I've been on vacation since June 23, and won't be back till July 2nd. So there probably won't be any exciting blog entry in the world of physics till then.
Hope the world doesn't get sucked into a blackhole before then. I'd hate to miss something like that!
:)
Zz.
Sunday, June 28, 2009
Monday, June 22, 2009
Work Begins on Homestake Mine
Ground breaking occurred today on the Homestake Mine as the new underground mine to study neutrinos and other things.
Zz.
Scientists, politicians and other officials gathered Monday for a groundbreaking of sorts at a lab 4,850 foot below the surface of an old gold mine that was once the site of Nobel Prize-winning physics research.
The site is ideal for experiments because its location is largely shielded from cosmic rays that could interfere with efforts to prove the existence of dark matter, which is thought to make up nearly a quarter of the mass of the universe.
Zz.
Sunday, June 21, 2009
Iconic Einstein Photo Sells For $74K
Just like Elvis, Einstein's memorabilia still fetches a lot of money half a century after his death.
The iconic, signed photo of Einstein sticking his tongue out was sold for more than $74,000 at an auction. In the short news article, I found out the circumstances surrounding that photo that I didn't know about.
I guess he was defiant till the end.
Zz.
The iconic, signed photo of Einstein sticking his tongue out was sold for more than $74,000 at an auction. In the short news article, I found out the circumstances surrounding that photo that I didn't know about.
Einstein had nine prints made. He signed the print that was auctioned on Thursday and gave it to journalist Howard K. Smith.
In his inscription, Einstein said his gesture was aimed at all of humanity. Livingston says it also was aimed at the Red Scare and the McCarthy anti-Communist hearings of the 1950s.
I guess he was defiant till the end.
Zz.
Saturday, June 20, 2009
The Golden Age of Cosmology
This is a fascinating article by Nobel Laureate George Smoot on our current understanding of Cosmology.
Zz.
The second reason why this is such an incredibly exciting time in cosmology is that these observations, combined with careful reasoning and an occasional brilliant insight, have allowed us to formulate an elegant and precisely quantitative model for the origin and evolution of the universe. This model reproduces to high accuracy everything that we observe over the history of the universe, images of which are displayed in the planetarium.
We now have precise observations of a very early epoch in the universe through the images made using the CMB radiation and we hope to start a newer and even more precise and illuminating effort with the launch of the Planck Mission on 14 May. However, we also have many impressive galaxy surveys and plans for even more extensive surveys using new ideas to see the relics of the acoustic oscillations in the very, very early universe, as well as the gravitational lensing caused by the more recently formed large-scale structures, such as clusters of galaxies that slightly warp the fabric of space–time by their presence. Each will give us new images and thus new information about the overall history of the universe.
Zz.
Friday, June 19, 2009
Quantum Entanglement
This is a monstrous review article on quantum entanglement[1]. It is 78 pages long!
Abstract: From the point of view of quantum information science, entanglement is a resource that can be used to perform tasks that are impossible in a classical world. In a certain sense, the more entanglement we have, the better we can perform those tasks. Thus, one of the main goals in this field has been to identify under which conditions two or more systems are entangled, and how entangled they are. This paper reviews the main criteria to detect entanglement as well as entanglement measures and also discusses the role of entanglement in quantum communication and cryptography.
Even if you can't read the whole thing (who can?), at the very least, the wealth of references is more than ample reason to keep a copy of this thing.
Zz.
[1] Horodecki et al., Rev. Mod. Phys. v.81, p865 (2009); the ArXiv version can be found here.
Abstract: From the point of view of quantum information science, entanglement is a resource that can be used to perform tasks that are impossible in a classical world. In a certain sense, the more entanglement we have, the better we can perform those tasks. Thus, one of the main goals in this field has been to identify under which conditions two or more systems are entangled, and how entangled they are. This paper reviews the main criteria to detect entanglement as well as entanglement measures and also discusses the role of entanglement in quantum communication and cryptography.
