The post What is the difference between a photon and a quantum? appeared first on Quantum Physics Lady.

]]>A photon is a type of quantum. So, it’s like the difference between a blue jay (photon) and a bird (quantum). If this answers your question, you can stop reading. If you want to know more about what a photon and a quantum really are, read on.

**A Photon Is a Bit of Light**

A photon is a bit of light. To see how light can be divided into bits, photons, it’s necessary to understand some things about light. Light travels as a wave, an electromagnetic wave. An electromagnetic wave is an electrical wave and a magnetic wave traveling together.

As the electrical wave rises and falls, it creates a magnetic wave and then, the magnetic wave rises and falls, creating an electrical wave, and on and on. This video shows how electrical and magnetic waves create each other: https://www.youtube.com/watch?v=1SQV9kBN_b4

When physicists speak of “light,” they mean any kind of electromagnetic wave. This includes visible light, the kind that we see with our eyes. But electromagnetic waves also include X-rays, ultraviolet rays, infrared, microwaves, radio waves, and many others. Any type of electromagnetic wave can also be called “radiation.” The difference between the various types of electromagnetic radiation or waves is their wavelength (see image above).

The red “spring” at the top of the accompanying image shows the spectrum of electromagnetic waves from radio waves on the left to gamma rays on the right.

**What about photons? **

When light, that is, an electromagnetic wave, strikes an object, it immediately collapses into tiny bits of energy. Each of these bits is a photon. It’s as if an ocean wave hits a rock, and shatters into a gazillion tiny droplets. Each “droplet” of the light wave is a photon, and each carries a bit of the energy of the light wave. If the light wave were to hit a piece of film, we would be able to see all the tiny spots of light. Each photon creates a bit of the photo, usually a small fraction of a pixel. Together, they form the image.

https://www.lanl.gov/discover/news-release-archive/2017/July/0731-single-photon-emitter.php

**So, what is a quantum?**

Subatomic particles travel as waves, as we have seen for electromagnetism. When these waves strike an object, they collapse into bits. In the case of electromagnetism, the bits are called photons. But the more general term is “quanta,” or in the singular, “quantum.” There are other types of waves at the subatomic level besides electromagnetic waves. For example, electrons travel as waves as do neutrinos, and other subatomic particles. Quanta are the bits that various subatomic waves create when they interact with objects.

I should clarify that the waves don’t physically shatter when they hit objects. It’s more like they interact with the objects and due to the laws of quantum physics, the waves transform into tiny energy-bearing particles, that is, quanta. And, if I really wanted to be accurate, waves at the subatomic level are not like ocean waves or sound waves. Their physical nature is still under debate, with one possibility being that they are no more a mathematical description of a wave. But this is diving deeper into quantum physics than is useful here.

The post What is the difference between a photon and a quantum? appeared first on Quantum Physics Lady.

]]>The post Why does the Born Rule predict quantum probabilities? appeared first on Quantum Physics Lady.

]]>First, the mathematical explanation: Let’s take the example of the Double Slit Experiment. A laser shoots photons one-at-a-time through the two slits of a

screen towards a photographic plate. The wave function is the equation that describes the behavior of the photon. The amplitudes calculated for the wave by the wave function are proportional to the probability of the photon being detected in any particular position on the photographic plate.The mathematical expressions for the wave amplitudes often include complex numbers (numbers that include the square root of negative 1). We cannot visualize such a number because what number multiplied times itself equals negative 1? There is no such number. We label this non-number as **i **and just don’t try to imagine what amount **i **really represents. Even though **i** does not describe anything that we’re familiar with in the physical universe, both mathematicians and physicists have found it useful to work equations which include** i**, that is, complex numbers.

But returning to the wave function in the Copenhagen Interpretation. Max Born (1882-1970) was the quantum physicist who first realized that the amplitude of the quantum wave predicts the probability of detecting a particle in a particular position. But this creates a problem. What if the amplitude includes a complex number?

