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AuthorsTitleJournalYear
W. Gao, X. Li, M. Bamba, & J. Kono Continuous transition between weak and ultra-strong coupling through exceptional points in carbon nanotube micro-cavity exciton polaritons Nature Photonics
published online
 
2018
BibTeX:
@article{Gao2018NP,
  author = {Weilu Gao and Xinwei Li and Motoaki Bamba and Junichiro Kono},
  title = {Continuous transition between weak and ultra-strong coupling through exceptional points in carbon nanotube micro-cavity exciton polaritons},
  journal = {Nature Photonics},
  year = {2018},
  pages = {published online},
  doi = {10.1038/s41566-018-0157-9}
}
X. Li, M. Bamba, Q. Zhang, S. Fallahi, G. C. Gardner, W. Gao, M. Lou, K. Yoshioka, M. J. Manfra, & J. Kono Vacuum Bloch-Siegert shift in Landau polaritons with ultra-high cooperativity Nature Photonics
published online
 
2018
Abstract: A two-level system resonantly interacting with an a.c. magnetic or electric field constitutes the physical basis of diverse phenomena and technologies. However, Schrodinger's equation for this seemingly simple system can be solved exactly only under the rotating-wave approximation, which neglects the counter-rotating field component. When the a.c. field is sufficiently strong, this approximation fails, leading to a resonance-frequency shift known as the Bloch-Siegert shift. Here, we report the vacuum Bloch-Siegert shift, which is induced by the ultra-strong coupling of matter with the counter-rotating component of the vacuum fluctuation field in a cavity. Specifically, an ultra-high-mobility two-dimensional electron gas inside a high-Q terahertz cavity in a quantizing magnetic field revealed ultra-narrow Landau polaritons, which exhibited a vacuum Bloch-Siegert shift up to 40?GHz. This shift, clearly distinguishable from the photon-field self-interaction effect, represents a unique manifestation of a strong-field phenomenon without a strong field.
BibTeX:
@article{Li2018NP,
  author = {Xinwei Li and Motoaki Bamba and Qi Zhang and Saeed Fallahi and Geoff C. Gardner and Weilu Gao and Minhan Lou and Katsumasa Yoshioka and Michael J. Manfra and Junichiro Kono},
  title = {Vacuum Bloch-Siegert shift in Landau polaritons with ultra-high cooperativity},
  journal = {Nature Photonics},
  year = {2018},
  pages = {published online},
  doi = {10.1038/s41566-018-0153-0}
}
M. Bamba & N. Imoto Circuit configurations which may or may not show superradiant phase transitions Physical Review A
Vol. 96, Issue 5, 053857, 11 pages

arXiv:1703.03533 [quant-ph]  
2017
Abstract: Several superconducting circuit configurations are examined on the existence of superradiant phase transitions (SRPTs) in thermal equilibrium. For some configurations consisting of artificial atoms, whose circuit diagrams are however not specified, and an LC resonator or a transmission line, we confirm the absence of SRPTs in the thermal equilibrium following the similar analysis as the no-go theorem for atomic systems. We also show some other configurations where the absence of SRPTs cannot be confirmed.
BibTeX:
@article{Bamba2017NogoCircuit,
  author = {Bamba, Motoaki and Nobuyuki Imoto},
  title = {Circuit configurations which may or may not show superradiant phase transitions},
  journal = {Physical Review A},
  publisher = {American Physical Society},
  year = {2017},
  month = {Nov},
  volume = {96},
  number = {5},
  pages = {053857},
  numpages = {11},
  url = {https://link.aps.org/doi/10.1103/PhysRevA.96.053857},
  doi = {10.1103/PhysRevA.96.053857},
  archivePrefix = {arXiv},
  eprint = {1703.03533},
  primaryClass = {quant-ph}
}
M. Bamba, K. Inomata, & Y. Nakamura Superradiant Phase Transition in a Superconducting Circuit in Thermal Equilibrium Physical Review Letters
Vol. 117, Issue 17, 173601, 5 pages

arXiv:1605.01124 [quant-ph]  
2016
Abstract: We propose a superconducting circuit that shows a superradiant phase transition (SRPT) in thermal equilibrium. The existence of the SRPT is confirmed analytically in the limit of an infinite number of artificial atoms. We also perform a numerical diagonalization of the Hamiltonian with a finite number of atoms and observe an asymptotic behavior approaching the infinite limit as the number of atoms increases. The SRPT can also be interpreted intuitively in a classical analysis.
BibTeX:
@article{Bamba2016circuitSRPT,
  author = {Bamba, Motoaki and Inomata, Kunihiro and Nakamura, Yasunobu},
  title = {Superradiant Phase Transition in a Superconducting Circuit in Thermal Equilibrium},
  journal = {Physical Review Letters},
  publisher = {American Physical Society},
  year = {2016},
  month = {Oct},
  volume = {117},
  number = {17},
  pages = {173601},
  numpages = {5},
  url = {http://link.aps.org/doi/10.1103/PhysRevLett.117.173601},
  doi = {10.1103/PhysRevLett.117.173601},
  archivePrefix = {arXiv},
  eprint = {1605.01124},
  primaryClass = {quant-ph}
}
M. Bamba & N. Imoto Maxwell boundary conditions imply non-Lindblad master equation Physical Review A
Vol. 94, Issue 3, 033802, 20 pages

arXiv:1603.00535 [quant-ph]  
2016
Abstract: From the Hamiltonian connecting the inside and outside of a Fabry-Perot cavity, which is derived from the Maxwell boundary conditions at a mirror of the cavity, a master equation of a non-Lindblad form is derived when the cavity embeds matters, although we can transform it to the Lindblad form by performing the rotating-wave approximation to the connecting Hamiltonian. We calculate absorption spectra by these Lindblad and non-Lindblad master equations and also by the Maxwell boundary conditions in the framework of the classical electrodynamics, which we consider the most reliable approach. We found that, compared to the Lindblad master equation, the absorption spectra by the non-Lindblad one agree better with those by the Maxwell boundary conditions. Although the discrepancy is highlighted only in the ultrastrong light-matter interaction regime with a relatively large broadening, the master equation of the non-Lindblad form is preferable rather than of the Lindblad one for pursuing the consistency with the classical electrodynamics.
BibTeX:
@article{Bamba2016nonLindblad,
  author = {Motoaki Bamba and Nobuyuki Imoto},
  title = {Maxwell boundary conditions imply non-Lindblad master equation},
  journal = {Physical Review A},
  publisher = {American Physical Society},
  year = {2016},
  month = {Sep},
  volume = {94},
  number = {3},
  pages = {033802},
  numpages = {20},
  url = {http://link.aps.org/doi/10.1103/PhysRevA.94.033802},
  doi = {10.1103/PhysRevA.94.033802},
  archivePrefix = {arXiv},
  eprint = {1603.00535},
  primaryClass = {quant-ph}
}
M. Bamba & T. Ogawa Laser under ultrastrong light-matter interaction: Qualitative aspects and quantitative influences by level and mode truncations Physical Review A
Vol. 93, Issue 3, 033811, 10 pages

