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K. Matsumoto

Publications and source records attributed to K. Matsumoto.

48 records · Page 3Linked to original sources
arXiv2002

Shor-Preskill Type Security-Proof for the Quantum Key Distribution without Public Announcement of Bases

We give a Shor-Preskill type security-proof to the quantum key distribution without public announcement of bases [W.Y. Hwang et al., Phys. Lett. A 244, 489 (1998)]. First, we modify the Lo-Chau protocol once more so that it finally reduces to the quantum key distribution without public announcement of bases. Then we show how we can estimate the error rate in the code bits based on that in the checked bits in the proposed protocol, that is the central point of the proof. We discuss the problem of imperfect sources and that of large deviation in the error rate distributions. We discuss when the bases sequence must be discarded.

quant-ph↗
arXiv2002

Quantum Gambling Using Three Nonorthogonal States

We provide a quantum gambling protocol using three (symmetric) nonorthogonal states. The bias of the proposed protocol is less than that of previous ones, making it more practical. We show that the proposed scheme is secure against non-entanglement attacks. The security of the proposed scheme against entanglement attacks is shown heuristically.

quant-ph↗
arXiv2002

WZ Sge-Type Star V592 Herculis

We observed the entire course of the 1998 outburst of V592 Her, which was originally reported as a nova in 1968. We have been able to construct a full light curve of the outburst, which is characterized by a rapid initial decline (0.98 mag/d), which smoothly developed into a plateau phase with a slower linear decline. We detected superhumps characteristic to SU UMa-type dwarf novae ~7 d after the optical maximum. The overall behavior of the light curve and the development of superhumps were characteristic to a WZ Sge-type dwarf nova. Combined with the past literature, we have been able to uniquely determine the superhump period to be 0.05648(2) d. From this period, together with a modern interpretation of the absolute magnitude of the outburst light curve, we conclude that the overall picture of V592 Her is not inconsistent with a lower main-sequence secondary star in contrast to a previous claim that V592 Her contains a brown dwarf.

astro-ph↗
arXiv2002

Generation of polarization-entangled photon pairs in a cascade of two type-I crystals pumped by femtosecond pulses

We report the generation of polarization-entangled photons by femtosecond-pulse-pumped spontaneous parametric down-conversion in a cascade of two type-I crystals. Highly entangled pulsed states were obtained by introducing a temporal delay between the two orthogonal polarization components of the pump field. They exhibited high-visibility quantum interference and a large concurrence value, without the need of post-selection using narrow-bandwidth-spectral filters. The results are well explained by the theory which incorporates the space-time dependence of interfering two-photon amplitudes if dispersion and birefringence in the crystals are appropriately taken into account. Such a pulsed entangled photon well localized in time domain is useful for various quantum communication experiments, such as quantum cryptography and quantum teleportation.

quant-ph↗
arXiv2002

A simple way to detect the state transition caused by the nondiagonal abelian Berry phase

In a nondegenerate syste, the abelian Berry's phase will never cause transitions among the Hamiltonian's eigenstate. However, in a degenerate syatem, it is well known that the state transition can be caused by the non-abelian Berry phase. Actually, in a such a system, the phase factor is not always nonabelian. Even in the case that the phase is a nondiagonal matrix, it still can be an abelian phase and can cause the state transitions. We then propose a simple scheme to detect such an effect of the Berry phase to the degenerate states by using the optical entangled pair state. In this scheme, we need not control any external parameters during the quantum state evolution.

quant-ph↗
arXiv2002

V893 Sco Is Not an ER UMa-Type Star

V893 Sco is a recently rediscovered bright eclipsing dwarf nova below the period gap. Most recently, Mason et al. (2001) proposed an idea that V893 Sco is an ER UMa-type dwarf nova. From the analysis of our CCD observations and reports to VSNET, we show that V893 Sco bears no similar characters with ER UMa stars. We propose that the arguments in Mason et al. (2001), including the evolutionary status of ER UMa star as inferred from the observation of V893 Sco, need to be reconsidered.

astro-ph↗
arXiv2001

Restoration of Entanglement by Spectral Filters

We experimentally demonstrate that entanglement of bi-photon polarization state can be restored by spectral filters. This restoration procedure can be viewed as a new class of quantum eraser, which retrieves entanglement rather than just interference by manipulating an ancillary degree of freedom.

quant-ph↗
arXiv2000

Theta constants associated to cubic three folds

For a cubic surface X, by considering the intermediate Jacobian J(Y) of the triple covering Y of the 3-dimensional projective space branching along X, Allcock, Carlson and Toledo constructed a period map per from the family of marked cubic surfaces to the four dimensional complex ball embedded in the Siegel upper half space of degree 5. We give an expression of the inverse of per in terms of theta constants by constructing an isomorphism between J(Y) and a Prym variety of a cyclic 6-ple covering of the projective line branching at seven points.

math.AG↗
arXiv2000

Discovery and Photometric Observation of the Optical Counterpart in a Possible Galactic Halo X-ray Transient, XTE J1118+480

We discovered the optical counterpart about 13 mag of a soft X-ray transient, XTE J1118+480 on 2000 March 30. We perform astrometry and provide the accurate position as R.A. = 11h18m10s.85, Decl. = +48o02'12".9. The outbursting object is identified with a 18.8 mag star in USNO catalog. Our pre-discovery data shows another outburst during 2000 January, again coinciding with an outburst detected in X-rays. Through the CCD time-series photometry, we found the presence of a periodic variation with the amplitude of 0.055 mag and the period of 0.17078(0.00004)d which we consider as promising candidate of orbital period. Because of the high galactic latitude and faint quiescence magnitude of 18.8, XTE J1118+480 is the possible first firmly identified black hole candidate (BHC) X-ray transient in the galactic halo.

astro-ph↗
arXiv2000

Discovery of a New Deeply Eclipsing SU UMa-Type Dwarf Nova, IY UMa (= TmzV85)

We discovered a new deeply eclipsing SU UMa-type dwarf nova, IY UMa, which experienced a superoutburst in 2000 January. Our monitoring revealed two distinct outbursts, which suggest a superoutburst interval of ~800 d, or its half, and an outburst amplitude of 5.4 mag. From time-series photometry during the superoutburst, we determined a superhump and orbital period of 0.07588 d and 0.0739132 d, respectively.

astro-ph↗