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Quantum Computer with Mixed States and Four-Valued Logic

Vasily E. Tarasov
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Abstract

In this paper we discuss a model of quantum computer in which a state is an operator of density matrix and gates are general quantum operations, not necessarily unitary. A mixed state (operator of density matrix) of n two-level quantum systems is considered as an element of 4^n-dimensional operator Hilbert space (Liouville space). It allows to use a quantum computer model with four-valued logic. The gates of this model are general superoperators which act on n-ququat state. Ququat is a quantum state in a four-dimensional (operator) Hilbert space. Unitary two-valued logic gates and quantum operations for an n-qubit open system are considered as four-valued logic gates acting on n-ququat. We discuss properties of quantum four-valued logic gates. In the paper we study universality for quantum four-valued logic gates.

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Vasily E. Tarasov. 2003-12-15. Quantum Computer with Mixed States and Four-Valued Logic. https://doi.org/10.1088/0305-4470%2F35%2F25%2F305

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