arXiv:1410.3912 [quant-ph]  
2016
Abstract: We investigate theoretically the light amplification by stimulated emission of radiation (laser) in the ultrastrong light-matter interaction regime under the two-level and single-mode approximations. The conventional picture of the laser is broken under the ultrastrong interaction. Instead, we must explicitly discuss the dynamics of the electric field and of the magnetic one distinctively, which make the glaserh qualitatively different from the conventional laser. We found that the laser generally accompanies odd-order harmonics of the electromagnetic fields both inside and outside the cavity and a synchronization with an oscillation of atomic population. A bistability is also demonstrated. However, since our model is quite simplified, we got quantitatively different results from the Hamiltonians in the velocity and length forms of the light-matter interaction, while the appearance of the multiple harmonics and the bistability is qualitatively reliable.
BibTeX:
@article{Bamba2016Laser,
  author = {Motoaki Bamba and Tetsuo Ogawa},
  title = {Laser under ultrastrong light-matter interaction: Qualitative aspects and quantitative influences by level and mode truncations},
  journal = {Physical Review A},
  publisher = {American Physical Society},
  year = {2016},
  month = {Mar},
  volume = {93},
  number = {3},
  pages = {033811},
  numpages = {10},
  url = {http://link.aps.org/doi/10.1103/PhysRevA.93.033811},
  doi = {10.1103/PhysRevA.93.033811},
  archivePrefix = {arXiv},
  eprint = {1410.3912},
  primaryClass = {quant-ph}
}
M. Bamba, S. Wakaiki, H. Ichida, K. Mizoguchi, D. Kim, M. Nakayama, & Y. Kanematsu Theory of the lifetime of an exciton incoherently created below its resonance frequency by inelastic scattering Physical Review B
Vol. 91, Issue 23, 235205, 13 pages

arXiv:1411.3430 [cond-mat.mes-hall]  
2015
Abstract: When an exciton in semiconductor is scattered and its energy is decreased far below the resonance energy of the bare exciton state, it has been considered that an exciton-polariton is created immediately by the scattering process because there is no exciton level at that energy. However, according to the recent time-resolved measurements of P emission originating from inelastic exciton-exciton scattering, it looks rather natural to consider that the exciton-polariton is created in a finite time scale which is restricted by a coherence volume of the exciton after the scattering. In this interpretation, the exciton remains in this time scale far below its resonance energy as a transient state in a series of processes. We propose an expression of the P-emission lifetime depending on the coherence volume of the scattered excitons through the conversion process from them to the polaritons. The coherence volume of the scattered excitons appears in the calculation of the inelastic scattering process on the assumption of a finite coherence volume of the bottleneck excitons. Time-resolved optical-gain measurements could be a way for investigating the validity of our interpretation.
BibTeX:
@article{Bamba2015Plifetime,
  author = {Motoaki Bamba and Shuji Wakaiki and Hideki Ichida and Kohji Mizoguchi and DaeGwi Kim and Masaaki Nakayama and Yasuo Kanematsu},
  title = {Theory of the lifetime of an exciton incoherently created below its resonance frequency by inelastic scattering},
  journal = {Physical Review B},
  publisher = {American Physical Society},
  year = {2015},
  month = {Jun},
  volume = {91},
  number = {23},
  pages = {235205},
  numpages = {13},
  url = {http://link.aps.org/doi/10.1103/PhysRevB.91.235205},
  doi = {10.1103/PhysRevB.91.235205},
  archivePrefix = {arXiv},
  eprint = {1411.3430},
  primaryClass = {cond-mat.mes-hall}
}
M. Bamba & T. Ogawa Stability of polarizable materials against superradiant phase transition Physical Review A
Vol. 90, Issue 6, 063825, 8 pages

arXiv:1406.2420 [quant-ph]  
2014
Abstract: The possibility of the superradiant phase transition in polarizable materials described by the minimal-coupling Hamiltonian with the longitudinal dipole-dipole interaction is examined. We try to reduce the Hamiltonian into the Dicke one in the homogeneous and infinite case, and discuss the stability of normal ground state by the formalism of the Green function in the spatially inhomogeneous case. The presence of the longitudinal dipole-dipole interaction does not enable the superradiant phase transition, if the transverse and longitudinal fields are decoupled. Although the full dipole-dipole interaction can be eliminated in the electric-dipole gauge in the absence of overlap between individual atomic dipoles, we cannot reduce the Hamiltonian to the Dicke one, because the elimination is justified only if all the transverse and longitudinal fields remain. Even if the transverse and longitudinal fields are mixed in spatially inhomogeneous systems, the normal ground state is still stable if the system does not show the superradiant phase transition in the homogeneous case.
BibTeX:
@article{Bamba2014SPT,
  author = {Motoaki Bamba and Tetsuo Ogawa},
  title = {Stability of polarizable materials against superradiant phase transition},
  journal = {Physical Review A},
  publisher = {American Physical Society},
  year = {2014},
  month = {Dec},
  volume = {90},
  number = {6},
  pages = {063825},
  numpages = {8},
  url = {http://link.aps.org/doi/10.1103/PhysRevA.90.063825},
  doi = {10.1103/PhysRevA.90.063825},
  archivePrefix = {arXiv},
  eprint = {1406.2420},
  primaryClass = {quant-ph}
}
M. Bamba & T. Ogawa Recipe for the Hamiltonian of system-environment coupling applicable to the ultrastrong-light-matter-interaction regime Physical Review A
Vol. 89, Issue 2, 023817, 18 pages

