| 11. |
- Lin, Qi, et al.
(author)
-
Organic carbon burial in a large, deep alpine lake (southwest China) in response to changes in climate, land use and nutrient supply over the past ~100 years
- 2021
-
In: Catena (Cremlingen. Print). - : Elsevier. - 0341-8162 .- 1872-6887. ; 202
-
Journal article (peer-reviewed)abstract
- Inland waterbodies play an important role in the global carbon cycle, acting both as carbon sources with organic carbon (OC) mineralization and as sinks with OC burial in sediments. Under recent impacts of global warming, anthropogenic land-use change and nutrient supply, however, there is a limited knowledge regarding OC dynamics in sediments of large, deep lakes especially in subtropical alpine regions. Here, we studied the patterns of OC burial and the potential regulating factors using multiple sedimentary proxies and observational records in Lugu Lake (southwest China) over the past ~100 years. Comparisons of 15 sediment cores in different areas of the lake reveal similar temporal trends in OC content and other sediment parameters, indicating coherent patterns of whole-lake sedimentary environmental change dominated by watershed human perturbation. Based on C/N ratios and δ13Corg analyses, the sediment OC has primarily been autochthonous in source. OC accumulation rates (OCAR) increased during 1880–1980, from ~14 to 43 g C m−2 yr−1 in a central core (LGS), mainly resulting from elevated primary production under increased phosphorus input and soil erosion. Subsequently, OCAR decreased considerably to ~15 g C m−2 yr−1, although the phosphorus supply and lake primary productivity remained high. We infer the OCAR decline likely resulted from increased organic matter decomposition and OC mineralization in the water column because of climate warming and lake-water thermal stratification. This phenomenon might mask the positive contribution of primary production to OC burial. Our findings suggest that the commonly observed synergistically positive effects of warming and eutrophication on sediment OC burial may be impaired in deep lakes, which needs further investigations across ecological, climatic and land-use gradients.
|
|
| 12. |
- Shen, Jian Qi
(author)
-
A Three-Dimensionally Isotropic and Perfectly Vacuum-Impedance-Matched Negative-Index Material
- 2014
-
In: Journal of the Physical Society of Japan. - 0031-9015 .- 1347-4073. ; 83:12, s. 124401-
-
Journal article (peer-reviewed)abstract
- A new scenario for realizing a gain left-handed atomic vapor medium based on both dressed-state mixed-parity transitions (for simultaneous electric-and magnetic-dipole resonance) and incoherently-pumped population transfer (for high gain amplification) in a four-level atomic system is suggested. Dressed-state assisted simultaneous electric-and magnetic-dipole allowed transitions in such a four-level atomic system (of, e.g., neutral alkali-metal atoms such as lithium and potassium atoms) are utilized for achieving negative refractive index with impedance perfectly matched to vacuum. The attractive features of the present scenario include: i) three-dimensionally isotropic negative indices; ii) incoherent-gain wave amplification; iii) perfect impedance matching to vacuum. All these important properties of the double-negative medium would have potential applications in designing some optical and photonic devices, including particularly subwavelength focusing system and negative-index superlens for perfect imaging.
|
|
| 13. |
- Shen, Jian Qi
(author)
-
A three-level dark state and double-control single-photon logic gates via quantum coherent control
- 2012
-
In: Annalen der Physik. - : Wiley-Blackwell. - 0003-3804 .- 1521-3889. ; 524:2, s. 85-96
-
Journal article (peer-reviewed)abstract
- Multilevel quantum coherence and its quantum-vacuum counterpart, where a three-level dark state is involved, are suggested in order to achieve new photonic and quantum optical applications. It is shown that such a three-level dark state in a four-level tripod-configuration atomic system consists of three lower levels, where constructive and destructive quantum interference between two control transitions (driven by two control fields) arises. We point out that the controllable optical response due to the double-control tunable quantum interference can be utilized to design some fascinating new photonic devices such as logic gates, photonic transistors and switches at quantum level. A single-photon two-input XOR logic gate (in which the incident gate photons are the individual light quanta of the two control fields) based on such an effect of optical switching control with an EIT (electromagnetically induced transparency) microcavity is suggested as an illustrative example of the application of the dark-state manipulation via the double-control quantum interference. The present work would open up possibility of new applications in both fundamental physics (e.g., field quantization and relevant quantum optical effects in artificial systems that can mimic atomic energy levels) and applied physics (e.g., photonic devices such as integrated optical circuits at quantum level).
