I love mysteries and am quite interested in the nature of reality (you, too?) and that gives us something in common with a couple of Perimeter Institute for Theoretical Physics (PI; Canada) researchers. From The Quantum Physicist as Causal Detective event page on the insidetheperimeter.ca website (notice received via email),
In their live webcast from Perimeter on October 7 , Robert Spekkens and Elie Wolfe will shed light on the exciting possibilities brought about by applying quantum thinking to the science of cause and effect.
Watch the live webcast on this page on Wednesday, October 7  at 7 pm ET.
What do data science and the foundations of quantum theory have to do with one another?
A great deal, it turns out. The particular branch of data science known as causal inference focuses on a problem which is central to disciplines ranging from epidemiology to economics: that of disentangling correlation and causation in statistical data.
Meanwhile, in a slightly different guise, this same problem has been pondered by quantum physicists as part of a continuing effort to make sense of various puzzling quantum phenomena. On top of that, the most celebrated result concerning quantum theory’s meaning for the nature of reality – Bell’s theorem – can be seen in retrospect to be built on the solution to a particularly challenging problem in causal inference.
Recent efforts to elaborate upon these connections have led to an exciting flow of techniques and insights across the disciplinary divide.
Perimeter researchers Robert Spekkens and Elie Wolfe have done pioneering work studying relations of cause and effect through a quantum foundational lens, and can be counted among a small number of physicists worldwide with expertise in this field.
In their joint webcast from Perimeter [at 7 pm ET] on October 7 , Spekkens and Wolfe will explore what is happening at the intersection of these two fields and how thinking like a quantum physicist leads to new ways of sussing out cause and effect from correlation patterns in statistical data.
For those of us on the West Coast, that webcast will be at 4 p.m. on Wednesday, Oct. 7, 2020 and I believe you can watch it here.
This supremacy, refers to an engineering milestone and a October 23, 2019 news item on ScienceDaily announces the milestone has been reached,
Researchers in UC [University of California] Santa Barbara/Google scientist John Martinis’ group have made good on their claim to quantum supremacy. Using 53 entangled quantum bits (“qubits”), their Sycamore computer has taken on — and solved — a problem considered intractable for classical computers.
“A computation that would take 10,000 years on a classical supercomputer took 200 seconds on our quantum computer,” said Brooks Foxen, a graduate student researcher in the Martinis Group. “It is likely that the classical simulation time, currently estimated at 10,000 years, will be reduced by improved classical hardware and algorithms, but, since we are currently 1.5 trillion times faster, we feel comfortable laying claim to this achievement.”
The feat is outlined in a paper in the journal Nature.
The milestone comes after roughly two decades of quantum computing research conducted by Martinis and his group, from the development of a single superconducting qubit to systems including architectures of 72 and, with Sycamore, 54 qubits (one didn’t perform) that take advantage of the both awe-inspiring and bizarre properties of quantum mechanics.
“The algorithm was chosen to emphasize the strengths of the quantum computer by leveraging the natural dynamics of the device,” said Ben Chiaro, another graduate student researcher in the Martinis Group. That is, the researchers wanted to test the computer’s ability to hold and rapidly manipulate a vast amount of complex, unstructured data.
“We basically wanted to produce an entangled state involving all of our qubits as quickly as we can,” Foxen said, “and so we settled on a sequence of operations that produced a complicated superposition state that, when measured, returns bitstring with a probability determined by the specific sequence of operations used to prepare that particular superposition. The exercise, which was to verify that the circuit’s output correspond to the equence used to prepare the state, sampled the quantum circuit a million times in just a few minutes, exploring all possibilities — before the system could lose its quantum coherence.
‘A complex superposition state’
“We performed a fixed set of operations that entangles 53 qubits into a complex superposition state,” Chiaro explained. “This superposition state encodes the probability distribution. For the quantum computer, preparing this superposition state is accomplished by applying a sequence of tens of control pulses to each qubit in a matter of microseconds. We can prepare and then sample from this distribution by measuring the qubits a million times in 200 seconds.”
“For classical computers, it is much more difficult to compute the outcome of these operations because it requires computing the probability of being in any one of the 2^53 possible states, where the 53 comes from the number of qubits — the exponential scaling is why people are interested in quantum computing to begin with,” Foxen said. “This is done by matrix multiplication, which is expensive for classical computers as the matrices become large.”
According to the new paper, the researchers used a method called cross-entropy benchmarking to compare the quantum circuit’s output (a “bitstring”) to its “corresponding ideal probability computed via simulation on a classical computer” to ascertain that the quantum computer was working correctly.
