Exceptional cavity quantum electrodynamics

An open quantum system operated at the spectral singularities where dimensionality reduces, known as exceptional points (EPs), demonstrates distinguishing behavior from the Hermitian counterpart. Based on the recently proposed microcavity with exceptional surface (ES), we report and explain the peculiar quantum dynamics in atom-photon interaction associated with EPs: cavity transparency, decoherence suppression beyond the limitation of Jaynes-Cummings (JC) system, and the population trapping of lossy cavity. An analytical description of the local density of states (LDOS) for ES microcavity is derived from an equivalent cavity quantum electrodynamics (QED) model, which goes beyond the single-excitation approximation and allows exploring the quantum effects of EPs on multiphoton process by parametrizing the extended cascaded quantum master equation. It reveals that a square Lorentzian term in LDOS induced by second-order EPs interferes with the linear Lorentzian profile, giving rise to cavity transparency for atom with special transition frequency in the weak coupling regime. This additional contribution from EPs also breaks the limit on dissipation rate of JC system bounded by bare components, resulting in the decoherence suppression with anomalously small decay rate of the Rabi oscillation and the long-time dynamics. Remarkably, we find that the cavity population can be partially trapped at EPs, achieved by forming a bound dressed state in the limiting case of vanishing atom decay. Our work unveils the exotic phenomena unique to EPs in cavity QED systems, which opens the door for controlling light-matter interaction at the quantum level through non-Hermiticity, and holds great potential in building high-performance quantum-optics devices.Comment: 11 pages, 6 figure

The Effects of Borehole Ovality on Bare Hole Horizontal Well Completion String Tripping in Friction

Under the effect of non-uniform ground stress, the borehole becomes oval. The deformation regulations and friction calculation in oval borehole has great difference with which in circular borehole. Researching the effect of the ovality of borehole on string tripping in friction is of great significance. In this paper, the string deformation model in oval borehole was established; the maximum displacement changes with different ratios of the major and minor axis and inclination angles were analyzed. The deformation model between two contacting points was established, and the determining method of the new contacting point of multi-packer completion string was proposed. The friction calculating model was established finally.The Hongping 9 well was used as an example to calculate the effect of borehole ovality on the bare hole completion string tripping in friction. By calculating, the friction calculated using the model was in good agreement with the measured value. The friction of completion string is almost zero in vertical section, and in blending and horizontal section the friction is increasing gradually. With the increasing of ovality the friction is increasing. The ovality increases from 1.0 to 1.3, the increasing value of friction is 36.59 kN.Key words: Borehole ovality; Completion string; Bare hole completion; Frictio

Improved Lower Bounds for Approximating Parameterized Nearest Codeword and Related Problems under ETH

In this paper we present a new gap-creating randomized self-reduction for parameterized Maximum Likelihood Decoding problem over $\mathbb{F}_p$ ($k$-MLD$_p$). The reduction takes a $k$-MLD$_p$ instance with $k\cdot n$ vectors as input, runs in time $f(k)n^{O(1)}$ for some computable function $f$, outputs a $(3/2-\varepsilon)$-Gap-$k'$-MLD$_p$ instance for any $\varepsilon>0$, where $k'=O(k^2\log k)$. Using this reduction, we show that assuming the randomized Exponential Time Hypothesis (ETH), no algorithms can approximate $k$-MLD$_p$ (and therefore its dual problem $k$-NCP$_p$) within factor $(3/2-\varepsilon)$ in $f(k)\cdot n^{o(\sqrt{k/\log k})}$ time for any $\varepsilon>0$. We then use reduction by Bhattacharyya, Ghoshal, Karthik and Manurangsi (ICALP 2018) to amplify the $(3/2-\varepsilon)$-gap to any constant. As a result, we show that assuming ETH, no algorithms can approximate $k$-NCP$_p$ and $k$-MDP$_p$ within $\gamma$-factor in $f(k)n^{o(k^{\varepsilon_\gamma})}$ time for some constant $\varepsilon_\gamma>0$. Combining with the gap-preserving reduction by Bennett, Cheraghchi, Guruswami and Ribeiro (STOC 2023), we also obtain similar lower bounds for $k$-MDP$_p$, $k$-CVP$_p$ and $k$-SVP$_p$. These results improve upon the previous $f(k)n^{\Omega(\mathsf{poly} \log k)}$ lower bounds for these problems under ETH using reductions by Bhattacharyya et al. (J.ACM 2021) and Bennett et al. (STOC 2023).Comment: 32 pages, 3 figure

Enhanced coherent light-matter interaction and room-temperature quantum yield of plasmonic resonances engineered by a chiral exceptional point

