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We demonstrate single-frequency stimulated Brillouin lasing in short fiber Fabry–Perot resonators. A sub-milliwatt threshold for lasing is observed in resonators with high quality factors of ∼1.5 × 108 and effective resonator lengths as short as ∼5 mm. The strong dispersion of fiber Bragg gratings results in unequal frequency separations for neighboring pairs of longitudinal modes with separation differences larger than the Brillouin gain bandwidth, thereby avoiding cascaded lasing. Our achievement will enable compact, robust, efficient narrow-linewidth light sources.

We analyze the requirements for fault-tolerant quantum computation with atom-atom gates based on cavity quantum electrodynamics (cQED) mediated by a photon with a finite pulse length. For short photon pulses, the distorted shape of the reflected pulses from the cQED system is a serious error source. We optimize the cQED system parameters to minimize the infidelity due to the shape distortion and the photon losses in a well-balanced manner for the fault-tolerant scheme using probabilistic gates [H. Goto and K. Ichimura, Phys. Rev. A 80, 040303(R) (2009)]. Our optimization greatly relaxes the requirements for fault-tolerant quantum computation in some parameter regions, compared with the conventional optimization method where only the photon loss is minimized without considering the shape distortion [H. Goto and K. Ichimura, Phys. Rev. A 82, 032311 (2010)]. Finally, we show that reducing the cavity length is an effective way to reduce the errors of this type of gate in the case of short photon pulses., 10 pages, 10 figures, 2 tables

Quantum silicon photonics must overcome considerable loss engineering challenges before it can scale to the millions of physical qubits required for fault tolerant quantum computation [1] . The first such challenge is the intrinsic two-photon absorption (TPA), present in silicon at telecommunications wavelengths. This places fundamental limits on the heralding or Klyshko efficiency of silicon photon-pair sources based on spontaneous four-wave mixing (SFWM) [2] . We have recently shown that by moving to a pump wavelength beyond 2-microns, in the mid-infrared (MIR), TPA in silicon can be curtailed, and by using 340-nm thick silicon waveguides, phase matching can be achieved for efficient SFWM [2] .

形態: カラー図版あり, Physical characteristics: Original contains color illustrations, Accepted: 2021-01-13, 資料番号: PA2110036000

Benzpyrimoxan (5-(1,3-dioxan-2-yl)-4-{[4-(trifluoromethyl)phenyl]methoxy}pyrimidine, NNI-1501) was discovered as a novel insecticide structurally characterized by a pyrimidine derivative substituted with 1,3-dioxanyl and 4-trifluoromethylbenzyloxy groups. The compound showed remarkable activity against nymphs of rice planthoppers, including strains resistant to existing insecticides. Furthermore, benzpyrimoxan had low adverse effects on pollinators and beneficial arthropods. Because of these features, benzpyrimoxan is expected to be a suitable part of an integrated pest management strategy. In this report, the history of the discovery to reach benzpyrimoxan and details of the structure-activity relationships are described.

Benzpyrimoxan, (5-(1,3-dioxan-2-yl)-4-[4-(trifluoromethyl)benzyloxy]pyrimidine), is a novel insecticide with a unique chemical structure that contains benzyloxy and cyclic acetal groups on the pyrimidine moiety. The compound showed molting inhibition and provided excellent residual efficacy against nymphs of rice plant hoppers, including populations that had developed resistance to the existing chemical groups of insecticides. In addition, benzpyrimoxan had low impacts on the natural enemies and honey bees, suitable for integrated pest management strategy. In this review the history of discovery to reach benzpyrimoxan, the discovery of insecticidal pyridine or pyrimidine derivatives as lead compounds, and the details of substituent optimizations are discussed.

We theoretically derive the optimal parameters of a cavity quantum-electrodynamics system such as the cavity length and the transmittance for achieving high speed quantum computation with low error rates.