Even if you can't read the whole thing (who can?), at the very least, the wealth of references is more than ample reason to keep a copy of this thing.
Zz.
[1] Horodecki et al., Rev. Mod. Phys. v.81, p865 (2009); the ArXiv version can be found here.
Dressing for a Job Interview
It's one of those things that isn't high on the list of things to pay attention to - dressing for an interview. Especially in academia/research, and especially in the physics profession, dressing appropriately isn't something that we pay that much emphasis on. I mean, during the summer months, I come to work in shorts, t-shirt, and sneakers. So one can already tell that I am not that "fashion conscious" (just don't anyone dare call Stacy and Clinton from "What Not To Wear"!).
Still, when one goes for a job interview, even for a job in physics/sciences, what would be appropriate to wear? Well, the Science career section this week has good tips for what to wear and what not to wear. It covers a wide enough situation, from formal to less formal, that one can buy a wardrobe to suit almost all the possible needs. And this covers for both men and women.
From the point of view of the interviewer, I would like your ability and your knowledge to stand out. This means that your outfit and how you are presented should NOT be a distraction. If you walk out of the interview and a day later, I don't remember what you wore, but I do remember exactly what you said, then you have done a good job in dressing yourself. We care more about your knowledge rather than your appearance, but your appearance can be a hindrance to our focus in deciding on what you know.
Luckily, I don't think I've ever come across an interviewee who hasn't dressed appropriately. And certainly I haven't come across anything similar to the person mentioned at the beginning of this article (it just shows lack of respect more than anything else, and that would have turned me off as an interviewer).
Zz.
Still, when one goes for a job interview, even for a job in physics/sciences, what would be appropriate to wear? Well, the Science career section this week has good tips for what to wear and what not to wear. It covers a wide enough situation, from formal to less formal, that one can buy a wardrobe to suit almost all the possible needs. And this covers for both men and women.
From the point of view of the interviewer, I would like your ability and your knowledge to stand out. This means that your outfit and how you are presented should NOT be a distraction. If you walk out of the interview and a day later, I don't remember what you wore, but I do remember exactly what you said, then you have done a good job in dressing yourself. We care more about your knowledge rather than your appearance, but your appearance can be a hindrance to our focus in deciding on what you know.
Luckily, I don't think I've ever come across an interviewee who hasn't dressed appropriately. And certainly I haven't come across anything similar to the person mentioned at the beginning of this article (it just shows lack of respect more than anything else, and that would have turned me off as an interviewer).
Zz.
Students Went Into Zero-G To Do Experiment
Well, this sounds like a lot of fun.
A number of students from New Jersey went into the "Weightless Wonder", a NASA plane that can make zero-g dives, to do their experiment on plasma dust clouds.
That's almost as an exotic of a "location" to do one's experiment as going to the Antarctica. Still, I wish the news report tells us a little bit more of the nature of the experiment and what exactly is being observed.
Zz.
A number of students from New Jersey went into the "Weightless Wonder", a NASA plane that can make zero-g dives, to do their experiment on plasma dust clouds.
In 2008, the first Team DPX -- comprised only of students -- boarded a DC-9. This year, NASA invited Zwicker, who was one of the mentors for both DPX teams, to join the students. The 2009 team -- including several additional students -- took aboard a second dusty plasma experiment, as well as upgraded equipment and additional cameras.
That's almost as an exotic of a "location" to do one's experiment as going to the Antarctica. Still, I wish the news report tells us a little bit more of the nature of the experiment and what exactly is being observed.
Zz.
Thursday, June 18, 2009
How Does Time Travel Really Work, Sean Carroll?
Caltech's Sean Carroll took time off from his work to answer a few questions about time travel that we have seen in the movies. If nothing else, this news article gets a chuckle or two. For example:
:)
Zz.
"Superman" (1978 version)
How time travel is achieved: Superman zips into space and flies faster than the speed of light, round and round, reversing the planet's spin and reversing time.
