Tag Archives: quantum

Academic and research collaboration to improve people to people contacts for peace and progress

Syed Faisal ur Rahman

Muslim world especially Middle East and surrounding regions, where we live, are facing some of the worst political turmoil of our history. We are seeing wars, terrorism, refugee crisis and resulting economic. The toughest calamities are faced by common people who have very little or no control over the policies which are resulting in the current mess. Worst thing which is happening is the exploitation of sectarianism as a tool to forward foreign policy and strategic agenda. Muslims in many parts of the world are criticizing western powers for this situation but we also need to seriously do some soul searching.

We need to see why are we in this mess?

For me one major reason is that OIC members have failed to find enough common constructive goals to bring their people together.

After the Second World War, Europe realized the importance of academic and economic cooperation for promoting peace and stability. CERN is a prime example of how formal foes can join hands for the purpose of discovery and innovation.

France and Germany have established common institutes and their universities regularly conduct joint research projects. UK and USA, despite enormous bloodshed the historical American war of independence, enjoy exemplary people to people relationships and academic collaboration is a major part of it. It is this attitude of thinking big, finding common constructive goals and strong academic collaboration, which has put them in the forefront of science and technology.

Over the last few decades, humanity has sent probes like Voyager which are challenging the limits of our solar system, countries are thinking about colonizing Mars, satellites like PLANCK and WMAP are tracking radiation from the early stages of our universe, quantum computing is now looking like a possibility and projects are being made for hyper-sonic flights. But in most of the so called Muslim world, we are stuck with centuries old and good for nothing sectarian issues.

Despite some efforts in the defense sector, OIC member countries largely lack the technology base to independently produce jets, automobiles, advanced electronics, precision instruments and many other things which are being produced by public or independent private sector companies in USA, China, Russia, Japan and Europe. Most of the things which are being indigenously produced by OIC countries rely heavily on foreign core components like engine or high precision electronics items. This is due to our lack of investment on fundamental research especially Physics.

OIC countries like Turkey, Pakistan, Malaysia, Iran, Saudi Arabia and some others have some basic infrastructure on which they can build upon to conduct research projects and joint ventures in areas like sending space probes, ground based optical and radio astronomy, particle physics, climate change and development of strong industrial technology base.  All we need is the will to start joint projects and promote knowledge sharing via exchange of researchers or joint academic and industrial research projects.

These joint projects will not only be helpful in enhancing people to people contacts and improving academic research standards but they will also contribute positively in the overall progress of humanity. It is a great loss for humanity as a whole that a civilization, which once led the efforts to develop astronomy, medicine and other key areas of science, is not making any or making very little contribution in advancing our understanding of the universe.

The situation is bad and if we look at Syria, Afghanistan, Iraq, Yemen or Libya then it seems we have hit the rock bottom. It is “Us” who need to find the way out of this mess as no one is going to solve our problems especially the current sectarian mess which is a result of narrow mindsets taking weak decisions. To come out of this dire state, we need broad minds with big vision and a desire of moving forward through mutual respect and understanding.

 

ight behaves both as a particle and as a wave. Since the days of Einstein, scientists have been trying to directly observe both of these aspects of light at the same time. Now, scientists at EPFL have succeeded in capturing the first-ever snapshot of this dual behavior.
Credit:EPFL

Entering 2016 with new hope

Syed Faisal ur Rahman


 

Year 2015 left many good and bad memories for many of us. On one hand we saw more wars, terrorist attacks and political confrontations, and on the other hand we saw humanity raising voices for peace, sheltering refugees and joining hands to confront the climate change.

In science, we saw first ever photograph of light as both wave and particle. We also saw some serious development in machine learning, data sciences and artificial intelligence areas with some voices raising caution about the takeover of AI over humanity and issues related to privacy. The big question of energy and climate change remained a key point of  discussion in scientific and political circles. The biggest break through came near the end of the year with Paris deal during COP21.

The deal involving around 200 countries represent a true spirit of humanity to limit global warming below 2C and commitments for striving to keep temperatures at above 1.5C pre-industrial levels. This truly global commitment also served in bringing rival countries to sit together for a common cause to save humanity from self destruction. I hope the spirit will continue in other areas of common interest as well.

