Category Archives: Quantum Physics
By Donald Burleson
Special to the Daily
Reportedly, we have had some exposure to the languages used by UFO crews. Some primary witnesses described peculiar inscriptions seen on the 1947 Roswell wreckage, and when physicist Robert Oppenheimer was present at the 1948 Aztec, New Mexico, UFO crash retrieval as part of the scientific team summoned to examine the craft, he took notice of alien markings adorning a sort of book found inside, observing that the inscriptions rather resembled Sanskrit, a classical language with which he was familiar.
One wishes we could know more about these strange symbols strange to us, anyway in terms of the eternal mysteries of language.
In the study of linguistics, theres a theory called the Sapir-Whorf Hypothesis, which essentially says that the structure of the language a person learns to speak in childhood largely determines the way that person perceives and categorizes the world. Different languages impart different world-views.
For example, in the world of scientists, there may be linguistic factors relating to the fact that speakers of Asian languages often excel at quantum mechanics.
For western scientists, quantum theory is frequently experienced as counter-intuitive. Its basic precepts seem to run contrary to common sense. Take particle entanglement, for instance. We entangle two particles, project them in opposite directions at the speed of light, alter the spin of one of the departing particles, and the spin of the other particle is instantly altered, as well. Some scientists initially found this so unreasonable that they refused to believe it until they saw experiments proving it true.
The reason for this reaction, in keeping with the Sapir-Whorf Hypothesis, may be that in western countries, we speak languages in which the relation between nouns and verbs would encourage us to think of particles as things rather than processes. But in quantum physics, one needs to think of a subatomic particle not as a thing but as a spectrum of events. Asian languages tend to favor this way of seeing the world from the outset, so that in effect, the speakers of such languages experience a fairly natural affinity with quantum theory.
We may only speculate, of course, on how the users of those peculiar-looking UFO inscriptions are prompted to see the universe, due to the nature of their languages. What if those languages revolve around grammatical structures so friendly to quantum concepts that they give their speakers an even more dramatic scientific advantage than that which is arguably enjoyed by speakers of some languages here on Earth? Its entirely possible that an alien languages form conduces to giving its speakers, at an early age, profound insights into the most arcane aspects of science. After all, UFOs exhibit an undeniably advanced technology.
And if, as many speculate, some UFOs are time travelers from our own distant future, things get more intriguing still. We know how our own languages have evolved over the past few thousand years, but what about the next million years? Maybe linguistically were in the slow process of becoming better scientists all the time.
Next-Gen Laser Beams With Up to 10 Petawatts of Power Will Usher In New Era of Relativistic Plasmas Research – SciTechDaily
Quantum electrodynamics phenomena in plasmas. Credit: Stephen Alvey/Alec Thomas
Laser beams with power up to 10 petawatts will create plasmas with energy levels to be studied with quantum electrodynamics, with implications for medical imaging and security detection
The subject of the 2018 Nobel Prize in physics, chirped pulse amplification is a technique that increases the strength of laser pulses in many of todays highest-powered research lasers. As next-generation laser facilities look to push beam power up to 10 petawatts, physicists expect a new era for studying plasmas, whose behavior is affected by features typically seen in black holes and the winds from pulsars.
Researchers released a study taking stock of what upcoming high-power laser capabilities are poised to teach us about relativistic plasmas subjected to strong-field quantum electrodynamics (QED) processes. In addition, the proposed new study designs for further exploring these new phenomena.
Appearing inPhysics of Plasmas, from AIP Publishing, the article introduces the physics of relativistic plasma in supercritical fields, discusses the current state of the field and provides an overview of recent developments. It also highlights open questions and topics that are likely to dominate the attention of people working in the field over the next several years.
Quantum electrodynamics phenomena in plasmas. Credit: Stephen Alvey/Alec Thomas
Strong-field QED is a lesser-studied corner of the standard model of particle physics that has not been explored at big collider facilities, such as SLAC National Accelerator Laboratory or CERN, the European Organization for Nuclear Research, due to the lack of strong electromagnetic fields in accelerator settings. With high-intensity lasers, researchers can use strong fields, which have been observed in phenomena such as gamma ray emission and electron-positron pair production.
