Search

Up-conversion single-photon detectors (UCSPD) are based on sum-frequency generation of the telecom band single-photons to near-infrared wavelengths at which efficient and low-noise silicon single-photon detectors are available. Moreover, because of high dynamic range of silicon single-photon detectors, UCSPD is suitable for high-speed quantum communication. UCSPDs reported to date, however, have a very narrow fixed window of detectable wavelengths, severely limiting their applications in wavelength-multiplexed quantum networks. In this work, we report a tunable UCSPD module that covers the complete telecom C band, making it suitable for quantum communication networks based on sharing wavelength-multiplexed entangled photons.

Four homalotine species-Anomognathus armatus (Sharp), Heterota onorum Maruyama, Neosilusa ceylonica (Kraatz), and Silusa lanuginosa Sharp-and three genera-Anomognathus Solier, Neosilusa Cameron, Silusa Erichson-are identified for the first time in Korea. The tribe Homalotini can be distinguished from other related tribes by the combination of the following characters: tarsal formula 4-4-5; mandible with patch or rows of denticles in ventral molar region; base of medial setae of prementum very close together, setal insertions in contact in many, setae displaced one behind the other in some; medial pseudopore field of prementum very narrow in many. Habitus photographs, diagnoses, and illustrations of male genitalia of these four species are provided.

Up-conversion single-photon detectors (UCSPD) are based on sum-frequency generation of the telecom band single-photons to near-infrared wavelengths at which efficient and low-noise silicon single-photon detectors are available. Moreover, because of high dynamic range of silicon single-photon detectors, UCSPD is suitable for high-speed quantum communication. UCSPDs reported to date, however, have a very narrow fixed window of detectable wavelengths, severely limiting their applications in wavelength-multiplexed quantum networks. In this work, we report a tunable UCSPD module that covers the complete telecom C band, making it suitable for quantum communication networks based on sharing wavelength-multiplexed entangled photons. [ABSTRACT FROM AUTHOR]

We report a quantum random number generator based on the photon-number--path entangled state that is prepared by means of two-photon quantum interference at a beam splitter. The randomness in our scheme is truly quantum mechanical in origin since it results from the projection measurement of the entangled two-photon state. The generated bit sequences satisfy the standard randomness test. OCIS codes: 270.5585, 030.5260, 190.7110.

A new active clamping zero-voltage switching (ZVS) pulse-width modulation (PWM) current-fed half-bridge converter (CFHB) is proposed in this paper. Its active clamping snubber (ACS) can not only absorb the voltage surge across the turned-off switch, but also achieve the ZVS of all power switches. Moreover, it can be applied to all current-fed power conversion topologies and its operation as well as structure is very simple. Since auxiliary switches in the snubber circuit are switched in a complementary way to main switches, an additional PWM IC is not necessary. In addition, it does not need any clamp winding and auxiliary circuit besides additional two power switches and one capacitor while the conventional current-fed half bridge converter has to be equipped with two clamp windings, two ZVS circuits, and two snubbers. Therefore, it can ensure the higher operating frequency, smaller-sized reactive components, lower cost of production, easier implementation, and higher efficiency. The operational principle, theoretical analysis, and design considerations are presented. To confirm the operation, validity, and features of the proposed circuit, experimental results from a 200-W, 24-200 Vdc prototype are presented. Index Terms--DC/DC power conversion, snubbers, switched mode power supplies.

Efficient photon–photon interaction is one of the key elements for realizing quantum information processing. The interaction, however, must often be mediated through an atomic medium due to the bosonic nature of photons, and the interaction time, which is critically linked to the efficiency, depends on the properties of the atom–photon interaction. While the electromagnetically induced transparency effect does offer the possibility of photonic quantum memory, it does not enhance the interaction time as it fully maps the photonic state to an atomic state. The stationary light pulse (SLP) effect, on the contrary, traps the photonic state inside an atomic medium with zero group velocity, opening up the possibility of enhanced interaction time. In this work, we report the first experimental demonstration of trapping a free-propagating single-photon into a cold atomic ensemble via the quantum SLP (QSLP) process. We conclusively show that the quantum properties of the single-photon state are preserved well during the QSLP process. Our work paves the way for new approaches for efficient photon–photon interactions, exotic photonic states, and many-body simulations in photonic systems. [ABSTRACT FROM AUTHOR]