We show that the requirement for fault-tolerant quantum computation based on cavity-QED is dramatically relaxed by applying the suitable fault-tolerant schemes and gate error optimization for chosen two-qubit gate method. © 2020 Rui Asaoka

Activation of blood cells during hemodialysis is considered to be a significant determinant of biocompatibility of the hemodialysis membrane because it may affect patient health adversely through microvascular inflammation and oxidative stress. This study found very different cell activation among various polysulfone (PSf) hemodialysis membranes. For example, CX-U, a conventional PSf membrane, induced marked adhesion of platelets to its surface and increased surface expression of activated CD11b and production of reactive oxygen species (ROS) by neutrophils; while NV-U, a hydrophilic polymer-immobilized PSf membrane, caused little platelet adhesion and slight CD11b expression and ROS production by neutrophils. Analysis of the molecular mechanisms of the above phenomena on CX-U and NV-U indicated that anti-integrin GPIIb/IIIa antibody blocked platelet adhesion, and that the combination of anti-CD11b (integrin α subunit of Mac-1) and anti-integrin αvβ3 antibodies blocked ROS production by neutrophils. Plasma-derived fibrinogen, a major ligand of GPIIb/IIIa, Mac-1, and αvβ3 on membranes, was thus analyzed and found to be more adsorbed to CX-U than to NV-U. Moreover, comparison between five PSf membranes showed that the number of adherent platelets and neutrophil ROS production increased with increasing fibrinogen adsorption. These results suggested that fibrinogen, adsorbed on membranes, induced GPIIb/IIIa-mediated platelet activation and Mac-1/αvβ3-mediated neutrophil activation, depending on the amount of adsorption. In conclusion, the use of biocompatible membranes like NV-U, which show lower adsorption of fibrinogen, is expected to reduce hemodialysis-induced inflammation and oxidative stress by minimizing cell activation.

We report on a combined experimental and theoretical investigation into the normal modes of an all-fiber coupled cavity-quantum-electrodynamics system. The interaction between atomic ensembles and photons in the same cavities, and that between the photons in these cavities and the photons in the fiber connecting these cavities, generates five nondegenerate normal modes. We demonstrate our ability to excite each normal mode individually. We study particularly the ``cavity dark mode,'' in which the two cavities coupled directly to the atoms do not exhibit photonic excitation. Through the observation of this mode, we demonstrate remote excitation and nonlocal saturation of atoms.

We investigate a tradeoff relation between the internal generation efficiency and the escape efficiency for single-photon generation based on cavity quantum electrodynamics, where cavity internal loss is treated explicitly. Consequently, we analytically derive an upper bound on the overall efficiency. The bound is expressed only with an internal cooperativity, introduced here as the cooperativity parameter with respect to the cavity internal loss rate. This result means that the internal cooperativity is a figure of merit for single-photon generation based on cavity QED. The bound is derived by optimizing the cavity external loss rate, which can be experimentally controlled by designing or tuning the transmissivity of the output coupler. The model here is general enough to treat various cavity-QED effects, such as the Purcell effect, on-resonant or off-resonant cavity-enhanced Raman scattering, and vacuum-stimulated Raman adiabatic passage. For typical optical systems, we additionally take into account a ``reexcitation'' process, where the atom is reexcited after its decay to the initial ground state.

In a cavity quantum electrodynamics (QED) system, where atoms coherently interact with photons in a cavity, the eigenstates of the system are the superposition states of atoms and cavity photons, the so-called dressed states of atoms. When two cavities are connected by an optical fiber with negligible loss, the coherent coupling between the cavities gives rise to photonic normal modes. One of these normal modes is the fiber-dark mode, in which photons are delocalized in the two distant cavities. Here we demonstrate the setting of coupled-cavities QED, where two nanofiber cavity-QED systems are coherently connected by a meter-long low-loss channel in an all-fiber fashion. Specifically, we observe dressed states of distant atoms with delocalized photons of the fiber-dark normal mode. Our system will provide a platform for the study of delocalized atomic and photonic states, photonic many-body physics, and distributed quantum computation., The coherent dynamics of coupled atoms that interact with a common mode is different from that of independent atoms. Here the authors demonstrate the delocalization of excited states of atoms and photons using two ensembles of cold Cs atoms in cavities connected with meter long optical fiber.

A semiclassical model is presented for characterizing the linear response of elementary quantum optical systems involving cavities, optical fibers, and atoms. Formulating the transmission and reflection spectra using a scattering-wave (transfer matrix) approach, the calculations become easily scalable. To demonstrate how useful this method is, we consider the example of a simple quantum network, i.e., two cavity-QED systems connected via an optical fiber. Differences between our quasi-exact transfer matrix approach and a single-mode, linearized quantum-optical model are demonstrated for parameters relevant to recent experiments with coupled nanofiber-cavity-QED systems.