A probability cannot be expressed using complex numbers. Probabilities are expressed as positive numbers ranging from 0% to 100%. That is, we can say that there’s a 50% chance when tossing a coin of getting heads. Or a 0% chance that every moment of the day will be fun. And a 100% chance that a human being will eventually die. But to say that the chances of an event are the square root of negative 1 makes no sense.

Born solved the problem by multiplying the amplitude of the wave by its complex conjugate. This squares the square root of negative 1, yielding simply negative 1. The result is probabilities calculated by the wave function are quite nice. They range from 0% to 100%.This calculation is the Born Rule. Experimental results show that the Born Rule is accurate in calculating quantum behavior. So, not only does the rule cancel out the troublesome complex numbers, it accords with empirical results. The Born Rule is an integral part of the Copenhagen Interpretation.

However, the Born Rule does not explain what is happening in the physical universe that requires that we multiply the wave amplitude by its complex conjugate. Nor does any other part of the Copenhagen Interpretation provide such an explanation. The Transactional Interpretation does. While it would be too lengthy to fully explain this interpretation here, an example gives a taste:

Let’s say take a look again at the Double Slit Experiment with a laser emitting a single photon towards a photographic plate. Until it arrives at the photographic plate, it’s a quantum wave that physicists can calculate a wave function for. The wave function identifies the possible positions where the quantum wave could deposit its energy on the photographic plate. So far, this is like the Copenhagen Interpretation. But the Transactional Interpretation adds something new. It says that if the photon is to land on the photographic plate, an electron in the plate must take action to absorb it. Electrons in the plate must send out their own waves. When the emitting wave and the receiving wave interact, the photon transfers energy to the electron, and takes its place in physical reality at a position on the plate.

The wave function of the absorbing electron in the plate has an amplitude that fits well with the amplitude of the photon: it’s the complex conjugate of the photon’s amplitude.

But why multiply the two amplitudes? This is how we find the probability of two events occurring, in this case both the photon heading towards a particular position on the plate and an electron in that position absorbing it. When we calculate the probability of any two events, we multiply the two probabilities. For example, the chances of a baby being born a girl with brown eyes is: 1) the probability of being a girl (about 48%) **times** (2) the probability any baby having brown eyes (about 80%). We multiply 48% times 80% and get 38%. There’s a 38% chance that a baby born anywhere in the world will be a girl with brown eyes.

The emitting wave and the absorbing wave have to interact if the photon is to land in any particular position. We multiply the probability of the photon landing in a particular position (the complex number describing the amplitude) times the amplitude of the receiving wave at that position on the plate (the complex conjugate).

The Transactional Interpretation is based on Absorber Theory developed by Richard Feynman and John Wheeler in the late 1930’s. It was fully developed as an interpretation of quantum mechanics by John Cramer in the 1980’s and further developed by Ruth E. Kastner. Kastner has written technical papers on the Transactional Interpretation and also a book for laypeople, *Understanding Our Unseen Reality*. I highly recommend the book because it provides a coherent and understandable explanation of the physical meaning quantum mechanics.

The post Why does the Born Rule predict quantum probabilities? appeared first on Quantum Physics Lady.

]]>The post How do we know a quantum particle is in a superposition if detecting the particle will destroy the superposition? appeared first on Quantum Physics Lady.

]]>The post How do we know a quantum particle is in a superposition if detecting the particle will destroy the superposition? appeared first on Quantum Physics Lady.

]]>The post What are some good online resources that can help me understand physics better? appeared first on Quantum Physics Lady.

]]>When I didn’t understand something in a particular lesson, I found videos on Youtube. I typed the subject into the Youtube search bar, for example, “inertia.” Then, I just started watching videos until I finally got it.

It’s important to understand all the jargon as it comes up. When terms came up I wasn’t sure of, like “mass,” I watched Youtube videos on the subject and/or googled the physics meaning. When googling, I often asked for images. Finding visuals really helps.

