Quantum physics sounds like a scary concept for many people, even if you're an avid lover of science.
It's one of those topics many of us wish we knew more about, but which seems impenetrably difficult to understand.
Entanglement, superposition, wave-particle duality: a brief look at the definitions of these concepts shows just how intriguing they are, even if to many of us they seem like fantastical science fiction.
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So is quantum physics just scientists theorising, or does it have real-world applications? How does quantum physics affect our everyday lives?
One of the biggest authorities on the subject is Paul Davies, a prominent British scientist whose book Quantum 2.0 seeks to de-mystify the concept and detail the history of how quantum physics burst onto the scientific scene.
We got the chance to ask Davies some of the big questions around this fascinating topic.
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Why do most quantum physics examples sound like riddles?
Quantum physics shreds everyday notions of common sense and our intuition about the nature of reality, so people struggle to imagine, in their mind’s eye, what is actually 'going on' in the quantum microworld. I do too!
Quantum theory presents a picture of the world 'out there' that is an amalgam of blended alternative realities, which remains in a weird state of limbo until an actual observation is made, when - Blam! – a single 'winner' reality in the Great Quantum Lottery snaps into being.
Which one? It’s simply a matter of chance, a fact that prompted Einstein to declare, appalled, that "God does not play dice with the Universe!"
Well, She does, it seems. You can ask a question like "Is the atom moving to the left or the right?" and quantum physics says that, in the absence of an actual observation, the answer is generally "both".
More precisely, there is simply no fact of the matter as to which way the atom is moving until you look to see.
Imagine your tumble dryer spins both clockwise and anticlockwise at the same time. Impossible!
For tumble dryers yes, but not for atoms, or even superconducting circuits.
These 'superpositions' of different possible realities are central to quantum theory, and what gives it such power for technology.
But another example, which may be easier to grasp, is quantum tunnelling, in which a particle like an electron can pass through an insurmountable barrier.
I liken it to throwing a stone at a window and, instead of the stone bouncing back, it enters the room beyond without breaking the window.
It is this tunnelling phenomenon, by the way, that enables the Sun to shine.
How does quantum physics make our lives better?
Quantum physics underpins almost all of modern technology, including electronics, computing, the internet, AI, GPS navigation – and those vivid TV screens (quantum dots).
But the most familiar impact is the supermarket checkout, where lasers instantly read the bar codes.
When I was young, checkout staff had to do mental arithmetic to tot up the price! How’s that for everyday impact?
When you were beginning to untangle quantum theory, was there a specific 'eureka' moment when it finally clicked?
Yes, I was about 19 and I finally realised that, if quantum theory is right, there is no 'real world out there'.
I remember telling my mother, expecting her to be sceptical or shocked, but she shrugged the comment aside as a typical riddle that her nerdy son came up with from time to time.
Are there any concepts – like teleportation, parallel universes, time travel, for example – that are impossible in classical physics, but which quantum physics may deem possible?
Many things. I just mentioned tunnelling for one. Another is teleportation – information transmitted from A to B without passing through the space in between.
Yet another is that black holes are strictly black in classical physics, but glow with heat when quantum physics is applied (this is the so-called Hawking effect – and the formula for the temperature can be seen on Stephen Hawking’s headstone in Westminster Abbey.)
A final one is superconductivity: perfectly resistance-less electricity flow at low temperature.
Quantum physics insists it is absolutely impossible to know both the position and motion of a particle (e.g. an electron or an atom) at the same time.
What, for you, is the most beautiful or satisfying concept in quantum physics?
It is that nature is vastly, unimaginably greater than our everyday senses suggest.
Human observations are limited to little pinhole portals into the staggeringly huge quantum world of amalgamated possibilities.
Quantum 2.0: The Past, Present, and Future of Quantum Physics, by Paul Davies, is published by Pelican.