We demonstrate the fabrication of ultra-low-loss, all-fiber Fabry–Perot cavities that contain a nanofiber section, optimized for cavity quantum electrodynamics. By continuously monitoring the finesse and fiber radius during the fabrication of a nanofiber between two fiber Bragg gratings, we were able to precisely evaluate taper transmission as a function of radius. The resulting cavities have an internal round-trip loss of only 0.31% at a nanofiber waist radius of 207 nm, with a total finesse of 1380, and a maximum expected internal cooperativity of ∼ 1050 for a cesium atom on the nanofiber surface. Our ability to fabricate such high-finesse nanofiber cavities may open the door for the realization of high-fidelity scalable quantum networks.

We report on experimentally measured light shifts of superconducting flux qubits deep-strongly coupled to LC oscillators, where the coupling constants are comparable to the qubit and oscillator resonance frequencies. By using two-tone spectroscopy, the energies of the six lowest levels of each circuit are determined. We find huge Lamb shifts that exceed 90% of the bare qubit frequencies and inversions of the qubits' ground and excited states when there are a finite number of photons in the oscillator. Our experimental results agree with theoretical predictions based on the quantum Rabi model., Comment: 19 pages, 7 figures, and 2 tables. Supplemental Material is included

Secrecy issues of free-space optical links realizing information theoretically secure communications as well as high transmission rates are discussed. We numerically study secrecy communication rates of optical wiretap channel based on on-off keying modulation under typical conditions met in satellite-ground links. It is shown that under reasonable degraded conditions on a wiretapper, information theoretically secure communications should be possible in a much wider distance range than a range limit of quantum key distribution, enabling secure optical links between geostationary earth orbit satellites and ground stations with currently available technologies. We also provide the upper bounds on the decoding error probability and the leaked information to estimate a necessary code length for given required levels of performances. This result ensures that a reasonable length wiretap channel code for our proposed scheme must exist., Comment: 12 pages, 17 figures

In a few Japanese populations of the loach Misgurnus anguillicaudatus (Teleostei: Cobitidae), clonal diploid lineages produce unreduced diploid eggs that normally undergo gynogenetic reproduction; however the origin of these clones remains elusive. Here, we show the presence of two diverse clades, A and B, within this loach species from sequence analyses of two nuclear genes RAG1 (recombination activating gene 1) and IRBP2 (interphotoreceptor retinoid-binding protein, 2) and then demonstrate heterozygous genotypes fixed at the two loci as the evidence of the hybrid nature of clonal lineages. All the clonal individuals were identified by clone-specific mitochondrial DNA haplotypes, microsatellite genotypes, and random amplified polymorphic DNA fingerprints; they commonly showed two alleles, one from clade A and another from clade B, whereas other wild-type diploids possessed alleles from either clade A or B. However, we also found wild-type diploids with clone-specific mitochondrial DNA and nuclear genes from clade B. One possible explanation is an introgression of a clone-specific mitochondrial genome from clonal to these wild-type loaches. These individuals likely arose by a cross between haploid sperm from bisexual B clade males and haploid eggs with clone-specific mtDNA and clade B nuclear genome, produced by meiotic hybridogenesis (elimination of unmatched A genome followed by meiosis after preferential pairing between two matched B genomes) in clone-origin triploid individual (ABB).

Nitrogen-Vacancy (NV) centers in diamond are promising solid-state quantum emitters that can be utilized for photonic quantum applications. Various diamond nanophotonic devices have been fabricated for efficient extraction of single photons emitted from NV centers to a single guided mode. However, for constructing scalable quantum networks, further efficient coupling of single photons to a guided mode of a single-mode fiber (SMF) is indispensable and a difficult challenge. Here, we propose a novel efficient hybrid system between an optical nanofiber and a cylindrical-structured diamond nanowire. The maximum coupling efficiency as high as 75% for the sum of both fiber ends is obtained by numerical simulations. The proposed hybrid system will provide a simple and efficient interface between solid-state quantum emitters and a SMF suitable for constructing scalable quantum networks.