This spectacular view from the NASA/ESA Hubble Space Telescope shows the rich galaxy cluster Abell 1689. The huge concentration of mass bends light coming from more distant objects and can increase their total apparent brightness and make them visible. One such object, A1689-zD1, is located in the box — although it is still so faint that it is barely seen in this picture. New observations with ALMA and ESO’s VLT have revealed that this object is a dusty galaxy seen when the Universe was just 700 million years old. Credit: NASA; ESA; L. Bradley (Johns Hopkins University); R. Bouwens (University of California, Santa Cruz); H. Ford (Johns Hopkins University); and G. Illingworth (University of California, Santa Cruz)
This spectacular view from the NASA/ESA Hubble Space Telescope shows the rich galaxy cluster Abell 1689. The huge concentration of mass bends light coming from more distant objects and can increase their total apparent brightness and make them visible. One such object, A1689-zD1, is located in the box — although it is still so faint that it is barely seen in this picture.
New observations with ALMA and ESO’s VLT have revealed that this object is a dusty galaxy seen when the Universe was just 700 million years old.
Credit:
NASA; ESA; L. Bradley (Johns Hopkins University); R. Bouwens (University of California, Santa Cruz); H. Ford (Johns Hopkins University); and G. Illingworth (University of California, Santa Cruz)

Space Sciences also saw some enormous advancements with New Horizon sending photographs from Pluto, SpaceX successfully landed the reusable Falcon 9 rocket back after a successful launch and we also saw the discovery of the largest regular formation in the Universe,by Prof Lajos Balazs, which is a ring of nine galaxies 7 billion light years away and 5 billion light years wide covering a third of our sky.We also learnt this year that Mars once had more water than Earth’s Arctic Ocean. NASA later confirmed the evidence that water flows on the surface of Mars. The announcement led to some interesting insight into the atmospheric studies and history of the red planet.

In the researchers' new system, a returning beam of light is mixed with a locally stored beam, and the correlation of their phase, or period of oscillation, helps remove noise caused by interactions with the environment. Illustration: Jose-Luis Olivares/MIT
In the researchers’ new system, a returning beam of light is mixed with a locally stored beam, and the correlation of their phase, or period of oscillation, helps remove noise caused by interactions with the environment.
Illustration: Jose-Luis Olivares/MIT

We also saw some encouraging advancements in neurosciences where we saw MIT’s researchers  developing a technique allowing direct stimulation of neurons, which could be an effective treatment for a variety of neurological diseases, without the need for implants or external connections. We also saw researchers reactivating neuro-plasticity in older mice, restoring their brains to a younger state and we also saw some good progress in combating Alzheimer’s diseases.

Quantum physics again stayed as a key area of scientific advancements. Quantu

ight behaves both as a particle and as a wave. Since the days of Einstein, scientists have been trying to directly observe both of these aspects of light at the same time. Now, scientists at EPFL have succeeded in capturing the first-ever snapshot of this dual behavior. Credit:EPFL
ight behaves both as a particle and as a wave. Since the days of Einstein, scientists have been trying to directly observe both of these aspects of light at the same time. Now, scientists at EPFL have succeeded in capturing the first-ever snapshot of this dual behavior.
Credit:EPFL

m computing is getting more closer to become a viable alternative to current architecture. The packing of the single-photon detectors on an optical chip is a crucial step toward quantum-computational circuits. Researchers at the Australian National University (ANU)  performed experiment to prove that reality does not exist until it is measured.

There are many other areas where science and technology reached new heights and will hopefully continue to do so in the year 2016. I hope these advancements will not only help us in growing economically but also help us in becoming better human beings and a better society.

 

 

 

 

 

Researchers use engineered viruses to provide quantum-based enhancement of energy transport:MIT Research

Quantum physics meets genetic engineering

Researchers use engineered viruses to provide quantum-based enhancement of energy transport.

By David Chandler


 

CAMBRIDGE, Mass.–Nature has had billions of years to perfect photosynthesis, which directly or indirectly supports virtually all life on Earth. In that time, the process has achieved almost 100 percent efficiency in transporting the energy of sunlight from receptors to reaction centers where it can be harnessed — a performance vastly better than even the best solar cells.

One way plants achieve this efficiency is by making use of the exotic effects of quantum mechanics — effects sometimes known as “quantum weirdness.” These effects, which include the ability of a particle to exist in more than one place at a time, have now been used by engineers at MIT to achieve a significant efficiency boost in a light-harvesting system.

Surprisingly, the MIT researchers achieved this new approach to solar energy not with high-tech materials or microchips — but by using genetically engineered viruses.

This achievement in coupling quantum research and genetic manipulation, described this week in the journal Nature Materials, was the work of MIT professors Angela Belcher, an expert on engineering viruses to carry out energy-related tasks, and Seth Lloyd, an expert on quantum theory and its potential applications; research associate Heechul Park; and 14 collaborators at MIT and in Italy.

