The opposite of quasiparticle, see notaby: quasiparticles vs elementary particles.
A suggested at Physics from Symmetry by Jakob Schwichtenberg (2015) chapter 3.9 "Elementary particles", it appears that in the Standard Model, the behaviour of each particle can be uniquely defined by the following five numbers:
Once you specify these properties, you could in theory just pluck them into the Standard Model Lagrangian and you could simulate what happens.
Setting new random values for those properties would also allow us to create new particles. It appears unknown why we only see the particles that we do, and why they have the values of properties they have.
Initially light was though of as a wave because it experienced interference as shown by experiments such as:
But then, some key experiments also start suggesting that light is made up of discrete packets:and in the understanding of the 2020 Standard Model the photon is one of the elementary particles.
- Compton scattering, also suggests that photons carry momentum
- photoelectric effect
- single photon production and detection experiments
This duality is fully described mathematically by quantum electrodynamics, where the photon is modelled as a quantized excitation of the photon field.
First people thought it was a particle, as per corpuscular theory of light, notably Newton supported the corpuscular theory of light.
But then evidence of the diffraction of light start to become unbearably strong, culminating in the Arago spot.
And finally it was undertood from Maxwell's equations that light is a form of electromagnetic radiation, as its speed was perfectly predicted by the theory.
But then evidence of particle nature started to surface once again with the photoelectric effect. Physicists must have been driven mad by all these changes.
The Quantum Story by Jim Baggott (2011) page 2 mentions how newton's support for the corpuscular theory of light led it to be held for a very long time, even when evidence of the wave theory of light was becoming overwhelming.
The Story of Light by Bell Labs (2015)
Source. Gives some ideas of the history of fiber optics. Features: Herwig Kogelnik.Fiber optics fundamentals by Shaoul Ezekiel
. Source. 2008 at MIT. Theory and demonstration.- youtu.be/0DCrIAxEv_Y?t=560:Terefore, the 1.5 micrometer window truly is the minimum.
- on smaller wavelengths, loss is due to Rayleigh scattering
- on longer wavelengths, loss is due to material absorption
These are closely related to lasers, as they do a similar basic job: take a DC source as input and amplify light. Lasers just happen to use the input voltage to also generate the incoming light.
This one was a huge advance it seems.
It's the thing that allows you to connect fiber optics into a compter, or the corresponding port for the thing.
Many of them can take two fibers as input/output because fiber optics cables often come in pairs because it is needed for duplex.
From a practical point of view single-mode:
As such, typical applications are:
- single-mode optical fiber: longer distance communications across buildings and cities
- multi-mode optical fiber: shorter distance communications e.g. within a single data center
Then there are some more hardcore threads actually pondering about specific cost trade-offs:
From a mathematical point of view:
- multi-mode: en.wikipedia.org/w/index.php?title=Optical_fiber&oldid=1229833804#Multi-mode_fiber:
Fiber with large core diameter (greater than 10 micrometers) may be analyzed by geometrical optics. Such fiber is called multi-mode fiber. In a step-index multi-mode fiber, rays of light are guided along the fiber core by total internal reflection.
- single-mode: en.wikipedia.org/w/index.php?title=Optical_fiber&oldid=1229833804#Single-mode_fiber:
Fiber with a core diameter less than about ten times the wavelength of the propagating light cannot be modeled using geometric optics. Instead, it must be analyzed as an electromagnetic waveguide structure, according to Maxwell's equations as reduced to the electromagnetic wave equation. As an optical waveguide, the fiber supports one or more confined transverse modes by which light can propagate along the fiber. Fiber supporting only one mode is called single-mode.
Another difference is that single-mode fiber usually uses lasers as the light soruce, while multi-mode fiber usually uses LED:
Bibliography:
2009 Nobel Prize lecture
. Poor Charles was too debilitated by Alzheimer's disease to give the talk himself! But if you've got a pulse, you can get the prize, so all good.This section is about stuff efficiently getting light into or out of optical fibers, or joining two optical fibers together end to end so that light goes through.
Historically this has been an important development, as it is much harder than with wires since optical fiber has to be very narrow to work properly, e.g. this is mentioned a lot in City of Light: The Story of Fiber Optics.
Bibliography:
- en.wikipedia.org/wiki/Speed_of_light#First_measurement_attempts Rømer and Christiaan Huygens reached 26% accuracy by the observation of Jupiter's moon!