“We made a lot of design choices in the development of our processor that are really advantageous,” said Chiaro. Among these advantages, he said, are the ability to experimentally tune the parameters of the individual qubits as well as their interactions.
While the experiment was chosen as a proof-of-concept for the computer, the research has resulted in a very real and valuable tool: a certified random number generator. Useful in a variety of fields, random numbers can ensure that encrypted keys can’t be guessed, or that a sample from a larger population is truly representative, leading to optimal solutions for complex problems and more robust machine learning applications. The speed with which the quantum circuit can produce its randomized bit string is so great that there is no time to analyze and “cheat” the system.
“Quantum mechanical states do things that go beyond our day-to-day experience and so have the potential to provide capabilities and application that would otherwise be unattainable,” commented Joe Incandela, UC Santa Barbara’s vice chancellor for research. “The team has demonstrated the ability to reliably create and repeatedly sample complicated quantum states involving 53 entangled elements to carry out an exercise that would take millennia to do with a classical supercomputer. This is a major accomplishment. We are at the threshold of a new era of knowledge acquisition.”
With an achievement like “quantum supremacy,” it’s tempting to think that the UC Santa Barbara/Google researchers will plant their flag and rest easy. But for Foxen, Chiaro, Martinis and the rest of the UCSB/Google AI Quantum group, this is just the beginning.
“It’s kind of a continuous improvement mindset,” Foxen said. “There are always projects in the works.” In the near term, further improvements to these “noisy” qubits may enable the simulation of interesting phenomena in quantum mechanics, such as thermalization, or the vast amount of possibility in the realms of materials and chemistry.
In the long term, however, the scientists are always looking to improve coherence times, or, at the other end, to detect and fix errors, which would take many additional qubits per qubit being checked. These efforts have been running parallel to the design and build of the quantum computer itself, and ensure the researchers have a lot of work before hitting their next milestone.
“It’s been an honor and a pleasure to be associated with this team,” Chiaro said. “It’s a great collection of strong technical contributors with great leadership and the whole team really synergizes well.”
Here’s a link to and a citation for the paper,
Quantum supremacy using a programmable superconducting processor by Frank Arute, Kunal Arya, Ryan Babbush, Dave Bacon, Joseph C. Bardin, Rami Barends, Rupak Biswas, Sergio Boixo, Fernando G. S. L. Brandao, David A. Buell, Brian Burkett, Yu Chen, Zijun Chen, Ben Chiaro, Roberto Collins, William Courtney, Andrew Dunsworth, Edward Farhi, Brooks Foxen, Austin Fowler, Craig Gidney, Marissa Giustina, Rob Graff, Keith Guerin, Steve Habegger, Matthew P. Harrigan, Michael J. Hartmann, Alan Ho, Markus Hoffmann, Trent Huang, Travis S. Humble, Sergei V. Isakov, Evan Jeffrey, Zhang Jiang, Dvir Kafri, Kostyantyn Kechedzhi, Julian Kelly, Paul V. Klimov, Sergey Knysh, Alexander Korotkov, Fedor Kostritsa, David Landhuis, Mike Lindmark, Erik Lucero, Dmitry Lyakh, Salvatore Mandrà, Jarrod R. McClean, Matthew McEwen, Anthony Megrant, Xiao Mi, Kristel Michielsen, Masoud Mohseni, Josh Mutus, Ofer Naaman, Matthew Neeley, Charles Neill, Murphy Yuezhen Niu, Eric Ostby, Andre Petukhov, John C. Platt, Chris Quintana, Eleanor G. Rieffel, Pedram Roushan, Nicholas C. Rubin, Daniel Sank, Kevin J. Satzinger, Vadim Smelyanskiy, Kevin J. Sung, Matthew D. Trevithick, Amit Vainsencher, Benjamin Villalonga, Theodore White, Z. Jamie Yao, Ping Yeh, Adam Zalcman, Hartmut Neven & John M. Martinis. Nature volume 574, pages505–510 (2019) DOI: https://doi.org/10.1038/s41586-019-1666-5 Issue Date 24 October 2019
Weaving a quantum processor from light is a jaw-dropping event (as far as I’m concerned). An October 17, 2019 news item on phys.org makes the announcement,
An international team of scientists from Australia, Japan and the United States has produced a prototype of a large-scale quantum processor made of laser light.