Carroll says: "It would cause earthquakes and kill millions. And really, if you can do this, then why, if you're Superman, don't you do this all the time? He should be held to a higher standard."
:)
Zz.
Tuesday, June 16, 2009
Prototype Nokia Cell Phone Recharges Using Ambient Radio Waves?
OK, I read this and I started laughing hysterically.
Sure, I was skeptical, but I also don't doubt that this COULD work. Still it looks like they will need quite a bit of work left to do before they could harvest enough energy just from the ambient EM wave.
Nokia thinks that they have developed a cell phone that doesn't need recharging. It recharges itself from the surrounding radio waves that is almost everywhere.
Question is, how SLOW does it recharge?
Zz.
Sure, I was skeptical, but I also don't doubt that this COULD work. Still it looks like they will need quite a bit of work left to do before they could harvest enough energy just from the ambient EM wave.
Nokia thinks that they have developed a cell phone that doesn't need recharging. It recharges itself from the surrounding radio waves that is almost everywhere.
While "traditional" (if there is such a thing) wireless power systems are specifically designed with a transmitter and receiver in mind, Nokia's system isn't finicky about where it gets its wireless waves. TV, radio, other mobile phone systems -- all of this stuff just bounces around the air and most of it is wasted, absorbed into the environment or scattered into the ether. Nokia picks up all the bits and pieces of these waves and uses the collected electromagnetic energy to create electrical current, then uses that to recharge the phone's battery. A huge range of frequencies can be utilized by the system (there's no other way, really, as the energy in any given wave is infinitesimal). It's the same idea that Tesla was exploring 100 years ago, just on a tiny scale.
Mind you, harvesting ambient electromagnetic energy is never going to offer enough electricity to power your whole house or office, but it just might be enough to keep a cell phone alive and kicking. Currently Nokia is able to harvest all of 5 milliwatts from the air; the goal is to increase that to 20 milliwatts in the short term and 50 milliwatts down the line. That wouldn't be enough to keep the phone alive during an active call, but would be enough to slowly recharge the cell phone battery while it's in standby mode, theoretically offering infinite power -- provided you're not stuck deep underground where radio waves can't penetrate.
Question is, how SLOW does it recharge?
Zz.
The Elusive Memristor: Properties of Basic Electrical Circuits
I'm guessing that there's a flurry of activity after last year's publication of the discovery of a memristor. There is a handy article in Eur. J. Phys. describing the basics of memristor and its properties as an electrical component[1].
Abstract: We present an introduction to and a tutorial on the properties of the recently discovered ideal circuit element, a memristor. By definition, a memristor M relates the charge q and the magnetic flux phi in a circuit and complements a resistor R, a capacitor C and an inductor L as an ingredient of ideal electrical circuits. The properties of these three elements and their circuits are a part of the standard curricula. The existence of the memristor as the fourth ideal circuit element was predicted in 1971 based on symmetry arguments, but was clearly experimentally demonstrated just last year. We present the properties of a single memristor, memristors in series and parallel, as well as ideal memristor–capacitor (MC), memristor–inductor (ML) and memristor–capacitor–inductor (MCL) circuits. We find that the memristor has hysteretic current–voltage characteristics. We show that the ideal MC (ML) circuit undergoes non-exponential charge (current) decay with two time scales and that by switching the polarity of the capacitor, an ideal MCL circuit can be tuned from overdamped to underdamped. We present simple models which show that these unusual properties are closely related to the memristor's internal dynamics. This tutorial complements the pedagogy of ideal circuit elements (R, C and L) and the properties of their circuits, and is aimed at undergraduate physics and electrical engineering students.
Zz.
[1] Y.N. Joglekar and S.J. Wolf, Eur. J. Phys. v.30, p.661 (2009).
