Physicist Steven Thompson summarises how our expanding understanding of quantum mechanical effects could herald the start of a second quantum revolution.
You might not realise it, but we are currently in the midst of what some are calling the second quantum revolution. From quantum computers to spintronics, from exotic superconductors to unbreakable encryption, we’re moving from the age of passively understanding and using quantum mechanics to the age of actively exploiting and creating quantum mechanical effects to do things previously thought to be impossible.
But what is quantum mechanics? What does it mean, and why is it so powerful?
Quantum mechanics originated in the early 20th century in the work of Max Planck. By suggesting that light came in discrete packets of energy called quanta, he laid the foundations of what was to become quantum theory. We now call these light quanta ‘photons’, and sometimes think of them as particles of light.
Back then, the suggestion that light – which behaved like a wave in most aspects – could be made up of a stream of tiny particles was highly controversial. Planck himself didn’t believe it, and thought the idea was a convenient mathematical trick and nothing more. It wasn’t until Einstein showed that the idea of light quanta explained a phenomenon known as the photoelectric effect (for which he was later awarded the Nobel Prize) that the idea was taken seriously. We now know that at its smallest level, everything in Nature seems to come in discrete quanta of some sort or another.
With the efforts of a group of now legendary physicists including Einstein, Bohr, Heisenberg, Pauli, Schrodinger, Dirac and others, quantum mechanics was born. At the heart of quantum mechanics is a concept called wave-particle duality, which says that depending on how you look at them, the fundamental building blocks of Nature can behave either as waves or as particles.
This duality has puzzled physicists and philosophers ever since, and many (including Einstein) never reconciled themselves to the idea that the nature of our reality depends on how you look at it. Regardless of the philosophical questions it raises, quantum mechanics has proven to be a fantastically successful framework. By harnessing the wavelike nature of reality, we can now design powerful devices to perform tasks once thought to be impossible.
In the 1940s, the world at large had its first demonstration of the power of quantum mechanics in the form of the atomic bomb. After the war, though, quantum mechanics was put to far more constructive uses: devices such as transistors, microprocessors, LEDs, CCD cameras and lasers all rely on quantum mechanics to operate.
Over the years our technology has evolved and our devices have gotten smaller and more powerful. From the lumbering computers that once filled rooms down to the smartphones in our pockets, technology has shot forward at an amazing rate, but we’re nearing the limit of what the technologies of the first quantum revolution can do for us. Now, scientists in the UK and elsewhere are looking to the future, no longer simply optimising and improving these technologies but instead designing wholly new ones.
Imagine having perfectly secure communications that can’t be intercepted, hacked or eavesdropped upon. Quantum communications technologies could harness the power of quantum entanglement to make this a reality. Imagine how powerful a computer the size of the solar system could be. Quantum computers could one day fit that much computational power into the palm of your hand. Or imagine how efficient our power grids could become if no electricity was lost as heat due to the resistance of the wires. High-temperature superconductivity could pave the way to this energy-efficient future, and could give us levitating trains as part of the bargain.
The future is almost here – welcome to the second quantum revolution.