2,251 research outputs found
Entropic bounds on coding for noisy quantum channels
In analogy with its classical counterpart, a noisy quantum channel is
characterized by a loss, a quantity that depends on the channel input and the
quantum operation performed by the channel. The loss reflects the transmission
quality: if the loss is zero, quantum information can be perfectly transmitted
at a rate measured by the quantum source entropy. By using block coding based
on sequences of n entangled symbols, the average loss (defined as the overall
loss of the joint n-symbol channel divided by n, when n tends to infinity) can
be made lower than the loss for a single use of the channel. In this context,
we examine several upper bounds on the rate at which quantum information can be
transmitted reliably via a noisy channel, that is, with an asymptotically
vanishing average loss while the one-symbol loss of the channel is non-zero.
These bounds on the channel capacity rely on the entropic Singleton bound on
quantum error-correcting codes [Phys. Rev. A 56, 1721 (1997)]. Finally, we
analyze the Singleton bounds when the noisy quantum channel is supplemented
with a classical auxiliary channel.Comment: 20 pages RevTeX, 10 Postscript figures. Expanded Section II, added 1
figure, changed title. To appear in Phys. Rev. A (May 98
Design of source coders and joint source/channel coders for noisy channels
A theory behind a proposed joint source/channel coding approach is developed and a variable rate design approach which provides substantial improvement over current joint source/channel coder designs is obtained. The Rice algorithm as applied to the output of the Gamma Ray Detector of the Mars Orbiter is evaluated. An alternative algorithm is obtained which outperforms the Rice both in terms of data compression and noisy channel performance. A high-fidelity low-rate image compression algorithm is developed which provides almost distortionless compression of high resolution images
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