Generating GHZ states with squeezing and post-selection

TL;DR

This paper introduces a novel method for preparing GHZ states using a sequence of rotation, spin squeezing, quantum measurement, and post-selection, resulting in faster state preparation compared to traditional unitary evolution methods.

Contribution

It demonstrates the use of measurement and post-selection to efficiently generate GHZ states from separable states, enhancing quantum state preparation techniques.

Findings

Achieves high overlap fidelity with GHZ states.

Reduces state preparation time compared to unitary methods.

Optimized parameters improve entanglement quality.

Abstract

Many quantum state preparation methods rely on a combination of dissipative quantum state initialization, followed by unitary evolution to a desired target state. Here we demonstrate the usefulness of quantum measurement as an additional tool for quantum state preparation. Starting from a pure separable multipartite state, a control sequence, which includes rotation, spin squeezing via one-axis twisting, quantum measurement and post-selection, generates a highly entangled multipartite state, which we refer to as Projected Squeezed states (or PS states). Through an optimization method, we then identify parameters required to maximize the overlap fidelity of the PS states with the maximally entangled Greenberger-Horne-Zeilinger states (or GHZ states). The method leads to an appreciable decrease in state preparation time of GHZ states when compared to preparation through unitary evolution with one-axis twisting only.