I’m writing definitions of physics terms in an on-line encyclopedia. It focuses on quantum physics, but many of the terms, like acceleration, are shared with classical physics. Classical physics is the first physics that you learn on websites like the PhysicsClassroom and KhanAcademy.org.

The post What are some good online resources that can help me understand physics better? appeared first on Quantum Physics Lady.

]]>The post How do I get started in learning quantum mechanics? appeared first on Quantum Physics Lady.

]]>For more of a light once-over, documentaries hosted by Brian Greene on Youtube are excellent. He’s a quantum physicist and a noted science writer.

Good beginning book on quantum mechanics is *Fields of Color* by Rodney Brooks.

I’m assuming here that you already know the basics of Newtonian physics. If not, study these first. The Physics Classroom is an excellent free on-line course on Newtonian physics. It’s step-by-step and gives practice problems. Khan Academy also has excellent free lessons on Newtonian physics.

Whenever I didn’t understand something in a particular video or book on quantum mechanics, I found videos or on-line articles about that particular thing until I had more understanding of it.

I’m writing definitions of quantum physics jargon for people who are interested in quantum physics but don’t want to dive into the math of it. It’s the definitions and the illustrations and examples that I wish I had when I was first watching these videos and floundering around. I’m hoping that it will help others.

The post How do I get started in learning quantum mechanics? appeared first on Quantum Physics Lady.

]]>The post Can quantum mechanics be understood? Does it make logical sense? appeared first on Quantum Physics Lady.

]]>However, quantum mechanics (QM) does not fit with the assumptions and principles of classical physics (physics prior to 1900 that we learned in high school). QM is the description of the quantum world. Classical physics is the description of the macroscopic world—the world of tables, chairs, apples, etc. The two worlds are described by two different systems of assumptions, principles, equations, and empirical data.

If we attempt to view the quantum world while retaining classical assumptions and principles, the quantum world seems full of paradoxes. For example, classical physics is based on the unspoken assumption that when an object changes position from Point A to Point B, it traverses the distance in between. This assumption is violated in the double slit experiment of quantum mechanics (QM). Another assumption of classical physics is that if one knows the initial conditions of a system, one can calculate its evolution through time. Due to the true randomness in the behavior of individual quantum particles, QM violates this assumption.

*Classical physics tells us that if we apply a specific force to a billiard ball, we can predict exactly where it will roll. This is called the billiard ball model of physics.*

Neither system is particularly intuitive. Newton’s First Law isn’t intuitive: no forces are needed to maintain an object at a constant velocity. Or gravity – Newtonian gravity is action-at-a-distance. Neither Newton nor we are able to describe the underlying nature of physical reality such that action-at-a-distance occurs.

But the principles of classical physics fit together into a self-consistent logical system. Classical physics was also consistent with experimental data until the late 1800’s. That’s when scientists started investigating atoms and the interiors of atoms. And, that’s when they need QM.

QM can be seen as describing a sublevel of reality which operates on different assumptions from those of the macroscopic world.

** The green film represents ordinary reality as we perceive it with our senses. The red grid represents the quantum world, a sublevel to our reality. A wave travels through the quantum world (red grid) and creates a particle (dot in the green film colored orange or blue) in our perceived reality. [**Image source: stills from Fermilab video by Dr. Don Lincoln, “Quantum Field Theory” (in the public domain) Jan. 14, 2016; See the video below.]

The quantum world is a sublevel of reality in the same sense that computer programmers work at a sublevel of a video game. Before they key the program into the computer and see the “macroscopic” world that they’ve created, they follow rules different from those that the characters in the video game follow. The programmers can program a character to exit screen left and enter screen right—no need to traverse the distance in between. The programmers can correct an action in an earlier “frame”–no need to go back in time—they just re-type some symbols.

Later, when the game is actually playing on the screen, the characters follow different rules, more like those of our macroscopic world. For example, a character in a video game can’t correct one of her actions by going back in time (unless it’s a sci fi game).

