159 research outputs found
Generation of 1.5-um band time-bin entanglement using spontaneous fiber four-wave mixing and planar lightwave circuit interferometers
This paper reports 1.5-um band time-bin entanglement generation. We employed
a spontaneous four-wave mixing process in a dispersion shifted fiber, with
which correlated photon pairs with very narrow bandwidths were generated
efficiently. To observe two-photon interference, we used planar lightwave
circuit based interferometers that were operated stably without feedback
control. As a result, we obtained coincidence fringes with 99 % visibilities
after subtracting accidental coincidences, and successfully distributed
entangled photons over 20-km standard single-mode fiber without any
deterioration in the quantum correlation.Comment: 4 pages, 3 figure
Quantum Noise in Optical Amplifiers
Noise is one of the basic characteristics of optical amplifiers. Whereas there are various noise sources, the intrinsic one is quantum noise that originates from Heisenberg’s uncertainty principle. This chapter describes quantum noise in optical amplifiers, including population-inversion–based amplifiers such as an Erbium-doped fiber amplifier and a semiconductor optical amplifier, and optical parametric amplifiers. A full quantum mechanical treatment is developed based on Heisenberg equation of motion for quantum mechanical operators. The results provide the quantum mechanical basis for a classical picture of amplifier noise widely used in the optical communication field
Quantum secret sharing based on modulated high-dimensional time-bin entanglement
We propose a new scheme for quantum secret sharing (QSS) that uses a
modulated high-dimensional time-bin entanglement. By modulating the relative
phase randomly by {0,pi}, a sender with the entanglement source can randomly
change the sign of the correlation of the measurement outcomes obtained by two
distant recipients. The two recipients must cooperate if they are to obtain the
sign of the correlation, which is used as a secret key. We show that our scheme
is secure against intercept-and-resend (I-R) and beam splitting attacks by an
outside eavesdropper thanks to the non-orthogonality of high-dimensional
time-bin entangled states. We also show that a cheating attempt based on an I-R
attack by one of the recipients can be detected by changing the dimension of
the time bin entanglement randomly and inserting two "vacant" slots between the
packets. Then, cheating attempts can be detected by monitoring the count rate
in the vacant slots. The proposed scheme has better experimental feasibility
than previously proposed entanglement-based QSS schemes.Comment: To appear in Phys. Rev.
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BB84 and DQPS-QKD experiments using one polarization-insensitive measurement setup with a countermeasure against detector blinding and control attacks
Entanglement formation and violation of Bell's inequality with a semiconductor single photon source
We report the generation of polarization-entangled photons, using a quantum
dot single photon source, linear optics and photodetectors. Two photons created
independently are observed to violate Bell's inequality. The density matrix
describing the polarization state of the postselected photon pairs is also
reconstructed, and agrees well with a simple model predicting the quality of
entanglement from the known parameters of the single photon source. Our scheme
provides a method to generate no more than one entangled photon pair per cycle,
a feature useful to enhance quantum cryptography protocols using entangled
photons.Comment: 4 pages, 3 figures, submitted to PR
Phase I Clinical Study of the Dietary Supplement, Agaricus blazei Murill, in Cancer Patients in Remission
Although many cancer patients use complementary and alternative medicine, including Agaricus blazei Murill (ABM), safety is not yet well understood. Cancer survivors took 1.8, 3.6, or 5.4 g ABM granulated powder (Kyowa Wellness Co., Ltd., Tokyo, Japan) per day orally for 6 months. Adverse events were defined by subjective/objective symptoms and laboratory data according to the National Cancer Institute Common Terminology Criteria for Adverse Events version 3.0 (NCI-CTCAE v3.0). Seventy-eight patients were assessed for safety of ABM (30/24/24 subjects at 1/2/3 packs per day, resp.). Adverse events were observed in 9 patients (12%). Most were digestive in nature such as nausea and diarrhea, and one patient developed a liver dysfunction-related food allergy, drug lymphocyte product. However, none of these adverse events occurred in a dose-dependent manner. This study shows that ABM does not cause problems in most patients within laboratory parameters at the dosages tested over 6 months. This trial supports previous evidence that the ABM product is generally safe, excluding possible allergic reaction
Scalable implementation of mutually unbiased bases for -dimensional quantum key distribution
A high-dimensional quantum key distribution (QKD) can improve error rate
tolerance and the secret key rate. Many -dimensional QKDs have used two
mutually unbiased bases (MUBs), while MUBs enable a more robust QKD.
However, a scalable implementation has not been achieved because the setups
have required devices even for two MUBs or a flexible convertor for a
specific optical mode. Here, we propose a scalable and general implementation
of MUBs using interferometers in prime power dimensions
. We implemented the setup for time-bin states and observed an average
error rate of 3.8% for phase bases, which is lower than the 23.17% required for
a secure QKD against collective attack in .Comment: 6 pages, 3 figures, followed by Supplemental Material of 8 pages, 1
figure, 1 tabl
Understanding and exploiting hTERT promoter regulation for diagnosis and treatment of human cancers
がん進展制御研究所 Telomerase activation is a critical step for human carcinogenesis through the maintenance of telomeres, but the activation mechanism during carcinogenesis remains unclear. Transcriptional regulation of the human telomerase reverse transcriptase (hTERT) gene is the major mechanism for cancer-specific activation of telomerase, and a number of factors have been identified to directly or indirectly regulate the hTERT promoter, including cellular transcriptional activators (c-Myc, Sp1, HIF-1, AP2, ER, Ets, etc.) as well as the repressors, most of which comprise tumor suppressor gene products, such as p53, WT1, and Menin. Nevertheless, none of them can clearly account for the cancer specificity of hTERT expression. The chromatin structure via the DNA methylation or modulation of nucleosome histones has recently been suggested to be important for regulation of the hTERT promoter. DNA unmethylation or histone methylation around the transcription start site of the hTERT promoter triggers the recruitment of histone acetyltransferase (HAT) activity, allowing hTERT transcription. These facts prompted us to apply these regulatory mechanisms to cancer diagnostics and therapeutics. Telomerase-specific replicative adenovirus (Telomelysin, OBP-301), in which E1A and E1B genes are driven by the hTERT promoter, has been developed as an oncolytic virus that replicates specifically in cancer cells and causes cell death via viral toxicity. Direct administration of Telomelysin was proved to effectively eradicate solid tumors in vivo, without apparent adverse effects. Clinical trials using Telomelysin for cancer patients with progressive stages are currently ongoing. Furthermore, we incorporated green fluorescent protein gene (GFP) into Telomelysin (TelomeScan, OBP-401). Administration of TelomeScan into the primary tumor enabled the visualization of cancer cells under the cooled charged-coupled device (CCD) camera, not only in primary tumors but also the metastatic foci. This technology can be applied to intraoperative imaging of metastatic lymphnodes. Thus, we found novel tools for cancer diagnostics and therapeutics by utilizing the hTERT promoter. © 2008 Japanese Cancer Association
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