# 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 } }

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

- Physics
- 1995

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.

- PhysicsPhysical 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 ScienceProceedings 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

Apparatus for application of a flat sealant, by hand, to a straight edge is provided comprising a pressure plate, an edge guide, a sealant guide, and a means to hold onto and move the applicator…

### ShorA l gori thm sforQ uantum C om putati on:D i screte l og and Factori ng AT & T Bel lLabs prepri nt M ay

- 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