quantum physics The world studied by home trained eyes is exactly the same as the world we non-scientists navigate every day. The only difference is that it is enlarged to a small and large scale that is difficult to understand.
Still, quantum physics remains a largely a vague subject—even for scientifically keen readers. News@Northeastern talks with Gregory Fiete, professor of physics at Northeastern, about some of the widespread applications of quantum research, from developing renewable energy and building more powerful computers to advancing human pursuit of discovering life outside the solar system. Fiete's comments have been edited to keep things simple and clear.
First, let us give our audience a deep understanding of the nature of your work and look down on the infinitely small world. What are the misunderstandings about the work quantum physicists like you do, and why it matters?
You mentioned quantum and small worlds. This is what most people think of when they think of quantum mechanics , and some early foundations of quantum theory , which considers hydrogen atom and how it has discrete energy levels, you can observe experimentally by observing spectrum , or how it absorbs and emits light, for example.
[hydrogen atom] absorbs and emits at specific frequencies, and we now understand that this is because of the quantum properties of atom - why only specific allowable electrons surround the orbit of nucleus . Therefore, we tend to think about quantum mechanics from this very important early example of hydrogen atoms, so we tend to think that quantum is about small. But in fact, it's not about small ones at all.
Take the sun as an example. The sun is very large - it is the largest object in our solar system; our planets orbit around it because of its gravity.
The way the sun works is to burn hydrogen. Its gravity is so great that it combines hydrogen into helium, which then combines helium into other elements. It is the fusing of atoms together, and the fusion process is a quantum phenomenon, behind one of the huge energy challenges on Earth, known as continuous fusion. This is just combining hydrogen into helium - if we can do this under magnetic constraints on the earth, then we will have a clean and renewable energy source.
basically has an unlimited amount of hydrogen that can be combined, and helium is not radioactive. Therefore, we can generate a lot of energy from something more or less infinitely abundant without producing waste in the form of radioactive substances . This is a dream physicist is working to realize. So some of the most important things in the universe are certainly quantum mechanics, including supermassive black hole , which can lose energy through a quantum phenomenon called Hawking radiation.
The second point is that people often think that quantum processing is very low in temperature. Again, take our sun for example - it's very hot, but that's quantum mechanics. Low temperatures are not a quantum requirement. This example is about stars, and the quantum nature of the nuclear fusion process and the high temperature associated with it - I just wanted to broaden the horizons of what quantum mechanics is and how ubiquitous it is.
When we write down the work you and your colleagues are doing, there will always be real-world applications. Can you talk about some of the ways quantum physicists are driving technological advancements outside their field?
I will list some of my favorite techniques. One thing that really excites me about quantum physics is that it is used in what I think is "forensics" or quantum forensics, if you will.
Because things like atoms have discrete energy levels associated with it, it turns out that this can be used to identify atoms. If you compare the energy levels allowed by hydrogen to the energy levels of helium or any other element, they are different. If you have any gas for gas, then you can determine what atoms are in the gas by observing how it absorbs and glows.If you are interested in something far away, like a planet that orbits a star that is not our own, this will have great practical value.
We used a powerful telescope to discover a wonderful exoplanet domain, detecting these planets moving between stars and Earth. Our telescopes – some of which are connected in space to satellites with incredible frequency resolution and sensitivity – are so powerful that we can observe thin layers of atmosphere around these planets and how light from stars passes through it. We then use spectral techniques to see how light from the stars behind is absorbed by the planet's atmosphere, which may be thousands of light years away. Therefore, we can detect which atoms are in the atmosphere.
This is very interesting. But it goes further. We can also detect what molecules are there. For example, are there two hydrogen atoms attached to one oxygen atom? In other words, is there water in the atmosphere? Molecules have their own spectral characteristics. So we can actually detect if some of these planets have water in the atmosphere, which is really exciting.
