235 research outputs found
Classical reconstruction of interference patterns of position-wavevector-entangled photon pairs by time-reversal method
The quantum interference of entangled photons forms a key phenomenon
underlying various quantum-optical technologies. It is known that the quantum
interference patterns of entangled photon pairs can be reconstructed
classically by the time-reversal method; however, the time-reversal method has
been applied only to time-frequency-entangled two-photon systems in previous
experiments. Here, for the first time, we apply the time-reversal method to the
position-wavevector-entangled two-photon systems: the two-photon Young
interferometer and the two-photon beam focusing system. We experimentally
demonstrate that the time-reversed systems classically reconstruct the same
interference patterns as the position-wavevector-entangled two-photon systems.Comment: 10 pages, 8 figure
Time-reversed two-photon interferometry for phase super-resolution
We observed two-photon phase super-resolution in an unbalanced Michelson
interferometer with classical Gaussian laser pulses. Our work is a
time-reversed version of a two-photon interference experiment using an
unbalanced Michelson interferometer. A measured interferogram exhibits
two-photon phase super-resolution with a high visibility of 97.9% \pm 0.4%. Its
coherence length is about 22 times longer than that of the input laser pulses.
It is a classical analogue to the large difference between the one- and
two-photon coherence lengths of entangled photon pairs.Comment: 6 pages, 4 figure
Observation of nonlinear variations in three-vertex geometric phase in two-photon polarization qutrit
We experimentally observed nonlinear variations in the three-vertex geometric
phase in a two- photon polarization qutrit. The three-vertex geometric phase is
defined by three quantum states, which generally forms a three-state (qutrit)
system. By changing one of the three constituent states, we observed two rapid
increases in the three-vertex geometric phase. The observed variations are
inherent in a three-state system and cannot be observed in a two-state system.
We used a time-reversed two-photon interferometer to measure the geometric
phase with much more intense signals than those of a typical two-photon
interferometer.Comment: 6 pages, 5 figure
Bloch sphere representation of three-vertex geometric phases
The properties of the geometric phases between three quantum states are
investigated in a high-dimensional Hilbert space using the Majorana
representation of symmetric quantum states. We found that the geometric phases
between the three quantum states in an N-state quantum system can be
represented by N-1 spherical triangles on the Bloch sphere. The parameter
dependence of the geometric phase was analyzed based on this picture. We found
that the geometric phase exhibits rich nonlinear behavior in a high-dimensional
Hilbert space.Comment: 5 pages, 4 figure
Direct measurement of ultrafast temporal wavefunctions
The large capacity and robustness of information encoding in the temporal
mode of photons is important in quantum information processing, in which
characterizing temporal quantum states with high usability and time resolution
is essential. We propose and demonstrate a direct measurement method of
temporal complex wavefunctions for weak light at a single-photon level with
subpicosecond time resolution. Our direct measurement is realized by ultrafast
metrology of the interference between the light under test and self-generated
monochromatic reference light; no external reference light or complicated
post-processing algorithms are required. Hence, this method is versatile and
potentially widely applicable for temporal state characterization.Comment: 10 pages, 7 figure
A Case of Thrombotic Thrombocytopenia Purpura Associated with Systemic Lupus Erythematosus: Diagnostic Utility of ADAMTS-13 Activity
Thrombotic thrombocytopenia purpura (TTP) caused by a deficiency in ADAMTS-13 activity is considered to involve a subset of thrombotic microangiopathy (TMA). Although concept of TTP is included under the umbrella of TMA, discrimination of TTP from TMA is occasionally difficult in an autoimmune disorder. Herein, we report a case with TTP associated with systemic lupus erythematosus (SLE). In this case, it was difficult to discriminate TTP from TMA and the measurement of ADAMTS-13 activity was useful for obtaining an accurate diagnosis. SLE patients having thrombocytopenia in complication with anemia should be considered a monitoring of ADAMTS-13 activity even though the patients lacked symptoms of TTP related to the microvascular coagulation
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