Quantum Physics part 2
In the previous article we learned about some important topics in quantum physics such as the double-slit experiment, wave-particle duality and the photoelectric effect. Click here to read 1st part
In today’s episode we will learn about what quantum entanglement is what quantum field theory is and what quantum tunneling is.
(Quantum Entanglement)
Quantum entanglement is an unresolved issue in quantum physics. This occurs when two particles are generated or interact in such a way that the quantum state of one cannot be described independently of the other particles.
Instead, the quantum state of the particles must be explained together.
That means that you cannot describe any one of the entangled particles relative to any other ordinary particle instead they must be described relative to each other.
This state persists even if the particles are separated by large distances. In other words the distance between two entangled particles does not matter.
For instance if one entangled particle is located in the GN-Z11 galaxy and the other in the Milky Way their relationship remains intact.
When measuring the position, momentum and spin of two entangled particles they are found to be related.
Suppose two entangled particles are produced in a process and their total spin is zero. In that case if one particle’s spin is clockwise the other particle’s spin will be counterclockwise. This can be said with certainty.
Understanding Quantum Entanglement with an Example
Suppose you have a box containing a pair of socks.
A particular characteristic of socks is that a sock for one hand can never be worn on the other hand. One sock is only for the right hand and the other is only for the left hand.
Now, you and your friend, for fun, blindly take a sock and pocket it without looking. One day both of you board different planes to different places for different tasks.
You head to Ukraine while your friend goes to Russia. It’s important to note that neither of you has seen your sock since taking it.
When you reach Ukraine and see that your sock is for the right hand, you can immediately understand that your friend has the left-hand sock.
In other words, even before your friend takes out the sock from their pocket, you can confidently state that they have the left-hand sock.
Here, we can say that the two socks were entangled. And a special feature of entangled objects is that if you know one object, you can easily know the other.
(Quantum Field Theory)
In 460 BCE Greek philosopher Democritus first proposed that matter has an indivisible unit. He believed that if a material is continuously divided eventually a tiny particle will be found that cannot be broken further. Democritus called this particle “atom” which means indivisible in Greek.
He also believed that everything around us is made of atoms. However it is important to note that although the term “atom” originally meant indivisible in modern physics it refers to the smallest unit of a chemical element.
The Discovery of Subatomic Particles
After Democritus hypothesis approximately 2300 years passed with little change in the idea.
Then in 1897 J. J. Thomson discovered a particle smaller than the atom and called it the electron. Thomson’s groundbreaking discovery proved that Democritus idea from about 2357 years ago was incorrect. Atoms are not indivisible and they can indeed be broken.
In 1911 physicist Ernest Rutherford discovered that the atom contains not only electrons but also a much smaller central particle which he named the nucleus. Then in 1919 during further research Rutherford discovered another particle in the nucleus which he named the proton.
Around 1932 James Chadwick found another particle in the nucleus alongside protons which he called the neutron. With the discovery of protons and neutrons it became clear that the nucleus consists of protons and neutrons.
The Quark Revolution
Until the 1960s, the common understanding was that the entire universe was made of three fundamental particles: electrons, protons, and neutrons.
However in 1964 scientists Murray Gell-Mann and George Zweig theoretically proposed the existence of a more fundamental particle called the quark.
Later in 1968, scientists at the Stanford Linear Accelerator tried to break protons to observe their structure in more detail. The results of these experiments revealed that protons were not fundamental particles either!
Protons were found to consist of two up quarks and one down quark. Similarly when neutrons were tested, they were found to be made of one up quark and two down quarks.
With the discovery of quarks, it became known that everything we see around us is made of three types of fundamental particles electrons, up quarks, and down quarks.
But is our understanding final?
Are these particles truly fundamental?
According to modern particle physics, these so-called fundamental particles do not actually exist.
The Rise of Fields Over Particles
Modern particle physics has revealed that the so-called fundamental are not particles at all.
Now you might wonder if they aren’t particles then what are they?
For years we’ve thought that the universe is built from various fundamental particles, but this belief is wrong. The universe is actually built from different types of fields. When these fields are disturbed in some way, waves are created. The so-called fundamental particles are actually just the waves of these fields.
When we say “field,” we often think of something like a cricket field or a football field.
But the fields we’re talking about here are nothing like those.
You might ask, “What exactly is a field, then?”
Mathematically, a field is something that continuously expresses a specific value at every point in empty space. Let me try to give a practical example: imagine a hospital room with an air conditioner.
In this case, you can assume that a specific temperature is maintained throughout the room, meaning that the temperature is the same at every point in the room.
We can consider this as the temperature field of the room. Similarly, a field is a continuous medium spread throughout the universe, and its value is the same at every point.
For instance, if water is spread evenly over a flat surface, the density of the water will be the same at every point. In the same way, the value of fields remains the same throughout the universe.
Virtual Particles and the Vacuum
In reality, the vast empty spaces in the universe that we call “vacuum” are not empty at all.
According to Heisenberg’s Uncertainty Principle, countless fundamental particles are being born in this vacuum at every moment. These are called virtual particles.
Shortly after their creation, they come into contact with each other and annihilate. This cycle of creation and destruction is happening every moment in the world around us.
Quantum Fields and the Structure of the Universe
One of the most important concepts in modern physics today is quantum fields. According to quantum field theory the vacuum of space is not truly empty. It is filled with many fields that are spread infinitely throughout the universe.
Or rather these fields together form a unified field composed of multiple distinct but interacting fields. These fields are arranged in parallel throughout space and are constantly interacting with each other.