Lloyd, a professor of mechanical engineering, explains that in photosynthesis, a photon hits a receptor called a chromophore, which in turn produces an exciton — a quantum particle of energy. This exciton jumps from one chromophore to another until it reaches a reaction center, where that energy is harnessed to build the molecules that support life.

But the hopping pathway is random and inefficient unless it takes advantage of quantum effects that allow it, in effect, to take multiple pathways at once and select the best ones, behaving more like a wave than a particle.

This efficient movement of excitons has one key requirement: The chromophores have to be arranged just right, with exactly the right amount of space between them. This, Lloyd explains, is known as the “Quantum Goldilocks Effect.”

That’s where the virus comes in. By engineering a virus that Belcher has worked with for years, the team was able to get it to bond with multiple synthetic chromophores — or, in this case, organic dyes. The researchers were then able to produce many varieties of the virus, with slightly different spacings between those synthetic chromophores, and select the ones that performed best.

In the end, they were able to more than double excitons’ speed, increasing the distance they traveled before dissipating — a significant improvement in the efficiency of the process.

The project started from a chance meeting at a conference in Italy. Lloyd and Belcher, a professor of biological engineering, were reporting on different projects they had worked on, and began discussing the possibility of a project encompassing their very different expertise. Lloyd, whose work is mostly theoretical, pointed out that the viruses Belcher works with have the right length scales to potentially support quantum effects.

In 2008, Lloyd had published a paper demonstrating that photosynthetic organisms transmit light energy efficiently because of these quantum effects. When he saw Belcher’s report on her work with engineered viruses, he wondered if that might provide a way to artificially induce a similar effect, in an effort to approach nature’s efficiency.

“I had been talking about potential systems you could use to demonstrate this effect, and Angela said, ‘We’re already making those,’” Lloyd recalls. Eventually, after much analysis, “We came up with design principles to redesign how the virus is capturing light, and get it to this quantum regime.”

Within two weeks, Belcher’s team had created their first test version of the engineered virus. Many months of work then went into perfecting the receptors and the spacings.

Once the team engineered the viruses, they were able to use laser spectroscopy and dynamical modeling to watch the light-harvesting process in action, and to demonstrate that the new viruses were indeed making use of quantum coherence to enhance the transport of excitons.

“It was really fun,” Belcher says. “A group of us who spoke different [scientific] languages worked closely together, to both make this class of organisms, and analyze the data. That’s why I’m so excited by this.”

While this initial result is essentially a proof of concept rather than a practical system, it points the way toward an approach that could lead to inexpensive and efficient solar cells or light-driven catalysis, the team says. So far, the engineered viruses collect and transport energy from incoming light, but do not yet harness it to produce power (as in solar cells) or molecules (as in photosynthesis). But this could be done by adding a reaction center, where such processing takes place, to the end of the virus where the excitons end up.

The research was supported by the Italian energy company Eni through the MIT Energy Initiative. In addition to MIT postdocs Nimrod Heldman and Patrick Rebentrost, the team included researchers at the University of Florence, the University of Perugia, and Eni.

Source:MIT News Office

Physicists solve quantum tunneling mystery

An international team of scientists studying ultrafast physics have solved a mystery of quantum mechanics, and found that quantum tunneling is an instantaneous process.

The new theory could lead to faster and smaller electronic components, for which quantum tunneling is a significant factor. It will also lead to a better understanding of diverse areas such as electron microscopy, nuclear fusion and DNA mutations.

“Timescales this short have never been explored before. It’s an entirely new world,” said one of the international team, Professor Anatoli Kheifets, from The Australian National University (ANU).

“We have modelled the most delicate processes of nature very accurately.”

At very small scales quantum physics shows that particles such as electrons have wave-like properties – their exact position is not well defined. This means they can occasionally sneak through apparently impenetrable barriers, a phenomenon called quantum tunneling.

Quantum tunneling plays a role in a number of phenomena, such as nuclear fusion in the sun, scanning tunneling microscopy, and flash memory for computers. However, the leakage of particles also limits the miniaturisation of electronic components.

Professor Kheifets and Dr. Igor Ivanov, from the ANU Research School of Physics and Engineering, are members of a team which studied ultrafast experiments at the attosecond scale (10-18 seconds), a field that has developed in the last 15 years.

Until their work, a number of attosecond phenomena could not be adequately explained, such as the time delay when a photon ionised an atom.