Based on a design ten years in the making, the processor has built-in scalability that allows the number of quantum components—made out of light—to scale to extreme numbers. The research was published in Science today [October 18, 2019; Note: I cannot explain the discrepancy between the dates]].
Quantum computers promise fast solutions to hard problems, but to do this they require a large number of quantum components and must be relatively error free. Current quantum processors are still small and prone to errors. This new design provides an alternative solution, using light, to reach the scale required to eventually outperform classical computers on important problems.
“While today’s quantum processors are impressive, it isn’t clear if the current designs can be scaled up to extremely large sizes,” notes Dr Nicolas Menicucci, Chief Investigator at the Centre for Quantum Computation and Communication Technology (CQC2T) at RMIT University in Melbourne, Australia.
“Our approach starts with extreme scalability – built in from the very beginning – because the processor, called a cluster state, is made out of light.”
Using light as a quantum processor
A cluster state is a large collection of entangled quantum components that performs quantum computations when measured in a particular way.
“To be useful for real-world problems, a cluster state must be both large enough and have the right entanglement structure. In the two decades since they were proposed, all previous demonstrations of cluster states have failed on one or both of these counts,” says Dr Menicucci. “Ours is the first ever to succeed at both.”
To make the cluster state, specially designed crystals convert ordinary laser light into a type of quantum light called squeezed light, which is then weaved into a cluster state by a network of mirrors, beamsplitters and optical fibres.
The team’s design allows for a relatively small experiment to generate an immense two-dimensional cluster state with scalability built in. Although the levels of squeezing – a measure of quality – are currently too low for solving practical problems, the design is compatible with approaches to achieve state-of-the-art squeezing levels.
The team says their achievement opens up new possibilities for quantum computing with light.
“In this work, for the first time in any system, we have made a large-scale cluster state whose structure enables universal quantum computation.” Says Dr Hidehiro Yonezawa, Chief Investigator, CQC2T at UNSW Canberra. “Our experiment demonstrates that this design is feasible – and scalable.”
The experiment was an international effort, with the design developed through collaboration by Dr Menicucci at RMIT, Dr Rafael Alexander from the University of New Mexico and UNSW Canberra researchers Dr Hidehiro Yonezawa and Dr Shota Yokoyama. A team of experimentalists at the University of Tokyo, led by Professor Akira Furusawa, performed the ground-breaking experiment.
Here’s a link to and a citation for the paper,
Generation of time-domain-multiplexed two-dimensional cluster state by Warit Asavanant, Yu Shiozawa, Shota Yokoyama, Baramee Charoensombutamon, Hiroki Emura, Rafael N. Alexander, Shuntaro Takeda, Jun-ichi Yoshikawa, Nicolas C. Menicucci, Hidehiro Yonezawa, Akira Furusawa. Science 18 Oct 2019: Vol. 366, Issue 6463, pp. 373-376 DOI: 10.1126/science.aay2645
Researchers at Columbia University and University of California, San Diego, have introduced a novel “multi-messenger” approach to quantum physics that signifies a technological leap in how scientists can explore quantum materials.
The findings appear in a recent article published in Nature Materials, led by A. S. McLeod, postdoctoral researcher, Columbia Nano Initiative, with co-authors Dmitri Basov and A. J. Millis at Columbia and R.A. Averitt at UC San Diego.
“We have brought a technique from the inter-galactic scale down to the realm of the ultra-small,” said Basov, Higgins Professor of Physics and Director of the Energy Frontier Research Center at Columbia. Equipped with multi-modal nanoscience tools we can now routinely go places no one thought would be possible as recently as five years ago.”
The work was inspired by “multi-messenger” astrophysics, which emerged during the last decade as a revolutionary technique for the study of distant phenomena like black hole mergers. Simultaneous measurements from instruments, including infrared, optical, X-ray and gravitational-wave telescopes can, taken together, deliver a physical picture greater than the sum of their individual parts.
The search is on for new materials that can supplement the current reliance on electronic semiconductors. Control over material properties using light can offer improved functionality, speed, flexibility and energy efficiency for next-generation computing platforms.
Experimental papers on quantum materials have typically reported results obtained by using only one type of spectroscopy. The researchers have shown the power of using a combination of measurement techniques to simultaneously examine electrical and optical properties.
The researchers performed their experiment by focusing laser light onto the sharp tip of a needle probe coated with magnetic material. When thin films of metal oxide are subject to a unique strain, ultra-fast light pulses can trigger the material to switch into an unexplored phase of nanometer-scale domains, and the change is reversible.