Everything we see around us is made up of fundamental particles.
These fundamental particles like electrons, quarks and photons are created through mutual interactions. At the core of each fundamental particle lies a distinct specific field.
Types of Quantum Fields
Some of the fields we are familiar with include:
- Electric field
- Magnetic field
- Gravitational field
Some lesser-known fields include:
- Higgs field
- Gluon field
- Electron field
- Quark field
For every point in space there is a specific value assigned to each field. As mentioned earlier, the fundamental particles we talk about are actually just waves in these various fields. The fascinating thing is that everything we see or feel around us is formed by just four specific fields.
Everything we encounter, like soil, stone, wood, water, humans, animals, electronics etc is made of these four fields. One of the most important things for us is light, which helps us see.
Light is essentially a wave formed by the vibrations in the electromagnetic field, composed of many photons. The electrons in an atom are vibrations in the electron field.
The nucleus of an atom is made of protons and neutrons, which are in turn composed of up quarks and down quarks. These up quarks and down quarks are created by vibrations in the quark fields.
Waves in Fields and Particle Creation
Every fundamental particle we’ve discovered so far is the result of vibrations in a specific field. Just like waves form on the surface of water when influenced by wind similarly waves are created in fields through vibrations.
These vibrations in the fields are what give rise to fundamental particles allowing them to manifest as particles.
When a field becomes excited by energy a tiny wave (quanta) or quantum particle emerges revealing itself as a fundamental particle. For instance take the electron field.
Under normal circumstances we cannot see the electron field, but when it becomes excited by energy waves form in the field and the smallest wave manifests as an electron particle. When a field stops vibrating the particle disappears back into the field.
For example if you strike the surface of water large waves will initially form spreading outwards in all directions. As the waves travel further they become smaller and smaller eventually calming down and the water returns to stillness. The same happens in fields!
When a field is excited by energy, waves form, but as the energy diminishes, the vibrations in the field decrease, causing the waves to reduce and the field to calm down. The fundamental particle created by the field’s wave dissolves back into the field.
The vibration at a particular point in the electron field is what we call an electron. This same concept applies to other fundamental particles connected to their respective fields.
Particle Interactions
Using the concept of fields the interaction between two particles can be easily explained. We have already learned that an electron is a tiny wave in the electron field.
If a photon is emitted from that electron it means some of the electron’s energy has transferred into the surrounding electromagnetic field. This transferred energy creates a wave in the electromagnetic field and a small portion of that wave manifests as a photon particle.
In quantum physics, the vacuum of space is seen as a collection of countless fields. Waves can form in these fields due to vibrations at any point, and the fields can interact with each other.
The creation and destruction of different types of particles can be explained by the interaction between these fields. When waves form in a particular field, the energy from that wave can excite a nearby field and cause a wave to form there. A tiny part of the wave in the originating field will reveal itself as a fundamental particle.
Particle and Antiparticle Creation
Particles and antiparticles are created from the same field, but with opposite vibrational directions. If the vibration of the particle’s wave is in one direction, the antiparticle’s wave will be in the opposite direction.
For example, an electron is created by a tiny part of the wave in the electron field, while a positron (the electron’s antiparticle) emerges from the opposite wave in the same field. Because their waves move in opposite directions when these two opposite waves meet (Annihilation) they destroy each other.
When an electron and a positron come into contact their opposing waves collide and annihilate each other. The energy released from this destruction creates waves in the electromagnetic field which manifest as photons.
The Standard Model and Quantum Fields
According to the Standard Model in particle physics there are approximately 17 fundamental particles. Quantum field theory suggests that each fundamental particle is a wave created by vibrations in its respective field. Therefore there should be around 17 distinct fields for all the fundamental particles in the Standard Model.
It’s important to note that we haven’t yet discovered a fundamental particle for gravity. If, in the future, the graviton is proven to exist as the carrier of gravitational force, the total number of fields would increase to 18.
Quantum Tunneling
Quantum tunneling is a physical phenomenon in quantum physics where a subatomic particle is able to pass through a potential barrier.
Quantum tunneling determines the size of transistors used in microprocessors. If the transistors are made too small, electrons can escape through tunneling. It is through quantum tunneling that energy produced in the sun’s core reaches its outer surface and from there reaches us.
Quantum tunneling is typically explained by Heisenberg’s Uncertainty Principle where a subatomic object is considered both a wave and a particle.
The concept of quantum tunneling was first observed during research into the radioactivity of matter.
In 1896, Henri Becquerel first discovered radioactivity in matter. Later Marie Curie and Pierre Curie conducted further research and experiments on radioactivity.
In 1927 Friedrich Hund first noticed quantum tunneling while calculating the basis state for a double well potential. Independently in the same year Leonid Mandelstam and Mikhail Leontovych while analyzing the wave equation of Erwin Schrödinger in a bounded potential field also discovered quantum tunneling.
Its first application was in providing a mathematical explanation for the decay of radioactive alpha rays which was part of the work of George Gamow in 1928. Gamow was aware of the discoveries of Mandelstam and Leontovych.
These two researchers simultaneously solved Schrodinger’s wave equation for an ideal nuclear potential and demonstrated the relationship between a particle’s half-life and its emission energy which directly depends on the mathematical properties of tunneling.
Later, Max Born understood the concept of tunneling. Born realized that the phenomenon of tunneling wasn’t limited to nuclear physics but was a general result of quantum physics.
Due to research on semiconductors and the invention of transistors and diodes, electron tunneling was discovered in 1957.
In 2016, quantum tunneling in water was discovered.
