Nonunitary quantum circuit

Abstract

A quantum circuit is generalized to a nonunitary one whose constituents are nonunitary gates operated by quantum measurement. It is shown that a specific type of one-qubit nonunitary gates, the controlled-NOT gate, as well as all one-qubit unitary gates constitute a universal set of gates for the nonunitary quantum circuit, without the necessity of introducing ancilla qubits. A reversing measurement scheme is used to improve the probability of successful nonunitary gate operation. A quantum NAND gate and Abrams-Lloyd's nonlinear gate are analyzed as examples. Our nonunitary circuit can be used to reduce the qubit overhead needed to ensure fault-tolerant quantum computation.

19 pages, 6 figures; added a reference

References in corpus (3)

• Quantum computation with optical coherent states
• Universal quantum computation using only projective measurement, quantum memory, and preparation of the 0 state
• Quantum Computer with Mixed States and Four-Valued Logic

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