Whether it's photovoltaics or fusion, sooner or later, human civilization
must turn to renewable energies. This is deemed inevitable, considering the
ever-growing energy demands of humanity and the finite nature of fossil
fuels. Much research has been pursued in order to develop alternative
sources of energy, most of which use electricity as the main energy carrier.
The extensive R&D in renewables has been accompanied by gradual societal
changes as the world adopted new products and devices running on renewables.
The most striking change has been the rapid adoption of electric vehicles.
While they were rarely seen on the roads even 10 years ago, now, millions of
electric cars are being sold annually. The electric car market is one of the
most rapidly growing sectors.
Unlike traditional cars, which derive energy from the combustion of
hydrocarbon fuels, electric vehicles rely on batteries as the storage medium
for their energy. For a long time, batteries had far lower energy density
than those offered by hydrocarbons, which resulted in very low ranges of
early electric vehicles. However, gradual improvement in battery
technologies eventually allowed the drive ranges of electric cars to be
within acceptable levels in comparison to gasoline-burning cars. It is no
understatement that the improvement in battery storage technology was one of
the main technical bottlenecks that had to be solved in order to kickstart
the current electric vehicle revolution.
However, despite the vast improvements in battery technology, today's
consumers of electric vehicles face another difficulty: slow battery
charging speed. Currently, cars take about 10 hours to fully recharge at
home. Even the fastest superchargers at the charging stations require up to
20 to 40 minutes to fully recharge the vehicles. This creates additional
costs and inconvenience to the customers.
To address this problem, scientists looked for answers in the field of
quantum physics. Their search has led to the discovery that quantum
technologies may promise new mechanisms to charge batteries at a faster
rate. Quantum battery technology was first proposed in a seminal paper
published by Alicki and Fannes in 2012. It was theorized that quantum
resources, such as entanglement, can be used to vastly speed up the battery
charging process by charging all cells within the battery simultaneously in
a collective manner.
This is particularly exciting, as modern, high-capacity batteries can
contain numerous cells. Such collective charging is not possible in
classical batteries, where the cells are charged in parallel independently
of one another. The advantage of this collective versus parallel charging
can be measured by the ratio called the quantum charging advantage. Around
2017, researchers noticed that there can be two possible sources behind this
quantum advantage—namely global operation (in which all the cells talk to
all others simultaneously, i.e., "all sitting at one table") and all-to-all
coupling (i.e., "many discussions, but every discussion has only two
participants"). However, it is unclear whether both these sources are
necessary, and whether there are any limits to the charging speed that can
be achieved.
Recently, scientists from the Center for Theoretical Physics of Complex
Systems within the Institute for Basic Science (IBS) further explored these
questions. The paper, which was chosen as an Editors Suggestion in the
journal Physical Review Letters, showed that all-to-all coupling is
irrelevant in quantum batteries and that the presence of global operations
is the only ingredient in the quantum advantage. The group went further to
pinpoint the exact source of this advantage while ruling out any other
possibilities and even provided an explicit way of designing such batteries.
In addition, the group was able to precisely quantify how much charging
speed can be achieved in this scheme. While the maximum charging speed
increases linearly with the number of cells in classical batteries, the
study showed that quantum batteries employing global operation can achieve
quadratic scaling in charging speed. To illustrate this, consider a typical
electric vehicle with a battery that contains about 200 cells. Employing
this quantum charging would lead to a 200 times speedup over classical
batteries, which means that at home charging time would be cut from 10 hours
to about 3 minutes. At high-speed charging stations, the charge time would
be cut from 30 minutes to mere seconds.
Researchers say that consequences are far-reaching and that the implications
of quantum charging can go well beyond electric cars and consumer
electronics. For example, it may find key uses in future fusion power
plants, which require large amounts of energy to be charged and discharged
in an instant. Of course, quantum technologies are still in their infancy
and there is a long way to go before these methods can be implemented in
practice. Research findings such as these, however, create a promising
direction and can incentivize the funding agencies and businesses to further
invest in these technologies.
Reference:
Quantum Charging Advantage Cannot Be Extensive Without Global Operations,
arXiv:2108.02491 [quant-ph]
arxiv.org/abs/2108.02491