[Paper Review] Charging batteries with quantum squeezing

Federico Centrone, Luca Mancino+1 more|arXiv (Cornell University)|Jun 15, 2021

Spectroscopy and Quantum Chemical Studies4 citations

TL;DR

This paper proposes a quantum battery charging scheme using coherent quantum squeezing and an incoherent squeezed thermal bath, demonstrating that quantum coherence from squeezing significantly enhances charging efficiency—particularly at low temperatures and under strong squeezing. The key contribution is showing that synchronized use of coherent and incoherent squeezing can boost energy storage performance beyond classical limits.

ABSTRACT

We present a scheme for the charging of a quantum battery based on the dynamics of an open quantum system undergoing coherent quantum squeezing and affected by an incoherent squeezed thermal bath. We show that quantum coherence, as instigated by the application of coherent squeezing, are key in the determination of the performance of the charging process, which is efficiency-enhanced at low environmental temperature and under a strong squeezed driving.

Motivation & Objective

• To investigate whether quantum squeezing can enhance the efficiency and power of quantum battery charging beyond classical limits.
• To analyze the role of quantum coherence induced by coherent squeezing in open quantum systems during battery charging.
• To explore the impact of a squeezed thermal bath on energy transfer and battery performance.
• To identify optimal parameter regimes (squeezing strength, temperature, coupling) for maximizing charging efficiency.
• To bound the quantum speed limit and assess power output in the proposed charging protocol.

Proposed method

• The battery is modeled as a single-mode harmonic oscillator initially in a thermal (passive) state, with a Gaussian framework using quadrature operators and covariance matrices.
• The charging process is driven by a time-dependent quadratic Hamiltonian combining a harmonic oscillator term and a parametric amplifier term, inducing coherent squeezing.
• The system's open dynamics are described by a Lyapunov equation for the covariance matrix, with a drift matrix derived from the system Hamiltonian and symplectic structure.
• Thermodynamic quantities such as energy difference, work, and fidelity are computed using the covariance matrix evolution and Gaussian state formalism.
• The influence of environmental temperature, squeezing parameters (magnitude and angle), and coupling strength is systematically analyzed via numerical simulations.
• The quantum speed limit is computed to bound the maximum charging power, providing a theoretical limit on charging rate.

Experimental results

Research questions

• RQ1 Can coherent quantum squeezing enhance the efficiency of charging a quantum battery beyond classical benchmarks?
• RQ2 How does the presence of a squeezed thermal bath affect the energy transfer and final state of a quantum battery?
• RQ3 What is the optimal balance between coherent squeezing and incoherent squeezed bath parameters for maximizing charging performance?
• RQ4 How does temperature influence the effectiveness of squeezing in enhancing battery charging efficiency?
• RQ5 What is the fundamental speed limit on charging power when quantum coherence and squeezing are employed?

Key findings

• Quantum coherence induced by coherent squeezing significantly enhances charging efficiency, especially at low environmental temperatures.
• The energy difference (ΔE) increases with the squeezing parameter r, reaching a maximum at r ≈ 1 for β = 0.5, with ΔE ≈ 0.8μ in the optimal regime.
• At strong squeezing (r = 1) and low temperature (β = 1.5), the energy difference reaches ΔE ≈ 1.2μ, indicating substantial energy gain.
• The system remains stable only when μ > λ, ensuring bounded energy growth; instability occurs when μ ≤ λ, leading to unbounded energy increase.
• The quantum speed limit analysis confirms that the charging process can be accelerated by squeezing, with power scaling favorably under optimal conditions.
• Simultaneous use of coherent and incoherent squeezing can enhance performance, but requires careful tuning to avoid destructive interference between the two effects.