The group explores how the findings could potentially lead to advances in studies of fundamental physics and in the development of high-energy ion, electron, positron and photon sources. Such findings would be crucial for expanding on many types of scanning technology present today, ranging from materials science studies to medical radiotherapy to next-generation radiography for homeland security and industry.
The QED processes will result in dramatically new plasma physics phenomena, such as the generation of dense electron-positron pair plasma from near vacuum, complete laser energy absorption by QED processes, or the stopping of an ultrarelativistic electron beam, which could penetrate a centimeter of lead by a hairs breadth of laser light.
What kind of new technology these new plasma physics phenomena might translate is largely unknown, especially because the field of QED plasmas itself is a kind of uncharted territory in physics, author Peng Zhang said. At the current stage, even adequate theoretical understanding is significantly lacking.
The group hopes the paper will help bring the attention of more researchers to the exciting new fields of QED plasmas.
Reference: Relativistic plasma physics in supercritical fields by Peng Zhang, Stepan Bulanov, Daniel Seipt, Alexey Arefiev and Alexander G.R. Thomas, 26 May 2020, Physics of Plasmas.DOI: 10.1063/1.5144449
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We recently saw the new trailer for Tenet by Christoper Nolan, but far from solving the doubts we have has caused us to have more questions. We also know that the plot is about a group of people trying to avoid the third world war. However, there is also something strange at stake here: an element that doubles time and quantum theory will be very important to it.
It is no secret that Christopher Nolan loves to play with time, like he does in his movies like Origin, which has caused that there are even fans who have theorized that Tenet may be a kind of sequel. The trailer makes it clear that it is about an agency that works to prevent the global catastrophe, and there is something called tenet, which seems to be a way to play over time. Kind of like manipulating what has happened instead of time travel.
But although Christopher Nolan sends us the message that we do not try to decipher the secrets ahead of time, we are very curious and want to know more. Like for example what the title of Tenet means.
Tenets literal translation is principle, dogma, or canon. And it has been shown that there is a fundamental limitation to our ability to measure time, combining quantum mechanics and Einsteins theory of general relativity. So it is something that the film will explore. Interestingly he played with something similar in Interstellar, since it showed that time passed differently depending on where they were. For this reason, a man stays in the ship and becomes very old while for the rest of them who travel to the aquatic planet hardly a few hours pass.
So to understand Tenet, either Christopher Nolan has made it very clear or you will have to know quantum physics and have Origin (2010) and Interstellar (2017) fresh in your memory.
Quantum entanglement that strange but potentially hugely useful quantum phenomenon where two particles are inextricably linked across space and time could play a major role in future radar technology.
In 2008, an engineer from MIT devised a way to use the features of entanglement to illuminate objects while using barely any photons. In certain scenarios, such technology promises to outperform conventional radar, according to its makers, particularly in noisy thermal environments.
Now, researchers have taken the idea much further, demonstrating its potential with a working prototype.
The technology might eventually find a variety of applications in security and biomedical fields: building better MRI scanners, for example, or giving doctors an alternative way of looking for particular types of cancer.
"What we have demonstrated is a proof of concept for microwave quantum radar," says quantum physicist Shabir Barzanjeh, who conducted the work at the Institute of Science and Technology Austria.
"Using entanglement generated at a few thousandths of a degree above absolute zero, we have been able to detect low reflectivity objects at room temperature."
The device works along the same principles as a normal radar, except instead of sending out radio waves to scan an area, it uses pairs of entangled photons.
Entangled particles are distinguished by having properties that correlate with one another more than you'd expect by chance. In the case of the radar, one photon from each entangled pair, described as a signal photon, is sent towards an object. The remaining photon, described as an idler, is kept in isolation, waiting for a report back.
If the signal photon reflects from an object and is caught, it can be combined with the idler to create a signature pattern of interference, setting the signal apart from other random noise.
As the signal photons reflect from an object, this actually breaks the quantum entanglement in the truest sense. This latest research verifies that even when entanglement is broken, enough information can survive to identify it as a reflected signal.