The University of Tokyo Atacama Observatory Project is to construct and operate a 6.5m infrared telescope at the summit of Co. Chajnantor (5640m altitude) in northern Chile, promoted by the Institute of Astronomy of the University of Tokyo. Thanks to the dry climate (PWV~0.5mm) and the high altitude, excellent observation condition in the NIR to MIR wavelengths is achieved. The telescope has two Nasmyth foci where two facility instruments, SWIMS for the near-infrared and MIMIZUKU for the mid-infrared, are installed and two folded- Cassegrain foci for carry-in instruments. All these four foci can be switched by rotating a tertiary mirror. The final focal ratio is 12.2 and the foci have large field-of-view of 25 arcmin in diameter. We adopted a 6.5-m F/1.25 light-weighted borosilicate honeycomb primary mirror and its support system that are developed by Steward Observatory Richard F. Caris Mirror Lab. An enclosure has the shape of carousel, and large ventilation windows with shutters control the wind to flush heat inside the enclosure. A support building with a control room, a mirror coating system and maintenance facilities is located at the side of the enclosure. The mirror coating system consists of a large aluminizing chamber and a mirror washing facility. The operation of the telescope will be remotely carried out from a base facility at San Pedro de Atacama, 50km away from the summit. Development of the two facility instruments has already been completed and they are transported to Hilo, Hawaii in 2017. We are going to carry out engineering observations of those instruments on the Subaru telescope for clearing up technical issues and verifying their performance. The existing summit access road from the ALMA concession area was laid in 2006, however, it is too narrow to carry large components of the telescope and the ancillary facilities such as the primary mirror, its cell, and the aluminizing chamber. The road is being expanded so that it has the width of

We present experimental data on message transmission in a free-space optical (FSO) link at an eye-safe wavelength, using a testbed consisting of one sender and two receiver terminals, where the latter two are a legitimate receiver and an eavesdropper. The testbed allows us to emulate a typical scenario of physical-layer (PHY) security such as satellite-to-ground laser communications. We estimate information-theoretic metrics including secrecy rate, secrecy outage probability, and expected code lengths for given secrecy criteria based on observed channel statistics. We then discuss operation principles of secure message transmission under realistic fading conditions, and provide a guideline on a multi-layer security architecture by combining PHY security and upper-layer (algorithmic) security., Comment: 16 pages, 8 figures

As with any viable technology, quantum-information processors have to deal with imperfections. The experimental implementation of a quantum-error correction code indicates how imperfections can be handled in a system where quantum information is encoded in continuous variables. Quantum computation and communication rely on the ability to manipulate quantum states robustly and with high fidelity. To protect fragile quantum-superposition states from corruption through so-called decoherence noise, some form of error correction is needed. Therefore, the discovery of quantum error correction1,2 (QEC) was a key step to turn the field of quantum information from an academic curiosity into a developing technology. Here, we present an experimental implementation of a QEC code for quantum information encoded in continuous variables, based on entanglement among nine optical beams3. This nine-wave-packet adaptation of Shor’s original nine-qubit scheme1 enables, at least in principle, full quantum error correction against an arbitrary single-beam error.

A beam rebuncher for the RIKEN radioactive-isotope beam factory project has been constructed and is placed in a long beam line between the first two ring cyclotrons in the accelerator cascade. The rebuncher resonator, having four rf gaps in it, operates at a fixed frequency of 109.5 MHz for the longitudinal focusing of heavy ion beams at 11.0 MeV / u . To reduce the sparking problem in the rf gaps, a new type of H-mode resonator has been adopted, where the distribution of the gap voltage is well equalized. In fact, the ratio of the gap voltages is about 1.26, whereas those of the interdigital-H (IH)- and crossed-bar-H (CH)-mode structures are larger than 2.0. The total gap voltage, which is defined as the sum of the four gap voltages, has reached 495 kV at a power consumption of 4.7 kW.

Beyond traditional nonlinear optics with large numbers of atoms and photons, qualitatively new phenomena arise in a quantum regime of strong interactions between single atoms and photons. By using a microscopic optical resonator, we achieved such interactions and demonstrated a robust, efficient mechanism for the regulated transport of photons one by one. With critical coupling of the input light, a single atom within the resonator dynamically controls the cavity output conditioned on the photon number at the input, thereby functioning as a photon turnstile. We verified the transformation from a Poissonian to a sub-Poissonian photon stream by photon counting measurements of the input and output fields. The results have applications in quantum information science, including for controlled interactions of single light quanta and for scalable quantum processing on atom chips.