Strong dissipation of plasmonic resonances is detrimental to quantum manipulation. To enhance the quantum coherence, we propose to tailor the local density of states (LDOS) of plasmonic resonances by integrating with a photonic cavity operating at a chiral exceptional point (CEP), where the phase of light field can offer a new degree of freedom to flexibly manipulate the quantum states. A quantized few-mode theory is employed to reveal that the LDOS of the proposed hybrid cavity can evolve into sub-Lorentzian lineshape, with order-of-magnitude linewidth narrowing and additionally a maximum of eightfold enhancement compared to the usual plasmonic-photonic cavity without CEP. This results in the enhanced coherent light-matter interaction accompanied by the reduced dissipation of polaritonic states. Furthermore, a scattering theory based on eigenmode decomposition is present to elucidate two mechanisms responsible for the significant improvement of quantum yield at CEP, the reduction of plasmonic absorption by the Fano interference and the enhancement of cavity radiation through the superscattering. Importantly, we find the latter allows achieving a near-unity quantum yield at room temperature; in return, high quantum yield is beneficial to experimentally verify the enhanced LDOS at CEP by measuring the fluorescence lifetime of a quantum emitter. Therefore, our work demonstrates that the plasmonic resonances in CEP-engineered environment can serve as a promising platform for exploring the quantum states control by virtue of the non-Hermiticity of open optical resonators and building the high-performance quantum devices for sensing, spectroscopy, quantum information processing and quantum computing.Comment: 20 pages,9 figure

The Effects of Pore Pressure and Temperature Difference Variation on Borehole Stability

Considering that drilling fluid filtration and the temperature difference between borehole wall rock and drilling fluid can cause the stress variation of the borehole wall. The stress distribution model was derived under the effect of thermal-flow-solid coupling. The safe mud density window calculating model considering pore pressure and temperature difference variation was established according to Moore-Coulomb criterion and borehole wall rock tensile failure criterion. The result calculated by the model can be expressed as follow. (1) When the temperature difference between borehole rock and drilling fluid is constant, with the enhancement of fluid filtration, borehole rock pore pressure increasing, the collapse pressure increasing, breakdown pressure decreasing, the stability of the borehole becomes deteriorating. (2) When the borehole wall rock pore pressure is constant, if drilling fluid makes wall rock temperature decreasing, with the temperature difference increasing, both the collapse pressure and breakdown pressure decreasing, the stability of the borehole becoming deteriorating, it is not conducive to drilling safely. If drilling fluid make wall rock temperature increasing, with the temperature difference increasing, both the collapse pressure and breakdown pressure increasing, the borehole tending to stabilize, it is conducive to drilling safely.Key words: Pore pressure; Temperature difference; Borehole stability; Safe mud density windo

Surface Studies on the Structure and Functionality of Bioactive Materials.

Bioactive materials are critical in many applications in the fields ranging from antibiofouling coatings to tissue engineering to biosensing devices. The construction of bioactive materials generally involves dispersion of bioactive components such as biocides, peptides or proteins in organic or inorganic matrices. However, when these bioactive components are incorporated to such matrices, their functionalities may be significantly hindered. As a result, it has spurred great attention seeking guidelines for future rational design and development of bioactive materials with optimal functionalities. This thesis proposes optimization strategies by investigating interfacial molecular interactions of various bioactive materials in situ using surface specific spectroscopies and correlating the structural and orientational information to their activity. Firstly, two biocide-incorporated antifouling polymeric materials are characterized using sum frequency generations vibrational spectroscopy at solid/liquid interfaces. The interaction mechanism is unraveled by varying both biocidal and the polymer components of the system. The structure of the alkyl chains from the biocidal components is determined and by comparing to their antifouling performance, it is concluded that the protruding-out state offers the best antifouling activity. Factors that affect the structure of the biocidal components are examined. Secondly, antimicrobial peptides are immobilized to various surface platforms. The immobilization processes are thoroughly monitored and the final immobilized peptide structures and orientations are determined using spectroscopic technique. The immobilization environment, the location of the attachment point and the peptide sequence all play important roles in determining the immobilization process and the final state of the immobilized peptides. Finally, a model enzyme is immobilized to solid surfaces and characterized by using combined spectroscopic measurements. These results are further correlated to the enzymatic activities and confirmed by molecular dynamics simulations performed by our collaborators. It is concluded that the surface properties, the location of the attachment point, the secondary structure of the attachment point are factors influencing the immobilized enzyme structure and further determining the activity and stability of the immobilized enzyme. In all, this thesis provides systematic understanding how structural differences are related to the difference in the functionality of the bioactive materials under study based on which the optimization designing rules are proposed.PHDChemistryUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/109042/1/yuweiliu_1.pd