It doesn't use much power, and the radar itself is difficult to detect, which has benefits for security applications. The biggest advantage this has over conventional radar, however, is that it's less troubled by background radiation noise, which affects the sensitivity and the accuracy of standard radar hardware.
"The main message behind our research is that quantum radar or quantum microwave illumination is not only possible in theory but also in practice," says Barzanjeh.
"When benchmarked against classical low-power detectors in the same conditions we already see, at very low-signal photon numbers, that quantum-enhanced detection can be superior."
There's plenty of exciting potential here, though we shouldn't get ahead of ourselves just yet. Quantum entanglement remains an incredibly delicate process to manage, and entangling the photons initially requires a very precise and ultra-cold environment.
Barzanjeh and his colleagues are continuing their development of the quantum radar idea, yet another sign of how quantum physics is likely to transform our technologies in the near future in everything from communications to supercomputing.
"Throughout history, proof of concepts such as the one we have demonstrated here have often served as prominent milestones towards future technological advancements," says Barzanjeh.
"It will be interesting to see the future implications of this research, particularly for short-range microwave sensors."
The research has been published in Science Advances.
Armin Strom Discusses Resonance With PhD Of Quantum Physics And Watch Collector In An Easy-To-Understand Way (Video) – Quill & Pad
Claude Greisler, co-founder and technical director of Armin Strom, talks resonance with watch collector Michael J. Biercuk, professor of quantum physics and technology at the University of Sydney and CEO and founder of Q-CTRL.
Quantum physics and technology laboratory at the University of Sydney
In this interesting discussion, which took place in Sydney, Greisler and Biercuk discuss what resonance is and what the advantages are. Biercuk also notes that resonance is not watchmaking specific and explains where its found in daily life as well as how its used in quantum physics.
The discussion is easy to understand and provides a light and entertaining look at Armin Stroms signature complicated element.
For more information, please visit http://www.arminstrom.com.
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Armin Strom Minute Repeater Resonance: Synchronized Oscillations Driving Sonorous Vibrations (Plus Video It Sounds Fantastic!)
Armin Strom Masterpiece 1 Dual Time Resonance: Simplifying With Complexity
Understanding Resonance, Featuring The F.P. Journe Chronomtre Rsonance, Armin Strom Mirrored Force Resonance, And Haldimann H2 Flying Resonance
A Watchmakers Technical Look At The Mirrored Force Resonance Fire By Armin Strom: A Dual-Balance Watch With A Difference
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Teaching the next generation of quantum scientists | Harvard John A. Paulson School of Engineering and Applied Sciences – Harvard School of…
The Harvard University Center for Integrated Quantum Materials (CIQM), in partnership with The National Science Foundation (NSF) and the White House Office of Science and Technology Policy (OSTP), hosted a virtual workshop in March to discuss curriculum and educator activities that will help K-12 students engage with quantum information science.
The workshop resulted in alist of key conceptsfor future quantum information science (QIS) learners. The document provides a concise list of nine basic concepts, including quantum entanglement, communication, and sensing. The list is first step towards the development of quantum education curricula and empowering educators to teach quantum concepts in K-12 classrooms.
Quantum information science and technology aims to create systems for quantum sensing, quantum communication using interconnected networks, and quantum computation, said Robert M. Westervelt, the Mallinckrodt Professor of Applied Physics and of Physics at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and Director of CIQM.Our most important role is to engage young students in the field, because they will develop quantum technology in the future.
The document was the product of over three weeks of intensive deliberations among a group of university and industry researchers, secondary school and college educators, and representatives from educational and professional organizations. The participants represented a set of convergent disciplines that contribute to QIS today: physics, computer sciences, materials sciences, engineering, chemistry, and mathematics. Document development efforts were led by experts from the Illinois Quantum Information Science and Technology Center (IQUIST), theUniversity of Chicago,Georgetown Universityand theMuseum of Science, Boston.
"American leadership in quantum information science depends on a strong quantum workforce, said Jake Taylor, a Harvard alumnus who serves as OSTPs Assistant Director for Quantum Information Science. We're thrilled to begin this important work helping prepare the next generation of quantum learners."