“At that timescale the time an electron takes to quantum tunnel out of an atom was thought to be significant. But the mathematics says the time during tunneling is imaginary – a complex number – which we realised meant it must be an instantaneous process,” said Professor Kheifets.

“A very interesting paradox arises, because electron velocity during tunneling may become greater than the speed of light. However, this does not contradict the special theory of relativity, as the tunneling velocity is also imaginary” said Dr Ivanov, who recently took up a position at the Center for Relativistic Laser Science in Korea.

The team’s calculations, which were made using the Raijin supercomputer, revealed that the delay in photoionisation originates not from quantum tunneling but from the electric field of the nucleus attracting the escaping electron.

The results give an accurate calibration for future attosecond-scale research, said Professor Kheifets.

“It’s a good reference point for future experiments, such as studying proteins unfolding, or speeding up electrons in microchips,” he said.

The research is published in Nature Physics.

Source: ANU

Experiment confirms quantum theory weirdness

The bizarre nature of reality as laid out by quantum theory has survived another test, with scientists performing a famous experiment and proving that reality does not exist until it is measured.

Physicists at The Australian National University (ANU) have conducted John Wheeler’s delayed-choice thought experiment, which involves a moving object that is given the choice to act like a particle or a wave. Wheeler’s experiment then asks – at which point does the object decide?

Common sense says the object is either wave-like or particle-like, independent of how we measure it. But quantum physics predicts that whether you observe wave like behavior (interference) or particle behavior (no interference) depends only on how it is actually measured at the end of its journey. This is exactly what the ANU team found.

“It proves that measurement is everything. At the quantum level, reality does not exist if you are not looking at it,” said Associate Professor Andrew Truscott from the ANU Research School of Physics and Engineering.

Despite the apparent weirdness, the results confirm the validity of quantum theory, which governs the world of the very small, and has enabled the development of many technologies such as LEDs, lasers and computer chips.

The ANU team not only succeeded in building the experiment, which seemed nearly impossible when it was proposed in 1978, but reversed Wheeler’s original concept of light beams being bounced by mirrors, and instead used atoms scattered by laser light.

“Quantum physics’ predictions about interference seem odd enough when applied to light, which seems more like a wave, but to have done the experiment with atoms, which are complicated things that have mass and interact with electric fields and so on, adds to the weirdness,” said Roman Khakimov, PhD student at the Research School of Physics and Engineering.

Professor Truscott’s team first trapped a collection of helium atoms in a suspended state known as a Bose-Einstein condensate, and then ejected them until there was only a single atom left.

The single atom was then dropped through a pair of counter-propagating laser beams, which formed a grating pattern that acted as crossroads in the same way a solid grating would scatter light.

A second light grating to recombine the paths was randomly added, which led to constructive or destructive interference as if the atom had travelled both paths. When the second light grating was not added, no interference was observed as if the atom chose only one path.

However, the random number determining whether the grating was added was only generated after the atom had passed through the crossroads.

If one chooses to believe that the atom really did take a particular path or paths then one has to accept that a future measurement is affecting the atom’s past, said Truscott.

“The atoms did not travel from A to B. It was only when they were measured at the end of the journey that their wave-like or particle-like behavior was brought into existence,” he said.

The research is published in Nature Physics.

Source: ANU

A cartoon illustration of a levitated drop of superfluid helium. A single photon circulating inside the drop (red arrow) will be used to produce the superposition. The drop's gravitational field (illustrated schematically in the background) may play a role in limiting the lifetime of such a superposition.

Credit: Yale News

Opening a window on quantum gravity

Yale University has received a grant from the W. M. Keck Foundation to fund experiments that researchers hope will provide new insights into quantum gravity. Jack Harris, associate professor of physics, will lead a Yale team that aims to address a long-standing question in physics — how the classical behavior of macroscopic objects emerges from microscopic constituents that obey the laws of quantum mechanics.

Very small objects like photons and electrons are known for their odd behavior. Thanks to the laws of quantum mechanics, they can act as particles or waves, appear in multiple places at once, and mysteriously interact over great distances. The question is why these behaviors are not observed in larger objects.

A cartoon illustration of a levitated drop of superfluid helium. A single photon circulating inside the drop (red arrow) will be used to produce the superposition. The drop's gravitational field (illustrated schematically in the background) may play a role in limiting the lifetime of such a superposition. Credit: Yale News
A cartoon illustration of a levitated drop of superfluid helium. A single photon circulating inside the drop (red arrow) will be used to produce the superposition. The drop’s gravitational field (illustrated schematically in the background) may play a role in limiting the lifetime of such a superposition.
Credit: Yale News

Scientists know that friction plays an important part in producing classical behavior in macroscopic objects, but many suspect that gravity also suppresses quantum effects. Unfortunately, there has been no practical way to test this possibility, and in the absence of a full quantum theory of gravity, it is difficult even to make any quantitative predictions.