arXiv:1306.2099 [quant-ph]  
2014
Abstract: When the light interacts with matters in a lossy cavity, in the standard cavity quantum electrodynamics, the dissipation of cavity fields is characterized simply by the strengths of the two couplings: the light-matter interaction and the system-environment coupling through the cavity mirror. However, in the ultrastrong-light-matter-interaction regime, the dissipation depends also on whether the two couplings are mediated by the electric field or the magnetic one (capacitive or inductive in superconducting circuits). Even if we know correctly the microscopic mechanism (Lagrangian) of the system-environment coupling, the coupling Hamiltonian itself is in principle modified due to the ultrastrong interaction in the cavity. In this paper, we show a recipe for deriving a general expression of the Hamiltonian of the system-environment coupling, which is applicable even in the ultrastrong-light-matter-interaction regime in the good-cavity and independent-transition limits.
BibTeX:
@article{Bamba2014SEC,
  author = {Motoaki Bamba and Tetsuo Ogawa},
  title = {Recipe for the Hamiltonian of system-environment coupling applicable to the ultrastrong-light-matter-interaction regime},
  journal = {Physical Review A},
  publisher = {American Physical Society},
  year = {2014},
  month = {Feb},
  volume = {89},
  number = {2},
  pages = {023817},
  numpages = {18},
  url = {http://link.aps.org/doi/10.1103/PhysRevA.89.023817},
  doi = {10.1103/PhysRevA.89.023817},
  archivePrefix = {arXiv},
  eprint = {1306.2099},
  primaryClass = {quant-ph}
}
T. Boulier, M. Bamba, A. Amo, C. Adrados, A. Lemaitre, E. Galopin, I. Sagnes, J. Bloch, C. Ciuti, E. Giacobino, & A. Bramati Polariton-generated intensity squeezing in semiconductor micropillars Nature Communications
Vol. 5, 3260, 7 pages

Post-print  
2014
Abstract: The generation of squeezed and entangled light fields is a crucial ingredient for the implementation of quantum information protocols. In this context, semiconductor materials offer a strong potential for the implementation of on-chip devices operating at the quantum level. Here we demonstrate a novel source of continuous variable squeezed light in pillar-shaped semiconductor microcavities in the strong coupling regime. Degenerate polariton four-wave mixing is obtained by exciting the pillar at normal incidence. We observe a bistable behaviour and we demonstrate the generation of squeezing near the turning point of the bistability curve. The confined pillar geometry allows for a larger amount of squeezing than planar microcavities due to the discrete energy levels protected from excess noise. By analysing the noise of the emitted light, we obtain a measured intensity squeezing of 20.3%, inferred to be 35.8% after corrections.
BibTeX:
@article{Boulier2014NC,
  author = {Boulier, T. and Bamba, M. and Amo, A. and Adrados, C. and Lemaitre, A. and Galopin, E. and Sagnes, I. and Bloch, J. and Ciuti, C. and Giacobino, E. and Bramati, A.},
  title = {Polariton-generated intensity squeezing in semiconductor micropillars},
  journal = {Nature Communications},
  publisher = {Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.},
  year = {2014},
  month = {Feb},
  volume = {5},
  pages = {3260},
  numpages = {7},
  url = {http://dx.doi.org/10.1038/ncomms4260},
  doi = {10.1038/ncomms4260}
}
M. Bamba & T. Ogawa Reply to ``Comment on `System-environment coupling derived by Maxwell's boundary conditions from the weak to the ultrastrong light-matter-coupling regime' '' Physical Review A
Vol. 89, Issue 1, 017802, 2 pages

arXiv:1311.1564 [quant-ph]  
2014
Abstract: As mentioned by De Liberato [Phys. Rev. A 89 017801 (2014)], when we suppose the metallic thin mirror and perform the renormalization to the approach starting from the frequently used system-environment-coupling Hamiltonian, we can certainly resolve the discrepancy of its result from that obtained by the reliable approach in the main discussion of our paper [Phys. Rev. A 88 013814 (2013)]. Although the suggested approach is currently applicable to the specific situation after checking its validity by our reliable but cumbersome approach, we instead propose to start from the system-environment-coupling Hamiltonian determined properly by the mechanism of the confinement and loss of the cavity fields. This approach is applicable to any cavity structure, in principle, and we do not face the renormalization problem appearing in the Comment.
BibTeX:
@article{Bamba2013Liberato,
  author = {Motoaki Bamba and Tetsuo Ogawa},
  title = {Reply to ``Comment on `System-environment coupling derived by Maxwell's boundary conditions from the weak to the ultrastrong light-matter-coupling regime' ''},
  journal = {Physical Review A},
  publisher = {American Physical Society},
  year = {2014},
  month = {Jan},
  volume = {89},
  number = {1},
  pages = {017802},
  numpages = {2},
  url = {http://link.aps.org/doi/10.1103/PhysRevA.89.017802},
  doi = {10.1103/PhysRevA.89.017802},
  archivePrefix = {arXiv},
  eprint = {1311.1564},
  primaryClass = {quant-ph}
}
M. Bamba & T. Ogawa System-environment coupling derived by Maxwell's boundary conditions from the weak to the ultrastrong light-matter-coupling regime Physical Review A
Vol. 88, Issue 1, 013814, 11 pages

arXiv:1301.3960 [quant-ph]  
2013
Abstract: In the standard theory of cavity quantum electrodynamics (QED), coupling between photons inside and outside a cavity (cavity system and environment) is given conserving the total number of photons. However, when the cavity photons (ultrastrongly) interact with atoms or excitations in matters, the system-environment coupling must be determined from a more fundamental viewpoint. Based on the Maxwell's boundary conditions in the QED theory for dielectric media, we derive the quantum Langevin equation and input-output relation, in which the total number of polaritons (not photons) inside the cavity and photons outside is conserved.
BibTeX:
@article{Bamba2013MBC,
  author = {Bamba, Motoaki and Ogawa, Tetsuo},
  title = {System-environment coupling derived by Maxwell's boundary conditions from the weak to the ultrastrong light-matter-coupling regime},
  journal = {Physical Review A},
  publisher = {American Physical Society},
  year = {2013},
  month = {Jul},
  volume = {88},
  number = {1},
  pages = {013814},
  numpages = {11},
  url = {http://link.aps.org/doi/10.1103/PhysRevA.88.013814},
  doi = {10.1103/PhysRevA.88.013814},
  archivePrefix = {arXiv},
  eprint = {1301.3960},
  primaryClass = {quant-ph}
}
L. Nguyen-thê, S. De Liberato, M. Bamba, & C. Ciuti Effective polariton-polariton interactions of cavity-embedded two-dimensional electron gases Physical Review B
Vol. 87, Issue 23, 235322, 12 pages