By means of THz pump and optical probe spectroscopy, we observed that the incident THz pulse induces a strong spectral modulation of the 1s heavy-hole exciton peak of GaAs quantum wells due to Rabi splitting. Our precise measurements in the time domain show that the Rabi splitting follows the instantaneous THz electric pulse at extremely strong fields but persists up to a negative delay time of ~1 ps at weak fields. This field dependent dynamics of the Rabi splitting indicates that the excitonic field ionization governs a nonperturbative nonlinear dynamics of excitons by causing a reduction of the dephasing time

In a few Japanese populations of the loach Misgurnus anguillicaudatus (Teleostei: Cobitidae), clonal diploid lineages produce unreduced diploid eggs that normally undergo gynogenetic reproduction; however the origin of these clones remains elusive. Here, we show the presence of two diverse clades, A and B, within this loach species from sequence analyses of two nuclear genes RAG1 (recombination activating gene 1) and IRBP2 (interphotoreceptor retinoid-binding protein, 2) and then demonstrate heterozygous genotypes fixed at the two loci as the evidence of the hybrid nature of clonal lineages. All the clonal individuals were identified by clone-specific mitochondrial DNA haplotypes, microsatellite genotypes, and random amplified polymorphic DNA fingerprints; they commonly showed two alleles, one from clade A and another from clade B, whereas other wild-type diploids possessed alleles from either clade A or B. However, we also found wild-type diploids with clone-specific mitochondrial DNA and nuclear genes from clade B. One possible explanation is an introgression of a clone-specific mitochondrial genome from clonal to these wild-type loaches. These individuals likely arose by a cross between haploid sperm from bisexual B clade males and haploid eggs with clone-specific mtDNA and clade B nuclear genome, produced by meiotic hybridogenesis (elimination of unmatched A genome followed by meiosis after preferential pairing between two matched B genomes) in clone-origin triploid individual (ABB).

We demonstrate time-bin entanglement generation in telecom wavelength using a 7 {\mu}m radius Si micro-ring resonator pumped by a continuous wave laser. The resonator structure can enhance spontaneous four wave mixing, leading to a photon pair generation rate of about 90-100 Hz with a laser pump power of as low as -3.92 dBm (0.41 mW). We succeed in observing time-bin entanglement with the visibility over 92%. Moreover, wavelength-tunability of the entangled photon pair is demonstrated by changing the operation temperature., Comment: 12 pages, 7 figures

By combining a tilted-pulse-intensity-front scheme using a LiNbO3 crystal and a chirped-pulse-beating method, we generated a narrowband intense terahertz (THz) pulse, which had a maximum electric field of more than 10 kV/cm at around 2 THz, a bandwidth of about 50 GHz,and frequency tunability from 0.5 to 2 THz. By performing THz-pump and near-infrared-probe experiments on GaAs quantum wells, we observed that the resonant excitation of the intraexcitonic 1s-2p transition induces a clear and large Autler-Townes splitting. Our time-resolved measurements show that the splitting energy observed in the rising edge region of electric field is larger than in the constant region. This result implies that the splitting energy depends on the time-averaged THz field over the excitonic dephasing time rather than that at the instant of the exciton creation by a probe pulse.

We demonstrate an all-fiber cavity quantum electrodynamics system with a trapped single atom in the strong coupling regime. We use a nanofiber Fabry-Perot cavity, that is, an optical nanofiber sandwiched by two fiber-Bragg-grating mirrors. Measurements of the cavity transmission spectrum with a single atom in a state-insensitive nanofiber trap clearly reveal the vacuum Rabi splitting.

In order to check the validity of Akasofu’s ε parameter and of the Vasyliunas et al. (1982) general formula, we examine the dependence of the ring current injection rate, calculated from the Dst index for the period of 1965–1990, on the interplanetary magnetic field (IMF). We compare the influence of the Bz component with the influence of the combination of sin(θ/2), where θ is the IMF clock angle, and the IMF magnitude, B, (or the transverse component of the IMF, BT = (By2 + Bz2)1/2) by using the regression analysis in a power law form. The main results are as follows: (1) the exponent for Bz shows higher consistency than that for sin(θ/2); (2) we never obtain B 2 sin4(θ/2) or B T 2 sin4(θ/2), which is the IMF dependence expected from the ε parameter; and (3) the ring current injection rate has a very low correlation with the Alfven Mach number, from which the IMF dependence of the Vasyliunas et al. general formula is assumed to arise. On the basis of the above results we conclude that the ε parameter and the Vasyliunas et al. general formula are less appropriate than a function of Bz, and that the energy coupling function between the solar wind and the Earth’s magnetosphere is described better by Bz than by the combination of B (or B T) and sin(θ/2). The above results and conclusions are the same as those obtained by Aoki (2005) through the analysis of the AL index.