To address this problem, Harris will create a novel instrument that will enable a drop of liquid helium to exhibit quantum mechanical effects. “A millimeter across,” Harris said, “our droplet will be five orders of magnitude more massive than any other object in which quantum effects have been observed. It will enable us to explore quantum behavior on unprecedentedly macroscopic scales and to provide the first experimental tests of leading models of gravity at the quantum level.”

Game-changing research

The W.M. Keck Foundation grant will fund five years of activity at the Harris lab, which is part of Yale’s Department of Physics. In the first year, Harris and his team will construct their apparatus, and in subsequent years they will use it to perform increasingly sophisticated experiments.

“We are extremely grateful to the W.M. Keck Foundation for this generous support,” said Steven Girvin, the Eugene Higgins Professor of Physics and deputy provost for research. “This is a forward-looking grant that will advance truly ground-breaking research.”

Girvin, whose own research interests include quantum computing, described the Harris project as a possible game-changer. “Truly quantum mechanical behaviors have been observed in the flight of molecules through a vacuum and in the flow of electrons through superconductive circuits, but nothing has been accomplished on this scale. If Jack succeeds, this would be the first time that an object visible to the naked eye has bulk motion that exhibits genuine quantum mechanical effects.”

Into the whispering gallery

To explain his project, Harris invokes an architectural quirk of St. Paul’s cathedral, a London landmark with a famous “whispering gallery.” High up in its main dome, a whisper uttered against one wall is easily audible at great distances, as the sound waves skim along the dome’s interior. Harris plans to create his own whispering gallery, albeit on a smaller scale, using a droplet of liquid helium suspended in a powerful magnetic field. Rather than sound waves, Harris’ gallery will bounce a single photon.

This approach is closely related to an idea proposed by Albert Einstein in the 1920s, but until now, it has remained beyond the technical capabilities of experimentalists. To complete the experiment, Harris will need to combine recent advances in three different areas of physics: the study of optical cavities (objects that can capture photons), magnetic levitation, and the strange, frictionless world of superfluid helium. “Superfluid liquid helium has particular properties, like absence of viscosity and near-absence of optical absorption,” Harris explained. “In our device, a drop of liquid helium will be made to capture a single photon, which will bounce around inside. We expect to see the drop respond to the photon. “A photon always behaves quantum mechanically,” he added. “If you have a macroscopic object — our helium drop — that responds appreciably to a photon, the quantum mechanical behavior can be transferred to the large object. Our device will be ideally suited to studying quantum effects in the drop’s motion.” Potential applications for Harris’ research include new approaches to computing, cryptography, and communications. But Harris is most excited about the implications for fundamental physics: “Finding a theory of quantum gravity has been an outstanding challenge in physics for several decades, and it has proceeded largely without input from experiments. We hope that our research can provide some empirical data in this arena.”

About the W.M. Keck Foundation

The W.M. Keck Foundation was established in 1954 by William Myron Keck, founder of the Superior Oil Company. The foundation supports pioneering research in science, engineering, and medicine and has provided generous funding for numerous research initiatives at Yale University. In 2014, the Keck Foundation awarded a separate grant to a team of scientists led by Corey O’Hern, associate professor of mechanical engineering at Yale, to explore the physics of systems composed of macro-sized particles. Source : Yale News

In the researchers' new system, a returning beam of light is mixed with a locally stored beam, and the correlation of their phase, or period of oscillation, helps remove noise caused by interactions with the environment.

Illustration: Jose-Luis Olivares/MIT

Quantum sensor’s advantages survive entanglement breakdown

Preserving the fragile quantum property known as entanglement isn’t necessary to reap benefits.

By Larry Hardesty 


CAMBRIDGE, Mass. – The extraordinary promise of quantum information processing — solving problems that classical computers can’t, perfectly secure communication — depends on a phenomenon called “entanglement,” in which the physical states of different quantum particles become interrelated. But entanglement is very fragile, and the difficulty of preserving it is a major obstacle to developing practical quantum information systems.

In a series of papers since 2008, members of the Optical and Quantum Communications Group at MIT’s Research Laboratory of Electronics have argued that optical systems that use entangled light can outperform classical optical systems — even when the entanglement breaks down.