|
|
| 14. |
|
|
| 15. |
- Shen, Jian Qi
(author)
-
Automatic generation of nonadiabatic conditional geometric phase shift with a noncoplanar fibre system
- 2006
-
In: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 73:1, s. 79-83
-
Journal article (peer-reviewed)abstract
- A new scheme for realizing a nonadiabatic conditional geometric phase shift via a noncoplanar (coiled) fibre system is presented. It is shown that the effective Hamiltonian that describes the interaction of polarized photons with a fibre medium is just the Wang-Matsumoto type of Hamiltonian. This, therefore, means that the coiled fibre system may be an ideal implementation for realizing the nonadiabatic geometric phase gates involved in the topological quantum computation. A remarkable feature of the present method is that it can automatically meet the conditions and requirements proposed in the Wang-Matsumoto nuclear magnetic resonance (NMR) scheme: specifically, (i) in the coiled fibre system, the dynamical phase of photon wavefunction caused by the interaction Hamiltonian automatically vanishes; (ii) the Wang-Matsumoto requirement for the parameters in the Wang-Matsumoto NMR Hamiltonian can be exactly satisfied automatically in such a fibre system; and (iii) the conditional initial state can be easily achieved by manipulating the initial wave vector of polarized photons.
|
|
| 16. |
- Shen, Jian Qi
(author)
-
Canonical Acoustics and Its Application to Surface Acoustic Wave on Acoustic Metamaterials
- 2016
-
In: Journal of the Physical Society of Japan. - : Physical society of Japan. - 0031-9015 .- 1347-4073. ; 85:8
-
Journal article (peer-reviewed)abstract
- In a conventional formalism of acoustics, acoustic pressure p and velocity field u are used for characterizing acoustic waves propagating inside elastic/acoustic materials. We shall treat some fundamental problems relevant to acoustic wave propagation alternatively by using canonical acoustics (a more concise and compact formalism of acoustic dynamics), in which an acoustic scalar potential and an acoustic vector potential (Phi, V), instead of the conventional acoustic field quantities such as acoustic pressure and velocity field (p, u) for characterizing acoustic waves, have been defined as the fundamental variables. The canonical formalism of the acoustic energy-momentum tensor is derived in terms of the acoustic potentials. Both the acoustic Hamiltonian density and the acoustic Lagrangian density have been defined, and based on this formulation, the acoustic wave quantization in a fluid is also developed. Such a formalism of acoustic potentials is employed to the problem of negative-mass-density assisted surface acoustic wave that is a highly localized surface bound state (an eigenstate of the acoustic wave equations). Since such a surface acoustic wave can be strongly confined to an interface between an acoustic metamaterial (e.g., fluid-solid composite structures with a negative dynamical mass density) and an ordinary material (with a positive mass density), it will give rise to an effect of acoustic field enhancement on the acoustic interface, and would have potential applications in acoustic device design for acoustic wave control.
|
|
| 17. |
- Shen, Jian Qi
(author)
-
Coherent Manipulation of Optical Waves with Microwave Quantum Interference
- 2013
-
In: Journal of the Physical Society of Japan. - 0031-9015 .- 1347-4073. ; 82:4, s. 044001-
-
Journal article (peer-reviewed)abstract
- An experimentally feasible scheme of a four-level atomic system driven by two microwaves and one optical field is suggested in order to realize destructive and constructive quantum interference between the two microwave-driven transition pathways and hence to coherently manipulate the applied optical field. The destructive quantum interference can be switched to the constructive interference and vice versa if one tunes the intensity ratio of the two microwaves. Such an effect of tunable optical response based on microwave quantum interference may have some potential applications to the technique for designing new photonic and quantum optical devices, e. g., photonic logic gates, optical switches, and photonic transistors.