Replicating the Fizeau Apparatus by AlphaPhoenix (2018)
Source. Modern reconstruction with a laser and digital camera.It is so mind blowing that people believed in this theory. How can you think that, when you turn on a lamp and then you see? Obviously, the lamp must be emitting something!!!
Then comes along this epic 2002 paper: pubmed.ncbi.nlm.nih.gov/12094435/ "Fundamentally misunderstanding visual perception. Adults' belief in visual emissions". TODO review methods...
One argument of why, is that if you could travel faster than light, then you could send a message to a point in Spacetime that is spacelike-separated from the present. But then since the target is spacelike separated, there exists a inertial frame of reference in which that event happens before the present, which would be hard to make sense of.
Spacetime diagram illustrating how faster-than-light travel implies time travel
. Legend an explanation are shown in this answer.Bibliography:
- physics.stackexchange.com/questions/13001/does-superluminal-travel-imply-travelling-back-in-time/615079#615079
- physics.stackexchange.com/questions/574395/why-would-ftl-imply-time-travel
- physics.stackexchange.com/questions/516767/how-does-a-tachyonic-antitelephone-work
- www.physicsmatt.com/blog/2016/8/25/why-ftl-implies-time-travel shows the causality violation on a Spacetime diagram
This is how Marie Curie was able to precisely detect radioactivity, which then led to her discovery of new elements.
Notably used for communication with submarines, so in particular crucial as part of sending an attack signal to that branch of the nuclear triad.
This is likely the easiest one to produce as the frequencies are lower, which is why it was discovered first. TODO original setup.
Also because it is transparent to brick and glass, (though not metal) it becomes good for telecommunication.
Some notable subranges:
Microwave production and detection is incredibly important in many modern applications:
- telecommunications, e.g. being used in
- Wi-Fi
- satellite communicationsyoutu.be/EYovBJR6l5U?list=PL-_93BVApb58SXL-BCv4rVHL-8GuC2WGb&t=27 from CuriousMarc comments on some piece of Apollo equipment they were restoring/reversing:Ah, Ciro Santilli really wishes he knew what that meant more precisely. Sounds so cool!
These are the boxes that brought you voice, data and live TV from the moon, and should be early masterpieces of microwave electronics, the blackest of black arts in analog electronics.
- 4G and other cellular network standards
- radar. As an example, 1965 Nobel Prize in Physics laureate Julian Schwinger did some notable work in the area in World War II, while most other physicists went to the Manhattan Project instead.This is well highlighted in QED and the men who made itby Silvan Schweber (1994). Designing the cavity wasn't easy. One of the key initial experiments of quantum electrodynamics, the Lamb-Retherford experiment from 1947, fundamental for modern physics, was a direct consequence of post-radar research by physicists who started to apply wartime developments to their scientific search.Wikipedia also mentions en.wikipedia.org/w/index.php?title=Microwave&oldid=1093188913#Radar_2:
The first modern silicon and germanium diodes were developed as microwave detectors in the 1930s, and the principles of semiconductor physics learned during their development led to semiconductor electronics after the war.
- microwave is the natural frequency of several important Atomic, Molecular and Optical Physics phenomena, and has been used extensively in quantum computing applications, including completely different types of quantum computer type:Likely part of the appeal of microwaves is that they are non-ionizing, so you don't destroy stuff. But at the same time, they are much more compatible with atomic scale energies than radio waves, which have way way too little energy.
- trapped ion quantum computer; Video "Trapping Ions for Quantum Computing by Diana Craik (2019)"
- superconducting quantum computer; e.g. this Junior Microwave Design Engineer job accouncement from Alice&Bob: archive.ph/wip/4wGPJ
Microwave only found applications into the 1940s and 1950s, much later than radio, because good enough sources were harder to develop.
One notable development was the cavity magnetron in 1940, which was the basis for the original radar systems of World War II.
Apparently, DC current comes in, and microwaves come out.
TODO: sample power efficiently of this conversion and output spectrum of this conversion on some cheap device we can buy today.
arstechnica.com/information-technology/2016/11/private-microwave-networks-financial-hft/ The secret world of microwave networks (2016) Fantastic article.
How Microwaves Work by National MagLab (2017)
Source. A bit meh. Does not mention the word cavity magnetron!How a Microwave Oven Works by EngineerGuy
. Source. Cool demonstration of the standing waves in the cavity with cheese!420 to 680 nm for sure, but larger ranges are observable in laboratory conditions.