The ε parameter of Akasofu and the general formula of Vasyliunas et al. (1982) have been widely used as functions representing the rate of the solar wind energy input into the Earth’s magnetosphere. These two functions have a feature that dependence on the interplanetary magnetic field (IMF) is assumed to be expressed by the combination of B, the magnitude of the IMF, and sin (θ/2), where θ is the clock angle, or by the combination of B T = (By 2 + Bz 2)1/2, the magnetic field perpendicular to the Sun-Earth line, and sin(θ/2), not by the Bz component. We check the validity of this assumption by presuming that the AL index has good correlation with the solar wind energy input rate and by applying the regression analysis in a power law form to hourly values of the AL index and of solar wind parameters during the period 1966–1987. We show that Bz generally gives high correlation coefficients and shows higher consistency in exponents than the combination of B (or B T ) and sin (θ/2). Thus we conclude that the IMF dependence of the rate of the solar wind energy input is described better by Bz than by the combination of B (or B T ) and sin(θ/2).

アレルギー疾患合併小児162例 (A群) (男/女: 92/70) とアレルギー疾患非合併小児47例 (B群) (男/女: 25/22) を対象としてインフルエンザワクチンの副反応を検討すると同時に, フマル酸ケトチフェンによる予防内服の有用性を調べた. A群のうち即時型の卵アレルギーを有する症例は15例であった. A群の79例とB群の15例 (計94例) ではワクチンの100倍希釈液で皮内テストを施行した. また, 全209例中44例でフマル酸ケトチフェンの予防内服を施行しその有効性を検討した. その結果, 皮内テスト施行例のうち皮膚スコア2 (発赤径20-39mm) を示した症例は, A群24% (卵アレルギー群での検討では13%), B群20%と差を認めなかった. しかし, 両群とも約10%に皮内テストから予測できない強い即時型局所反応がワクチン接種部位に認められた. 遅発型局所反応は209例中24例 (11%) に認められ, A群18例 (11%), B群6例 (11%) であった. 即時型局所反応ろコアとワクチン接種回数との関係では, 即時型局所反応スコアが2以上を示した割合はそれぞれ, 初年度例の6%, 2年度例の23%, 3年度例の26%, 4年以上例の42%であり, 複数回接種により接種部位の即時型局所反応が出やすくなることが判明した. また, 遅延型局所反応でも同様の関係が認められた. フマル酸ケトチフェンによる予防内服の効果に関しては, 即時型局所反応, 遅延型局所反応ともに有効性が認められた.

Diamond nanowires are fabricated on a bulk, single crystalline diamond near an edge of aluminum coating using inductively coupled plasma reactive ion etching. Two different density areas are simultaneously appeared where the dense area has 9 times higher density than that of the sparse area while keeping the size of nanowires almost uniform in these areas. The nanowire sizes realized in the dense (sparse) area are 858 ± 22 nm (876 ± 25 nm) in height and 126 ± 6 nm (124 ± 7 nm) in diameter, which is suitable for applications in optical quantum information processing.

We study the elimination of the chirp of narrowband terahertz pulses generated by chirped laser pulse beating using a laser pulse stretcher with two grating pairs that cancel out the third-order spectral phase. First, we show that positively chirped terahertz pulses can be generated using a pulse stretcher with a grating pair and internal lenses. We then combine this with a second grating pair, the spectral phase of which has the opposite sign to that of the first one. By varying the separation of the second grating pair, we experimentally verify that the chirp of the generated terahertz pulses can be eliminated.

The University of Tokyo Atacama Observatory (TAO) is a project to construct a 6.5-meter telescope optimized for infrared observations at the summit of Co. Chajnantor, 5,640 m altitude. The high altitude and low water vapor (0.5mm in 25% percentile) of the site provide wide wavelength coverage from 0.3 to 38 micron including continuous window from 0.9 to 2.5 micron and new windows at wavelength longer than 25 micron. We report on the design and the current status of the mirror, the telescope, the summit and the base facilities in this paper.