arXiv:1211.5039 [cond-mat.other]  
2013
Abstract: Intersubband polaritons are light-matter excitations originating from the strong coupling between an intersubband quantum well electronic transition and a microcavity photon mode. In this paper, we study how the Coulomb electron-electron interaction and the Pauli saturation of the electronic transitions affect the physics of intersubband polaritons. We develop a microscopic many-body theory for the physics of such composite bosonic excitations in a microcavity-embedded two-dimensional electron gas. As a first application, we calculate the modification of the depolarization shift and the efficiency of intersubband polariton-polariton scattering processes, which is large enough to induce interesting nonlinear optical effects in the mid- and far-infrared.
BibTeX:
@article{Nguyen-the2013PRB,
  author = {Nguyen-thê, Luc and De Liberato, Simone and Bamba, Motoaki and Ciuti, Cristiano},
  title = {Effective polariton-polariton interactions of cavity-embedded two-dimensional electron gases},
  journal = {Physical Review B},
  publisher = {American Physical Society},
  year = {2013},
  month = {Jun},
  volume = {87},
  number = {23},
  pages = {235322},
  numpages = {12},
  url = {http://link.aps.org/doi/10.1103/PhysRevB.87.235322},
  doi = {10.1103/PhysRevB.87.235322},
  archivePrefix = {arXiv},
  eprint = {1211.5039},
  primaryClass = {cond-mat.other}
}
M. Bamba & T. Ogawa Dissipation and detection of polaritons in the ultrastrong-coupling regime Physical Review A
Vol. 86, Issue 6, 063831, 16 pages

arXiv:1208.5181 [quant-ph]  
2012
Abstract: We have investigated theoretically a dissipative polariton system in the ultrastrong light-matter coupling regime without using the rotating-wave approximation on system-reservoir coupling. Photons in a cavity and excitations in matter respectively couple two large ensembles of harmonic oscillators (photonic and excitonic reservoirs). Inheriting the quantum statistics of polaritons in the ultrastrong coupling regime, in the ground state of the whole system, the two reservoirs are not in the vacuum states but they are squeezed and correlated. We presume the reservoirs to be in this nonvacuum state in the master equation and in the input-output formalism with Langevin equations. Both approaches consistently guarantee the decay of the polariton system to its ground state; no photon detection is also obtained when the polariton system is in the ground state.
BibTeX:
@article{Bamba2012DissipationUSC,
  author = {Bamba, Motoaki and Ogawa, Tetsuo},
  title = {Dissipation and detection of polaritons in the ultrastrong-coupling regime},
  journal = {Physical Review A},
  publisher = {American Physical Society},
  year = {2012},
  month = {Dec},
  volume = {86},
  number = {6},
  pages = {063831},
  numpages = {16},
  url = {http://link.aps.org/doi/10.1103/PhysRevA.86.063831},
  doi = {10.1103/PhysRevA.86.063831},
  archivePrefix = {arXiv},
  eprint = {1208.5181},
  primaryClass = {quant-ph}
}
H. Tahara, M. Bamba, Y. Ogawa, & F. Minami Observation of a dynamical mixing process of exciton-polaritons in a ZnSe epitaxial layer using four-wave mixing spectroscopy Physical Review B
Vol. 86, Issue 23, 235208, 6 pages
 
2012
Abstract: We have observed a coherent spectral change of exciton-polaritons in a ZnSe epitaxial layer through spectrally resolved four-wave mixing spectroscopy. The spectra exhibit an exchange of the dominant peak position between the different polariton branches depending on the delay time of the second pulse. This result reflects the initial creation process of polaritons with many-body interactions. The calculation based on the exciton-photon microscopic model reveals that the spectral change occurs due to the four-particle correlations between heavy-hole and light-hole excitons; it clearly shows the dynamical mixing process of exciton-polaritons in the initial creation.
BibTeX:
@article{Tahara2012PRB,
  author = {Tahara, H. and Bamba, M. and Ogawa, Y. and Minami, F.},
  title = {Observation of a dynamical mixing process of exciton-polaritons in a ZnSe epitaxial layer using four-wave mixing spectroscopy},
  journal = {Physical Review B},
  publisher = {American Physical Society},
  year = {2012},
  month = {Dec},
  volume = {86},
  number = {23},
  pages = {235208},
  numpages = {6},
  url = {http://link.aps.org/doi/10.1103/PhysRevB.86.235208},
  doi = {10.1103/PhysRevB.86.235208}
}
M. Bamba & C. Ciuti Counter-polarized single-photon generation from the auxiliary cavity of a weakly nonlinear photonic molecule Applied Physics Letters
Vol. 99, Issue 17, 171111, 3 pages

arXiv:1108.5061 [quant-ph]  
2011
Abstract: We propose a scheme for the resonant generation of counter-polarized single photons in double asymmetric cavities with a small Kerr optical nonlinearity (as that created by a semiconductor quantum well) compared to the mode broadening. Due to the interplay between spatial intercavity tunneling and polarization coupling, by weakly exciting with circularly polarized light one of the cavities, we predict strong antibunching of counter-polarized light emission from the non-pumped auxiliary cavity. This scheme due to quantum interference is robust against surface scattering of pumping light, which can be suppressed both by spatial and polarization filters.
BibTeX:
@article{Bamba2011SinglePhoton,
  author = {Motoaki Bamba and Cristiano Ciuti},
  title = {Counter-polarized single-photon generation from the auxiliary cavity of a weakly nonlinear photonic molecule},
  journal = {Applied Physics Letters},
  publisher = {American Institute of Physics},
  year = {2011},
  month = {Oct},
  volume = {99},
  number = {17},
  pages = {171111},
  numpages = {3},
  doi = {10.1063/1.3656250},
  archivePrefix = {arXiv},
  eprint = {1108.5061},
  primaryClass = {quant-ph}
}
M. Bamba & H. Ishihara Generation of entangled-photon pairs from biexcitons in CuCl thin films: Nano-to-bulk crossover regime Physical Review B
Vol. 84, Issue 4, 045125, 16 pages