[For more detail on the idea of the quantum world as a sublevel of reality, see this excellent short video by Fermilab. Also see the entry for quantum field theory in the quantum physics encyclopedia for laypeople QuantumPhysicsLady.org.]

Some interpretations of QM are better than others at logical descriptions of reality. The Copenhagen Interpretation, the original interpretation, doesn’t even try. The slogan of this interpretation has come to be known as “Shut up and calculate!” In other words, physicists use the highly useful math of QM in developing things like computer technology but don’t worry about the implications for the nature of reality. They know that the implications are self-consistent if we confine our attention to the quantum world; but they’re not consistent with the laws of Newton that describe our experiences in the macroscopic world of tables and chairs.

The Transactional Interpretation* does well at providing a logical description of reality. In describing QM as describing a sublevel of reality, I’ve relied on this interpretation.

In short, QM follows its own logic. As long as we don’t make assumptions based on our everyday experience or on classical physics, QM makes logical sense of experimental results.

* See the book: Ruth E. Kastner, *Understanding Our Unseen Reality.*

The post Can quantum mechanics be understood? Does it make logical sense? appeared first on Quantum Physics Lady.

]]>The post Why study quantum physics? appeared first on Quantum Physics Lady.

]]>Quantum physics is part of the answer—a huge part. But the trouble is, physicists don’t understand how quantum particles create the solid objects that our senses perceive. After all, quantum particles are just vibrations in what appears to be huge quantities of empty space.

Many physicists are unperturbed by this question. They use the mathematics of quantum physics for running experiments or for developing technologies, and they leave the Big Questions alone. However, some physicists/mathematicians have gone ahead and speculated about the Big Questions.

One speculation of particular interest to me is that Information Theory can cast light on this question. Information Theory reduces the universe to mathematical patterns. It reduces the vibrations of quantum particles to the mathematical equations which calculate the vibrations. These equations describe **changes** in matter and energy, what physicists call “evolutions.” The equations are not just static descriptions like the formula for the composition of water: H_{2}O.

The entire universe can be seen as an intermeshing of equations, one supplying data to another, each equation being influenced by others. The physicist, Max Tegmark, wrote the book *Our Mathematical Universe *on this premise. Another good book on the subject is *Programming the Universe *by one of the inventors of the quantum computer, Seth Lloyd.

Information Theory is illuminating. But there’s a big piece of the puzzle that’s still missing. How do mathematical equations become subjective experience? We experience colors, sounds, tastes, and other sensations as if they were out in the world. But, actually, these are our subjective experiences of electrical impulses in the brain. After all, our skulls don’t have holes in them to let the world in. The only thing going on in our brains are electrical impulses.

Here’s whereBut, how exactly, do we experience electrical impulses traveling through the brain as colors, sounds, tastes, and so on? **How do mathematical equations become subjective experience?**

The quantum physicist, Amit Gswami in *The Self-Aware Universe*, suggests how this happens. He proposes that our consciousness codes equations into the images, sounds, smells, and tastes of our subjective experience. In other words, the world is really in our minds. Or possibly, there is one mind, and we’re all tuned into it, each one of us experiencing it somewhat differently due to our own unique filters. The traditional Buddhist view has things to say about this.

*“I regard consciousness as fundamental. I regard matter as derivative from consciousness. We cannot get behind consciousness. Everything that we talk about, everything that we regard as existing, postulates consciousness.”*

Rene Descartes proposed another view called “Dualism” in the 1600’s. He saw both matter and consciousness as fundamental but also as very different substances. Dualism formed one of the basic unspoken assumptions of the worldview that I grew up with and probably most Westerners have grown up with. It is the worldview that most Westerners who aren’t paid to think, unthinkingly adopt.

Starting in the middle of the 20The post Why study quantum physics? appeared first on Quantum Physics Lady.

]]>The post What is the relationship between quantum physics and consciousness? appeared first on Quantum Physics Lady.

