子存储方案。这是基于最近的观察，即在强耦合腔机制中，单光子脉冲与腔中的λ型原子之间的量子态交换在某些特定情况下是通过散射理想地实现的[T. W. Chen C.，马缨丹属K.法律，和PT。Leung，Phys.Rev.A69，063810（2004）]。我们推导出一个简单的公式来计算这种原子-光子交换对量子存储器的保真度。我们进一步提出了一种可行的方法，即使在原子-光子耦合不太强的情况下，也可以有条件地实现保真度几乎为1的量子存储操作。这种方法也可以应用于在空间分离的原子量子存储器中存储光子纠缠。
Giant-atom-enabled quantum optics with valley-polarized photons
Quantum Advanced Research Center (QuARC), CSIC（量子先进研究中心 (QuARC)，西班牙国家科学研究委员会）；Institute of Fundamental Physics (IFF), CSIC（基础物理研究所 (IFF)，西班牙国家科学研究委员会）；National Institute of Optics (CNR-INO)（意大利国家光学研究所 (CNR-INO)）；European Laboratory for Non-Linear Spectroscopy (LENS)（欧洲非线性光谱学实验室 (LENS)）
The giant atom system is a new paradigm in quantum optics, in which the traditional dipole approximation is not available. In this paper, we construct an artificial giant atom model by coupling a superconducting circuits to a transmission line by two coupling points. In the ultrastrong coupling regime, we show that the Lamb shift of the giant atom, which is induced by the non-negligible counter-rotating atom-waveguide coupling term, will modify its dissipation process. Furthermore, we investigate quantum Zeno and anti-Zeno effect where the size of the giant atom serves as a sensitive controlle…
We investigate the dynamics of giant atom(s) in a waveguide QED scenario, where the atom couples to the coupled resonator waveguide via two sites. For a single giant atom setup, we find that the atomic dissipation rate can be adjusted by tuning its size. For the two giant atoms system, the waveguide will induce the controllable individual and collective dissipation as well as effective inter-atom coupling. As a result, we can theoretically realize the robust entangled state preparation and non-reciprocal excitation evolution. We hope our study can be applied in quantum information processing b…
We propose tunable chiral bound states in a system composed of superconducting giant atoms and a Josephson photonic-crystal waveguide (PCW), with no analog in other quantum setups. The chiral bound states arise due to interference in the nonlocal coupling of a giant atom to multiple points of the waveguide. The chirality can be tuned by changing either the atom-waveguide coupling or the external bias of the PCW. Furthermore, the chiral bound states can induce directional dipole-dipole interactions between multiple giant atoms coupling to the same waveguide. Our proposal is ready to be implemen…
Quantum optics with giant emitters has shown a new route for the observation and manipulation of non-Markovian properties in waveguide-QED. In this paper we extend the theory of giant atoms, hitherto restricted to the perturbative light-matter regime, to deal with the ultrastrong coupling regime. Using static and dynamical polaron methods we address the low energy subspace of a giant atom coupled to an Ohmic waveguide beyond the standard rotating wave approximation. We analyze the equilibrium properties of the system by computing the atomic frequency renormalization as a function of the coupli…
The interaction between the quantum emitter and topological photonic system makes both the emitter and the photon behave in exotic ways. We here study a system that a giant atom is coupled to two points of a one-dimensional topological waveguide formed by the Su-Schrieffer-Heeger (SSH) chain. The topological nature of the hybrid system is studied. We find that the giant atom can act as an effective boundary and induce the chiral zero energy modes for the waveguide under the periodical boundary. The properties of these modes are similar to those in the SSH model with open boundary. Meanwhile, t…
Emitters coupled simultaneously to distant positions of a photonic bath, the so-called giant atoms, represent a new paradigm in quantum optics. When coupled to one-dimensional baths, as recently implemented with transmission lines or SAW waveguides, they lead to striking effects such as chiral emission or decoherence-free atomic interactions. Here, we show how to create giant atoms in dynamical state-dependent optical lattices, which offers the possibility of coupling them to structured baths in arbitrary dimensions. This opens up new avenues to a variety of phenomena and opportunities for qua…
In this paper, we begin with a model of a $Λ$-type atom whose both transitions are chirally coupled to a waveguide and then extend the model to its giant-atom version. We investigate the single-photon scatterings of the giant-atom model in both the Markovian and non-Markovian regimes. It is shown that the chiral atom-waveguide couplings enable nonreciprocal, reflectionless, and efficient frequency conversion, while the giant-atom structure introduces intriguing interference effects to the scattering behaviors, such as ultra-narrow scattering windows. The chiral giant-atom model exhibits quite …
Giant atoms -- quantum emitters that couple to light at multiple discrete points -- are emerging as a new paradigm in quantum optics thanks to their many promising properties, such as decoherence-free interaction. While most previous work has considered giant atoms coupled to open continuous waveguides or a single giant atom coupled to a structured bath, here we study the interaction between two giant atoms mediated by a structured waveguide, e.g., a photonic crystal waveguide. This environment is characterized by a finite energy band and a band gap, which affect atomic dynamics beyond the Mar…
We investigate the single-photon scattering spectra of a giant atom coupled to a one dimensional waveguide via multiple connection points or a continuous coupling region. Using a full quantum mechanical method, we obtain the general analytic expressions for the single-photon scattering coefficients, which are valid in both the Markovian and the non-arkovian regimes. We summarize the influences of the non-dipole effects, mainly caused by the phases accumulated by photons traveling between coupling points, on the scattering spectra. We find that under the Markovian limit, the phase decay is detu…