arXiv:1104.0374 [quant-ph]  
2011
Abstract: We have constructed a theoretical framework of biexciton-resonant hyperparametric scattering for pursuit of high-power and high-quality generation of entangled-photon pairs. Our framework is applicable to the nano-to-bulk crossover regime where the center-of-mass motions of excitons and biexcitons are confined and material surroundings and the polarization correlation of generated photons can be considered. We have analyzed the generation of ultraviolet entangled photons from CuCl film with and without dielectric microcavity and revealed that in the nano-to-bulk crossover regime we generally get a high performance from the viewpoint of statistical accuracy and the generation efficiency can be enhanced by the optical cavity while maintaining the high performance. The nano-to-bulk crossover regime has a variety of degrees of freedom to control the entangled-photon generation, and the scattering spectra explicitly reflect quantized exciton-photon coupled modes in finite structures.
BibTeX:
@article{Bamba2011EntangleLong,
  author = {Motoaki Bamba and Hajime Ishihara},
  title = {Generation of entangled-photon pairs from biexcitons in CuCl thin films: Nano-to-bulk crossover regime},
  journal = {Physical Review B},
  publisher = {American Physical Society},
  year = {2011},
  month = {Jul},
  volume = {84},
  number = {4},
  pages = {045125},
  numpages = {16},
  url = {http://link.aps.org/doi/10.1103/PhysRevB.84.045125},
  doi = {10.1103/PhysRevB.84.045125},
  archivePrefix = {arXiv},
  eprint = {1104.0374},
  primaryClass = {quant-ph}
}
M. Bamba, A. Imamoğlu, I. Carusotto, & C. Ciuti Origin of strong photon antibunching in weakly nonlinear photonic molecules Physical Review A
Vol. 83, Issue 2, 021802(R), 4 pages

arXiv:1007.1605 [quant-ph]  
2011
Abstract: In a recent work [Liew and Savona, Phys. Rev. Lett. 104, 183601 (2010)] it was numerically shown that a resonantly driven photonic "molecule" consisting of two coupled cavities can exhibit strong photon antibunching with a surprisingly weak Kerr nonlinearity. Here, we analytically identify the subtle quantum interference effect that is responsible for the predicted efficient photon blockade effect. We then extend the theory to the experimentally relevant Jaynes-Cummings system consisting of a single quantum emitter in a coupled-cavity structure and predict the strong antibunching even for single-atom cooperativity on the order of or smaller than unity. The potential of this quantum interference effect in the realization of strongly correlated photonic systems with only weak material nonlinearities is assessed by comparing on-site and inter-site correlations in a ring of three coupled photonic molecules.
BibTeX:
@article{Bamba2011Antibunching,
  author = {Motoaki Bamba and Atac Imamoğlu and Iacopo Carusotto and Cristiano Ciuti},
  title = {Origin of strong photon antibunching in weakly nonlinear photonic molecules},
  journal = {Physical Review A},
  publisher = {American Physical Society},
  year = {2011},
  month = {Feb},
  volume = {83},
  number = {2},
  pages = {021802(R)},
  numpages = {4},
  url = {http://link.aps.org/doi/10.1103/PhysRevA.83.021802},
  doi = {10.1103/PhysRevA.83.021802},
  archivePrefix = {arXiv},
  eprint = {1007.1605},
  primaryClass = {quant-ph}
}
M. Bamba & H. Ishihara Entangled-Photon Generation in Nano-to-Bulk Crossover Regime Physical Review Letters
Vol. 105, Issue 12, 123906, 4 pages

arXiv:1003.0406 [cond-mat.other]  
2010
Abstract: We have theoretically investigated the generation of entangled photons from biexcitons in a semiconductor film with a thickness in the nano-to-bulk crossover regime. In contrast with the cases of quantum dots and bulk materials, we can highly control the generated state of entangled photons through the design of a peculiar energy structure of exciton-photon coupled modes in the thickness range between nanometers and micrometers. Owing to the enhancement of the radiative decay rate of excitons (exciton superradiance), the statistical accuracy of generated photons can be increased beyond the trade-off problem with signal intensity. By implementing an optical cavity structure in the strong-coupling regime, the generation efficiency can be enhanced while maintaining the high statistical accuracy.
BibTeX:
@article{Bamba2010EntangleLetter,
  author = {Motoaki Bamba and Hajime Ishihara},
  title = {Entangled-Photon Generation in Nano-to-Bulk Crossover Regime},
  journal = {Physical Review Letters},
  publisher = {American Physical Society},
  year = {2010},
  month = {Sep},
  volume = {105},
  number = {12},
  eid = {123906},
  pages = {123906},
  numpages = {4},
  url = {http://link.aps.org/doi/10.1103/PhysRevLett.105.123906},
  doi = {10.1103/PhysRevLett.105.123906},
  archivePrefix = {arXiv},
  eprint = {1003.0406},
  primaryClass = {cond-mat.other}
}
L. Ferrier, S. Pigeon, E. Wertz, M. Bamba, P. Senellart, I. Sagnes, A. Lemaitre, C. Ciuti, & J. Bloch Polariton parametric oscillation in a single micropillar cavity Applied Physics Letters
Vol. 97, Issue 3, 031105, 3 pages
 
2010
Abstract: We demonstrate parametric oscillation of discrete polariton states in a single squared GaAs/GaAlAs micropillar cavity. Resonantly exciting a selected polariton mode with a continuous wave pump laser, parametric oscillation is evidenced on the two neighbored modes (signal and idler). Abrupt switch-off of the device is observed under high excitation. We present comprehensive results concerning the power-dependence of the energy and linewidth of the emission resonances as well as their far-field patterns. Quantum Monte Carlo calculations give a quantitative understanding of the physics of this micro-optical parametric oscillator involving fully confined discrete polariton modes.
BibTeX:
@article{Ferrier2010APL,
  author = {Lydie Ferrier and Simon Pigeon and Esther Wertz and Motoaki Bamba and Pascale Senellart and Isabelle Sagnes and Aristide Lemaitre and Cristiano Ciuti and Jacqueline Bloch},
  title = {Polariton parametric oscillation in a single micropillar cavity},
  journal = {Applied Physics Letters},
  publisher = {AIP},
  year = {2010},
  month = {Jul},
  volume = {97},
  number = {3},
  eid = {031105},
  pages = {031105},
  numpages = {3},
  doi = {10.1063/1.3466902}
}
M. Bamba, S. Pigeon, & C. Ciuti Quantum squeezing generation versus photon localization in a disordered planar microcavity Physical Review Letters
Vol. 104, Issue 21, 213604, 4 pages