By scanning the probe over the surface of their thin film sample, the researchers were able to trigger the change locally and simultaneously manipulate and record the electrical, magnetic and optical properties of these light-triggered domains with nanometer-scale precision.
The study reveals how unanticipated properties can emerge in long-studied quantum materials at ultra-small scales when scientists tune them by strain.
“It is relatively common to study these nano-phase materials with scanning probes. But this is the first time an optical nano-probe has been combined with simultaneous magnetic nano-imaging, and all at the very low temperatures where quantum materials show their merits,” McLeod said. “Now, investigation of quantum materials by multi-modal nanoscience offers a means to close the loop on programs to engineer them.”
The work was done jointly by the US National Institute of Standards and Technology (NIST) and JILA (Joint Institute for Laboratory Astrophysics), which is operated ‘jointly’ by NIST and the University of Colorado. On to buckyballs, a nickname for buckminsterfullerenes or C60.
JILA researchers have measured hundreds of individual quantum energy levels in the buckyball, a spherical cage of 60 carbon atoms. It’s the largest molecule that has ever been analyzed at this level of experimental detail in the history of quantum mechanics. Fully understanding and controlling this molecule’s quantum details could lead to new scientific fields and applications, such as an entire quantum computer contained in a single buckyball.
There are two types of spherical objects in the image: the smooth blue ones, which are not buckyballs, and the ones with ridged spheres, which are.
The buckyball, formally known as buckminsterfullerene, is extremely complex. Due to its enormous 60-atom size, the overall molecule has a staggeringly high number of ways to vibrate–at least 100,000,000,000,000,000,000,000,000 vibrational quantum states when the molecule is warm. That’s in addition to the many different energy states for the buckyball’s rotation and other properties.
As described in the January 4  issue of Science, the JILA team used an updated version of their frequency comb spectroscopy and cryogenic buffer gas cooling system to observe isolated, individual energy transitions among rotational and vibrational states in cold, gaseous buckyballs. This is the first time anyone has been able to prepare buckyballs in this form to analyze its rotations and vibrations at the quantum level.
JILA is jointly operated by the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder.
Buckyballs, first discovered in 1984, have created great scientific excitement. But high-resolution spectroscopy, which can reveal the details of the molecule’s rotational and vibrational properties, didn’t work at ordinary room temperatures because the signals were too congested, NIST/JILA Fellow Jun Ye said. Low temperatures (about -138 degrees Celsius, which is -216 degrees Fahrenheit) enabled researchers to concentrate the molecules into a single rotational-vibrational quantum state at the lowest energy level and probe them with high-resolution spectroscopy.
The buckyball is the most symmetric molecule known, with a soccer-ball-like shape known as a modified icosahedron. It is small enough to be fully understood with basic quantum mechanics principles. Yet it is large enough to reveal insights into the extreme quantum complexity that emerges in huge systems.
As an example of practical applications, buckyballs could act as a pristine network of 60 atoms. The core of each atom possesses an identical property known as “nuclear spin,” which enables it to interact magnetically with its environment. Therefore, each spin could act as a magnetically controlled quantum bit or “qubit” in a quantum computer.
“If we had a buckyball made of pure isotopic carbon-13, each atom would have a nuclear spin of 1/2, and each buckyball could serve as a 60-qubit quantum computer,” Ye said. “Of course, we don’t have such capabilities yet; we would need to first capture these buckyballs in traps.”
A key part of the new quantum revolution, a quantum computer using qubits made of atoms or other materials could potentially solve important problems that are intractable using today’s machines. NIST has a major stake in quantum science
“There are also a lot of astrophysics connections,” Ye continued. “There are abundant buckyball signals coming from remote carbon stars,” so the new data will enable scientists to better understand the universe.
After they measured the quantum energy levels, the JILA researchers collected statistics on buckyballs’ nuclear spin values. They confirmed that all 60 atoms were indistinguishable, or virtually identical. Precise measurements of the buckyball’s transition energies between individual quantum states revealed its atoms interacted strongly with one another, providing insights into the complexities of its molecular structure and the forces between atoms.
For the experiments, an oven converted a solid sample of material into gaseous buckyballs. These hot molecules flowed into a cell (container) anchored to a cryogenic cold apparatus, such that the molecules were cooled by collisions with cold argon gas atoms. Then laser light at precise frequencies was aimed at the cold gas molecules, and researchers measured how much light was absorbed. The observed structure in the infrared spectrum encoded details of the quantum-mechanical energy-level structure.
