# Maintaining coherence in quantum computers.

@article{Unruh1995MaintainingCI,
title={Maintaining coherence in quantum computers.},
author={Unruh},
journal={Physical review. A, Atomic, molecular, and optical physics},
year={1995},
volume={51 2},
pages={
992-997
}
}
• Unruh
• Published 9 June 1994
• Physics
• Physical review. A, Atomic, molecular, and optical physics
The effects of the inevitable coupling to external degrees of freedom of a quantum computer are examined. It is found that for quantum calculations (in which the maintenance of coherence over a large number of states is important), not only must the coupling be small, but the time taken in the quantum calculation must be less than the thermal time scale \ensuremath{\Elzxh}/${\mathit{k}}_{\mathit{B}}$T. For longer times the condition on the strength of the coupling to the external world becomes…
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## References

SHOWING 1-7 OF 7 REFERENCES

### Is quantum mechanics useful

A transistor, despite its roots in energy band structure, does not invoke quantum mechanically coherent transmission between terminals. The impressive progress in the past decade in mesoscopic

### Reduction of a wave packet in quantum Brownian motion.

• Physics
Physical review. D, Particles and fields
• 1989
In an open quantum system, dissipation can cause decorrelation on a time scale significantly shorter than the relaxation time which characterizes the approach of the system to thermodynamic equilibrium, and it is demonstrated that the density matrix decays rapidly toward a mixture of approximate eigenstates'' of the pointer observable,'' which commutes with the system-environment interaction Hamiltonian.

### Rapid solution of problems by quantum computation

• Computer Science
Proceedings of the Royal Society of London. Series A: Mathematical and Physical Sciences
• 1992
A class of problems is described which can be solved more efficiently by quantum computation than by any classical or stochastic method. The quantum computation solves the problem with certainty in

### The Development of the Number Field Sieve

• Engineering
• 1994
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• 1994

### Shor Algorithms for Quantum Computation: Discrete log and Factoring AT&T Bell Labs preprint

• Shor Algorithms for Quantum Computation: Discrete log and Factoring AT&T Bell Labs preprint
• 1994

### See “ Is Quantum Mechanics Useful ” Rolf Landauer ( to appear in

• See papers on the Number Field Sieve in The Development of the Number Field Sieve
• 1993