Abstract: We present an introduction to and a tutorial on the properties of the recently discovered ideal circuit element, a memristor. By definition, a memristor M relates the charge q and the magnetic flux phi in a circuit and complements a resistor R, a capacitor C and an inductor L as an ingredient of ideal electrical circuits. The properties of these three elements and their circuits are a part of the standard curricula. The existence of the memristor as the fourth ideal circuit element was predicted in 1971 based on symmetry arguments, but was clearly experimentally demonstrated just last year. We present the properties of a single memristor, memristors in series and parallel, as well as ideal memristor–capacitor (MC), memristor–inductor (ML) and memristor–capacitor–inductor (MCL) circuits. We find that the memristor has hysteretic current–voltage characteristics. We show that the ideal MC (ML) circuit undergoes non-exponential charge (current) decay with two time scales and that by switching the polarity of the capacitor, an ideal MCL circuit can be tuned from overdamped to underdamped. We present simple models which show that these unusual properties are closely related to the memristor's internal dynamics. This tutorial complements the pedagogy of ideal circuit elements (R, C and L) and the properties of their circuits, and is aimed at undergraduate physics and electrical engineering students.
Zz.
[1] Y.N. Joglekar and S.J. Wolf, Eur. J. Phys. v.30, p.661 (2009).
High-Tc Superconductors Are Very Kinky - Update 6
Another preprint appears today on the origin of the "kink" that in ARPES spectra of high-Tc superconductors. This time, there is a careful analysis of the role of phonons in producing such an effect[1]. By making the assumption that the magnetic effects play no role at all, they calculated the possible outcome of the phonon mode as the sole source of the band kink. They concluded that for optimally-doped Bi2212, phonons contribute only 10% to this effect.
So from this work, phonons are not the dominant factor in causing the kink.
I have updated the original blog entry to contain this reference.
Zz.
[1] http://arxiv.org/abs/0906.2627
So from this work, phonons are not the dominant factor in causing the kink.
I have updated the original blog entry to contain this reference.
Zz.
[1] http://arxiv.org/abs/0906.2627
Monday, June 15, 2009
Another "Hoax Paper" Accepted For Publication
As much as we whine about peer-reviewed process and the prestige of certain journals that try to uphold a very rigorous acceptance process, when we read something like this, it drives home the fact that, more often than not, quality beats quantity on any given day.
A hoax paper was accepted to be published in an open access journal that I've never heard about until now {link available for free only for a limited time}.
The editor of the journal is resigning from the journal in dispute with the publisher. I find it entirely VERY strange that the journal publisher is claiming that the paper has been reviewed by more than one referee, and yet, the editor in chief is not able to access or verify that such a review has taken place. Typically, the editor, of all people, are the ones assigning the referring process and has full access to all the reviews. So something is definitely fishy here.
This is reminiscent of the Alan Sokal hoax in "Social Text", even though the aim of that hoax is on an entirely different matter than this one. Still, the review process failed, and that something that is essentially garbage made it through the process and got through. This is one clear example of what would happen without proper scrutiny and review.
Of course, someone might ask "But ZapperZ, even those prestigious journals like Nature and Science are not immune to publishing such "hoaxes", as illustrate by the Hendrik Schon debacle".
Ah, but there's a difference here. When you either forge data or being unethical, it is very difficult to spot something like that, as opposed to the nonsensical paper written by Sokal and in this latest case. Any reviewer who knows the subject matter can immediately spot such "word salad" that are contained in these cases. In Schon's case, it isn't easy to spot because the deception is in THE DATA itself. It requires others to try and reproduce that experiment as a means to verify what was obtained, i.e. it requires the wheel of scientific independent verification to kick in. You'll never see such word salad manuscript getting published in Nature, Science, PRL, etc.
Zz.
A hoax paper was accepted to be published in an open access journal that I've never heard about until now {link available for free only for a limited time}.
The fake, computer-generated manuscript was submitted to The Open Information Science Journal by Philip Davis, a graduate student in communication sciences at Cornell University in Ithaca, New York, and Kent Anderson, executive director of international business and product development at The New England Journal of Medicine. They produced the paper using software that generates grammatically correct but nonsensical text, and submitted the manuscript under pseudonyms in late January.
