How to reconcile relativity with quantum mechanics ? What is spin? Where does the electric charge come from ? All these answers in 15 minutes!
Back in 2015, the two detectors that make up the experiment called LIGO detected gravitational waves generated by two merging black holes. And now, some researchers believe they can build instruments that can detect gravitational waves even LIGO can’t see — instruments that would be small enough to fit on a table top.
Though the device is yet to be built, researchers believe a device like this that’s as small as 1 meter long could reveal low frequency gravitational waves. The proposed device would use nanoscale diamonds with defects, called nitrogen-vacancy centers or NV centers.
Find out more about how this new tech will work and how it might help us study the quantum character of gravity in this Elements.
Ever heard of the term “wave function” in relation to quantum mechanics? What does it mean? How is it interpreted?
Hey everyone, I’m back with a new video! This time, we’re going back to basics and understanding exactly what a wave function is, as well as what it represents, in the world of quantum physics. This video is going to be the first in a series I’m going to call “Quantum Mechanics… But Quickly”. In this series, I want to discuss some fundamental quantum concepts, and explain them in as visual and intuitive a way as possible – without having to sit through an hour long lecture, or understanding complicated graduate level mathematics.
A physicist named Louis de Broglie once suggested something amazing. While scientists were busy debating whether light was a wave or a particle, de Broglie suggested that even matter – things with mass (e.g. electrons, protons, atoms, etc.) – could behave like waves. This idea was revolutionary due to the mountains of evidence scientists had up until that point that matter behaved like particles. However, the quantum world was soon to revolutionise everything we thought we knew about the universe. And as it turns out, de Broglie’s suggestion was right.
His suggestion of matter waves permeated into the work of Erwin Schrodinger. Combining the idea of matter waves with the principle of Conservation of Energy, Schrodinger came up with the equation we now know as the Schrodinger Equation. This ended up being the governing equation of quantum mechanics, and crucially contained a function known as the wave function. This wave function contained mathematical information about any quantum system we happened to be studying.
The key question, then, was about what the wave function actually related to. What did it correspond to in real life? How should we interpret it? Well, there are a few different interpretations of quantum mechanics and how it relates to our real-life universe. The most commonly accepted one is the Copenhagen interpretation. And this interpretation suggests that a wave function is directly related to the probability distribution of a system. Specifically, if we take a system’s wave function and square it (well, technically if we take its square modulus), then this will give us the probabilities of various results occurring when we make a measurement on a system. For example, the wave function of a system could tell us the probability of finding a particle at a certain position in space. Or it could tell us the probabilities of finding different spin states when measuring the spin of an electron, for example.
In this video, we discuss these examples in detail. Additionally, we briefly look at the consequences of wave functions having imaginary parts. Lastly, we look at how the Schrodinger Equation (or at least the time dependent Schrodinger Equation) governs how a wave function changes over time – apart from when we make a measurement on the system. This measurement causes a discontinuous and jarring change in the wave function, known as the “collapse of the wave function”. This collapse has caused many philosophical problems for physicists over the years, and it continues to do so to this day.
In the quantum world, dynamic localization is when a system stays the same temperature even when it has an energy input that should be making it hotter, and physicists have now pushed this phenomenon further than ever before. A team of researchers investigated mathematical models to see if dynamical localization can still arise when many quantum particles interact.
A quantum internet is in the works. The U.S. Department of Energy recently rolled out a blueprint describing research goals and engineering barriers on the way to quantum internet. The DOE’s latest blueprint for a quantum internet in the U.S. has four key milestones. The first is to make sure quantum information sent over current fiber optic cables is secure. Then to establish entangled networks across colleges or cities, then throughout states, and finally for the whole country. But what exactly is quantum internet? There is no real clear meaning beyond “sending quantum signals back and forth,” and there are a few ways to go about doing it. In February 2020, the Department of Energy announced they had sent two entangled photons over two separate 42 kilometer fiber optic loops and had verified they were still correlated when they returned. They hailed it as a milestone on the way to developing a national quantum internet.
Quantum physics is dominated by the idea that quantum objects remain in superposition until thy are measured, which causes its wave function to collapse. But there is another interpretation of quantum mechanics, one with mind-blowing implications about the universe and our lives. It’s the many worlds interpretation, and some believe it imbues us with a kind of immortality.
Arguably the most likely way we will first discover alien life on another planet will be using the power of atomic spectroscopy.
Aliens will most likely leave a tell tale trace of their life in the atmosphere’s of their planet. But how do we know what chemicals the atmosphere of a distant planet contains? The answer is atomic spectroscopy. If we see a planet passing in front of it’s star, some of that starlight is absorbed in a very specific pattern called an atomic absorption spectrum. Each element has a specific pattern like a barcode, so through careful analysis of the light it can tell us which gasses are in the atmosphere and their proportions. We already use this technique for other space objects like stars and nebulae, measuring properties like temperature, density, ionization and relative velocity. This is a gift that nature and quantum physics has given us and the majority of what we know about the universe is based on this technique.
Quantum consciousness. Is quantum mechanics responsible for consciousness and free will? There is a reductionist claim that the universe is a sophisticated kind of clock ruled by the laws of physics. Are we sophisticated automatons?
But doesn’t this unpredictability of natural laws via quantum mechanics give us free will?
Sir Roger Penrose tried to tackle this. Is there a quantum physics connection to consciousness that ensures that we have free will?
Reductionism is the idea that any complex system is the sum of its simpler fundamental individual parts. Matter, energy, and the laws of physics that determine how they interact is all there is.
Counter argument is that consciousness is somehow different. If a human being was nothing more than matter and energy, then what would be the difference between a person who is alive, and the same person immediately after his death. All the matter and energy of the person would not have changed. There seems to be one main difference – consciousness.Continue reading “Quantum Mind: Is quantum physics responsible for consciousness & free will?”
In this video, I explain why some scientists believe that our universe is a hologram and we really live in the 2-dimensional projection of a higher dimensional space. First, I explain just what physicists mean by the “holographic principle.” The holographic principle says that the degrees of freedom inside a volume of space can be described by information on the surface of that volume at the same resolution. Then I explain that this relation goes back to ideas about the black hole entropy and string theory in space with a negative cosmological constant, the so-called Anti-de Sitter space. I briefly mention what the problems are with these arguments. I then discuss a recent idea of Verlinde & Zurek about how one could test holography experimentally. Finally, I tell you my own opinion about this. As so often, I am highly skeptical that wild speculation will lead to progress.
This is the Map of Quantum Physics and quantum mechanics covering everything you need to know about this field in one image.
I made this map of quantum physics to lay out the ideas within the subject, to set some bounds on it so you know its not endless and to introduce you to lots of concepts that if you are interested in them you can dig deeper. When you are approaching a subject like this that’s so complicated it can be quite challenging because you don’t know where to start and you don’t know how all the concepts relate to each other so hopefully this will put everything in context.