Quantum Circuits with Mixed States
| dc.creator | Aharonov, Dorit | |
| dc.creator | Kitaev, Alexei | |
| dc.creator | Nisan, Noam | |
| dc.date | 1998-06-08 | |
| dc.date.accessioned | 2026-07-07T06:15:11Z | |
| dc.date.available | 2026-07-07T06:15:11Z | |
| dc.description | We define the model of quantum circuits with density matrices, where non-unitary gates are allowed. Measurements in the middle of the computation, noise and decoherence are implemented in a natural way in this model, which is shown to be equivalent in computational power to standard quantum circuits. The main result in this paper is a solution for the subroutine problem: The general function that a quantum circuit outputs is a probabilistic function, but using pure state language, such a function can not be used as a black box in other computations. We give a natural definition of using general subroutines, and analyze their computational power. We suggest convenient metrics for quantum computing with mixed states. For density matrices we analyze the so called ``trace metric'', and using this metric, we define and discuss the ``diamond metric'' on superoperators. These metrics enable a formal discussion of errors in the computation. Using a ``causality'' lemma for density matrices, we also prove a simple lower bound for probabilistic functions. | |
| dc.description | 20 pages, Latex. In ``Proceedings of the Thirtieth Annual ACM Symposium on Theory of Computation (STOC)'', pages 20-30, 1997 | |
| dc.identifier | https://arxiv.org/abs/quant-ph/9806029 | |
| dc.identifier | http://arxiv.org/abs/quant-ph/9806029 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/93720 | |
| dc.subject | Quantum Physics | |
| dc.title | Quantum Circuits with Mixed States | |
| dc.type | text |