Davis says he decided to submit the fake manuscript after receiving several unsolicited invitations by e-mail to submit papers to open-access journals published by Bentham under the author-pays-for-publication model. He wanted to test if the publisher would "accept a completely nonsensical manuscript if the authors were willing to pay".
Davis was informed by Bentham on 3 June that his manuscript was accepted for publication. The publisher requested that Davis pay US$800 to its subscriptions department, based in the United Arab Emirates, before the article was published. At this point, Davis retracted the article.
The editor of the journal is resigning from the journal in dispute with the publisher. I find it entirely VERY strange that the journal publisher is claiming that the paper has been reviewed by more than one referee, and yet, the editor in chief is not able to access or verify that such a review has taken place. Typically, the editor, of all people, are the ones assigning the referring process and has full access to all the reviews. So something is definitely fishy here.
This is reminiscent of the Alan Sokal hoax in "Social Text", even though the aim of that hoax is on an entirely different matter than this one. Still, the review process failed, and that something that is essentially garbage made it through the process and got through. This is one clear example of what would happen without proper scrutiny and review.
Of course, someone might ask "But ZapperZ, even those prestigious journals like Nature and Science are not immune to publishing such "hoaxes", as illustrate by the Hendrik Schon debacle".
Ah, but there's a difference here. When you either forge data or being unethical, it is very difficult to spot something like that, as opposed to the nonsensical paper written by Sokal and in this latest case. Any reviewer who knows the subject matter can immediately spot such "word salad" that are contained in these cases. In Schon's case, it isn't easy to spot because the deception is in THE DATA itself. It requires others to try and reproduce that experiment as a means to verify what was obtained, i.e. it requires the wheel of scientific independent verification to kick in. You'll never see such word salad manuscript getting published in Nature, Science, PRL, etc.
Zz.
Sunday, June 14, 2009
Oppenheimer and Fermi: Two Developers of the First Atomic Bomb
This is the transcript of a radio broadcast (I'm assuming, on Voice of America) on a show summarizing the contribution (and brief history) of Oppenheimer and Fermi in the development of the atomic bomb.
If you haven't read or heard much about such a history, this would be a "Cliff Notes" version of it that has been highly condensed for casual consumption.
Zz.
If you haven't read or heard much about such a history, this would be a "Cliff Notes" version of it that has been highly condensed for casual consumption.
Zz.
Physics Is Beauty
This is a rather good article on the journey and reason someone pursues a degree and research work in physics.
Unlike crackpots, who continue to make grandiose claims of finding the "theory of everything" and solving the question of the universe, the overwhelming majority of physicists really do not have such pretentious goal. We tend to want to solve a particular problem, or work in a particular area, because these are the ones that peaked our curiosity, and we want to find the answer to their questions. We just want to add to the huge body of knowledge, even if it is just a small portion of it. Of course, some of us are more aware of the application of what we do, and that certainly can be a motivating factor in addition to the curiosity angle.
Zz.
Physics is worth knowing because it is beautiful. It is the hidden secret of the scientist. We may claim to be researching some topic or other because it is "useful to society" or it will revolutionize some technology but, more often than not, we are simply fascinated by some small detail about how the world works and we can't stop thinking about it until we understand it better. We are constantly astounded by the way a few basic principles work together to explain so many different things, and sit in wonder and awe at the beauty of the world. Like an artist, I want to share this beauty with others. I want them to know what it is to see through my eyes.
Unlike crackpots, who continue to make grandiose claims of finding the "theory of everything" and solving the question of the universe, the overwhelming majority of physicists really do not have such pretentious goal. We tend to want to solve a particular problem, or work in a particular area, because these are the ones that peaked our curiosity, and we want to find the answer to their questions. We just want to add to the huge body of knowledge, even if it is just a small portion of it. Of course, some of us are more aware of the application of what we do, and that certainly can be a motivating factor in addition to the curiosity angle.
Zz.