William Coolidge explains medical imaging and X-rays (1940).
Source. Video sponsored by General Electric. A cool insight of this video is that a hot cathode is a more reliable electron source. Previous systems, and presumably including the discovery of X-rays, leftover gas in the tube was used. But this makes things more difficult to control, as we also want to remove as much gas as possible from the vacuum, otherwise electrons collide with the gas and lose energy before hitting the anode.How Does X ray Tube Works by BiomedEngg
. Source. Describes in particular the rotating cathode method. Interesting observation that this is especially important since the cathode cannot cool quickly due to the vacuum.Original 1931 experiment by Raman and Bhagavantam: dspace.rri.res.in/bitstream/2289/2123/1/1931%20IJP%20V6%20p353.pdf
Experimental setup to observe radiation pressure in the laboratory.
Application of radiation pressure.
First live example: en.wikipedia.org/wiki/IKAROS
The particular case of the double-slit experiment will be discussed at: single particle double slit experiment.
Detectors are generally called photomultipliers:
Bibliography:
- iopscience.iop.org/book/978-0-7503-3063-3.pdf Quantum Mechanics in the Single Photon Laboratory by Waseem, Ilahi and Anwar (2020)
How to use an SiPM - Experiment Video by SensLTech (2018)
Source. Single-photon detectors - Krister Shalm by Institute for Quantum Computing (2013)
Source. You can then detect one of the photons, and when you do you know that the other one is there as well and ready to be used. two photon interference experiment comes to mind, which is the basis of photonic quantum computer, where you need two photons to be produced at the exact same time to produce quantum entanglement.
Features Alan Migdall of the National Institute of Standards and Technology. Produced by the Joint Quantum Institute (JQI).
Mentions that this phenomena is useful to determine the efficiency of a single photon detector, as you have the second photon of the pair as a control.
Also briefly describes how the input energy and momentum must balance out the output energy and momentum of the two photons coming out (determined by the output frequency and angle).
Shows the crystal close up of the crystal branded "Cleveland Crystals Inc.". Mentions that only one in a billion photon gets scattered.
Also shows a photomultiplier tube.
Then shows their actual optical table setup, with two tunnels of adjustable angle to get photons with different properties.
Very short whiteboard video by Peter Mosley from the University of Bath, but it's worth it for newbs. Basically describes spontaneous parametric down-conversion.
One interesting thing he mentions is that you could get single photons by making your sunglasses thicker and thicker to reduce how many photons pass, but one big downside problem is that then you don't know when the photon is going to come through, that becomes essentially random, and then you can't use this technique if you need two photons at the same time, which is often the case, see also: two photon interference experiment.
Can be used to detect single photons.
Richard Feynman likes them, he describes the tube at Richard Feynman Quantum Electrodynamics Lecture at University of Auckland (1979) at one point.
It uses the photoelectric effect multiple times to produce a chain reaction. In particular, as mentioned at youtu.be/5V8VCFkAd0A?t=74 from Video 1. "Using a Photomultiplier to Detect single photons by Huygens Optics" this means that the device has a lowest sensitive light frequency, beyond which photons don't have enough energy to eject any electrons.
Using a Photomultiplier to Detect single photons by Huygens Optics
. Source. 2024. Wow this dude is amazing as usual. Unfortunately he's not using a single photon source, just an LED.Here is a vendor showcasing their device. They claim in that video that a single photon is produced and detected:
Concrete device described at: Video "How to use an SiPM - Experiment Video by SensLTech (2018)".
Can be achieved in two ways it seems:
- macroscopic beam splitter and optical table
- photolithography
Animation of Hong-Ou-Mandel Effect on a silicon like structure by Quantum Light University of Sheffield (2014): www.youtube.com/watch?v=ld2r2IMt4vg No maths, but gives the result clear: the photons are always on the same side.
- quantum dot source. TODO how do you produce identical photons from two separate quantum dots? See also: quantum dot single photon source.
- superconducting nanowire detector. So the device has to be cooled then? Video "Jeremy O'Brien: "Quantum Technologies" by GoogleTechTalks (2014)" youtube.com/watch?v=7wCBkAQYBZA&t=2497 however says that semiconducting devices can also be used
Often just called collimated light due to the collimator being the main procedure to obtain it.
However, you move very far away from the source, e.g. the Sun, you also get essentially parallel light.
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