We introduce a new Fabry-Perot based interferometnc gravitational wave detector that, compared with previous designs, greatly decreases the amount ofpower that must be transmitted through optical substrates to obtain a given light power in its arms. This significantly reduces the effects ofwavefront distortions caused by heating due to absorption in the optics, and allows an improved broadband sensitivity to be achieved.To obtain a good sensitivity in long-baseline interferometric gravitational wave detectors, one requires high light power in the arms of the interferometer to increase the photon-statistic limited signal-to-noise ratio. In the standard Fabry-Perot configuration, which consists of a Michelson interferometer having a Fabry-Perot cavity in each arm [1], this can be done by increasing the finesse of the cavities (made possible by the availability of very low-loss mirror coatings). The storage-time for the signal sidebands must, however,be kept short enough to give the desired detection bandwidth (since cavities act like low-pass filters). This determines what is referred to as the storage-time limit. A high laser power, or a "power recycling mirror" [1], must then be used to compensate for the limitation that the storage-time puts on the power enhancement in the arm cavities. To obtain a sensitivity and a bandwidth which are desirable in future advanced detectors, one is then required to have extremely high light power incident on the beamsplitter, potentially in excess of 10 kW. Thermally induced lensing in the beamsplitter and mirror substrates will make it exceedingly difficult to reach this power [2,31. By using the principles of coupled cavities, it is possible to increase the finesse of the arm cavities beyond M 2a M1 a Mib M2bFrom ___________ Laser i~= M~Fig. 1. Schematic diagram of the optical configuration of reso-• nant sidebandextraction. The storage-time for the carrier light in the arms is longer than the storage-timelimit, whereas the stor. r Photodetector age-time for differentially generated sidebands is reduced by the existence of the signal extraction mirror (M3).

We discuss image formation in phase-shifting digital holography by developing an analytical formulation based on the Fresnel-Kirchhoff diffraction theory. Image-plane position and imaging magnification are derived for general configurations in which a spherical reference is employed. The influences of discrete sampling of the resulting interference patterns by a CCD and numerical reconstruction on qualities of point images are investigated. Dependence of the point images on the ratio of the minimum fringe spacing to pixel pitch of the CCD is numerically analyzed. Two-point resolution and magnification are also investigated as a function of pixel numbers by a simulation using a one-dimensional model. In experiments magnified images of biological objects and a resolution target were reconstructed with the same quality as by conventional microscopy.

The electrochemistry and electrogenerated chemiluminescence (ECL) of four kinds of electron donor-acceptor molecules exhibiting thermally activated delayed fluorescence (TADF) is presented. TADF molecules can harvest light energy from the lowest triplet state by spin up-conversion to the lowest singlet state because of small energy gap between these states. Intense green to red ECL is emitted from the TADF molecules by applying a square-wave voltage. Remarkably, it is shown that the efficiency of ECL from one of the TADF molecule could reach about 50%, which is comparable to its photoluminescence quantum yield.

Protein secretion, a key intercellular event for transducing cellular signals, is thought to be strictly regulated. However, secretion dynamics at the single-cell level have not yet been clarified because intercellular heterogeneity results in an averaging response from the bulk cell population. To address this issue, we developed a novel assay platform for real-time imaging of protein secretion at single-cell resolution by a sandwich immunoassay monitored by total internal reflection microscopy in sub-nanolitre-sized microwell arrays. Real-time secretion imaging on the platform at 1-min time intervals allowed successful detection of the heterogeneous onset time of nonclassical IL-1β secretion from monocytes after external stimulation. The platform also helped in elucidating the chronological relationship between loss of membrane integrity and IL-1β secretion. The study results indicate that this unique monitoring platform will serve as a new and powerful tool for analysing protein secretion dynamics with simultaneous monitoring of intracellular events by live-cell imaging.

The amount of information transmissible through a communications channel is determined by the noise characteristics of the channel and by the quantities of available transmission resources. In classical information theory, the amount of transmissible information can be increased twice at most when the transmission resource (e.g. the code length, the bandwidth, the signal power) is doubled for fixed noise characteristics. In quantum information theory, however, the amount of information transmitted can increase even more than twice. We present a proof-of-principle demonstration of this super-additivity of classical capacity of a quantum channel by using the ternary symmetric states of a single photon, and by event selection from a weak coherent light source. We also show how the super-additive coding gain, even in a small code length, can boost the communication performance of conventional coding technique.PACS numbers: 03.67. Hk, 03.65.Ta, In any transmission of signals at the quantum level, such as a long-haul optical communication where the signals at the receiving end are weak coherent pulses, ambiguity among signals may be more a matter of noncommutativity of quantum states, i.e.ρ 0ρ1 =ρ 1ρ0 rather than any classical noise. Such states can never be distinguished perfectly even in principle. This imposes an inevitable error in signal detection even in an ideal communications system. It was only recently that communication theory was extended into quantum domain to include this aspect of ambiguity, and the expressions of channel capacity were finally obtained [1]. Classical communication theory [2] describes the special case of the signals prepared in commuting density matrices.For reliable transmission in the presence of noise, redundancy must be introduced in representing messages by letters, such as {0, 1}, so as to correct errors at the receiving side. The capacity is associated with the functional meaning of this channel coding. Messages of k [bit] are encoded into block sequences of given letters in length n (> k). The n − k [bit] redundancy allows one to correct errors at the receiving side. For a channel with a capacity C [bit/letter], it is possible [2] with the rate R = k/n < C to reproduce k bit messages with an error probability as small as desired by appropriate encoding and decoding in the limit n → ∞.In extending the theory of capacity into quantum domain, primary concern is decoding of codewords made of non-commuting density matrices of letters. This is a nontrivial problem of quantum measurement. Actually, the optimal decoding essentially uses a process of entangling letter states constituting codewords prior to the measurement to enhance the distinguishability of signals. Such a process is nothing but a quantum computation on codeword states. This is a new aspect, not found in conventional coding techniques, and leads to a larger capacity. A significant consequence of this so called quantum collective decoding, is that the capacity can increase even more than twice when the code length is dou...