Quantum Optimal Control for Pure-State Preparation Using One Initial State

TL;DR

This paper introduces a numerical optimal control framework for pure-state preparation in quantum systems, using a basis of density matrices and an ensemble approach that is scalable across system dimensions.

Contribution

It develops a novel density matrix basis and ensemble method for pure-state preparation, applicable to open quantum systems with multiple qubits.

Findings

Effective pure-state preparation demonstrated for one and two qubits.

Framework is scalable and independent of system dimension.

Applicable to open quantum systems with dispersive coupling.

Abstract

This paper presents a framework for solving the pure-state preparation problem using numerical optimal control. As an example, we consider the case where a number of qubits are dispersively coupled to a readout cavity. We model open system quantum dynamics using the Markovian Lindblad master equation, driven by external control pulses. The main result of this paper develops a basis of density matrices (a parameterization) where each basis element is a density matrix itself. Utilizing a specific objective function, we show how an ensemble of the basis elements can be used as a single initial state throughout the optimization process - independent of the system dimension. We apply the general framework to the specific application of ground-state reset of one and two qubits coupled to a readout cavity.