We propose a scheme for single-atom, quantum control of the direction of propagation of a coherent field incident, via a tapered fiber, upon a microtoroidal whispering-gallery-mode (WGM) resonator. The scheme involves overcoupling of the fiber-taper to the resonator and strong coupling of an atom to the evanescent field of the WGM, i.e., an atom-field coupling that exceeds the total WGM linewidth. In contrast to previous, related schemes that operate in the bad-cavity regime, the proposed scheme can operate effectively with much stronger incident fields, while also preserving their coherent nature. It can also serve to prepare an entangled state of the atom and coherent optical pulses propagating in opposite directions along the fiber. We evaluate the fidelity of preparation of such a state taking into account absorption and atomic spontaneous emission and demonstrate that high fidelities should be possible with realistic parameters., 13 pages, 9 figures

Single-photon sources are important elements in quantum optics and quantum information science. It is crucial that such sources be able to couple photons emitted from a single quantum emitter to a single propagating mode, preferably to the guided mode of a single-mode optical fiber, with high efficiency. Various photonic devices have been successfully demonstrated to efficiently couple photons from an emitter to a single mode of a cavity or a waveguide. However, efficient coupling of these devices to optical fibers is sometimes challenging. Here we show that up to 38% of photons from an emitter can be directly coupled to a single-mode optical fiber by utilizing the flat tip of a silica nanofiber. With the aid of a metallic mirror, the efficiency can be increased to 76%. The use of a silicon waveguide further increases the efficiency to 87%. This simple device can be applied to various quantum emitters.

Suppression of the chirp of terahertz (THz) pulses by using a single-mode optical fiber as a pulse stretcher is investigated.We theoretically show that the chirp obtained with fiber-based pulse stretcher can be suppressed below the fundamental limit for a grating-based pulse stretcher. We experimentally verify the validity of this theory and demonstrate generation of low-chirp THz pulses.

Efficient coupling of photons from a single-photon source to the single-mode optical fiber is necessary for quantum cryptography and quantum information technology. Nanoemitters such as quantum dots, NV centers in nanodiamonds, and atoms are employed as a single-photon source. A typical method to collect photons from a nanoemitter is to use a lens with high numerical aperture (NA). However, further coupling of the photons collected by a lens to a single-mode optical fiber reduces the actual coupling efficiency. Recently the uses of silica nanofibers to collect light from a nanoemitter have been proposed and demonstrated[1-4]. A nanofiber is adiabatically connected to a standard single-mode optical fiber through a tapered region with low losses. In previous studies, photons from a nanoemitter are coupled to the guided mode of a nanofiber through the evanescent field around the nanofiber surface. In this study, we propose a new method utilizing a nanofiber tip to collect light from a nanoemitter to a nanofiber. We numerically simulated the coupling efficiency of light into the nanofiber when a point dipole source is located in the vicinity of a tip of nanofiber. Figure (a) depicts the simulation geometry. Figure (b) shows the dependence of the coupling efficiency on the nanofiber radius. Simulations are performed for radial and axial polarizations of the source. Up to 38% of the light radiated by a source is coupled to the fundamental guided mode of the nanofiber. Therefore these devices utilizing a nanofiber tip can be applied to efficient singlephoton sources.

Optical microresonators confine light at resonant frequency strongly in small volumes and are applied in various fields of quantum optics and nonlinear optics [1]. Figures of merit for microresonators in these applications are proportional to Q/V or Q 2 /V, where Q is the Q-factor and V is the cavity mode volume. Q-factors of 8 × 10 9 have been observed with silica spherical resonators with 750 μm in diameter fabricated by fusing silica rods [2][3]. However, it has been difficult to fabricate high-Q spheres with diameters smaller than 20 μm [4]. Here we fabricate high-Q monolithic microspherical resonators on a silicon chip with a diameter as small as 18 μm.

Chirped laser pulses are widely used in coherent control of various quantum systems. In order to apply such techniques to terahertz (THz) frequencies, it is desirable to develop a method to generate THz pulses with controlled linear chirp. Difference frequency generation with chirped laser pulse pairs [1, 2], or chirped pulse beating, is a simple way of generating tunable narrowband THz pulses. In our previous study [3], we have derived the direct relationship between the spectral phase of the pulse stretcher and the linear chirp of the generated THz pulse in the chirped pulse beating, and experimentally demonstrated generation of THz pulses with minimal chirp. In this study, we show that the chirped pulse beating can be also used to generate strongly chirped THz pulse by numerical simulations.