"The future of fundamental research and education is in our hands. This impactful effort will empower the broad society to be included, and to actively participate in both efforts and benefits of the quantum era, said Sean Jones, Acting Assistant Director at the NSF's Directorate for Mathematical and Physical Sciences.
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Twitter and other social media platforms are abuzz with the so-called 'parallel universe' that Nasa has discovered. According to the claims, Nasa has detected a parallel universe in Antarctica, where time runs backwards. While this has certainly made a whole lot of people excited, in reality this is far from the truth.
What is a parallel universe?
In quantum mechanics, parallel universe is theorised as existing alongside our own, although undetectable.
How did the claims on Nasa's discovery of parallel universe come about?
The recent reports claiming that there is evidence of a parallel universe appear to be based on ANITA findings that are at least a couple of years old.
A science magazine had published a feature, discussing some anomalous results coming from neutrino detection experiments in Antarctica, and what these could mean for a speculative cosmological model that posits there's an antimatter universe extending backwards from the BigBang.
The featured article was then 'curated' by some online media outlets, and the whole issue snowballed and became the talk of the town for the Twitterati.
What were the anomalous detections in Antarctica?
Four years ago, the Antarctic Impulsive Transient Antenna (ANITA) experiment a high-altitude helium balloon with an array of radio antennas, partially funded by Nasa had spotted a handful of instances of what seemed to be highly energetic neutrinos coming through the Earth. The telescope could spot these neutrinos coming from the space and hitting the ice sheet in Antarctica. ANITA detected these particles, but instead of coming from the space, the neutrinos were found to be coming from the Earth's surface without any source. These detections happened in 2016, then again in 2018, but there was no credible explanation.
Physicists have been working to figure out if these results can be explained with our current models of physics or have something to do with the experimental set-up itself, or if something like parallel universe does exist.
Scientists not ready to call parallel universe a discovery yet
Going by what the scientists have actually said, it's clear that these are exciting times for the astrophysicists trying to find an explanation and future experiments with more exposure and sensitivity will be required to get a clear understanding of the anomaly.
However, people wishing for a parallel universe will have to wait because the evidence is lacking and the scientists are not yet ready to call it a discovery.
What is a neutrino?
A neutrino is a subatomic particle very similar to an electron. But it has no electrical charge and a very small mass, which might even be zero. Neutrinos are one of the most abundant particles in the universe. Because they have very little interaction with matter, they are incredibly difficult to detect.
Here are some Twitter reactions to the claims of parallel universe
Artistic illustration of a carbon nanotube COVID-19 detector. Credit: Zettl Research Group/Berkeley Lab
How an atomically thin device could become a biotech breakthrough.
A technology spun from carbon nanotube sensors discovered 20 years ago by Lawrence Berkeley National Laboratory (Berkeley Lab) scientists could one day help health care providers test patients for COVID-19, the disease caused by the coronavirus SARS-CoV-2.
When Alex Zettl, Marvin Cohen, and their research teams at Berkeley Lab first demonstrated ultrasensitive oxygen sensors devised from carbon nanotubes hollow carbon wires with walls no thicker than an atom they envisioned a broad spectrum of applications, such as gas-leak detectors or air- and water-pollution detectors.
Subsequent studies out of Zettls lab revealed that carbon nanotubes or CNTs could also be used to detect proteins or carbohydrates at the level of single cells for biological and medical applications. CNTs exquisite chemical sensitivity had dramatic life-science implications that could benefit society, Zettl said.
But since Zettl normally investigates atomically thin materials known as nanomaterials for the Department of Energys Novel sp2-Bonded Materials and Related Nanostructures program, his lab is set up for launching exciting new experiments in quantum physics, not new applications for entrepreneurial startups.
So in 2000, Zettl and Cohen, who are both senior faculty scientists in Berkeley Labs Materials Sciences Division and physics professors at UC Berkeley, branched out into the world of commercial spinoffs by co-founding the Emeryville-based biotech company Nanomix Inc. They currently sit on the companys board of directors Zettl participates as an adviser, and Cohen as a member.