]]>**The Universe Works in Accordance with Math **

A basic principle of quantum physics is that elementary particles like electrons can be completely described mathematically.* For example, an electron has a charge of minus 1, a mass of 1/1836 that of the proton, and so on. Every electron is identical to every other electron and can be described by these same numbers. You don’t need a sample of an electron to give it a complete description. It’s as if electrons are just pieces of math. The same is true for every photon (a particle of light), every proton (a particle of matter), and so on for all the tiniest particles of matter and energy.

This isn’t like the flavor of a cherry or the color of a sunflower. No amount of mathematical description would suffice to communicate how a cherry tastes nor how the color of a sunflower looks. For these, you need to provide a sample which can be experienced.

A cherry is made up solely of electrons, protons, photons, etc. And these tiny bits are just a bunch of math. So, why does the flavor of a cherry go beyond math? Why do we have the physical experience of the sharp, sweet taste of a cherry? A spiritual interpretation would be that the cherry taste is the conscious experience of quantum-level mathematical descriptions. It is the experience that our consciousness assigns to a particular mathematical expression.

The same is true for color. The yellow color of the sunflower is not inherent in the photons coming from the sunflower. Photons which have a middle-range frequency shoot from the sunflower into our eyes.* These photons are vibrating very quickly, but they’re not vibrating very “yellowly.” Photons which have the right frequency stimulate our brains and create a specific brainwave pattern. And consciousness experiences that brainwave pattern as yellow.

The mathematical descriptions of electrons, photons, and their interactions are like the mathematics of computer code. This mathematical coding shows up as pixels lighting up on a computer screen. And consciousness looks at the screen and experiences, for example, characters shooting each other in a video game. That mathematical coding creates physical reality is the premise of the movie, “The Matrix.”

Going further, one can ask, who or what created all the mathematics that describes quantum particles and their interactions? One possible answer is: no one, it’s all just an incredible series of accidents. Another answer is that God is a mathematician. (Or one can substitute for “God” whatever name one wants to call the consciousness of all that is.) The notion that physical reality accords with mathematics and arises from consciousness was popular among early quantum physicists. Max Planck, Nobel Laureate, whose work launched the field of quantum physics, expressed this in a famous quote (see illustration).

We live in a physical universe that many physicists believe will one day be fully described by mathematics. Yet, we don’t experience the physical universe as a bunch of mathematical expressions and equations. And we don’t experience it as computer code. Possibly, we perceive the math or the coding, and our consciousness gives it meaning—the sharp, sweet taste of the cherry and the yellow of the sunflower. It’s like a computer programmer creating a program for the video game that he can, then, play and experience.

Physics experiments have ruled out the possibility that the two electrons are pre-programmed. If the entangled particles were pre-programmed, they would come in matched pairs, like if one glove is for the right hand, the other, of course, is for the left. However, experiments have ruled out this explanation. Physicists have not come up with a theory to explain entanglement. Possibly, such a theory could derive from the spiritual principle that, at bottom, all things are one.

Several other key aspects of quantum physics fit well with spiritual principles. Perhaps, the most important is that quantum particles are in a state of potentiality, possibly having this property and possibly becoming having that property, until they interact with some aspect of the physical universe. Only then, do they enter our physical reality as a particle with definite properties. This aspect of quantum physics may connect with the spiritual idea that our intentions, conscious or subconscious, causes potential realities to manifest. For more on this aspect of quantum physics, read about Quantum Field Theory.

But I would like to address a misinterpretation of quantum physics that some people say “proves” that human consciousness is essential to the existence of matter and energy.

Sometimes, people say that the importance of the “observer” in quantum physics tells us that without human consciousness, quantum particles would not have physical reality. As quantum particles are the sub-microscopic level of matter and energy, this requires that the physical reality of matter and energy depends upon human consciousness.