arXiv:1002.4804 [cond-mat.other]  
2010
Abstract: We investigate theoretically the nonlinear dynamics induced by an intense pump field in a disordered planar microcavity. Through a self-consistent theory, we show how the generation of quantum optical noise squeezing is affected by the breaking of the in-plane translational invariance and the occurrence of photon localization. We find that the generation of single-mode Kerr squeezing for the ideal planar case can be prevented by disorder as a result of multimode nonlinear coupling, even when the other modes are in the vacuum state. However, the excess noise is a nonmonotonic function of the disorder amplitude. In the strong localization limit, we show that the system becomes protected with respect to this fundamental coupling mechanism and that the ideal quadrature squeezing generation can be obtained.
BibTeX:
@article{Bamba2010Squeez,
  author = {Motoaki Bamba and Simon Pigeon and Cristiano Ciuti},
  title = {Quantum squeezing generation versus photon localization in a disordered planar microcavity},
  journal = {Physical Review Letters},
  publisher = {American Physical Society},
  year = {2010},
  month = {May},
  volume = {104},
  number = {21},
  eid = {213604},
  pages = {213604},
  numpages = {4},
  url = {http://link.aps.org/doi/10.1103/PhysRevLett.104.213604},
  doi = {10.1103/PhysRevLett.104.213604},
  archivePrefix = {arXiv},
  eprint = {1002.4804},
  primaryClass = {cond-mat.other}
}
M. Bamba & H. Ishihara Crossover of exciton-photon coupled modes in a finite system Physical Review B
Vol. 80, Issue 12, 125319, 11 pages

Post-print
selected for Virtual Journal of Nanoscale Science & Technology, Vol. 20, Issue 14 (October 2009)  
2009
Abstract: An exciton and a photon behave as a polariton in macroscopic materials while they can be treated almost independently in nanostructured ones. We have theoretically investigated the crossover of exciton-photon coupled modes, each of which is characterized with a resonance frequency and a radiative decay rate, in a semiconductor film by continuously increasing the thickness. The resonance frequency and the radiative decay rate are calculated from poles of exciton correlation functions renormalizing the exciton-photon interaction in the film, and we also introduce an intuitive calculation method with considering additional boundary conditions in order to derive the crossover condition. The general properties of the coupled modes are analytically discussed by the intuitive method.
BibTeX:
@article{bamba09crossover,
  author = {Motoaki Bamba and Hajime Ishihara},
  title = {Crossover of exciton-photon coupled modes in a finite system},
  journal = {Physical Review B},
  publisher = {APS},
  year = {2009},
  month = {Sep},
  volume = {80},
  number = {12},
  eid = {125319},
  pages = {125319},
  numpages = {11},
  url = {http://link.aps.org/abstract/PRB/v80/e125319},
  doi = {10.1103/PhysRevB.80.125319}
}
M. Bamba & H. Ishihara Breakdown of Fermi's Golden Rule in Exciton-Photon Interaction Journal of the Physical Society of Japan
Vol. 78, No. 4, 043701, 4 pages

Post-print  
2009
Abstract: According to Fermi's golden rule, the radiative decay rate of excitons in a thin film becomes higher with increasing film thickness because of the increment of the interaction volume between excitons and photons. However, for a thick film, the decay rate is inversely proportional to the film thickness, because the excitons behave as polaritons and the decay time is proportional to the time of flight. This contradiction reflects a breakdown of Fermi's golden rule in the exciton-photon interaction. We have revealed the breakdown condition by a rigorous calculation method that connects the two radiative decay schemes.
BibTeX:
@article{bamba09radlett,
  author = {Motoaki Bamba and Hajime Ishihara},
  title = {Breakdown of Fermi's Golden Rule in Exciton-Photon Interaction},
  journal = {Journal of the Physical Society of Japan},
  year = {2009},
  month = {Mar},
  volume = {78},
  number = {4},
  pages = {043701},
  numpages = {4},
  doi = {10.1143/JPSJ.78.043701}
}
M. Bamba & H. Ishihara QED of excitons with nonlocal susceptibility in arbitrarily structured dielectrics Physical Review B
Vol. 78, Issue 8, 085109, 22 pages

arXiv:0708.2952 [physics.optics]
selected for Virtual Journal of Nanoscale Science & Technology, Vol. 18, Issue 8 (August 2008)  
2008
Abstract: We have constructed a complete quantum theory for an optical process of excitons with nonlocal susceptibility originating from their center-of-mass motion. This theory provides a practical calculation method for arbitrary-structured nanoscale to macroscale dielectrics where excitons are weakly confined. We obtain good correspondences with underlying theories, semiclassical microscopic nonlocal theory, and QED theories for dispersive and absorptive materials with local susceptibility.
BibTeX:
@article{bamba08qed,
  author = {Motoaki Bamba and Hajime Ishihara},
  title = {QED of excitons with nonlocal susceptibility in arbitrarily structured dielectrics},
  journal = {Physical Review B},
  publisher = {APS},
  year = {2008},
  month = {Aug},
  volume = {78},
  number = {8},
  eid = {085109},
  pages = {085109},
  numpages = {22},
  url = {http://link.aps.org/abstract/PRB/v78/e085109},
  doi = {10.1103/PhysRevB.78.085109},
  archivePrefix = {arXiv},
  eprint = {0708.2952},
  primaryClass = {physics.optics}
}
H. Ishihara, A. Syouji, Y. Segawa, & M. Bamba Anomalous exciton-radiation coupling in the nano-to-bulk crossover regime Journal of Physics: Condensed Matter
Vol. 19, No. 44, 445008, 20 pages
 