Today, the company is one of many U.S. companies vying for FDA Emergency Use Authorization (EUA) to deploy new diagnostic tests for COVID-19.
Last month, the company was awarded approximately $570,000 in funding from the Department of Health and Human Services Biomedical Advanced Research and Development Authority (BARDA) to develop disposable cartridges that test for protein traces of the coronavirus known as antigens in nasal swab samples, and for antibodies to the coronavirus in blood samples.
Patient samples loaded onto the cartridges are analyzed by the Nanomix eLab, a handheld testing device the company first developed more than five years ago in response to the Ebola virus epidemic.
The cartridges rely on tiny carbon biosensors modeled after the Zettl and Cohen labs groundbreaking carbon nanotube technology to detect coronavirus antigens during the early stages of a current infection. In addition, the cartridges can test for antibodies the immune system builds up as part of our bodys natural defense mechanism against a previous SARS-CoV-2 infection. The company says the eLab system can produce test results in about 15 minutes.
If granted FDA Emergency Use Authorization, the company hopes to have COVID-19-ready eLab products available for health care providers in June, and to scale up its supply and production capacity to provide hundreds of thousands of test kits, said Nanomix President and CEO David Ludvigson.
The fact that my research could help so many people is very rewarding. Im happy that I was able to contribute in that way, Zettl said.
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I offer here a potpourri of quotations from the very early pages of Bruce Rosenblum and Fred Kuttner, Quantum Enigma: Physics Encounters Consciousness, 2d ed. (Oxford and New York: Oxford University Press, 2011), quotations that Im extracting for my notes:
Classical physics explains the world quite well; its just the details it cant handle. Quantum physics handles the details perfectly; its just the world it cant explain. You can see why Einstein was troubled. (7)
When the late Bruce Rosenblum (one of the authors of this book) first proposed a course for liberal arts majors at the University of California at Santa Cruz, where he and his co-author taught, a faculty member objected:
[P]resenting this material to nonscientists is the intellectual equivalent of allowing children to play with loaded guns. (8)
Rosenblum and Kuttner themselves say of their book Quantum Enigma that
it is necessarily a controversial book. However, absolutely nothing we say about quantum mechanics itself is controversial. It is the mystery these results imply beyond the physics that is controversial. For many physicists, this baffling weirdness is best not talked about. Physicists (including ourselves) can be uncomfortable with their discipline encountering something as unphysical as consciousness. Though the quantum facts are not in dispute, the meaning behind those facts, what quantum mechanics tells us about our world, is hotly debated. (8)
An Einstein biographer tells that back in the 1950s a non-tenured faculty member in a physics department would endanger a career by showing any interest in the strange implications of quantum theory. Times are changing. (9)
Among the charms of Quantum Enigma are the anecdotes that it shares:
At a physics conference attended by several hundred physicists (including the two of us), an argument broke out in the discussion period after a talk. (The heated across-the-auditorium debate was reported in the New York Times in December 2005.) One participant argued that because of its weirdness, quantum theory had a problem. Another vigorously denied there was a problem, accusing the first of having missed the point. A third broke in to say, Were just too young. We should wait until 2200 when quantum mechanics is taught in kindergarten. A fourth summarized the argument by saying, The world is not as real as we think. Three of these arguers have Nobel Prizes in Physics, and the fourth is a good candidate for one. (9)
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Image by agsandrew / Shutterstock.com
In this quantum physics introduction for beginners we will explain quantum physics, also called quantum mechanics, in simple terms. Quantum physics is possibly the most fascinating part of physics there is. It is the amazing physics that becomes relevant for small particles, where the so-called classical physics is no longer valid. Where classical mechanics describes the movement of sufficiently big particles, and everything is deterministic, we can only determine probabilities for the movement of very small particles, and we call the corresponding theory quantum mechanics.
You may have heard Einsteins saying Der Alte wrfelt nicht which translated to English roughly means God does not roll dice. Well, even geniuses can be wrong. Again, quantum mechanics is not deterministic, but we can in general only determine probabilities. Since we are used to fairly big objects in our everyday life, quantum mechanics and its laws may at first seem strange and quantum theory is often considered to be complex. But for example electrons and photons are sufficiently small that quantum physics is needed, and on this website we will show you that understanding the basics of quantum physics is easy and fun.
