We present a basic building block of a quantum network consisting of a quantum dot coupled to a source cavity, which in turn is coupled to a target cavity via a waveguide. The single photon emission from the high-Q/V source cavity is characterized by a twelve-fold spontaneous emission (SE) rate enhancement that results in a SE coupling efficiency near 0.98 into the source cavity mode. Single photons are efficiently transferred into the target cavity through the waveguide, with a source/target field intensity ratio of 0.12 (up to 0.49 observed in other structures without coupled quantum dots). This system shows great promise as a building block of future on-chip quantum information processing systems.

https://arxiv.org/pdf/quant-ph/0609053.pdf

Generation and transfer of single photons on a photonic crystal chip

Excitation of a bound state in the continuum (BIC) through scattering is problematic since it is by definition uncoupled. Here, we consider a type of dressed BIC and show that it can be excited in a nonlinear system through multiphoton scattering and delayed quantum feedback. The system is a semi-infinite waveguide with linear dispersion coupled to a qubit, in which a single-photon, dressed BIC is known to exist. We show that this BIC can be populated via multiphoton scattering in the non-Markovian regime, where the photon delay time (due to the qubit-mirror distance) is comparable with the qubit's decay. A similar process excites the BIC existing in an infinite waveguide coupled to two distant qubits, thus yielding stationary entanglement between the qubits. This shows, in particular, that single-photon trapping via multiphoton scattering can occur without band edge effects or cavities, the essential resource being instead the delayed quantum feedback provided by a single mirror or the emitters themselves.

Exciting a Bound State in the Continuum through Multiphoton Scattering Plus Delayed Quantum Feedback

At the start of this millennium, the principles of structured illumination microscopy (SIM) had been established and the concept of resolution doubling demonstrated experimentally in two dimensions. Breathtaking advances have since taken place, making SIM one of the most powerful and versatile superresolution methods available today, routinely used in the study of biochemical processes in laboratories around the world. In theory there is no inherent limit to the resolution obtainable with certain modalities of SIM, and new variants have the potential to operate at even higher speeds and sensitivity than currently realized. In this review, we focus on the very latest innovations in SIM theory and practice, which are set to continue the revolution of this method into the future. Examples include confocal implementations of the SIM principle, which can be used in combination with two-photon excitation and adaptive optics. We present recent applications of such approaches in the life sciences, which illustrate their potential to revolutionize intravital research, by providing the ability to watch life at the molecular scale, at high speeds, and deep within living organisms. A different variant makes use of standing plasmonic waves or localized surface plasmons to confer performance enhancements to 2D SIM modalities. Research on these latter techniques is in its infancy but already shows great potential for their development into powerful in vitro probes for chemical processes at solid/liquid interfaces. Physical concepts are reviewed in detail, and future directions are presented along which the field might fruitfully develop, holding promise for new discoveries on the molecular scale.

Frontiers in structured illumination microscopy

Collective coupling between dipoles can dramatically modify the optical response of a medium. Such effects depend strongly on the geometry of the medium and the polarization of the light. Using a classical coupled dipole model, here we investigate the simplest case of one-dimensional arrays of interacting atomic dipoles driven by a weak laser field. Changing the polarization and direction of the driving field allows us to separately address superradiant, subradiant, redshifted, and blueshifted eigenmodes, as well as observe strong Fano-like interferences between different modes. The cooperative eigenvectors can be characterized by the phase difference between nearest-neighbor dipoles, ranging from all oscillating in phase to all oscillating out of phase with their nearest neighbors. Investigating the eigenvalue behavior as a function of atom number and lattice spacing, we find that certain eigenmodes of an infinite atomic chain have the same decay rate as a single atom between two mirrors. The effects we observe provide a framework for collective control of the optical response of a medium, giving insight into the behavior of more complicated geometries, as well as providing further evidence for the dipolar analog of cavity QED.

/pdf/cooperative-eigenmodes-and-scattering-in-one-dimensional-1k3h0y2tgi.pdf

Cooperative eigenmodes and scattering in one-dimensional atomic arrays.

https://iopscience.iop.org/article/10.1088/0031-8949/91/6/063004/pdf

Photon transport in a one-dimensional nanophotonic waveguide QED system

We study the dynamics of a single-photon pulse traveling through a linear atomic chain coupled to a one-dimensional (1D) single mode photonic waveguide. We derive a time-dependent dynamical theory for this collective many-body system which allows us to study the real time evolution of the photon transport and the atomic excitations. Our analytical result is consistent with previous numerical calculations when there is only one atom. For an atomic chain, the collective interaction between the atoms mediated by the waveguide mode can significantly change the dynamics of the system. The reflectivity of a photon can be tuned by changing the ratio of coupling strength and the photon linewidth or by changing the number of atoms in the chain. The reflectivity of a single-photon pulse with finite bandwidth can even approach $100%$. The spectrum of the reflected and transmitted photon can also be significantly different from the single-atom case. Many interesting physical phenomena can occur in this system such as the photonic band-gap effects, quantum entanglement generation, Fano-like interference, and superradiant effects. For engineering, this system may serve as a single-photon frequency filter, single-photon modulation, and may find important applications in quantum information.

Single-photon transport through an atomic chain coupled to a one-dimensional nanophotonic waveguide

Using graphene plasmons (GPs), we can realize a nanometer-scale microscopy. Our scheme takes advantage of the extremely large wave number of GPs and the low loss of graphene. Comparing with conventional nonlinear structured-illumination microscopy based on high-order nonlinearity associated with high intensity light, our proposal only requires linear response. Consequently we need a very weak field, which means less damage to the sample and which may play a significantly important role in the imaging of the biological systems.

/pdf/nanometer-scale-microscopy-via-graphene-plasmons-2a1khfzlqx.pdf

Nanometer-scale microscopy via graphene plasmons

The Goos-Hanchen (GH) shift of light beam incident on graphene ribbon array is investigated by Green’s function method. Due to the resonance effects of leaky surface plasmons on ribbons, the zeroth-order reflection field shows both giant positive and negative GH shifts. By tuning the graphene Fermi level, we can control the shift conveniently. This effect is important to graphene-based metasurface and electro-optical devices.

Tunable Goos-Hänchen shift from graphene ribbon array.

The dielectric cylinder covered with graphene (DCCG) is found to be a promising platform for studying multi-qubit collective effects. The plasmons supported by DCCG have huge wave numbers and low loss. Under some conditions, the zeroth- and first-order modes even have the same wavelength. Qubits along DCCG can interact with each other strongly by coupling with the plasmons within tens to hundreds of plasmonic wavelengths. Additionally, the electro-optical tunability of graphene means that we can manipulate the plasmonic wavelength and subsequently the dynamic evolutions of the qubits mediated by the DCCG conveniently. These properties make the graphene be a potential choice for quantum information device.

https://iopscience.iop.org/article/10.1209/0295-5075/115/14002/pdf

Xiaodong Zeng

Papers

Photon transport in a one-dimensional nanophotonic waveguide QED system

Single-photon transport through an atomic chain coupled to a one-dimensional nanophotonic waveguide

Nanometer-scale microscopy via graphene plasmons

Tunable Goos-Hänchen shift from graphene ribbon array.

Controllable waveguide via dielectric cylinder covered with graphene: Tunable entanglement