The laser light was produced by an optical frequency comb, or “ruler of light,” and aimed into an optical cavity surrounding the cold cell to enhance the absorption signals. The comb contained about 1000 “teeth” at optical frequencies spanning the full band of buckyball vibrations. The comb light was generated from a single fiber laser.
It sounds like an old-school vinyl record, but the distinctive crackle in the music streamed into Chris Holloway’s laboratory is atomic in origin. The group at the National Institute for Standards and Technology, Boulder, Colorado, spent a long six years finding a way to directly measure electric fields using atoms, so who can blame them for then having a little fun with their new technology?
“My vision is to cut a CD in the lab — our studio — at some point and have the first CD recorded with Rydberg atoms,” said Holloway. While he doesn’t expect the atomic-recording’s lower sound quality to replace digital music recordings, the team of research scientists is considering how this “entertaining” example of atomic sensing could be applied in communication devices of the future.
“Atom-based antennas might give us a better way of picking up audio data in the presence of noise, potentially even the very weak signals transmitted in deep space communications,” said Holloway, who describes his atomic receiver in AIP Advances, from AIP Publishing.
The atoms in question — Rydberg atoms — are atoms excited by lasers into a high energy state that responds in a measurable way to radio waves (an electric field). After figuring out how to measure electric field strength using the Rydberg atoms, Holloway said it was a relatively simple step to apply the same atoms to record and play back music — starting with Holloway’s own guitar improvisations in A minor.
They encoded the music onto radio waves in much the same way cellphone conversations are encoded onto radio waves for transmission. The atoms respond to these radio waves, and in turn, the laser beams shined through the Rydberg atoms are affected. These changes are picked up on a photodetector, which feeds an electric signal into the speaker or computer — and voila! The atomic radio was born
The team used their quantum system to pick up stereo — with one atomic species recording the instrumental and another the vocal at two different sets of laser frequencies. They selected a Queen track — “Under Pressure” — to test if their system could handle Freddie Mercury’s extensive vocal range.
“One of the reasons for cutting stereo was to show that this one receiver can pick up two channels simultaneously, which is difficult with conventional receivers,” said Holloway, who explained that although it is the early days for atomic communications, there is potential to use this to improve the security of communications.
For now, Holloway’s team are staying tuned into atomic radio as they try to determine how weak a signal the Rydberg atoms can detect, and what data transfer speeds can be achieved.
They are not forgetting the atomic record they want to produce, with which they hope to inspire the next generation of quantum scientists.
A new performance that explores the world of quantum physics will feature the music of the Jupiter String Quartet, a fire juggler and a fantastical “Alice in Quantumland” scene.
“Quantum Rhapsodies,” the vision of physics professor Smitha Vishveshwara, looks at the foundational developments in quantum physics, the role it plays in our world and in technology such as the MRI, and the quantum mysteries that remain unanswered.
“The quantum world is a world that inspires awe, but it’s also who we are and what we are made of,” said Vishveshwara, who wrote the piece and guided the visuals.
The performance will premiere April 10  as part of the 30th anniversary celebration of the Beckman Institute for Advanced Science and Technology. The event begins with a 5 p.m. reception, followed by the performance at 6 p.m. and a meet-and-greet with the show’s creators at 7 p.m. The performance will be in the atrium of the Beckman Institute, 405 N. Mathews Ave., Urbana, [emphases mine] and it is free and open to the public. While the available seating is filling up, the atrium space will allow for an immersive experience in spite of potentially restricted viewing.
The production is a sister piece to “Quantum Voyages,” a performance created in 2018 by Vishveshwara and theatre professor Latrelle Bright to illustrate the basic concepts of quantum physics. It was performed at a quantum physics conference celebrating Nobel Prize-winning physicist Anthony Leggett’s 80th birthday in 2018.
While “Quantum Voyages” was a live theater piece, “Quantum Rhapsodies” combines narration by Bright, video images and live music from the Jupiter String Quartet. It ponders the wonder of the cosmos, the nature of light and matter, and the revolutionary ideas of quantum physics. A central part of the narrative involves the theory of Nobel Prize-winning French physicist Louis de Broglie that matter, like light, can behave as a wave.
The visuals – a blend of still images, video and animation – were created by a team consisting of the Beckman Visualization Laboratory; Steven Drake, a video producer at Beckman; filmmaker Nic Morse of Protagonist Pizza Productions; and members of a class Vishveshwara teaches, Where the Arts Meet Physics.