Two years ago, they showed that systems that begin with entangled light could offer much more efficient means of securing optical communications. And now, in a paper appearing in Physical Review Letters, they demonstrate that entanglement can also improve the performance of optical sensors, even when it doesn’t survive light’s interaction with the environment.

In the researchers' new system, a returning beam of light is mixed with a locally stored beam, and the correlation of their phase, or period of oscillation, helps remove noise caused by interactions with the environment. Illustration: Jose-Luis Olivares/MIT
In the researchers’ new system, a returning beam of light is mixed with a locally stored beam, and the correlation of their phase, or period of oscillation, helps remove noise caused by interactions with the environment.
Illustration Credit: Jose-Luis Olivares/MIT

“That is something that has been missing in the understanding that a lot of people have in this field,” says senior research scientist Franco Wong, one of the paper’s co-authors and, together with Jeffrey Shapiro, the Julius A. Stratton Professor of Electrical Engineering, co-director of the Optical and Quantum Communications Group. “They feel that if unavoidable loss and noise make the light being measured look completely classical, then there’s no benefit to starting out with something quantum. Because how can it help? And what this experiment shows is that yes, it can still help.”

Phased in

Entanglement means that the physical state of one particle constrains the possible states of another. Electrons, for instance, have a property called spin, which describes their magnetic orientation. If two electrons are orbiting an atom’s nucleus at the same distance, they must have opposite spins. This spin entanglement can persist even if the electrons leave the atom’s orbit, but interactions with the environment break it down quickly.

In the MIT researchers’ system, two beams of light are entangled, and one of them is stored locally — racing through an optical fiber — while the other is projected into the environment. When light from the projected beam — the “probe” — is reflected back, it carries information about the objects it has encountered. But this light is also corrupted by the environmental influences that engineers call “noise.” Recombining it with the locally stored beam helps suppress the noise, recovering the information.

The local beam is useful for noise suppression because its phase is correlated with that of the probe. If you think of light as a wave, with regular crests and troughs, two beams are in phase if their crests and troughs coincide. If the crests of one are aligned with the troughs of the other, their phases are anti-correlated.

But light can also be thought of as consisting of particles, or photons. And at the particle level, phase is a murkier concept.

“Classically, you can prepare beams that are completely opposite in phase, but this is only a valid concept on average,” says Zheshen Zhang, a postdoc in the Optical and Quantum Communications Group and first author on the new paper. “On average, they’re opposite in phase, but quantum mechanics does not allow you to precisely measure the phase of each individual photon.”

Improving the odds

Instead, quantum mechanics interprets phase statistically. Given particular measurements of two photons, from two separate beams of light, there’s some probability that the phases of the beams are correlated. The more photons you measure, the greater your certainty that the beams are either correlated or not. With entangled beams, that certainty increases much more rapidly than it does with classical beams.

When a probe beam interacts with the environment, the noise it accumulates also increases the uncertainty of the ensuing phase measurements. But that’s as true of classical beams as it is of entangled beams. Because entangled beams start out with stronger correlations, even when noise causes them to fall back within classical limits, they still fare better than classical beams do under the same circumstances.

“Going out to the target and reflecting and then coming back from the target attenuates the correlation between the probe and the reference beam by the same factor, regardless of whether you started out at the quantum limit or started out at the classical limit,” Shapiro says. “If you started with the quantum case that’s so many times bigger than the classical case, that relative advantage stays the same, even as both beams become classical due to the loss and the noise.”

In experiments that compared optical systems that used entangled light and classical light, the researchers found that the entangled-light systems increased the signal-to-noise ratio — a measure of how much information can be recaptured from the reflected probe — by 20 percent. That accorded very well with their theoretical predictions.

But the theory also predicts that improvements in the quality of the optical equipment used in the experiment could double or perhaps even quadruple the signal-to-noise ratio. Since detection error declines exponentially with the signal-to-noise ratio, that could translate to a million-fold increase in sensitivity.

