computational complexity

, Volume 12, Issue 1–2, pp 48–84 | Cite as

On the complexity of simulating space-bounded quantum computations

  • John WatrousEmail author
Original Article


This paper studies the space-complexity of predicting the long-term behavior of a class of stochastic processes based on evolutions and measurements of quantum mechanical systems. These processes generalize a wide range of both quantum and classical space-bounded computations, including unbounded error computations given by machines having algebraic number transition amplitudes or probabilities. It is proved that any space s quantum stochastic process from this class can be simulated probabilistically with unbounded error in space O(s), and therefore deterministically in space O(s 2).


Space-bounded quantum computation quantum computational complexity space-bounded computation 

Mathematics Subject Classification (2000).

03D15 68Q15 


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Copyright information

© Birkhäuser-Verlag 2003

Authors and Affiliations

  1. 1.Department of Computer ScienceUniversity of CalgaryCalgaryCanada

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