The biggest challenge in illustrating the ideas in the script was conveying the scope of the piece, from the galactic scale of the cosmos to the subatomic scale of the quantum world, Drake said. The concepts of quantum physics “are not something you can see. It’s theoretical or so small you can’t put it under a microscope or go out into the real world and film it,” he said.
Much of the work involved finding images, both scientific and artistic, that would help illustrate the concepts of the piece and complement the poetic language that Vishveshwara used, as well as the music.
Students and teaching assistant Danielle Markovich from Vishveshwara’s class contributed scientific images and original paintings. Drake used satellite images from the Hubble Space Telescope and other satellites, as well as animation created by the National Center for Supercomputing Applications in its work with NASA, for portions of the script talking about the cosmos. The Visualization Laboratory provided novel scientific visualizations.
“What we’re good at doing and have done for years is taking research content and theories and visualizing that information. We do that for a very wide variety of research and data. We’re good at coming up with images that represent these invisible worlds, like quantum physics,” said Travis Ross, the director of the lab.
Some ideas required conceptual images, such as footage by Morse of a fire juggler at Allerton Park to represent light and of hands moving to depict the rotational behavior of water-based hydrogen within a person in an MRI machine.
Motion was incorporated into a painting of a lake to show water rippling and light flickering across it to illustrate light waves. In the “Alice in Quantumland” sequence, a Mad Hatter’s tea party filmed at the Illini Union was blended with cartoonlike animated elements into the fantasy sequence by Jose Vazquez, an illustrator and concept artist who works in the Visualization Lab.
“Our main objective is making sure we’re representing it in a believable way that’s also fun and engaging,” Ross said. “We’ve never done anything quite like this. It’s pretty unique.”
In addition to performing the score, members of the Jupiter String Quartet were the musical directors, creating the musical narrative to mesh with the script. The music includes contemplative compositions by Beethoven to evoke the cosmos and playful modern compositions that summon images of the movements of particles and waves.
“I was working with such talented people and creative minds, and we had fun and came up with these seemingly absurd ideas. But then again, it’s like that with the quantum world as well,” Vishveshwara said.
“My hope is not necessarily for people to understand everything, but to infuse curiosity and to feel the grandness and the beauty that is part of who we are and the cosmos that we live in,” she said..
Here’s a preview of this free public performance,
How to look at SciArt (also known as, art/science depending on your religion)
There’s an intriguing April 8, 2019 post on the Science Borealis blog by Katrina Vera Wong and Raymond Nakamura titled: How to look at (and appreciate) SciArt,
The recent #SciArt #TwitterStorm, in which participants tweeted their own sciart and retweeted that of others, illustrated the diversity of approaches to melding art and science. With all this work out there, what can we do, as advocates of art and science, to better appreciate sciart? We’d like to foster interest in, and engagement with, sciart so that its value goes beyond how much it costs or how many likes it gets.
An article by Kit Messham-Muir based on the work of art historian Erwin Panofsky outlines a three-step strategy for looking at art: Look. See. Think. Looking is observing what the elements are. Seeing draws meaning from it. Thinking links personal experience and accessible information to the piece at hand.
Looking and seeing is also part of the Visual Thinking Strategies (VTS) method originally developed for looking at art and subsequently applied to science and other subjects as a social, object-oriented learning process. It begins by asking, “What is going on here?”, followed by “What do you see that makes you think that?” This allows learners of different backgrounds to participate and encourages the pursuit of evidence to back up opinions.
Let’s see how these approaches might work on your own or in conversation. Take, for example, the following work by natural history illustrator Julius Csotonyi:
I hope some of our Vancouver-based (Canada) art critics get a look at some of this material. I read a review a few years ago and the critic seemed intimidated by the idea of looking at work that explicitly integrated and reflected on science. Since that time (Note: there aren’t that many art reviewers here), I have not seen another attempt by an art critic.
Thermodynamics is one of the most human of scientific enterprises, according to Kater Murch, associate professor of physics in Arts & Sciences at Washington University in St. Louis.
“It has to do with our fascination of fire and our laziness,” he said. “How can we get fire” — or heat — “to do work for us?”
Now, Murch and colleagues have taken that most human enterprise down to the intangible quantum scale — that of ultra low temperatures and microscopic systems — and discovered that, as in the macroscopic world, it is possible to use information to extract work.
There is a catch, though: Some information may be lost in the process.
“We’ve experimentally confirmed the connection between information in the classical case and the quantum case,” Murch said, “and we’re seeing this new effect of information loss.”
