| 1. |
- Gharibi, Arash, et al.
(författare)
-
Tunable transient evolutional behaviours of a four-level atomic vapour and the application to photonic logic gates
- 2009
-
Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 42:5, s. 055502-
-
Tidskriftsartikel (refereegranskat)abstract
- The evolutional optical behaviours (turn-on dynamics) of a four-level N-configuration atomic system are considered based on the transient solution to the equations of motion of atomic probability amplitudes. It is shown that the quantum interference between the signal and control fields can lead to the controllable absorption and transparency properties of the atomic vapour. One of the most remarkable properties of the present scheme is that the absorption (or transmittance) of the probe light in the atomic vapour depends on the intensity ratio of the signal field to the control field, and thus the tunable optical features (transparency or opaqueness to the probe light) can be realized by tuning the quantum interferences between the signal and control fields. The present mechanism can be applicable to designs of some new photonic and quantum optical devices such as logic and functional devices as well as optical switches. Two typical photonic logic gates (NOT and NOR gates) designed based on the tunable four-level optical responses are presented as illustrative examples.
|
|
| 2. |
|
|
| 3. |
- Shen, Jian Qi
(författare)
-
Automatic generation of nonadiabatic conditional geometric phase shift with a noncoplanar fibre system
- 2006
-
Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 73:1, s. 79-83
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 4. |
- Shen, Jian Qi
(författare)
-
Isotropic negatively-refracting atomic-vapor medium
- 2007
-
Ingår i: Modern physics letters B. - 0217-9849. ; 21:12, s. 717-728
-
Tidskriftsartikel (refereegranskat)abstract
- A new scenario to realize negative refraction with a photonic-resonant vapor material that can exhibit both electric and magnetic responses via multilevel quantum coherence is suggested. Compared with the previous method of artificial composite metamaterial, where the mechanism was considered by means of classical electromagnetic theory and the materials produced have anisotropic millimetre-scale composite structures, the present scheme suggested within the framework of quantum optics can be used to design and fabricate isotropic negatively-refracting materials with atomic-scale microscopic structure units. Such an advantage may lead to a potentially important application in the techniques of superlens and perfect imaging.
|
|
| 5. |
- Shen, Jian Qi, et al.
(författare)
-
Momentum transfer at quantum-vacuum level inside an anisotropic magnetoelectric medium
- 2007
-
Ingår i: Wuli xuebao. - : Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences. - 1000-3290. ; 56:5, s. 2719-2724
-
Tidskriftsartikel (refereegranskat)abstract
- The breaking of universal symmetry of electromagnetic field distribution in an anisotropic magnetoelectric material will give rise to nonzero vacuum momentum. This may lead to the transfer of momentum between the anisotropic quantum vacuum and the magnetoelectric material. Very recently, Feigel considered the quantum vacuum contribution to the momentum transfer effect [Phys. Rev. Lett. 92 (2004) 020404]. An alternative approach is proposed based on the eigenvector equation of electromagnetic field to calculate the total mechanical contribution of all anisotropic quantum-vacuum modes to the material momentum. It is suggested that the said macroscopic mechanical effect of quantum vacuum on the anisotropic material can be detected by current technology (e. g. fiber optical sensor), which can measure nanoscale velocity. Physical mechanism of such quantum vacuum effects and potential applications are discussed.
|
|
| 6. |
- Shen, Jian Qi, et al.
(författare)
-
Momentum transfer from vacuum field to anisotropic electromagnetic media
- 2006
-
Ingår i: Optics Communications. - : Elsevier BV. - 0030-4018 .- 1873-0310. ; 257:1, s. 84-90
-
Tidskriftsartikel (refereegranskat)abstract
- it is demonstrated that many novel vacuum effects will be caused if an anisotropic electromagnetic environment, which can break the universal symmetry of vacuum, is achieved. It is thus possible for the momentum to be transferred from the vacuum zero-point field to the anisotropic electromagnetic media. In addition to the effect considered by Feigel more recently [A. Feigel, Phys. Rev. Lett. 92 (2004) 020404], there may exist another vacuum-fluctuation contribution to the momentum of a medium. Such an effect has a relativistic origin (resulting from the relativistic transformation of the optical constants), which, however, was not taken into account by Feigel.
|
|
| 7. |
- Shen, Jian Qi
(författare)
-
Negatively refracting atomic vapour
- 2006
-
Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 53:15, s. 2195-2205
-
Tidskriftsartikel (refereegranskat)abstract
- A new mechanism for realizing negative refractive index with a four-level atomic system is suggested. The explicit expressions for the electric permittivity and magnetic permeability at probe frequency are presented. It is shown that there is a frequency band in which the four-level photonic-resonant atomic vapour may exhibit simultaneously negative permittivity and permeability, and that such an atomic vapour may become a left-handed material ( negatively refracting medium). Compared with the previous schemes to realize negative refraction within the framework of classical electromagnetic theory, the most remarkable features of the present scenario are as follows: ( i) isotropic material with microscopic structure units at atomic-scale level, ( ii) negative refraction in visible and infrared frequency bands, ( iii) controllable manipulation by external fields and ( iv) based on quantum coherence in a multilevel atomic system.
|
|
| 8. |
- Shen, Jian Qi
(författare)
-
Photonic-resonant left-handed medium
- 2006
-
Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 357:1, s. 54-60
-
Tidskriftsartikel (refereegranskat)abstract
- A new scheme to realize simultaneously negative permittivity and permeability in a coherent atomic vapor medium (photonic-resonant material) via a coherent driving mechanism is suggested. It is verified that the atomic system coherently driven by a strong optical field will give rise to a negative refractive index in certain probe frequency ranges. One of the most remarkable features of the present scheme is such that a slab fabricated by the left-handed vapor medium is an ideal candidate for designing perfect lenses since the photonic-resonant atomic vapor cannot only exhibit an isotropic negative refractive index, but also provide a good impedance match at the air-medium interfaces.
|
|
| 9. |
- Shen, Jian Qi
(författare)
-
Simultaneous negative permittivity and permeability in a coherent atomic vapour
- 2007
-
Ingår i: Chinese Physics. - : IOP Publishing. - 1009-1963 .- 1741-4199. ; 16:7, s. 1976-1985
-
Tidskriftsartikel (refereegranskat)abstract
- A new quantum optical mechanism to realize simultaneously negative electric permittivity and magnetic permeability is suggested. In order to obtain a negative permeability, we choose a proper atomic configuration that can dramatically enhance the contribution of the magnetic- dipole allowed transition via the atomic phase coherence. It is shown that the atomic system chosen with proper optical parameters can give rise to striking electromagnetic responses (leading to a negative refractive index) and that the atomic vapour becomes a left-handed medium in an optical frequency band. Differing from the previous schemes of artificial composite metamaterials (based on classical electromagnetic theory) to achieve the left-handed materials, which consist of anisotropic millimetre- scale composite structure units, the left- handed atomic vapour presented here is isotropic and homogeneous at the atomic-scale level. Such an advantage may be valuable in realizing the superlens (and hence perfect image) with left- handed atomic vapour.
|
|
