Feynman’s double-slit experiment brought to life
The precise methodology of Richard Feynman’s famous double-slit thought-experiment – a cornerstone of quantum mechanics that showed how electrons behave as both a particle and a wave – has been followed in full for the very first time.
Although the particle-wave duality of electrons has been demonstrated in a number of different ways since Feynman popularised the idea in 1965, none of the experiments have managed to fully replicate the methodology set out in Volume 3 of Feynman’s famous Lectures on Physics.
“The technology to do this experiment has been around for about two decades; however, to do a nice data recording of electrons takes some serious effort and has taken us three years,” said lead author of the study Professor Herman Batelaan from the University of Nebraska-Lincoln.
“Previous double-slit experiments have successfully demonstrated the mysterious properties of electrons, but none have done so using Feynman’s methodology, specifically the opening and closing of both slits at will and the ability to detect electrons one at a time.
“Akira Tonomura’s brilliant experiment used a thin, charged wire to split electrons and bring them back together again, instead of two slits in a wall which was proposed by Feynman. To the best of my knowledge, the experiments by Guilio Pozzi were the first to use nano-fabricated slits in a wall; however, the slits were covered up by stuffing them with material so could not be open and closed automatically.”
In their experiments, which have been published today, Thursday 14 March, in the Institute of Physics and German Physical Society’s New Journal of Physics, Batelaan and his team, along with colleagues at the Perimeter Institute of Theoretical Physics, created a modern representation of Feynman’s experiment by directing an electron beam, capable of firing individual electrons, at a wall made of a gold-coated silicon membrane.
The wall had two 62-nm-wide slits in it with a centre-to-centre separation of 272 nm. A 4.5 µm wide and 10 µm tall moveable mask, controlled by a piezoelectric actuator, was placed behind the wall and slid back and forth to cover the slits.
“We’ve created an experiment where both slits can be mechanically opened and closed at will and, most importantly, combined this with the capability of detecting one electron at a time.
“It is our task to turn every stone when it comes to the most fundamental experiments that one can do. We have done exactly that with Feynman’s famous thought-experiment and have been able to illustrate the key feature of quantum mechanics,” continued Batelaan.
Feynman’s double-slit experiment
In Feynman’s double-slit thought-experiment, a specific material is randomly directed at a wall which has two small slits that can be opened and closed at will – some of the material gets blocked and some passes through the slits, depending on which ones are open.
Based on the pattern that is detected beyond the wall on a backstop – which is fitted with a detector – one can discern whether the material coming through behaves as either a wave or particle.
When particles are fired at the wall with both slits open, they are more likely to hit the backstop in one particular area, whereas waves interfere with each other and hit the backstop at a number of different points with differing strength, creating what is known as an interference pattern.
In 1965, Feynman popularised that electrons – historically thought to be particles – would actually produce the pattern of a wave in the double-split experiment.
Unlike sound waves and water waves, Feynman highlighted that when electrons are fired at the wall one at a time, an interference pattern is still produced. He went on to say that this phenomenon “has in it the heart of quantum physics [but] in reality, it contains the only mystery.”
Illustrated Misconception: NASA is already over-funded, and will not be affected by the recent budget cuts.
In a 1997 poll, people were found to estimate NASA’s share of the federal budget was around 20%. “Had this been true,” Launius writes, “NASA’s budget in 1997 would have been $328 billion.” In actuality NASA receives less than one percent of the Federal budget each year- a budget that has been diminishing since the early 1990s. [Launius 174, “Public Opinion Polls and Perceptions of US Human Spaceflight”]
For those of you who want to continue NASA’s progress- you’re not alone! Popular television host and “Big Think” speaker, Bill Nye, has this to say on the matter: “If the Earth gets hit by an asteroid, it’s game over. It’s control-alt-delete for civilization.” The benefits of improving the budget for NASA don’t just end at defense, but to improve current technology, including noninvasive medical technology.
