56 research outputs found
Dynamical theory of single photon transport in a one-dimensional waveguide coupled to identical and non-identical emitters
We develop a general dynamical theory for studying a single photon transport
in a one-dimensional (1D) waveguide coupled to multiple emitters which can be
either identical or non-identical. In this theory, both the effects of the
waveguide and non-waveguide vacuum modes are included. This theory enables us
to investigate the propagation of an emitter excitation or an arbitrary single
photon pulse along an array of emitters coupled to a 1D waveguide. The
dipole-dipole interaction induced by the non-waveguide modes, which is usually
neglected in the literatures, can significantly modify the dynamics of the
emitter system as well as the characteristics of output field if the emitter
separation is much smaller than the resonance wavelength. Non-identical
emitters can also strongly couple to each other if their energy difference is
smaller than or of the order of the dipole-dipole energy shift. Interestingly,
if their energy difference is close but non-zero, a very narrow transparency
window around the resonance frequency can appear which does not occur for
identical emitters. This phenomenon may find important applications in quantum
waveguide devices such as optical switch and ultra narrow single photon
frequency comb generator.Comment: 17 pages, 8 figure
Magnetic Resonance Lithography with Nanometer Resolution
We propose an approach for super-resolution optical lithography which is
based on the inverse of magnetic resonance imaging (MRI). The technique uses
atomic coherence in an ensemble of spin systems whose final state population
can be optically detected. In principle, our method is capable of producing
arbitrary one and two dimensional high-resolution patterns with high contrast
Single Photon Transport through an Atomic Chain Coupled to a One-dimensional Nanophotonic Waveguide
We study the dynamics of a single photon pulse travels 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 . 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 bandgap 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
Optical Lithography and Atom Localization beyond the Diffraction Limit via Rabi Gradient
The resolution of traditional optical microscope and optical lithography is limited by about half wavelength of the light source, which is well known as the diffraction limit or Abbe limit. The resolution limit is due to the missing of high spatial frequency components in the far-field. One way to achieve high resolution is to move the detector into the near-field region where the evanescent wave can be collected. However, these methods are surface-bound and usually very slow which have limited applications. It has long been an interesting and important question about how to overcome the diffraction limit in the far-field.
For optical lithography, a number of methods have been proposed to overcome the diffraction limit such as multi-photon scanning, quantum entanglement, quantum inspired process (e.g., dopperlon), and quantum dark state. However, these methods either require multi-photon absorber, quantum entanglement, or multi-energy levels, which restrict them from extending to higher resolution in practice. In this thesis, we showed that sub-diffraction-limited resolution can be generated by the coherent Rabi gradient. This method does not require multi-photon absorber or quantum entanglement but just quantum coherence of the medium. Extension from lower resolution to higher resolution is very straightforward where we just need to increase the pulse intensity or pulse duration. We also proposed two atom lithography experiments based on the Rabi gradient. The first one uses Rubidium Rydberg atom and microwave where we showed that sub-micrometer line spacing is possible. The second one uses Chromium atom and optical field where we showed that sub-10nm line spacing is possible while the wavelength of the light is about 400nm.
For optical imaging, a number of methods have also been proposed to achieve super-resolution such as multi-photon microscope, stimulated-emission-depletion, structured illumination microscopy, centroid-based techniques and metamaterial-based lens. Here, we will show a new method to achieve resolution beyond the diffraction limit which we called it resonance fluorescence microscopy. Resonance fluorescence has been proposed to localize a single atom with resolution beyond the diffraction limit. The separation between two atoms can also be extracted from the resonance
fluorescence spectrum. To develop it as microscopy, we need to evaluate the resonance fluorescence spectrum of multiple-atom system. We analytically solved the general feature of the spectrum when the Rabi frequency is much larger than the dipole-dipole interaction and showed how to extract the spatial information of the atoms with resolution far beyond the diffraction limit. This method is entirely based on far-field techniques and it does not require point-by-point scanning
Dressed bound states at chiral exceptional points
Atom-photon dressed states are a basic concept of quantum optics. Here, we
demonstrate that the non-Hermiticity of open cavity can be harnessed to form
the dressed bound states (DBS) and identify two types of DBS, the vacancy-like
DBS and Friedrich-Wintgen DBS, in a microring resonator operating at a chiral
exceptional point. With the analytical DBS conditions, we show that the
vacancy-like DBS occurs when an atom couples to the standing wave mode that is
a node of photonic wave function, and thus is immune to the cavity dissipation
and characterized by the null spectral density at cavity resonance. While the
Friedrich-Wintgen DBS can be accessed by continuously tuning the system
parameters, such as the atom-photon detuning, and evidenced by a vanishing Rabi
peak in emission spectrum, an unusual feature in the strong-coupling
anticrossing. We also demonstrate the quantum-optics applications of the
proposed DBS. Our work exhibits the quantum states control through
non-Hermiticity of open quantum system and presents a clear physical picture on
DBS at chiral exceptional points, which holds great potential in building
high-performance quantum devices for sensing, photon storage, and nonclassical
light generation.Comment: 13 pages, 5 figure
Protecting quantum entanglement from amplitude damping
Quantum entanglement is a critical resource for quantum information and
quantum computation. However, entanglement of a quantum system is subjected to
change due to the interaction with the environment. One typical result of the
interaction is the amplitude damping that usually results in the reduction of
the entanglement. Here we propose a protocol to protect quantum entanglement
from the amplitude damping by applying Hadamard and CNOT gates. As opposed to
some recently studied methods, the scheme presented here does not require weak
measurement in the reversal process, leading to a faster recovery of
entanglement. We propose a possible experimental implementation based on linear
optical system
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