Source: MIT News Office

The first ever photograph of light as both a particle and wave

Light behaves both as a particle and as a wave. Since the days of Einstein, scientists have been trying to directly observe both of these aspects of light at the same time. Now, scientists at EPFL have succeeded in capturing the first-ever snapshot of this dual behavior.

ight behaves both as a particle and as a wave. Since the days of Einstein, scientists have been trying to directly observe both of these aspects of light at the same time. Now, scientists at EPFL have succeeded in capturing the first-ever snapshot of this dual behavior. Credit:EPFL
ight behaves both as a particle and as a wave. Since the days of Einstein, scientists have been trying to directly observe both of these aspects of light at the same time. Now, scientists at EPFL have succeeded in capturing the first-ever snapshot of this dual behavior.
Credit:EPFL

Quantum mechanics tells us that light can behave simultaneously as a particle or a wave. However, there has never been an experiment able to capture both natures of light at the same time; the closest we have come is seeing either wave or particle, but always at different times. Taking a radically different experimental approach, EPFL scientists have now been able to take the first ever snapshot of light behaving both as a wave and as a particle. The breakthrough work is published in Nature Communications.

When UV light hits a metal surface, it causes an emission of electrons. Albert Einstein explained this “photoelectric” effect by proposing that light – thought to only be a wave – is also a stream of particles. Even though a variety of experiments have successfully observed both the particle- and wave-like behaviors of light, they have never been able to observe both at the same time. 

 Alternate Link on YTPAK: http://www.ytpak.com/?component=video&task=view&id=UQ-qseLBnxc

A new approach on a classic effect

A research team led by Fabrizio Carbone at EPFL has now carried out an experiment with a clever twist: using electrons to image light. The researchers have captured, for the first time ever, a single snapshot of light behaving simultaneously as both a wave and a stream of particles particle.

The experiment is set up like this: A pulse of laser light is fired at a tiny metallic nanowire. The laser adds energy to the charged particles in the nanowire, causing them to vibrate. Light travels along this tiny wire in two possible directions, like cars on a highway. When waves traveling in opposite directions meet each other they form a new wave that looks like it is standing in place. Here, this standing wave becomes the source of light for the experiment, radiating around the nanowire.

This is where the experiment’s trick comes in: The scientists shot a stream of electrons close to the nanowire, using them to image the standing wave of light. As the electrons interacted with the confined light on the nanowire, they either sped up or slowed down. Using the ultrafast microscope to image the position where this change in speed occurred, Carbone’s team could now visualize the standing wave, which acts as a fingerprint of the wave-nature of light.

While this phenomenon shows the wave-like nature of light, it simultaneously demonstrates its particle aspect as well. As the electrons pass close to the standing wave of light, they “hit” the light’s particles, the photons. As mentioned above, this affects their speed, making them move faster or slower. This change in speed appears as an exchange of energy “packets” (quanta) between electrons and photons. The very occurrence of these energy packets shows that the light on the nanowire behaves as a particle.

“This experiment demonstrates that, for the first time ever, we can film quantum mechanics – and its paradoxical nature – directly,” says Fabrizio Carbone. In addition, the importance of this pioneering work can extend beyond fundamental science and to future technologies. As Carbone explains: “Being able to image and control quantum phenomena at the nanometer scale like this opens up a new route towards quantum computing.”

This work represents a collaboration between the Laboratory for Ultrafast Microscopy and Electron Scattering of EPFL, the Department of Physics of Trinity College (US) and the Physical and Life Sciences Directorate of the Lawrence Livermore National Laboratory. The imaging was carried out EPFL’s ultrafast energy-filtered transmission electron microscope – one of the two in the world.

Reference

Piazza L, Lummen TTA, Quiñonez E, Murooka Y, Reed BW, Barwick B, Carbone F.Simultaneous observation of the quantization and the interference pattern of a plasmonic near-field. Nature Communications 02 March 2015. DOI: 10.1038/ncomms7407

Source: EPFL

Illustration by Michael S. Helfenbein

Yale physicists find a new form of quantum friction


Physicists at Yale University have observed a new form of quantum friction that could serve as a basis for robust information storage in quantum computers in the future. The researchers are building upon decades of research, experimentally demonstrating a procedure theorized nearly 30 years ago.

The results appear in the journal Science and are based on work in the lab of Michel Devoret, the F.W. Beinecke Professor of Applied Physics.

Quantum computers, a technology still in development, would rely on the laws of quantum mechanics to solve certain problems exponentially faster than classical computers. They would store information in quantum systems, such as the spin of an electron or the energy levels of an artificial atom. Called “qubits,” these storage units are the quantum equivalent of classical “bits.” But while bits can be in states like 0 or 1, qubits can simultaneously be in the 0 and 1 state. This property is called quantum superposition; it is a powerful resource, but also very fragile. Ensuring the integrity of quantum information is a major challenge of the field.