The conventional high-frequency phase-shifted zero-voltage-switching (ZVS) full-bridge dc/dc converter has a disadvantage, in that a circulating current flows through transformer and switching devices during the freewheeling interval. Due to this circulating current, rms current stress, conduction losses of the transformer and switching devices are increased. To alleviate this problem, this paper proposes an improved zero-voltage zero-current switching (ZVZCS) phase-shifted full-bridge (FB) dc/dc converter with a modified energy-recovery snubber (ERS) attached at the secondary side of transformer. Also, the small signal model of the proposed ZVZCS FB dc/dc converter is derived by incorporating the effects introduced by a transformer leakage inductance and an ERS to achieve ZVZCS. Both analysis and experiment are performed to verify the proposed topology by implementing a 7-kW (120 Vdc, 58 A) 30-kHz insulated-gate-bipolar-transistor-based experimental circuit Index Terms--Energy-recovery snubber, full-bridge (FB) dc/dc converter, small-signal modeling, zero-voltage switching (ZVS), zero-voltage zero-current switching (ZVZCS).

Fuel cell generation system consists of a stack, a reformer, and converters. The stack generates DC power by electrochemical reaction. For system design and analysis, it is necessary to obtain electrical models. Simplified electrical models of a fuel cell generation system for system control are proposed. Then using the electrical models, system performance of a fuel cell generation system in which power is boosted by step-up choppers is analyzed. A fuzzy controller is designed for improved system performance. Simulation and experimental results confirmed the high performance capability of the designed system.

An improved soft-switching topology of a full-bridge (FB) pulsewidth-modulated (PWM) dc/dc converter is described. The new topology employs an energy-recovery snubber to minimize a circulating current flowing through the transformer and switching devices. By using an energy-recovery snubber instead of adding a tapped inductor and a saturable reactor to reduce rms current stress, the converter achieves zero-current switching (ZCS) for the right leg due to the minimized circulating current and achieves zero-voltage switching (ZVS) for the left leg due to the reflected output current during the interval of left leg transition. Both analysis and experiments are performed to verify the proposed topology by implementing a 7-kW (120 VDC, 58 A) 30-kHz insulated gate bipolar transistor (IGBT)-based experimental circuit. Index Terms - Circulating current, conduction losses, soft-switching full-bridge dc/dc converter, zero-voltage-zero-current switching.

A new technique of reducing torque ripples in inverter-fed brushless dc motor (BDCM) drives is proposed. The proposed technique reduces torque ripple components by controlling switching angles of the inverter. The simulation and experimental results indicate that the proposed technique can reduce the torque ripples significantly and improve the performance of the system. Index Terms - Brushless dc motor, torque ripples.

In designing interface circuits to a battery, often the battery is assumed to be a simple voltage source. However, the battery itself has internal parameters. This means that the internal parameters of the battery models need to be considered for the interface design. Several electrical battery models are presented. Then, using the electrical battery models, the analysis and the design of the interface circuit are described. The analysis and experimental results show that the electrical battery model which reflects battery characteristics has to be used for the optimal design of the interface circuit. Finally, the analysis results indicate that the required size of the condenser filter can be smaller with battery power supplies than with other power supplies, such as bridge-type ac source dc power supplies.

In a quantum network involving multiple communicating parties, an important goal is to establish high-quality pairwise entanglement among the users without introducing multiple entangled-photon sources which would necessarily complicate the overall network setup. Moreover, it is preferable that the pairwise entanglement of photons is in the time-bin degree of freedom as the photonic time-bin qubit is ideally suited for fiber-optic distribution. Here, we report an experimental demonstration of a field-deployable quantum communication network involving multiple users, all of whom share pairwise entanglement in the time-bin degree of freedom of photons. In particular, by utilizing a single spontaneous-parametric down-conversion source which produces a broadband pair of photons and the wavelength-division demultiplexing/multiplexing technology, all the communicating parties within the network are always simultaneously ready for quantum communication. To further demonstrate the practical feasibility of a quantum network with time-bin entanglement over a wavelength-multiplexed fiber network, we demonstrate entangled-photon quantum key distribution with three users, each separated by 60 km of optical fibers. [ABSTRACT FROM AUTHOR]