2007
Abstract: Anomalous exciton-radiation coupling in the sample-size regime beyond the long-wavelength approximation (LWA) is discussed. In high-quality samples fabricated using the latest technologies, the long-range excitonic coherence and non-LWA effect cause a peculiar interplay between the spatial structures of the radiation and excitonic waves, which emerge as an anomalous level structure of the exciton-radiation coupled system including an extremely large radiative correction. We theoretically demonstrated such a situation for a thin film by a microscopic nonlocal theory in which a size-resonant enhancement of the radiative damping constant and successive interchanges of the confined polariton states can be observed. In order to verify the predicted level structure of confined polaritons, we present the results of non-degenerate two-photon scattering spectroscopy investigations and a corresponding analysis based on the nonlocal theory for the second-order nonlinear process. This scheme has successfully elucidated peculiar level structures of confined polaritons in the non-LWA regime. In the last half of the paper, a new type of resonant hyper-parametric scattering (RHPS) spectroscopy with a non-degenerate induced excitation is theoretically proposed as another method to study confined polaritons in the non-LWA regime. Some calculations for thin films are demonstrated to reveal the potentiality of this method that provides rich information on confined biexcitons and polaritons.
BibTeX:
@article{ishihara07,
  author = {Ishihara, H. and Syouji, A. and Segawa, Y. and Bamba, M.},
  title = {Anomalous exciton-radiation coupling in the nano-to-bulk crossover regime},
  journal = {Journal of Physics: Condensed Matter},
  year = {2007},
  month = {Oct},
  volume = {19},
  number = {44},
  pages = {445008},
  numpages = {20},
  doi = {10.1088/0953-8984/19/44/445008}
}
K. Cho, J. Ushida, & M. Bamba Optical Response of Photonic Crystals Requiring High Precision Band Calculation in the Form of k(ƒึ) Including Evanescent Waves Journal of the Physical Society of Japan
Vol. 74, No. 11, pp. 3088-3092

arXiv:cond-mat/0311496 [cond-mat.mtrl-sci]  
2005
Abstract: We give a general method to calculate photonic band structure in the form of wave number k as a function of frequency ƒึ, which is required whenever we want to calculate signal intensity related with photonic band structure. This method is based on the fact that the elements of the coefficient matrix for the plane wave expansion of the Maxwell equations contain wave number up to the second order, which allows us to rewrite the original eigenvalue equation for ƒึ^2 into that for wave number. This method is much better, especially for complex wave numbers, than the transfer matrix method of Pendry, which gives the eigenvalues in the form of exp[ikd]. The present method leads to a good improvement in the calculation of reflectivity spectrum by eliminating unphysical part due to insufficient precision of numerical results, showing the cross-section dependence of a surface of given Miller index more precisely.
BibTeX:
@article{cho05,
  author = {Cho, K. and Ushida, J. and Bamba, M.},
  title = {Optical Response of Photonic Crystals Requiring High Precision Band Calculation in the Form of k(ƒึ) Including Evanescent Waves},
  journal = {Journal of the Physical Society of Japan},
  year = {2005},
  month = {Nov},
  volume = {74},
  number = {11},
  pages = {3088--3092},
  doi = {10.1143/JPSJ.74.3088},
  archivePrefix = {arXiv},
  eprint = {cond-mat/0311496},
  primaryClass = {cond-mat.mtrl-sci}
}

Proceedings

AuthorsTitleJournalYear
S. Wakaiki, H. Ichida, M. Bamba, T. Kawase, M. Kawakami, K. Mizoguchi, D. Kim, M. Nakayama, & Y. Kanematsu Emission-energy dependence of ultrafast P-emission decay in ZnO from bulk to nanofilm Journal of Luminescence
Vol. 152, pp. 250-253

18th International Conference on Dynamical Processes in Excited States of Solids 
2014
Abstract: We have performed time-resolved photoluminescence (PL) spectroscopy for ZnO thin films with thicknesses of 90, 460, and 2800 nm under intense excitation condition. We clearly observed the P emission due to inelastic exciton-exciton scattering. It was found that, in the 460- and 2800-nm thick samples, the decay time of the P emission considerably depends on the detection energy inversely proportional to the group velocity of the polariton in a bulk crystal with each factor of proportionality. In contrast, the energy dependence is less remarkable in the 90-nm thick sample. The decay times are basically shortened with a decrease in the film thickness. The thickness dependence of the P-emission-decay profiles is explained by considering the crossover from the polariton modes in the 2800-nm thick sample (bulk-like film) to the exciton-/photon-like modes in the 90-nm thick sample (nanofilm).
BibTeX:
@inproceedings{Wakaiki2014JL,
  author = {Shuji Wakaiki and Hideki Ichida and Motoaki Bamba and Toshiki Kawase and Masaki Kawakami and Kohji Mizoguchi and DaeGwi Kim and Masaaki Nakayama and Yasuo Kanematsu},
  title = {Emission-energy dependence of ultrafast P-emission decay in ZnO from bulk to nanofilm},
  booktitle = {18th International Conference on Dynamical Processes in Excited States of Solids},
  journal = {Journal of Luminescence},
  address = {Fuzhou, China},
  year = {2014},
  month = {Aug},
  volume = {152},
  pages = {250--253},
  doi = {http://dx.doi.org/10.1016/j.jlumin.2013.12.024}
}
H. Tahara, M. Bamba, Y. Ogawa, & F. Minami Coherent spectral change of four-wave mixing signals from exciton-polaritons in ZnSe epitaxial layer AIP Conference Proceedings
Vol. 1566, pp. 484-485

THE PHYSICS OF SEMICONDUCTORS: Proceedings of the 31st International Conference on the Physics of Semiconductors (ICPS) 2012 
2013
Abstract: We have investigated a coherent spectral change of exciton-polaritons in a ZnSe epitaxial layer. Using spectrally resolved four-wave mixing spectroscopy, we have observed the dramatically changed spectra, which exhibit an exchange of the dominant peak position between the different polariton branches. This result reflects the initial creation process of polaritons including the exciton-exciton interaction.
BibTeX:
@inproceedings{Tahara2013ICPS,
  author = {H. Tahara and M. Bamba and Y. Ogawa and F. Minami},
  title = {Coherent spectral change of four-wave mixing signals from exciton-polaritons in ZnSe epitaxial layer},
  booktitle = {THE PHYSICS OF SEMICONDUCTORS: Proceedings of the 31st International Conference on the Physics of Semiconductors (ICPS) 2012},
  journal = {AIP Conference Proceedings},
  publisher = {AIP Publishing},
  address = {Zurich, Switzerland},
  year = {2013},
  month = {Dec},
  volume = {1566},
  pages = {484--485},
  doi = {http://dx.doi.org/10.1063/1.4848496}
}
M. Bamba & H. Ishihara Radiative decay theory of excitons in nano-to-macro crossover International School of Physics "Enrico Fermi"
Vol. 171, pp. 521

