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One of the quietest revolutions Our century today was the entry of quantum mechanics into our everyday technology. In the past, quantum effects were limited to physics laboratories and delicate experiments. However, modern technology increasingly relies on quantum mechanics, and the importance of quantum effects will only increase in the coming decades. As such, the physicist Miguel F. Morales has taken on the Herculean task of explaining quantum mechanics to laypeople in this seven-part series (not mathematics, as we promise). Below is the series finale, but you can always find the starting story as well as a landing page for the entire series on location.
Exploring the quantum world
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The future is already here – it just isn't very evenly distributed – William Gibson
As a toolmaker, we were only able to use quantum mechanics recently. Understanding and manipulating quantum devices has been like a heady new superpower – there are so many things we can build now that would have been impossible just a few years ago.
We got to know some of these quantum technologies in the previous articles. Some of them, like the quantum dots in televisions, have already become commonplace; others, such as optical clocks, exist but are still very rare.
As this is the last article in this series, I want to look to the near future where quantum technologies are likely to affect our daily lives. You don't have to look far – all of the technologies we are going to explore today already exist. Most of them are still rare, in isolation in laboratories or as technology demonstrators. Others hide in sight, like the MRI machine in the local hospital or the hard drive on your desk. In this article, we'll focus on some of the technologies that we haven't seen in previous articles: superconductivity, particle polarization, and quantum electronics.
As you look at these quantum technologies, imagine what it will be like to live in a world where quantum devices are everywhere. What does it mean to be tech savvy when knowledge of quantum mechanics is a prerequisite for understanding everyday technology?
So grab your binoculars and let's take a look at the quantum technologies coming over the next comb.
MRI magnets under construction at Philips Healthcare manufacturing facility in 2010.
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A magnet hovering over a superconductor – that's a great demonstration in the classroom!
In a normally conducting wire you can attach a battery and measure how fast the electrons move through it (current or number and speed of electrons). It takes some pressure (voltage) to push the electrons through, and in the process, some heat is released – think of the red glow of the coils in a space heater or hairdryer. The difficulty in pushing electrons through a material is resistance.
But we know that electrons move as waves. As you cool all the atoms in a material, the size of the electron waves that carry the electric current increases. As soon as the temperature is low enough, this ripple can change from a disturbing subtlety to a determining property of the electrons. Suddenly the electron waves pair and move effortlessly through the material – the resistance drops to zero.
The temperature at which the ripple of the electrons becomes excessive depends on the crystal in which the electrons are located. However, it is always cold and includes temperatures at which gases like nitrogen or helium turn into liquids. Despite the challenge of keeping things this cold, superconductivity is such an amazing and useful property that we are using it anyway.
Electromagnets. Superconductivity is most commonly used for electromagnets in MRI (magnetic resonance imaging) machines. As a kid, you may have made an electromagnet by wrapping a wire around a nail and attaching the wire to a battery. The magnet in an MRI machine is similar in that it is just a large coil of wire. However, if ~ 1000 amps of current is flowing through the wire, it becomes expensive to keep the magnet running. Usually it looks like the largest space heater in the world.
So the answer is to use a special wire and cool it down in liquid helium. Once it's superconducting, you can plug it into a power source and turn the electricity on (this takes 2-3 days – there is a great video on how to plug in an MRI magnet). Then pull out the magnet and walk away. Since there is no resistance, the current continues to flow as long as you keep the magnet cold. When a hospital installs a new MRI, the magnet is turned on when it is installed, then unplugged and left on for the rest of its life.
Enlarge /. A superconducting magnet used for a particle detector.
While MRI machines are the most visible examples, superconducting magnets are actually widely used. Every good chemistry laboratory or department has several superconducting magnets in their nuclear magnetic resonance (NMR) and mass spectrometers. Superconducting magnets line 18 km of the Large Hadron Collider and appear in other ways in physics departments. When we had a small project, we grabbed a superconducting magnet from the warehouse alley behind my laboratory and renovated it. Physicists receive glossy catalogs from manufacturers of superconducting magnets.
Transmission lines. The next obvious application is to stretch a superconducting wire and use it to transport electricity. There are several demonstration projects around the world that use superconducting power lines. As with most industrial applications, it's just a matter of finding cases where a superconductor's performance is worth its high price. As prices go down, long-distance superconducting transmission lines can be critical as we bring more renewable solar and wind energy into the grid. The loss-free delivery of electricity over long distances can compensate for local fluctuations in the generation of renewable energy.
Generators and Motors. When you have incredibly powerful superconducting magnets, you'll want to use them in electrical generators and motors. Cooling is a problem as always, but the much stronger magnets can make the motor / generators significantly smaller and more efficient. This is particularly attractive for wind turbines (reduced weight of the tower) and electric drives for boats and aircraft (reduced weight and improved efficiency).