Bose-Einstein condensate soliton qubit states for metrological applications

TL;DR

This paper proposes using Bose-Einstein condensate soliton states as macroscopic qubits for quantum metrology, demonstrating their potential to reach Heisenberg-limited phase estimation and improve frequency standards.

Contribution

It introduces a novel approach to quantum metrology using soliton qubits in BECs, including state predictions and phase space analysis for enhanced measurement precision.

Findings

Macroscopic soliton states can achieve Heisenberg-limited phase estimation.

Predicted Schrödinger-cat and N00N states for macroscopic quantum superpositions.

Potential applications in improving frequency standards technologies.

Abstract

By utilizing Bose-Einstein condensate solitons, optically manipulated and trapped in a double-well potential, coupled through nonlinear Josephson effect, we propose novel quantum metrology applications with two soliton qubit states. In addition to steady-state solutions in different scenarios, phase space analysis, in terms of population imbalance - phase difference variables, is also performed to demonstrate macroscopic quantum self-trapping regimes. Schr\"odinger-cat states, maximally path-entangled ($N00N$) states, and macroscopic soliton qubits are predicted and exploited for the distinguishability of obtained macroscopic states in the framework of binary (non-orthogonal) state discrimination problem. For arbitrary phase estimation in the framework of linear quantum metrology approach, these macroscopic soliton states are revealed to have a scaling up to the Heisenberg limit (HL). The examples are illustrated for HL estimation of angular frequency between the ground and first excited macroscopic states of the condensate, which opens new perspectives for current frequency standards technologies.