1991 Fiscal Year Final Research Report Summary
Basic study on quantum communication and measurement
| Project/Area Number |
02650284
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
電子機器工学
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| Research Institution | University of Tokyo |
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Principal Investigator |
KIKUCHI K. Univ. Tokyo, Electronic Engn., Associate Prof., 工学部, 助教授 (50134458)
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| Project Period (FY) |
1990 – 1991
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| Keywords | Shot noise / optical communication / parametric oscillator / light emitting diode / semiconductor laser |
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| Research Abstract |
The receiver-sensitivity limit in present optical communication systems is determined from the shot noise of the light source. It has been believed that we can not control the shot noise. However, if we can read out the photon-number fluctuation without absorbing any plioton, such fluctuation is able to be reduced by using feedback or fecdforward control of the plioton number.
We tried two methods for reducing the shot noise of the light source : the optical parametric oscillator and the semiconductor light-emitting devices. We designed and constructed a low-threshold parametric oscillator having a monolithic cavity made of KTP crystal ; However, the long-term stability is not high enough for achieving the efficient shot-noise reduction.
We developed a theory of quantum noise in semiconductor light-emitting devices based on the rate equations. The condition of operation, where the shot noise is suppressed, was discussed. NN7e have actually achieved 0.45-dB and 2-dB reduction of shot noise by using light emitting diodes and semiconductor lasers, respectively.
The state control of light at the receiving end was also investigated, aiming at breaking the shot-noise limit of the receiver sensitivity. This inetliod seems more practical than the metliods mentioned above, because the receiver sensitivity can be improved inde endent of the quantum state of the light source and the loss existing in the transmission line.
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