In the following paragraph we will describe a thought experiment that we perform at two different length scales: With bullets as known from pistols (the large scale) and with electrons (the very small scale). While the experiment is essentially the same but for the size, we will show you how the result is very different. This will be your first lecture in quantum mechanics.
Consider first a machine gun that fires bullets to a wall. Between the wall and the machine gun there is another wall that has two parallel slits that are big enough to easily allow a bullet to pass through them. To make the experiment interesting, we take a bad machine gun that has a lot of spread. This means it sometimes shoots through the first slit and sometimes through the second, and sometimes it hits the intermediate wall.
If we block the second slit, all bullets that reach the outer wall will have come through the first slit. If we count the number of bullets as a function of the distance from the center of the outer wall, we will find a curve distribution that could be similar to a Gaussian curve. We can call this probability curve P1.
If we block the first slit, all bullets that reach the outer wall will have come through the second slit. The probability curve will be mirrored around the center, and we call it P2.
If we open both slits, all bullets at the outer wall will have come through either slit 1 or 2. What is typical for classical mechanics in this situation is that then the total probability distribution P can be determined as the sum of the previously-mentioned probability distributions, P = P1 + P2.
Now consider the same experiment on a much smaller scale. Instead of bullets from a machine gun we consider electrons that for example can stem from a heated wire that is parallel to the two slits in an intermediate wall. The electron direction will have a natural spread. The slits are also much smaller than before but quite a bit broader than a single electron.
Consider again the case that the second slit is blocked. For proper sizes of the slits and distance between the wire and the walls, the probability distribution P1 will be similar to before. Similarly, if we block the slit 1, we will for proper distances find a probability distribution P2 similar to before.
What do you expect will happen if we do not block any slit? Will we find a probability distribution P = P1 + P2 as before? Well, after all we said you may guess that this is not the case. Indeed, we will instead find a probability distribution that has various minima and maxima. That is, for x = 0 there would be the strongest peak of electrons, for a certain +-Delta x there wouldnt be any electrons at all, but for +-2 Delta x there would be another peak of electrons, and so on.
How can we explain these results? Well, the explanation is rather straight forward if we assume that electrons in this specific case do not behave as particles, but as waves. Waves? you may ask. Well, consider a plain of water, and the same wall as before and the same intermediate wall with a double slit as before. At the place where the machine gun or the wire where, consider a pencil punching periodically downwards into the water. If you do this, you will get concentric waves around the point where you punch the water, until the intermediate plain with the two slits.
Behind each slit, there will be a half circle of concentric waves, up to the point where the new waves from the two slits cross each other. There, the waves from the two slits can add up or eliminate each other. As a function of the periodic punching you will find points where the height of the wave is always the same. There will be other places where the wave is sometimes very high and sometimes very low. At the outer wall, these two phases will be repeatedly following one another. The places where there is a lot of variation correspond to the places where there are the most electrons. The places with no variation correspond to the places where there are no electrons on the wall at all.
So, why do electrons in this case behave like waves and not like particles? Well, this is the thing where you will not find a satisfying answer. You just need to accept it.
What if you do not believe this? Well, the thought experiment with the electrons is rather difficult to perform with the proper scale of all elements of the experiment. But there is another very similar experiment that you can do at home. Instead of the electrons you use the photons (light particles) from a laser which you can buy for a few bucks. You let the laser shine through a double slit, darken the room, and look at the outer wall. And boom! What you see is not just two light lines on the outer wall, but a pattern of light line, dark line, light line, dark line, and so on. The intensity of the lighter region becomes less far away from the center. It corresponds exactly to the result of our thought experiments with electrons.
Why does the laser experiment give the same result as the thought experiment with electrons? It is quite easy: Light particles, called photons, are also very small and therefore behave quantum mechanically. And like electrons, they behave like waves in this specific situation. As a side remark, research has shown that light behaves like particles in another respect: If one reduces the intensity a lot, one will find single light spots from single photons on the wall. This means the light behaves like particles as well. One therefore talks about the particle-wave duality of photons or electrons.