The international team included Eric Lutz of the University of Stuttgart; J. J. Alonzo of the University of Erlangen-Nuremberg; Alessandro Romito of Lancaster University; and Mahdi Naghiloo, a Washington University graduate research assistant in physics.
That we can get energy from information on a macroscopic scale was most famously illustrated in a thought experiment known as Maxwell’s Demon. [emphasis mine] The “demon” presides over a box filled with molecules. The box is divided in half by a wall with a door. If the demon knows the speed and direction of all of the molecules, it can open the door when a fast-moving molecule is moving from the left half of the box to the right side, allowing it to pass. It can do the same for slow particles moving in the opposite direction, opening the door when a slow-moving molecule is approaching from the right, headed left.
After a while, all of the quickly-moving molecules are on the right side of the box. Faster motion corresponds to higher temperature. In this way, the demon has created a temperature imbalance, where one side of the box is hotter. That temperature imbalance can be turned into work — to push on a piston as in a steam engine, for instance. At first the thought experiment seemed to show that it was possible create a temperature difference without doing any work, and since temperature differences allow you to extract work, one could build a perpetual motion machine — a violation of the second law of thermodynamics.
“Eventually, scientists realized that there’s something about the information that the demon has about the molecules,” Murch said. “It has a physical quality like heat and work and energy.”
His team wanted to know if it would be possible to use information to extract work in this way on a quantum scale, too, but not by sorting fast and slow molecules. If a particle is in an excited state, they could extract work by moving it to a ground state. (If it was in a ground state, they wouldn’t do anything and wouldn’t expend any work).
But they wanted to know what would happen if the quantum particles were in an excited state and a ground state at the same time, analogous to being fast and slow at the same time. In quantum physics, this is known as a superposition.
“Can you get work from information about a superposition of energy states?” Murch asked. “That’s what we wanted to find out.”
There’s a problem, though. On a quantum scale, getting information about particles can be a bit … tricky.
“Every time you measure the system, it changes that system,” Murch said. And if they measured the particle to find out exactly what state it was in, it would revert to one of two states: excited, or ground.
This effect is called quantum backaction. To get around it, when looking at the system, researchers (who were the “demons”) didn’t take a long, hard look at their particle. Instead, they took what was called a “weak observation.” It still influenced the state of the superposition, but not enough to move it all the way to an excited state or a ground state; it was still in a superposition of energy states. This observation was enough, though, to allow the researchers track with fairly high accuracy, exactly what superposition the particle was in — and this is important, because the way the work is extracted from the particle depends on what superposition state it is in.
To get information, even using the weak observation method, the researchers still had to take a peek at the particle, which meant they needed light. So they sent some photons in, and observed the photons that came back.
“But the demon misses some photons,” Murch said. “It only gets about half. The other half are lost.” But — and this is the key — even though the researchers didn’t see the other half of the photons, those photons still interacted with the system, which means they still had an effect on it. The researchers had no way of knowing what that effect was.
They took a weak measurement and got some information, but because of quantum backaction, they might end up knowing less than they did before the measurement. On the balance, that’s negative information.
And that’s weird.
“Do the rules of thermodynamics for a macroscopic, classical world still apply when we talk about quantum superposition?” Murch asked. “We found that yes, they hold, except there’s this weird thing. The information can be negative.
“I think this research highlights how difficult it is to build a quantum computer,” Murch said.
“For a normal computer, it just gets hot and we need to cool it. In the quantum computer you are always at risk of losing information.”
A US-France-Germany collaboration has led to some intriguing work with carbon nanotubes. From a June 18, 2018 news item on ScienceDaily,
Researchers at Los Alamos and partners in France and Germany are exploring the enhanced potential of carbon nanotubes as single-photon emitters for quantum information processing. Their analysis of progress in the field is published in this week’s edition of the journal Nature Materials.
“We are particularly interested in advances in nanotube integration into photonic cavities for manipulating and optimizing light-emission properties,” said Stephen Doorn, one of the authors, and a scientist with the Los Alamos National Laboratory site of the Center for Integrated Nanotechnologies (CINT). “In addition, nanotubes integrated into electroluminescent devices can provide greater control over timing of light emission and they can be feasibly integrated into photonic structures. We are highlighting the development and photophysical probing of carbon nanotube defect states as routes to room-temperature single photon emitters at telecom wavelengths.”