Proceedings of International School of Physics "Enrico Fermi": Course CLXXI "Quantum Coherence in Solid State Systems" 
2009
BibTeX:
@inproceedings{bamba09summer,
  author = {M. Bamba and H. Ishihara},
  title = {Radiative decay theory of excitons in nano-to-macro crossover},
  booktitle = {Proceedings of International School of Physics "Enrico Fermi": Course CLXXI "Quantum Coherence in Solid State Systems"},
  journal = {International School of Physics "Enrico Fermi"},
  publisher = {IOS Press},
  year = {2009},
  month = {Sep},
  volume = {171},
  pages = {521},
  url = {http://www.sif.it/SIF/it/portal/libri/collane/rendiconti_fermi}
}
M. Bamba & H. Ishihara Radiative decay theory: What suppresses exciton superradiance? physica status solidi (c)
Vol. 6, Issue 1, pp. 128-132

Post-print
Proceedings of 8th Internatioanl Conference on Excitonic Processes in Condensed Matter (EXCON'08) 
2009
Abstract: We have theoretically studied the exciton superradiance which occurs under a phase-match between the exciton center-of-mass motion and the radiation field in a film with thickness over a light wavelength. With continuously increasing the film thickness, the radiative decay rates of excitons are calculated from extreme values of exciton correlation functions renormalizing the exciton-photon interaction in the film with finite thickness. Due to a consideration of intra- and inter-state retarded interactions, in the simplest system, we have derived the correct suppression thickness of the exciton superradiance. The correctness is verified from the general suppression condition derived from the polariton dispersion relation consisting of complex frequency and wavenumber for finite thickness.
BibTeX:
@inproceedings{bamba08excon,
  author = {Motoaki Bamba and Hajime Ishihara},
  title = {Radiative decay theory: What suppresses exciton superradiance?},
  booktitle = {Proceedings of 8th Internatioanl Conference on Excitonic Processes in Condensed Matter (EXCON'08)},
  journal = {physica status solidi (c)},
  address = {Kyoto, Japan},
  year = {2009},
  month = {Jan},
  volume = {6},
  number = {1},
  pages = {128--132},
  doi = {http://dx.doi.org/10.1002/pssc.200879811}
}
M. Bamba & H. Ishihara QED theory for excitons with microscopic nonlocality physica status solidi (c)
Vol. 5, Issue 7, pp. 2387-2390

Post-print
Proceedings of 10th Conference on the "Optics of Excitons in Confined Systems" (OECS10) 
2008
Abstract: We have constructed QED theory for excitons with microscopic nonlocality or nonlocal susceptibility originating from their center-of-mass motion. The nonlocality must be properly considered in excitons' weak (center-of-mass) confinement regime where the long wavelength approximation is breakdown. This theory keeps good correspondences with its underlying theories, the QED theory for dispersive and absorptive local dielectrics and the microscopic nonlocal theory developed in the semiclassical framework. Our theory provides correlation functions of excitons, which renormalize radiative shift, transition between exciton states via electromagnetic fields, radiative and nonradiative relaxation processes. By using these functions, we can systematically study various nonlinear, dephasing, and emission processes of excitons in weak-confinement to bulk-like systems.
BibTeX:
@inproceedings{bamba08oecs,
  author = {Motoaki Bamba and Hajime Ishihara},
  title = {QED theory for excitons with microscopic nonlocality},
  booktitle = {Proceedings of 10th Conference on the "Optics of Excitons in Confined Systems" (OECS10)},
  journal = {physica status solidi (c)},
  address = {Messina, Patti, Italy},
  year = {2008},
  month = {Jun},
  volume = {5},
  number = {7},
  pages = {2387--2390},
  doi = {http://dx.doi.org/10.1002/pssc.200777616}
}
M. Bamba & H. Ishihara Entangled-photon generation via biexcitons in nano-structures physica status solidi (c)
Vol. 3, Issue 10, pp. 3460-3463

Post-print
Proceedings of 7th Internatioanl Conference on Excitonic Processes in Condensed Matter (EXCON'06) 
2006
Abstract: We have constructed quantum electrodynamics theory for excitons whose center-of-mass motion is confined in arbitrary-structured dielectrics with considering their nonlocal optical susceptibility. We systematically investigate entangled-photon generation via biexcitons in nano-to-macro scale materials by this theory. It is revealed that nano-structured materials provide scattering spectra explicitly reflecting quantum states of confined exciton-polaritons and are promising sources of entangled photons from the viewpoints of both efficiency and signal-to-noise ratio.
BibTeX:
@inproceedings{bamba06,
  author = {Motoaki Bamba and Hajime Ishihara},
  title = {Entangled-photon generation via biexcitons in nano-structures},
  booktitle = {Proceedings of 7th Internatioanl Conference on Excitonic Processes in Condensed Matter (EXCON'06)},
  journal = {physica status solidi (c)},
  publisher = {Wiley-VCH},
  address = {Winston-Salem, NC. USA},
  year = {2006},
  month = {Nov},
  volume = {3},
  number = {10},
  pages = {3460--3463},
  doi = {http://dx.doi.org/10.1002/pssc.200672106}
}

Technical Reports

AuthorsTitleJournalYear
M. Bamba & H. Ishihara Entangled-Photon Generation via Biexcitons in Semiconductor Nano-Structures Conference on Lasers and Electro-Optics / Quantum Electronics and Laser Science Conference and Photonic Applications Systems Technologies (CLEO/QELS and PhAST) 2006 Technical Digest
Optical Society of America
Washington, DC, USA
May 2006
JTuD4  
2006
BibTeX:
@techreport{bamba06qels,
  author = {Motoaki Bamba and Hajime Ishihara},
  title = {Entangled-Photon Generation via Biexcitons in Semiconductor Nano-Structures},
  booktitle = {Conference on Lasers and Electro-Optics / Quantum Electronics and Laser Science Conference and Photonic Applications Systems Technologies (CLEO/QELS and PhAST) 2006 Technical Digest},
  institution = {Optical Society of America},
  address = {Washington, DC, USA},
  year = {2006},
  month = {May},
  pages = {JTuD4},
  doi = {http://dx.doi.org/10.1109/CLEO.2006.4628630}
}

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