THE LITHIUM-ION BATTERY is the unsung hero of the modern world. Since it was first commercialised in the early 1990s, it has transformed the technology industry with its ability to store huge amounts of energy in a relatively small amount of space. Without lithium, there would be no iPhone or Tesla – and your laptop would be a lot bigger and heavier.
But the world is running out of this precious metal – and it could prove to be a huge bottleneck in the development of electric vehicles, and the energy storage solutions we’ll need to switch to renewables. Some of the world’s top scientists are engaged in a frantic race to find new battery technologies that can replace lithium-ion with something cleaner, cheaper and more plentiful. Quantum computers could be their secret weapon.
It’s a similar story in agriculture, where up to five per cent of the world’s consumption of natural gas is used in the Haber-Bosch process, a century-old method for turning nitrogen in the air into ammonia-based fertiliser for crops. It’s hugely important – helping sustain about 40 per cent of the world’s population – but also incredibly inefficient compared to nature’s own methods. Again, quantum computers could provide the answer.
So far, researchers have been working on these problems with blunt tools. They can perform increasingly powerful simulations using classical devices, but the more complicated the reactions get, the harder they become for supercomputers to handle. This means that right now, scientists are limited to looking only at very small problems, or they are forced to sacrifice accuracy for speed.
A hydrogen atom, for instance, has one positively charged proton and one electron and is easy to simulate on a laptop – you could even work out its chemistry by hand. Helium, next step along on the periodic table, has two protons, orbited by two negatively charged electrons – but it’s more challenging to simulate, because the electrons are entangled, so the state of one is linked to the state of the other, which means they all need to be calculated simultaneously.
By the time you get to thulium – which has 69 orbiting electrons, all entangled with each other – you’re far beyond the capability of classical computers. If you wrote down one of each of the possible states of thulium per second it would take 20 trillion years – more than a thousand times the age of the universe. In his 2013 book Schrödinger’s Killer App, John Dowling calculates that to simulate thulium on a classical computer, you would need to buy up Intel’s entire worldwide production of chips for the next 1.5 million years, at a cost of some $600 trillion.
A much quicker alternative would be to simply measure the atom directly. “Classical computers seem to experience an exponential slowdown when put to simulating entangled quantum systems,” Dowling writes.