Representation in terms of displaced number states and realization of elementary linear operators based on it

TL;DR

This paper introduces a novel quantum state representation using displaced number states and demonstrates how to construct elementary linear operators, including quantum gates, with high fidelity in realistic scenarios.

Contribution

It presents a new method for representing quantum states with displaced number states and applies it to realize elementary linear operators like quantum gates.

Findings

Exact implementation of quantum gates with high fidelity

Representation method applicable to various quantum states

Construction of two-qubit control-sign and Hadamard gates

Abstract

We develop a new method of representation of quantum states in terms of the displaced number states. We call it representation, where is an amplitude of the base displaced states. In particular, representation was obtained for set of the displaced number states with different amplitude of the displacement, two-mode squeezed vacuum (TMSV) and superposition of vacuum and single photon. The treatment is employed for building of elementary linear operators, in particular, two-qubit control-sign gate, Hadamard matrix between two two-dimensional Hilbert spaces. Main idea underlying the method is extraction of the displaced number state from initial state. Coherent qubit with large amplitude taken simultaneously two modes shifts two-mode target qubit on phase plane and constructive interference appears after measurement of single photon. The results are exact, any approximations are not exploited. We show implementation of the gates with almost unity fidelity of the output states is possible in realistic scenario.