The contemporary world of quantum, and where it’s headed.
Quantum in the Modern World
We will now embark on a whistle-stop tour of the major ways quantum ideas are being utilized to enhance our lives or develop new and exciting technologies that push the boundary of what’s possible. While some more imaginative applications of quantum physics may seem far off, many current technologies already employ quantum principles. To illustrate how this field’s influence can be found everywhere – even in the places you’d least expect – let’s quickly talk about a common kitchen appliance that demonstrates one of the phenomena that inspired the founding of quantum mechanics.
Toasters contain a metallic element which glows red when it heats up. Any material in fact, when heated to the same temperature will glow red, then yellow, and finally white as it gets hotter. The restricted range of visible light wavelengths being emitted from the heated elements is a direct result of the quantum nature of energy! It’s in fact one of the things which tipped physicists off!
Quantum computing leverages quantum phenomena such as quantum bits – or ‘qubits’ – superposition and entanglement to perform data operations at lightning speed. In classical computing, a ‘bit’ is a unit of information which is stored as either 1 or 0. A qubit on the other hand is a two-level quantum system which can either be in the 1 state, the 0 state, or some combination of both states via superposition, allowing for information to be processed far more quickly.
Qubits can be used to tackle extremely difficult tasks which ordinary computers simply cannot perform on their own. This added flexibility means that quantum computers can process numerous operations at the same time rather than one by one as our usual computers do. There’s a reason this new breed of computer is predicted to have a huge impact on understanding climate change and the vast amount of data that needs to be processed to model it!
As we know, when atoms are exposed to particular frequencies of electromagnetic radiation, the electrons orbiting the atom’s nucleus are made to “jump” between well-known, discrete energy states. Clocks based on this jumping in theory would offer an extremely precise way to measure time. That’s exactly why the quantum clock – more commonly known as an ‘atomic clock’ – has been successfully built!
Just as a classical clock is an apparatus that counts a repetitive event – for example, a mechanical clock with a pendulum that swings once every second or an electronic clock that uses a vibrating quartz crystal to keep time – an atomic clock relies on the quantum transitions of electrons to achieve an unfathomable level of accuracy. Using this technology, time can be measured within a margin of error of just one second in up to 100 million years! They are integral to Global Positioning Systems (GPS) and are also used to send signals to spacecraft to determine their position.
Lasers are only able to emit a concentrated beam of light because all the individual light waves – using the term ‘wave’ loosely now that we know the dual nature of light! – are ‘coherent’. Coherent in this scientific sense means that each of these light waves have completely identical frequencies and waveforms, i.e., they are in perfect synchronization with each other. To generate laser light that meets this stringent definition we rely on a technique called ‘stimulated emission’.
In stimulated emission, a photon is used to stimulate an already excited atomic electron to drop down to a lower quantum energy state and release two identical photons in the process which are travelling coherently. By repeating this process countless times in a reflective chamber, we can amass a huge number of photons which are coherent and once emitted together form what we know as a laser. The word ‘laser’ is an acronym which stands for “Light Amplification by Stimulated Emission of Radiation”!
You may be surprised to hear that the ubiquitous fluorescent bulb only works because of quantum phenomena! They contain electrodes which eject high-energy electrons when heated up. These electrons in turn bombard a tiny sample of mercury placed inside of the bulb, supplying energy to the electrons in the mercury atoms and causing them to jump up to a higher energy quantum state.
The inherent instability present in an ‘excited atom’ ensures that these electrons eventually return to their stable ground state, in the process emitting electromagnetic radiation in the form of visible light photons. The production of these photons in the bulb, as dictated by the theory quantum mechanics, provides the light which we see radiated from the bulb!
Other Applications of Quantum Mechanics
Before closing out this Pathway, there are two hugely influential areas which simply would not be possible without an understanding of quantum mechanics.
The first of these applications is in ‘semiconductors’, which are materials which possess an electrical conductivity somewhere between that of a conductor – which has ample shared or ‘delocalized’ electrons in its atomic structure and can carry a current with ease – and an insulator, which prevents the flow of electricity. Semiconductors are complex, and function via quantum effects to accommodate a wide range of possible currents and voltages, making them vital in all sorts of everyday electronics such as computers, TVs, and phones.
Secondly, there’s Magnetic Resonance Imaging (MRI). This medical imaging technique uses the quantum property of particle ‘spin’ in hydrogen protons to infer whether each small area of the body is composed of water or fat, culminating in a beautifully clear image of a slice of the body.