3,447 research outputs found
Effect of ancilla's structure on quantum error correction using the 7-qubit Calderbank-Shor-Steane code
In this work we discuss the ability of different types of ancillas to control
the decoherence of a qubit interacting with an environment. The error is
introduced into the numerical simulation via a depolarizing isotropic channel.
After the correction we calculate the fidelity as a quality criterion for the
qubit recovered. We observe that a recovery method with a three-qubit ancilla
provides reasonable good results bearing in mind its economy. If we want to go
further, we have to use fault-tolerant ancillas with a high degree of
parallelism, even if this condition implies introducing new ancilla
verification qubits.Comment: 24 pages, 10 Figures included. Accepted in Phys. Rev. A 200
An Universal Quantum Network - Quantum CPU
An universal quantum network which can implement a general quantum computing
is proposed. In this sense, it can be called the quantum central processing
unit (QCPU). For a given quantum computing, its realization of QCPU is just its
quantum network. QCPU is standard and easy-assemble because it only has two
kinds of basic elements and two auxiliary elements. QCPU and its realizations
are scalable, that is, they can be connected together, and so they can
construct the whole quantum network to implement the general quantum algorithm
and quantum simulating procedure.Comment: 8 pages, Revised versio
Integrated software package STAMP for minor planets
The integrated software package STAMP allowed for rapid and exact reproduction of the tables of the year-book 'Ephemerides of Minor Planets.' Additionally, STAMP solved the typical problems connected with the use of the year-book. STAMP is described. The year-book 'Ephemerides of Minor Planets' (EMP) is a publication used in many astronomical institutions around the world. It contains all the necessary information on the orbits of the numbered minor planets. Also, the astronomical coordinates are provided for each planet during its suitable observation period
On the distribution of minor planet inclinations
The distribution of minor planet orbits with inclination to the ecliptic plane and with respect to the Jupiter orbit is studied. Position of the plane considered as the mean plane of the asteroid belt is determined
Degenerate Quantum Codes for Pauli Channels
A striking feature of quantum error correcting codes is that they can
sometimes be used to correct more errors than they can uniquely identify. Such
degenerate codes have long been known, but have remained poorly understood. We
provide a heuristic for designing degenerate quantum codes for high noise
rates, which is applied to generate codes that can be used to communicate over
almost any Pauli channel at rates that are impossible for a nondegenerate code.
The gap between nondegenerate and degenerate code performance is quite large,
in contrast to the tiny magnitude of the only previous demonstration of this
effect. We also identify a channel for which none of our codes outperform the
best nondegenerate code and show that it is nevertheless quite unlike any
channel for which nondegenerate codes are known to be optimal.Comment: Introduction changed to give more motivation and background. Figure 1
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Fault-Tolerant Error Correction with Efficient Quantum Codes
We exhibit a simple, systematic procedure for detecting and correcting errors
using any of the recently reported quantum error-correcting codes. The
procedure is shown explicitly for a code in which one qubit is mapped into
five. The quantum networks obtained are fault tolerant, that is, they can
function successfully even if errors occur during the error correction. Our
construction is derived using a recently introduced group-theoretic framework
for unifying all known quantum codes.Comment: 12 pages REVTeX, 1 ps figure included. Minor additions and revision
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