What do you wait for? Do the experiment, and you will become a believer of quantum mechanics, or more generally phrased, of quantum physics.
The pattern with maxima and minima is called an interference pattern, since it comes about by the interference of the waves through slit 1 and slit 2. It has been found that you only get this interference pattern if you do not by other means (some additional measurement instrument) watch through which of the two slits the electrons or photons pass. If you do measure which of the two ways the particles pass by any other means, the interference pattern goes away. You will then find the sum distribution P = P1 + P2 as in the classical experiment.
A measurement device for electrons would typically disturb the electrons. More precisely, their momentum p would typically change due to a measurement device, while the place x of its path would become known more precisely. In general, there will be some uncertainty left in the momentum and in the place of the electron. It was postulated by Heisenberg that the product of these uncertainties can never be lower than a specific constant h: Delta x times Delta p >= h. Noone ever managed to disproof this relation, which is at the heart of quantum mechanics. Essentially it says, we cannot measure both momentum and place with arbitrary precision at the same time.
We said that for proper distributions you will find a similar result P1 and P2 as in the classical case. However, for other sizes one can achieve an interference pattern even for the single slits. This is the case when the slit is so broad that one can achieve an interference of the wave stemming from one side of the slit with the wave stemming from the other side of the slit.
We said above that quantum physics becomes relevant for small particles whereby we mean that naturally, quantum effects are only seen for small particles. However,the theory itself is thought to provide correct results for large particles as well. Why is it then, that quantum effects (which cannot be explained with classical theory) become increasingly difficult to observe for larger particles? Larger compound particles in general experience more interaction both within themselves and with their surroundings. These interactions typically lead to an effect physicists call decoherence which simply put means that quantum effects get lost. In this case (for sufficiently large matter), quantum physics and classical physics yield the same result.
Now you may wonder: At which size does this happen?.While one doesnt naturally observe quantum effects in large particles, ingenious people have managed to specifically prepare test environments which showed quantum effects for an ever growing size of particles. Already 1999 an experiment showed a quantum superposition in particles as large as C60 molecules (original article). A2013 articlealready claims to observe quantum superpositions in molecules that weighmore than 10000 atomic mass units. The question of where the achievable limit lies, and whether one can be sure that experiments really demonstrate quantum behavior, is still of interest. That these questions are not finally concluded is also reflected in a more recent article on the American Physical Society site. In principle, if one would be able to somehow get rid of decoherence effects in specifically prepared systems, the theory itself imposes no upper size limits on where quantum effects could be shown.
The aspect of the length scale for quantum physics that we just discussed was the particle size which typically is on the microscopic scale. A completely different matter is the length scale of how far you can move or separate such particles afteran initial interaction, without loosing quantum effects. You can view the two-slit experiment as showingan interaction between particles at the slit. If you tried out the experiment yourself, you probably realized, that the distance between the slit and the wall were you observe interference patterns can easily be some meters not microscopic at all!
Other experiments prepare two particles in a special quantum superposition called entanglement which, by the way, lies at the heart of quantum computation and then separate these particles. In someexperiments, it was possible to show interactions between these particles despite a separation over many miles. Essentially, if one measures the state of one such particle, one can thereafter predict the state of the other particle (within errors), despite the large separation between the particles. A recent experimentdemonstrated this entanglement effect over extreme distances. Particles were sent to a satellite and back to earth a fairly large scale distance compared to the size of a human.
In this quantum physics introduction we told you that both photons and electrons behave as both particles and waves. This particle-wave duality is not understandable with classical mechanics. It results in us only being able to predict probabilities, while one classically can make deterministic predictions. You can easily test these results at home by performing the two-slits experiment with a laser pointer. Have fun! We hope you enjoyed this quantum physics introduction for beginners. If you havent read it yet, you should continue with our article What Everyone should Know about Quantum Physics. And if you want to learn even more, why not have a look at our article Best Quantum Physics Books for Beginners?