However, we can go one step further. When it comes to temperature, these spectral lines, as they call it, are broadened. There is a frequency range where you can see absorption and emission. It expands the amount to tell you the temperature of a molecule - in other words, the atmospheric temperature of these planets.
Surprisingly, we can determine what the atmospheres of these planets contain - planets that humans cannot access. We can look for the characteristics of life, such as whether there are molecules associated with life floating in these planets, at least if it is Earth-like life; then we may be able to determine that there are some planets there that humans will never be able to access, own life. Or maybe we can find other candidate life forms. This is a very inspiring example, which ultimately relies on quantum physics and spectroscopy techniques.
I think another example that has attracted widespread interest is that quantum physics is producing energy that solar energy cannot reach. So when you send an deep space probe to observe the exoplanets of our solar system, let's say Pluto (technically no longer considered a planet). If you want to observe Pluto, you need to send a deep space probe – it will take years to get there. You might ask, what kind of power can you provide to the computer on this probe so that you can send back the beautiful pictures we saw? OK, you can put the battery there. It takes years to get there, space has a lot of radiation and batteries can be damaged; they may not work properly when they are launched through all the heat changes in the atmosphere and the coldness of space, etc. This is not very practical. There is not enough light from the sun, you can use solar panels to run the computer system and send back the image.
So, how do they power the computers on these deep space detectors? They use radiation. They use radioactive matter, and radioactivity is another quantum process in which heavy elements decay into lighter elements; when they do so, they pop up a portion of nucleus . But these ejected nuclei carry energy that can be captured.
There are some materials, some of which are very close to the work I'm doing, they are called thermoelectric material . They take high temperature zones and connect them to low temperature zones, converting this high and low temperature difference into voltages, and then function like a battery. Once you have voltage in your electrical system, you can now move the current and operate your computer or circuit in more or less normal ways.
It's all very interesting. It sounds like quantum physics is indeed the fundamental work that transforms our energy infrastructure, as well as other technologies. Is this the right way to think?
Yes, that's right.This is a good point - considering climate change and renewable energy and technologies that don't pollute our environment.
If we just think about energy, like the example we discussed fusion, it is a green technology—assuming we can make it work. If we give up nuclear fusion, there are other green technologies now. Take wind turbine as an example. What is the relationship between wind turbines and quantum physics? The way wind turbines work is that when the wind turns the propeller , they have a magnet connected to the propeller, and rotating the magnet will generate electric current. This is how you generate electricity: you twist the magnet inside the coil.
But the question is: Which magnet should you use? So that's where basic research—in fact, I was involved in this research to some extent at Northeastern University—used the use of the weapon: thinking about magnetic systems with ideal characteristics for applications such as wind turbines.
You need to have a very strong magnet that needs to survive at high temperatures, which means much higher than room temperature, as it gets hot as the sun shines there. It also has to have sufficiently strong properties to withstand any strain and stress as it is twisted in this turbine system. These are so-called hard magnets. So, how to develop better magnets? This is a quantum problem.
As a final thought, I want to know what your huge hope for your research and this field is. What do you want to see in your lifetime, and have any progress we have at the forefront?
This is a difficult question to answer. Everyone in this field is asking: What are the progress we are truly at the forefront? A widely cited example is quantum computing . Having quantum computer does not solve every computing problem that anyone can dream of. Quantum computers have proven to be particularly good at certain categories of problems, which can provide what are called "quantum advantages." There are some specific problems that quantum computers are more useful; but others may be better solved by traditional supercomputers.
Therefore, one problem in the field is trying to provide a sharper solution that illustrates the specific problems that quantum computers will help us solve. This is an evolving field, just like what is the real niche problem of quantum computers. I think all of us who work in this field feel that there will be some specific application, and quantum computers really go beyond everything else - everyone wants to be involved; everyone makes sense to every developed country. Everyone wants to be part of the next quantum revolution, which is not just about developing quantum mechanics into a new science, but about converting quantum mechanics into very widespread applications. And computing is just the cutting-edge field.
