There's an old adage among tech journalists like me - you can either explain quantum accurately, or in a way that people understand, but you can't do both.
That's because quantum mechanics - a strange and partly theoretical branch of physics - is a fiendishly difficult concept to get your head around.
It involves tiny particles behaving in weird ways. And this odd activity has opened up the potential of a whole new world of scientific super power.
Its mind-boggling complexity is probably a factor in why quantum has ended up with a lower profile than tech's current rockstar - artificial intelligence (AI).
This is despite a steady stream of recent big quantum announcements from tech giants like Microsoft and Google among others.
Broadly speaking, we tend to think about quantum more commonly in the form of hardware like sensors and computers, while AI is more software-based – it requires hardware to operate.
Put them together, and we might one day have a new form of technology that's more powerful than anything we have ever created… although the word "might" is doing some heavy lifting in that particular prediction, warns Brian Hopkins, VP and principal analyst in emerging tech at research firm Forresters.
"The potential is there, but the jury is still out," he says.
"Initial experiments suggest promise, but they all indicate that we require much more powerful quantum computers and further innovative research to effectively apply quantum effects to AI."
In terms of their value, both are lucrative. The quantum sector could be worth up to $97bn (£74bn) by 2035, according to market research group McKinsey.
Meanwhile, AI's value is forecast in the trillions. But they both live under the shadow of hype and the bursting of bubbles.
"I used to believe that quantum computing was the most-hyped technology until the AI craze emerged," jokes Mr Hopkins.
In mid-October analysts warned some key quantum stocks could fall by up to 62%, while mutterings about an AI bubble grow ever louder.
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Quantum and AI have one more thing in common - errors. While we are largely familiar now with the "hallucinations" of generative AI tools, quantum is plagued by a different kind of error.
These are caused because the state in which the particles have to operate is so fragile. The slightest change to the environment, including light and noise, can disrupt them.
It's tricky to sustain such an environment. This week Elon Musk suggested on X that quantum computing would run best on the "permanently shadowed craters of the moon".
Quantum computers don't look anything like a traditional machines. There is no design blueprint, but they are currently very big.
They exist in laboratories, and the most commonly adopted format seems to include a kind of jellyfish-inspired shape.
They require extremely cold temperatures and lasers. It's not the sort of thing you're likely to have in your home, let alone in your pocket.
They're also a bit bling - researchers have found that using synthetic diamonds to create qubits, which are the building blocks of quantum computers, enables them to work much closer to room temperature.
The luxury jeweller De Beers has a subsidiary company called Element Six, which claims to have launched the world's first general-purpose quantum-grade diamond in 2020. And it has worked with Amazon Web Services on optimising artificial diamonds for future networks of quantum machines.
These machines are all in their infancy right now, there are believed to be around 200 of them in the whole world (China however has not disclosed how many it has) – this doesn't stop quantum experts making bold claims about their potential.
"We as consumers will touch the impacts of quantum computing in almost every walk of our lives," said Rajeeb Hazra, the boss of Quantinuum, a firm recently valued at $10bn. He was talking to the BBC's Tech Life podcast.
"The area of quantum computing is, in my mind, when you look at the applications, as big if not bigger than AI."
Prof Sir Peter Knight is one of the UK's top quantum experts. "Things that could take the age of the universe to calculate, even on the most powerful supercomputer, could be performed probably in seconds," he told Dr Dr Jim Al-Khalili on BBC Radio 4's The Life Scientific.
So what exactly are these gigantic, life-changing things that the machines might do once they're ready?
As with AI, there's a lot of quantum research directed towards improving healthcare.
Quantum computers could one day be able to effortlessly churn through endless combinations of molecules to come up with new drugs and medications – a process that currently takes years and years using classical computers.
To give you an idea of that scale - in December 2024, Google unveiled a new quantum chip called Willow, which it claimed could take five minutes to solve a problem that would currently take the world's fastest super computers 10 septillion years - or 10,000,000,000,000,000,000,000,000 years – to complete.
Hazra says this could pave the way for personalised medication, where instead of getting a standard prescription, you get a specific drug tailormade for your individual body, that's most likely to work for you.
And that applies to wider chemical processes too, such as new ways to produce fertilizers more efficiently, potentially a huge boost for global farmers.
Quantum sensors, which use the principles of quantum mechanics to measure things incredibly precisely, already exist and are found in atomic clocks.
In 2019, scientists at Nottingham University put them in a prototype device the size of a bike helmet, and used them in a new system to conduct non-intrusive brain scans on children with conditions such as epilepsy.
"The foundations for human cognition are laid down in the first decades of life, but there have always been limited ways to study them due to restrictions in brain scanning technology," said researcher Ryan Hill at the time.
"A particular problem has always been movement and the fact that the large traditional fixed scanners have always required patients to stay completely still.
"Not only does this fail to give an accurate picture of the brain operating in a natural environment, but it also places severe restrictions on who can be scanned, with children representing the biggest challenge."
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