With conventional energy sources like fossil fuels depleting fast, not to mention their adverse effects on the environment, the world has been in desperate need of alternative means to address our ever-growing energy needs. Attempts include solar, wind, geothermal and hydro-energy, nuclear fusion reactors, hydrogen energy and sodium-ion batteries, to name a few. While all these have certainly been laudable efforts, most have faced severe challenges and as a result, have achieved low to moderate success. The search for a viable substitute to fossil fuels goes on, once again putting human ingenuity to the test. The answer may come, however, from the unlikeliest of places, the quantum nature of reality itself.
Having been established more than a century ago, quantum theory remains a subject of much discussion and debate within the physics community itself. This is partly owing to the non-intuitive nature of the subject since it is extremely difficult for us to visualise how the world functions on such a microscopic scale. It turns out that the universe is quite peculiar at the quantum scale, and seems to defy conventional logic. In short, quantum theory is just strange. Consequently, despite being the most successful and accurate theory to date, it is nowhere near complete, and there are fundamental questions which remain unanswered.
With conventional energy sources like fossil fuels depleting fast, not to mention their adverse effects on the environment, the world has been in desperate need of alternative means to address our ever-growing energy needs.
This long pursuit to understand how nature works on a fundamental level led us down an unexpected path, something which we could not have foreseen, and is now begging us to ask an important question—Is it possible to utilise the quantum nature of matter itself to create an alternative source of energy? Ongoing research in the field seems to suggest that the answer to this question is a resounding “yes.” Recent work on “quantum batteries” and “quantum engines” indicates that quantum technology may indeed hold the key to the future of energy generation, and we have barely even scratched the surface.
Quantum Batteries
While they seemed to be a distant reality for the time being, a research group comprising scientists from the University of Tokyo and the Beijing Computational Research Centre has made a recent breakthrough which could make quantum batteries a practical reality sooner than expected. Conventional chemical batteries rely on materials like lithium to store charge. Quantum batteries, on the other hand, use individual particles like photons to store energy.
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The essential idea the group used is a purely quantum phenomenon known as “Indefinite Causal Order (ICO)” which modifies our usual notion of the flow of time. The macroscopic world follows the rule of “causality,” if event 1 precedes event 2, the reverse cannot happen. This, however, is not necessarily the case when it comes to the quantum world. ICO implies that event 1 leading to event 2, and event 2 leading to event 1, can take place simultaneously via the principle of “superposition.” This led to the unexpected result that a lower-power charger could provide higher energies with greater efficiency compared to a higher-power charger using the same apparatus.
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Figure 1: Charging quantum batteries in indefinite causal order. In the classical world, if you tried to charge a battery using two chargers, you would have to do so in sequence, limiting the available options to just two possible orders. However, leveraging the novel quantum effect called ICO opens the possibility to charge quantum batteries in a distinctively unconventional way. Here, multiple chargers arranged in different orders can exist simultaneously, forming a quantum superposition. Source: Chen et al (2023).
Quantum engines
Though quantum engines are a more ambitious undertaking than batteries, the recent work by researchers at the University of Kaiserslautern, Germany, suggests they may hold massive potential in the future. While conventional engines use the “Carnot cycle” to convert heat or thermal energy into mechanical work, this particular quantum engine works on the energy differences which arise as a result of the statistical properties of quantum particles.
The bosons pile up in the lowest energy state, while the fermions keep ascending and stacking on top of each other, thereby increasing the energy of the system.
According to quantum mechanics, nature consists of two kinds of particles: bosons and fermions. While any energy state can accommodate an infinitely large number of bosons, it can only hold one fermion at a given point in time, meaning that no two fermions can occupy the same state. This is the foundation of the famous “Pauli Exclusion Principle.”
Although this effect is not important at room temperature, it becomes increasingly dominant as we cool the particles down to absolute zero temperatures (-273o Celsius or 0 Kelvin). The bosons pile up in the lowest energy state, while the fermions keep ascending and stacking on top of each other, thereby increasing the energy of the system. Therefore, at very low temperatures, fermions possess much more energy than bosons.
Figure 2: Blue balls indicate bosons and red and green balls indicate fermions. Green and red balls correspond to two spin states (spin up and spin down). Bosons pile up at the ground state while fermions keep ascending in energy. Source: S. Will (2011).
In the early 2000s, it was discovered that it is possible to convert a gas of fermions into bosons and vice-versa using magnetic fields. When this process is performed cyclically, the energy difference between fermions and bosons can in principle be converted into mechanical energy, similar to how a conventional engine works. The main difference here is that instead of using heat, the driving force in quantum engines turns out to be the difference in the fundamental nature of the quantum particles themselves.
While the experiment was a proof-of-concept demonstration, there is no denying the possibilities it presents. While quantum engines seem poised to be a viable source of energy for powering quantum computers and quantum sensors in the future, it is entirely within the realm of possibility that they may be able to power something even bigger down the road.
Conclusion
There have been numerous technological advancements in the field of alternative and renewable energy lately. However, most, if not all of them, are critically dependent on limited resources, which are bound to run out eventually. For instance, nuclear fusion, despite being one of the cleanest sources of energy, is still completely reliant on scarce materials like tritium. The severe shortage in the supply of semiconductors recently had an adverse impact on the manufacture of electric vehicles in 2023, an industry which is already set to contend with a lithium supply crunch in the future. And while green hydrogen seems like an exciting prospect, it is too expensive and inefficient to be economically viable at the moment, and it remains to be seen whether this will change in the future.
The severe shortage in the supply of semiconductors recently had an adverse impact on the manufacture of electric vehicles in 2023, an industry which is already set to contend with a lithium supply crunch in the future.
In this context, quantum technology may offer a way out since it is not directly dependent on any external resource, rather it relies on the nature of matter itself to generate energy. Though the aforementioned developments are just small steps in the right direction, and it may take years before quantum technology becomes a viable source of energy creation, the potential here is immense. Quantum batteries could, for instance, offer a reliable replacement for lithium-ion batteries in the future. Given the environmental cost of lithium mining, not to mention its increasing scarcity, the world is in dire need of an alternative and quantum technology can do just that.
India continues to invest sizeable resources into alternative energy as part of its 2070 net zero goals, the National Green Hydrogen Mission constituting a recent example. What has not really been explored so far is quantum energy generation. With the National Quantum Mission having been announced in the 2023 budget, the groundwork has already been laid out. Including quantum energy generation under the ambit of the NQM would be a good way to kickstart India’s endeavour into this novel and exciting field, one which has the potential to completely transform the landscape of energy production as we know it. The future of energy generation may lie in the microscopic domain of quantum mechanics.
Prateek Tripathi is a Research Assistant Centre For Security Strategy and Technology at the Observer Research Foundation
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