Saturday, June 13, 2009
The Physics of Nothing
This is a news article of one of the sessions that went on during this year's World Science Festival, currently running in NY City. It is essentially a dialog and Q&A involving Frank Wilczek, John Barrow, Paul Davies, and George Ellis. All they talked about was "nothing"!
Unfortunately, this is also a favorite topic of crackpots. I'm sure this news article will be used, somehow, to bastardize the physics of vacuum state.
Zz.
“Nothing is unstable,” Frank Wilczek, a physicist and Nobel laureate from MIT, finally said to a general murmur of agreement of his colleagues on stage, John Barrow of Cambridge University in England, Paul Davies of Arizona State and George Ellis of the University of Cape Town in South Africa.
Given a chance, nature will make nothingness boil with activity.
Unfortunately, this is also a favorite topic of crackpots. I'm sure this news article will be used, somehow, to bastardize the physics of vacuum state.
Zz.
Friday, June 12, 2009
To What Extent Iron-Pnictide New Superconductors Have Been Clarified: A Progress Report
It has only been a few years since the discovery of superconductivity in the iron-arsenic compound family. Yet, a lot of work, both theoretical and experimental, has been done on this material. So it is inevitable that, at some point, a review of what we know so far will appear. This is one such review.
Abstract: In this review, the authors present a summary of experimental reports on newly discovered iron-based superconductors as they were known at the end of 2008. At the same time, this paper is intended to be useful for experimenters to know the current status of these superconductors. The authors introduce experimental results that reveal basic physical properties in the normal and superconducting states. The similarities and differences between iron-pnictide superconductors and other unconventional superconductors are also discussed.
Certainly helpful to have a catalog of something like this periodically.
Zz.s
Abstract: In this review, the authors present a summary of experimental reports on newly discovered iron-based superconductors as they were known at the end of 2008. At the same time, this paper is intended to be useful for experimenters to know the current status of these superconductors. The authors introduce experimental results that reveal basic physical properties in the normal and superconducting states. The similarities and differences between iron-pnictide superconductors and other unconventional superconductors are also discussed.
Certainly helpful to have a catalog of something like this periodically.
Zz.s
Speed Networking for Scientists?
No, this isn't "very fast" networking, but rather something similar to speed dating...
I'm not making this up! :)
An article in this week's Science Career section discussed something that is getting some "speed" in popularity - speed networking.
Er.... yeah.
I suppose whatever works in getting to meet others. Can't see any harm in that, other than a greater risk of exposure to the H1N1 virus! :)
Zz.
I'm not making this up! :)
An article in this week's Science Career section discussed something that is getting some "speed" in popularity - speed networking.
Our so-called Translational Research Bazaar, which took place in October, used a format popularized by speed dating: Two groups of people--in this case, basic scientists and clinical/translational researchers--sit on opposite sides of a table and chat for a few minutes until a bell rings, signaling that it's time to move on and strike up a new conversation. This process continues until everyone in one group has met everyone in the other group. The goal, for translational research as for dating, is to find a match.
More than 80 people registered for the event, and follow-ups with the attendees suggest it worked as planned: Eighty-five percent of participants said they met at least one potential collaborator, and seven pairs of researchers applied for internal pilot funding. Word has gotten out: Other institutions and organizations have contacted us hoping to learn how to run their own events.
Er.... yeah.
I suppose whatever works in getting to meet others. Can't see any harm in that, other than a greater risk of exposure to the H1N1 virus! :)
Zz.
Thursday, June 11, 2009
Lorentz Contraction, Bell's Spaceships, and Rigid Body Motion in Special Relativity
I don't know if this manuscript has been published elsewhere, or if it has been submitted for publication. However, I found it a rather interesting reading. It explores certain "misconception" in Special Relativity, especially on the issue of "length contraction" that appears to be a standard part of physics education. Read it and see what you think.
I suppose this is another one that tries to correct certain popular misconception, or the use of inappropriate description, in SR. We already had papers dealing with issues of "relativistic mass" and why such a use is not accurate. It only serves to show the complexity in the trying to "visualize" the concept in something that has been developed for more than 100 years already, and a tribute to how revolutionary Relativity is.
