The modern battery has come a long way in its 224-year history. In the place of Alessandro Volta’s piles of metal disks and brine-soaked cloth, we now have batteries the dimensions of a graham cracker that can last days before needing a recharge.
But what is the ceiling of the devices currently on the market? What sort of technical challenges must be overcome to break that ceiling, and when will such hurdles be cleared? What is the future of energy storage?
A handful of scientists around the world are working on an answer: a battery technology that uses the laws of quantum physics, rather than classical physics, to hold a charge. It’s a long, long way out, but Rome wasn’t built in a day—and it certainly wasn’t powered in one.
The basic, beloved battery
A battery is a piece of technology that uses chemical reactions to produce electrical energy. Household batteries produce electrical energy via the flow of electrons through a circuit. Different battery cells have been developed over the centuries; Benjamin Franklin is considered to have coined the term “electrical battery” in a 1749 letter, which he concluded with an amusing riff on the marvels of electricity:
A Turky is to be killed for our Dinners by the Electrical Shock; and roasted by the electrical Jack, before a Fire kindled by the Electrified Bottle; when the Healths of all the Famous Electricians in England, France and Germany, are to be drank in Electrified Bumpers, under the Discharge of Guns from the Electrical Battery.
Fast forward through a few different battery cells, mostly named for the scientists who developed them using chemical reactions of various acids and metals, and in 1859 we got the lead-acid battery—the first with the capacity to recharge by reversing current through the system. In the late 20th century, the lithium-ion battery became in vogue and has basically remained popular since, using different permutations of lithium combined with other metals and phosphates. But throughout the modern battery’s history, the basic principle of a chemical reaction begetting electrical power has not changed.
Okay, forget the battery. What the heck is ‘quantum’?
Let’s quickly review quantum physics in broad strokes. Particles in quantum states operate under an entirely different set of rules from everything you see around you, from the water in clouds to the blood vessels coursing through your veins. Particles enter quantum states under extreme conditions: very cold temperatures and in vacuums. In these conditions, particles can act like multiple things at once, making them useful for doing things like complicated mathematical operations (as a quantum computer does) and checking whether time travel (in a sense) is possible.
Quantum systems can also exhibit entanglement, a phenomenon by which two or more quantum particles define the characteristics of each other. In quantum computers, atoms in an array carry the information necessary for the given operation, as bits do in an ordinary computer. These atoms are quantum bits, or qubits.
But quantum operations are delicate. The moment any value in a quantum system is made certain, the operation falls apart. The entire system—for example, atoms in an array—is then back in a classical state.
Quantum states can persist for a long time. Take time crystals, a state of matter first proposed in 2012 which earlier this year physicists showed could persist for at least 40 minutes, about 10 million times longer than other known crystals. These crystals are far afield from quantum batteries but showcase how fleeting some quantum systems normally are—an important issue to solve if we’re ever going to rely on such regimes for power.
So how do the rules of quantum mechanics apply to a battery, the technology that allows you to keep reading this article and maybe more thereafter, once you recharge?
Quantum batteries, as currently imagined
Like normal batteries, quantum batteries—as they are imagined—store energy. But that’s where the similarities end. Unlike the chemical reactions that both charge up and expend a battery’s stored energy, quantum batteries are powered by quantum entanglement or behaviors that more closely tether the battery and its source.
“Quantum batteries are composed of many quantum cells that act like one big quantum battery,” said Ju-Yeon Gyhm, a quantum researcher at Seoul National University in South Korea, in an email to Gizmodo. “The challenge is how to maintain the quantum properties for a long time.”
Since the same properties apply to quantum batteries as quantum computers, a major technical challenge must be cleared to see the technology become a reality outside of research settings: Physicists must figure out how to keep quantum systems in their delicate states outside of the most carefully managed research settings. A room-temperature superconductor would be such a grail, but these days the only folks claiming such a discovery had their work debunked within months.
“Thermodynamics at equilibrium does not set bounds on how fast energy is transformed into heat and work,” wrote a team of five scientists in a recent colloquium on quantum batteries, currently hosted on the preprint server arXiv. “Therefore it seems natural to seek thermodynamic quantum advantages in quantum systems that are driven out of equilibrium.”
