[LINK] Entanglement phenomenon increases the output efficiency of quantum engines

[Stephen Loosley]

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Chinese scientists harness power of ‘entanglement’ to fuel quantum engine

    • Breakthrough study is the first experimental realisation of a quantum engine with ‘entangled characteristics’, researchers said.

    • The technology uses the mysterious phenomenon that allows a pair of separated light particles to remain intimately linked, regardless of the distance between them.

By Zhang Tong in Beijing Published: SCMP 12:00pm, 2 Jun 2024   https://archive.md/AEXjx


Researchers in China have tapped into one of the strangest phenomenon in quantum physics to show that it could one day be used to power the next generation of computers.

The entanglement phenomenon allows a pair of separated photons to remain intimately linked – regardless of the distance between them – as if there is a secret, faster-than-light communication between the two particles.

The researchers, from the Chinese Academy of Sciences’ Innovation Academy of Precision Measurement Science and technology, said the breakthrough shows that quantum engines can use their own entangled states as a form of fuel.

“Our study’s highlight is the first experimental realisation of a quantum engine with entangled characteristics. [It] quantitatively verified that entanglement can serve as a type of ‘fuel’,” said Zhou Fei, one of the corresponding authors, on Monday.

Unlike traditional engines that operate on thermal combustion, a quantum engine uses lasers to transition the particles between quantum states, converting light into kinetic energy.

Zhou, along with fellow corresponding author Feng Mang and the rest of the team, showed that the entanglement phenomenon increases the output efficiency of quantum engines, according to the study, published on April 30 by the journal Physical Review Letters.

Quantum engines could theoretically surpass the limits of classical thermodynamics, potentially achieving energy conversion efficiencies of more than 25 per cent – enough to power large-scale quantum computers and circuits.

Using ultra-cold 40Ca+ ions confined in an ion trap as the working substance for the quantum engine, the team designed a thermodynamic cycle that converts the external laser energy into the vibrational energy of the ions.

“We chose the entangled states of two spinning ions as the working substance, with [their] vibrational modes acting as the load. Through precise adjustments of laser frequency, amplitude, and duration, the ions were transitioned from their initial pure states to highly entangled states,” Zhou said.

“We measured how well the engine works by looking at two things: conversion efficiency, which is how many vibrations (phonons) it produces for every bit of light (photons) it uses, and mechanical efficiency, which is how much of the energy we can actually use compared to all the energy it puts out.”

More than 10,000 experiments revealed that higher degrees of ion entanglement led to greater mechanical efficiency, although the conversion efficiency remained largely unaffected by the level of entanglement.

“This indicates that quantum entanglement, despite its mysterious mechanism to physicists, acts as a “fuel” in quantum engines,” Zhou said.

“Quantum engines are currently a very active research field, with many theoretical analyses and studies, but very few experimental results are provided.”

The study’s conclusions open new perspectives for the development of micro-energy devices such as quantum motors and batteries, suggesting that the entanglement properties of the working material can enhance the maximum extractable energy.

According to Zhou, while quantum batteries might not store as much energy as those used in electric vehicles, their real benefit would come from their ability to power large-scale quantum computers and circuits.

“The future challenge lies in increasing the number of working materials without compromising fidelity of the entanglement state, thereby enhancing output,” he said.


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