Anonymous nay-sayers to the idea of stopping the 2013 budget cuts to NASA funding say ”Perhaps NASA needs to sharpen its priorities, and drop the whiz bang stuff. “Because its there” is not a sufficient justification for a bunch of new toys.” (sfbaywalk, Washington Post) However, if you enjoy satellite television, artificial limbs, MRI and CAT scans, breast cancer screenings, heating protection materials used by firefighters, freeze-dried food, solar energy, water filters, smoke detectors, or even memory foam mattresses then you have NASA to thank for these devices, and the lists goes on and on and on…
A few points on the Samsung Galaxy S4
Shiny plastics aside*, the soap bar design of the Samsung Galaxy S4 seems to be very, very size effective. The S4 really makes a case for that 5 inch phones are totally manageable. The phone has about the same dimension as the 4.7 inch — already tightly designed — HTC One, and just slightly larger than the 4.5 inch Nexus 4 and the 4.2 inch Blackberry Z10. The Galaxy S4 is the second slimmest phone of the current top players, beaten only by the iPhone 5, but it still manages to include the largest battery. The Blackberry’s bezel size as well as its hardware specs are starting to look very last gen. And the device has barely hit the stores. The Galaxy’s soft round corners and back should also make the device easy to slip in and out of your pockets. Even though the difference in design from last year’s S3 is small, I think the impossible thin bezels of the new S4 makes the design pop and come into its own.
I don’t know how much of a difference the increase from 720p to 1080p on 4.5-5 inch screens really makes in real life usage, but I know one thing all these 1080p Android phones are doing very effectively: They make the 640p screens in iPhones look very long in the tooth. Again, I don’t know how much you gain in real life usage, but the difference on paper is now disturbingly big.
PenTile pixel arrangement. Really, Samsung?
Much have been said about Samsung moving away from Android, but the Galaxy S4 it still very much an Android device. Even though Samsung goes a long way to embed a lot of software and hardware features in order to make it stand out from the crowd. Btw, the ability to easily implement brand differentiation was one of the biggest factors why Android got its widespread adoption in the first place. It’s a platform feature. Which might, or might not get out of hand. But more on that another time. With that being said, I don’t have too high hopes for all of these Samsung services, The company’s software services are usually kind of gimmicky and/or poorly implemented. That health tracker do however look interesting.
Glove enabled touch as in the Nokia Lumia 920 is a welcome addition. So is wireless charging.
It will be interesting to see how the camera performs against the iPhone 5, HTC One and the Lumia 920.
Latest available version of Android from the get go. Nice work.
I’ve actually seen some LAG in a couple of hands-on videos of the device. Has Samsung gone overboard with Touchwiz and the added features and somehow ruined project butter? I played with an old Galaxy S2 with Android 4.1 the other day, and it didn’t lag at all.
*Some of you have misunderstood how I feel about plastics. I have nothing against plastics, it’s a great material. But I think that there’s good and bad plastics, and Samsung often use very thin, cheap feeling and shiny plastics. Which I don’t like. But given the popularity of the Galaxy line of devices, I’m clearly in the minority. Even so, I believe Samsung has succeeded in spite of the shiny plastics, not because of it.
Artificial Dust Devils
The word ‘tornado’ is usually associated with death and destruction, but mechanical engineers Mark Simpson and Ari Glezer at the Georgia Institute of Technology have figured out a way to harness them for renewable energy. They’re not out braving huge natural tornadoes, but rather they’re artificially creating small, controlled vortexes and using them to produce cheap, renewable energy. After seeing dust devils in Arizona sparked the idea, Glezer and Simpson built a metre-wide prototype that looks a bit like the inside of an aircraft engine rotor. Called the Solar Vortex, it relies on the temperature difference between hot air near the ground and cooler air just a metre above it. When the hot air rises and the cool air descends, convection currents form between the layers (convection currents are basically the continual cycle of heat transfer up and down). Well-positioned vanes force the airflow to spontaneously form into a vortex, which sucks in more warm air to maintain itself and turns a turbine at the centre of the device, generating energy—and no power is needed to kick-start it. The Department of Energy’s Advanced Research Projects Agency have agreed to fund large-scale trials, and they hope to build a 10 kilowatt model within two years and a 50 kilowatt model in the future. Glezer estimates that a square kilometre array of the turbines would produce 16 megawatts of energy—much more than the 3 to 5 megawatts of conventional wind turbines. It would be 20% cheaper than traditional wind power generation and 65% cheaper than solar panels, and the Solar Vortex doesn’t even need to be elevated to catch the wind, so it could be installed on building and factory rooftops where sufficient waste heat escapes.
On May 25, 1961, three weeks after Mercury astronaut Alan Shepard became the first American in space, President John F. Kennedy announced the goal of sending astronauts to the moon before the end of the decade.
To facilitate this goal, NASA expanded the existing manned space flight program in December 1961 to include the development of a two-man spacecraft. The program was officially designated Gemini on January 3, 1962.