The group went on to note that quantum entanglement is linked with how fast energy can be stored in many-body quantum systems, a discovery that has prompted research into quantum systems as energy storage devices.
In 2018, a team modeled the Dicke quantum battery, the first proposed to exist in a solid-state architecture, and in 2022, a team tested out a basic framework for a quantum battery in a lab setting using a target, mirrors, and laser light.
Recent experiments are poking around the problem
Late last year, a team of quantum researchers proposed a system by which quantum batteries could charge in an indefinite causal order, or ICO. Their findings—published in Physical Review Letters—posited that a charging system with ICO could outperform conventional charging protocols.
“Roughly speaking, ICO can be used to construct quantum processes which are not possible in the standard quantum theory, where causal order must be definite, or fixed,” said Yuanbo Chen, a researcher at the University of Tokyo and lead author of the research, in an email to Gizmodo. “This flexibility allows for a wider variety of quantum processes, some of which can show advantageous and interesting properties.”
“We saw huge gains in both the energy stored in the system and the thermal efficiency. And somewhat counterintuitively, we discovered the surprising effect of an interaction that’s the inverse of what you might expect: A lower-power charger could provide higher energies with greater efficiency than a comparably higher-power charger using the same apparatus,” Chen said at the time.
Different experimental setups of quantum battery systems—both proposed and realized—mean there are different pathways to innovate on the design of such a futuristic technology. Last month, a team from the University of Gdansk and the University of Calgary proposed a quantum battery charging system that maximizes the amount of energy stored in the battery while minimizing the amount of energy that dissipates (or is lost) in the charging process. Part of the team’s redesign is that the quantum battery and its charger are coupled to the same reservoir, producing an interference-like pattern which improves the efficiency of energy’s transfer between the two. The team estimate that the battery can store four times as much energy through the new charging process than using a conventional charger.
“Quantum batteries act more like a wave where the molecules or atoms act in unison, whereas in conventional batteries the molecules or atoms act more like individual particles,” said James Quach, a quantum researcher at the University of Adelaide in Australia, in an email to Gizmodo. “This collective behavior is what underpins the superextensive charging properties of quantum batteries, where it takes less time to charge quantum batteries of larger capacity.”
In 2022, a team led by Quach tested out a basic framework of a quantum battery by putting molecular dye called Lumogen-F orange in a small cavity, and pulsed light at it to see how it stored the energy transmitted by the photons of light. The team found that the system charged up remarkably fast, and that larger systems generally ought to charge faster.
“Currently it takes femto- to picoseconds to charge a quantum battery that stores about a microjoule of energy for nano- to milliseconds,” Quach said. “Although this does not sound like a long time, its storage time is actually more than million times longer than its charging time. As a comparison, this would be equivalent to a conventional battery which takes minutes to charge, being able to hold that charge for hundreds of years.”
As reported by New Scientist, some physicists theorize that a quantum battery’s charge time is inversely proportional to the number of qubits in the system; in other words, the bigger the battery, the faster it charges.
So…when can I get a quantum battery?
Quantum battery research is gaining traction, but it’s still very much in its infancy. Though their promise is remarkable, what the ultimate design of the technology will be remains an open question. Commercialization? That’s but a twinkle in the eye of the most business-minded physicist at the moment.
The chief issue remains getting quantum systems to stay in a quantum state when they scale up. Quach believes that quantum batteries could be used as a mobile energy source in phones and cars, but many quantum systems currently need very cold, noiseless conditions to stay that way (as an aside, Quach’s 2022 experimental setup operated at room temperature). Not to demoralize you, dear reader, but nuclear fusion is probably closer to reality than quantum batteries in our devices.
Though many a skeptical reporter is loathe to admit it, I’d love to eat my words. The only thing better than being right is finding the world a better place at the expense of being wrong. Quantum batteries could charge faster and more efficiently than classical devices, and could integrate with budding quantum technologies that are used for lofty simulations and measurements. A fully operational quantum battery has not yet been demonstrated, but according to the recent colloquium, such a technology could revolutionize the way we harvest, deliver, and control energy. Given humanity’s obvious reliance on electricity, energy storage could use a quantum leap.
More: Physicists Got a Quantum Computer to Work by Blasting It With the Fibonacci Sequence
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