This kind of statement is based on a misunderstanding of the term “observer.” Quantum physicists use the term “observer” to mean something that a quantum particle interacts with. This might be a particle in the experimenter’s eye or just another quantum particle. For example, when a photon (a particle of light) is absorbed by an electron (a particle of matter), an exchange of information and energy occur: the photon disappears, and the electron becomes more active. When this happens in a solar panel, electricity is generated. The physicist would say that the electron is the observer and has “observed” the photon. Odd terminology, I know.

Prior to the absorption of the photon by the electron, the photon has no specific position in the universe and has other undetermined properties. Upon absorption by the electron, its position and other physical properties become concrete. They become a part of the history of the physical universe. So, the role of the observer in quantum physics is critical to creating physical existence, but the observer need not involve human consciousness.***

Principles of quantum physics do not **prove** that human consciousness or any consciousness is essential to creation of our physical universe. But some of the principles of quantum physics accord well with certain basic spiritual principles of Buddhism and New Age philosophies.

*Yellow light is electromagnetic radiation with a frequency of 510-540 Terahertz. Terahertz means 10 to the power of 12 oscillations per second. Suffice it to say, that’s many, many.

**For more information, read *Our Mathematical Universe* by noted quantum physicist, Max Tegmark.

*** For more information, read *Understanding Our Unseen Reality: Solving Quantum Riddles*, by Ruth E. Kastner, quantum physicist.

The post What is the relationship between quantum physics and consciousness? appeared first on Quantum Physics Lady.

]]>The post Can you explain the essence of quantum mechanics in three sentences? appeared first on Quantum Physics Lady.

]]>We can’t see the tiniest components of matter and energy. Our eyes cannot perceive the quantum level of reality. Nor do we have microscopes sufficiently powerful. But this animation is suggestive of how such components might look if we could see them.

The post Can you explain the essence of quantum mechanics in three sentences? appeared first on Quantum Physics Lady.

]]>The post What is the difference between theoretical quantum physics and experimental quantum physics? appeared first on Quantum Physics Lady.

]]>Explanation: Experimental physicists do experiments to find out how accurately physics theories describe the real world. For example, they shoot atoms and bits of atoms around in particle accelerators. They measure the speed of light when it travels through water versus empty space, and so on.

Theoretical physicists don’t do experiments. They read articles and books about physics experiments. They think. And they play with a lot of mathematical equations on black boards or white boards. Then, if these equations accord with experimental results, they publish them along with explanatory text in physics journals. The job of theoretical physicists is to develop mathematical equations and verbal explanations that describe the results of physics experiments. Ideally, theoretical physicists also use their explanations and mathematical equations to predict experimental results. Albert Einstein and Stephen Hawking were both theoretical physicists. They did not do experiments. They studied, thought, and developed new theories and equations.

Now to turn to quantum physics. Quantum physics is the field of physics in which physicists learn about certain types of unusual behavior of particles smaller than atoms but sometimes the size of atoms or even larger. They focus on the “quantum state.” This is the state in which these tiny particles can be in many positions at the same time and where they can act as both waves and particles. Many quantum physicists are theoretical physicists. But many others do experiments.

This is the same in most other fields of physics. For example, physicists who study the physics of heavenly bodies, astrophysicists, can be either theoreticians or experimentalists. The experimentalists often use telescopes for their work. The theoreticians write equations, these days, on white boards.

Before the mid-1900’s, most physicists were both experimentalists and theoreticians. For example, Isaac Newton, who founded modern physics, did many famous experiments. For example, he shot beams of light through prisms. But he also was one of the inventors of calculus, which he used when developing theories which explained the results of his experiments on the motion of objects. Isaac Newton developed the modern type of physics theory—ones which are expressed using mathematical equations. As an example of a mathematical theory, Einstein’s equation, e = mc^{2}, is his theory of the relationship between the quantity of energy and of mass.

Today, few, if any, physicists do both theoretical and experimental work. Both fields require extremely specialized knowledge and skills. But theoreticians and experimentalists work closely with each other to push physics forward.

The post What is the difference between theoretical quantum physics and experimental quantum physics? appeared first on Quantum Physics Lady.

]]>