Edit: This paper has now appeared in publication. Here is the complete reference:
J. Franklin, Eur. J. Phys. v.31, p.291 (2010).
Zz.
I suppose this is another one that tries to correct certain popular misconception, or the use of inappropriate description, in SR. We already had papers dealing with issues of "relativistic mass" and why such a use is not accurate. It only serves to show the complexity in the trying to "visualize" the concept in something that has been developed for more than 100 years already, and a tribute to how revolutionary Relativity is.
Edit: This paper has now appeared in publication. Here is the complete reference:
J. Franklin, Eur. J. Phys. v.31, p.291 (2010).
Zz.
Wednesday, June 10, 2009
Astronomy and the Media: a Love Story?
Another fun article to read about Astronomy. This time the article questions on whether there is ample and adequate media coverage of Astronomy, or whether the subject has been neglected in general, despite high-profiled stories about black holes, dark matter, dark energy, etc.
We can couple this with an earlier article on the public perception of astronomers throughout history. They make a rather interesting reading.
Zz.
We can couple this with an earlier article on the public perception of astronomers throughout history. They make a rather interesting reading.
Zz.
ac-Driven Atomic Quantum Motor
A very interesting and intriguing theoretical proposal.
A. V. Ponomarev et al., "ac-Driven Atomic Quantum Motor", Phys. Rev. Lett. v.102, p.230601 (2009) .
Abstract: We propose an ac-driven quantum motor consisting of two different, interacting ultracold atoms placed into a ring-shaped optical lattice and submerged in a pulsating magnetic field. While the first atom carries a current, the second one serves as a quantum starter. For fixed zero-momentum initial conditions the asymptotic carrier velocity converges to a unique nonzero value. We also demonstrate that this quantum motor performs work against a constant load.
ScienceNow has a review of this paper as well.
Now let's see which experimental group will be the first to produce something similar to this! The race is on! :)
Zz.
A. V. Ponomarev et al., "ac-Driven Atomic Quantum Motor", Phys. Rev. Lett. v.102, p.230601 (2009) .
Abstract: We propose an ac-driven quantum motor consisting of two different, interacting ultracold atoms placed into a ring-shaped optical lattice and submerged in a pulsating magnetic field. While the first atom carries a current, the second one serves as a quantum starter. For fixed zero-momentum initial conditions the asymptotic carrier velocity converges to a unique nonzero value. We also demonstrate that this quantum motor performs work against a constant load.
ScienceNow has a review of this paper as well.
Now, Alexey Ponomarev, Peter Hänggi, and colleagues at the University of Augsburg, Germany, have devised the quantum-mechanical equivalent of such a motor. Their motor consists of bright spots of laser light that form a circle like so many pearls in a bracelet (see picture). The spots of laser light can trap two ultracold atoms: The first, called the carrier, is missing an electron and so is electrically charged; the second, called the starter, is uncharged. Instead of applying an oscillating current in a coil, the researchers envision applying an oscillating electric field perpendicular to the plane of the ring.
This will set the carrier into motion--but not in a simple way. Because it's a quantum particle, the carrier atom must be described by quantum waves that give the probability for finding it at one position or another. Applying an oscillating field alone will send waves of equal strength rippling around the ring in both directions, with the net result that, on average, the particle doesn't budge. To get it going, the physicists have to include the starter atom, which gives the carrier a shove whenever the two atoms happen to hop into the same light spot.
Even that is not quite enough. To make the motor turn over, the researchers find, the electric field has to oscillate in a pattern that would appear different if it were suddenly reversed--much as a song sounds different if you play it backward. Such oscillations set off quantum waves that flow predominantly either to the left or to the right, setting the motor in motion, the researchers report in a paper published online this week in Physical Review Letters.
Now let's see which experimental group will be the first to produce something similar to this! The race is on! :)
Zz.
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