|
|
| 18. |
- Shen, Jian Qi
(author)
-
Dispersion-sensitive surface plasmon wave assisted by incoherent gain
- 2014
-
In: Optics Communications. - : Elsevier BV. - 0030-4018 .- 1873-0310. ; 329, s. 15-22
-
Journal article (peer-reviewed)abstract
- A three-level system with pumped electric-dipole allowed transition for incoherent-gain negative permittivity is suggested in order to realize dispersion-sensitive surface plasmon wave. The present surface wave modes occurring at an interface between an incoherent-gain negative-permittivity "plasmonic" medium (e.g., a semiconductor-quantum-dot material) and an ordinary dielectric can be amplified due to population transfer in the three-level system of the negative-permittivity medium. The issues of complex phase constant and the attenuation coefficients in the adjacent media are considered for addressing the problem of loss compensation of surface plasmon wave. The effect of incoherent-gain amplification exhibited by the dispersion-sensitive surface plasmon wave can be utilized for designing new quantum optical and photonic devices, e.g., photonic transistors and logic gates.
|
|
| 19. |
- Shen, Jian Qi
(author)
-
Double-negative atomic vapor assisted by two-photon quantum coherence
- 2012
-
In: Journal of the Optical Society of America. B, Optical physics. - : The Optical Society. - 0740-3224 .- 1520-8540. ; 29:11, s. 3192-3200
-
Journal article (peer-reviewed)abstract
- A scenario for realizing simultaneously negative permittivity and permeability of a two-photon quantum-coherent atomic vapor is suggested in order to achieve a left-handed atomic medium with a negative refractive index. One of the remarkable features of the present scheme is that it can lead to a controllable manipulation of the negative refractive index of the atomic vapor. Since the electric- and magnetic-dipole allowed transitions of atoms can be excited by visible and infrared lightwaves, the refractive index of the atomic vapor can exhibit its negative refractive index at optical and near-optical frequency bands. This may be a new scheme to fabricate a negatively refracting material based on the quantum optical approach. Such a three-dimensionally isotropic negative refractive index at visible and infrared wavelengths induced by the two-photon-resonant quantum coherence would find a potential application in fabrication of superlenses for perfect imaging and subwavelength focusing.
|
|
| 20. |
- Shen, Jian Qi
(author)
-
Electric and magnetic dipole allowed transitions of atoms for three-dimensionally isotropic left handedness in a mixed atomic vapor
- 2014
-
In: Progress of Theoretical and Experimental Physics. - : Oxford University Press (OUP). - 2050-3911. ; :3, s. 033A01-
-
Journal article (peer-reviewed)abstract
- Since previous negative-index atomic media based on quantum optical approaches are highly lossy, a proposal for realizing a three-dimensionally isotropic left-handed atomic vapor medium is suggested based on a mechanism of incoherent gain assisted atomic transitions. Two three-level atomic systems are utilized for producing simultaneously negative permittivity and negative permeability, respectively, in the same frequency band. We suggest that fine and hyperfine level transitions of atoms (e.g., a hyperfine level transition in a hydrogen atomic system and a fine level transition in an alkali-metal atomic system) would be applicable to realization of such a negatively refracting atomic vapor. The attractive features of the present scenario include: i) three-dimensionally isotropic negative indices; ii) incoherent gain wave amplification in the negative-index atomic vapor; iii) tunable negative indices depending upon external fields. Such a left-handed quantum optical medium can serve as a supporting substrate for lossy negative-index materials for loss compensation. It can also be used in designing new quantum optical and photonic devices (e.g., a subwavelength focusing system and a negative-index superlens for perfect imaging) because of its attractive properties of three-dimensional isotropy and high-gain wave amplification.
|
|