The team’s overview was produced in collaboration with colleagues in Paris (Christophe Voisin [Ecole Normale Supérieure de Paris (ENS)]) who are advancing the integration of nanotubes into photonic cavities for modifying their emission rates, and at Karlsruhe (Ralph Krupke [Karlsruhe Institute of Technology (KIT]) where they are integrating nanotube-based electroluminescent devices with photonic waveguide structures. The Los Alamos focus is the analysis of nanotube defects for pushing quantum emission to room temperature and telecom wavelengths, he said.
As the paper notes, “With the advent of high-speed information networks, light has become the main worldwide information carrier. . . . Single-photon sources are a key building block for a variety of technologies, in secure quantum communications metrology or quantum computing schemes.”
The use of single-walled carbon nanotubes in this area has been a focus for the Los Alamos CINT team, where they developed the ability to chemically modify the nanotube structure to create deliberate defects, localizing excitons and controlling their release. Next steps, Doorn notes, involve integration of the nanotubes into photonic resonators, to provide increased source brightness and to generate indistinguishable photons. “We need to create single photons that are indistinguishable from one another, and that relies on our ability to functionalize tubes that are well-suited for device integration and to minimize environmental interactions with the defect sites,” he said.
“In addition to defining the state of the art, we wanted to highlight where the challenges are for future progress and lay out some of what may be the most promising future directions for moving forward in this area. Ultimately, we hope to draw more researchers into this field,” Doorn said.
Here’s a link to and a citation for the paper,
Carbon nanotubes as emerging quantum-light sources by X. He, H. Htoon, S. K. Doorn, W. H. P. Pernice, F. Pyatkov, R. Krupke, A. Jeantet, Y. Chassagneux & C. Voisin. Nature Materials (2018) DOI: https://doi.org/10.1038/s41563-018-0109-2 Published online June 18, 2018
It seems sound is becoming more prominent as a means of science data communication (data sonification) and in this upcoming case, data transfer. From a June 5, 2018 news item on ScienceDaily,
Quantum physics is on the brink of a technological breakthrough: new types of sensors, secure data transmission methods and maybe even computers could be made possible thanks to quantum technologies. However, the main obstacle here is finding the right way to couple and precisely control a sufficient number of quantum systems (for example, individual atoms).
A team of researchers from TU Wien and Harvard University has found a new way to transfer the necessary quantum information. They propose using tiny mechanical vibrations. The atoms are coupled with each other by ‘phonons’ — the smallest quantum mechanical units of vibrations or sound waves.
“We are testing tiny diamonds with built-in silicon atoms – these quantum systems are particularly promising,” says Professor Peter Rabl from TU Wien. “Normally, diamonds are made exclusively of carbon, but adding silicon atoms in certain places creates defects in the crystal lattice where quantum information can be stored.” These microscopic flaws in the crystal lattice can be used like a tiny switch that can be switched between a state of higher energy and a state of lower energy using microwaves.
Together with a team from Harvard University, Peter Rabl’s research group has developed a new idea to achieve the targeted coupling of these quantum memories within the diamond. One by one they can be built into a tiny diamond rod measuring only a few micrometres in length, like individual pearls on a necklace. Just like a tuning fork, this rod can then be made to vibrate – however, these vibrations are so small that they can only be described using quantum theory. It is through these vibrations that the silicon atoms can form a quantum-mechanical link to each other.
“Light is made from photons, the quantum of light. In the same way, mechanical vibrations or sound waves can also be described in a quantum-mechanical manner. They are comprised of phonons – the smallest possible units of mechanical vibration,” explains Peter Rabl. As the research team has now been able to show using simulation calculations, any number of these quantum memories can be linked together in the diamond rod thanks to these phonons. The individual silicon atoms are “switched on and off” using microwaves. During this process, they emit or absorb phonons. This creates a quantum entanglement of different silicon defects, thus allowing quantum information to be transferred.
The road to a scalable quantum network
Until now it was not clear whether something like this was even possible: “Usually you would expect the phonons to be absorbed somewhere, or to come into contact with the environment and thus lose their quantum mechanical properties,” says Peter Rabl. “Phonons are the enemy of quantum information, so to speak. But with our calculations, we were able to show that, when controlled appropriately using microwaves, the phonons are in fact useable for technical applications.”
The main advantage of this new technology lies in its scalability: “There are many ideas for quantum systems that, in principle, can be used for technological applications. The biggest problem is that it is very difficult to connect enough of them to be able to carry out complicated computing operations,” says Peter Rabl. The new strategy of using phonons for this purpose could pave the way to a scalable quantum technology.