 Illustration by Michael S. Helfenbein
Illustration by Michael S. Helfenbein

Zaki Leghtas, first author on the paper and a postdoctoral researcher at Yale, offered the following metaphor to explain this new form of quantum friction:

Imagine a hill surrounded by two basins. If you put a ball at the top of the hill, it will roll down the sides and settle in one of the basins. As it rolls, it loses energy due to the friction between the ball and the ground, and it slows down. This is why it stops at the bottom of the basin. But friction also causes the ball to leave a path in its wake. By looking at either side of the hill and seeing where grass is flattened and stones are pushed aside, you can tell whether the ball rolled into the right or left basin.

This figure depicts the position of a quantum particle over a time of 19 micro-seconds. Dark colors indicate high probability of the particle existing at the specified position. It is a plot of the time-evolution of the Winger function W (⍺) of the quantum system, with black corresponding to 1.0, white to 0, and blue to –0.05.
This figure depicts the position of a quantum particle over a time of 19 micro-seconds. Dark colors indicate high probability of the particle existing at the specified position. It is a plot of the time-evolution of the Winger function W (⍺) of the quantum system, with black corresponding to 1.0, white to 0, and blue to –0.05.

If you replace the ball with a quantum particle, however, you run into a problem. Quantum particles can exist in many states at the same time, so in theory, the particle could occupy both basins simultaneously. But as the particle is rolling down, the friction between the particle and the hill leaves an impact on the environment, which can be measured. The same friction that stops the particle at the bottom also carves the path. This destroys the superposition and forces the particle to exist in only one basin.

Previously, researchers had been able to take advantage of this friction to trap quantum particles in particular basins. But now, Devoret’s lab demonstrates a new type of friction — one that slows the particle as it rolls, but does not carve a path that tells which side it is choosing. This allows the particle to simultaneously exist in both the left and right basins at the same time.

Each of these “basin” states is both stable and steady. While the quantum particle might move around in the basins, small perturbations won’t kick it out of the basins. Furthermore, any superpositions of these two basin states are also stable and steady. This means they could be used as a basis for storing quantum information.

Technically, this is called a two-dimensional quantum steady-state manifold. Devoret and Leghtas point out that the next step is expanding this two-dimensional manifold to four dimensions — adding two more basins to the landscape. This will allow scientists to redundantly encode quantum information and to do error correction within the manifold. Error correction is one of the key components that must be developed in order to make a practical quantum computer feasible.

Additional authors are Steven Touzard, Ioan Pop, Angela Kou, Brian Vlastakis, Andrei Petrenko, Katrina Sliwa, Anirudh Narla, Shyam Shankar, Michael Hatridge, Matthew Reagor, Luigi Frunzio, Robert Schoelkopf, and Mazyar Mirrahimi of Yale. Mirrahimi also has an appointment at the Institut National de Recherche en Informatique et en Automatique Paris-Rocquencourt.

(Main illustration by Michael S. Helfenbein)

Source: Yale News

Quantum computer as detector shows space is not squeezed

 Robert Sanders


 

Ever since Einstein proposed his special theory of relativity in 1905, physics and cosmology have been based on the assumption that space looks the same in all directions – that it’s not squeezed in one direction relative to another.

A new experiment by UC Berkeley physicists used partially entangled atoms — identical to the qubits in a quantum computer — to demonstrate more precisely than ever before that this is true, to one part in a billion billion.

The classic experiment that inspired Albert Einstein was performed in Cleveland by Albert Michelson and Edward Morley in 1887 and disproved the existence of an “ether” permeating space through which light was thought to move like a wave through water. What it also proved, said Hartmut Häffner, a UC Berkeley assistant professor of physics, is that space is isotropic and that light travels at the same speed up, down and sideways.

“Michelson and Morley proved that space is not squeezed,” Häffner said. “This isotropy is fundamental to all physics, including the Standard Model of physics. If you take away isotropy, the whole Standard Model will collapse. That is why people are interested in testing this.”

The Standard Model of particle physics describes how all fundamental particles interact, and requires that all particles and fields be invariant under Lorentz transformations, and in particular that they behave the same no matter what direction they move.

Häffner and his team conducted an experiment analogous to the Michelson-Morley experiment, but with electrons instead of photons of light. In a vacuum chamber he and his colleagues isolated two calcium ions, partially entangled them as in a quantum computer, and then monitored the electron energies in the ions as Earth rotated over 24 hours.

As the Earth rotates every 24 hours, the orientation of the ions in the quantum computer/detector changes with respect to the Sun’s rest frame. If space were squeezed in one direction and not another, the energies of the electrons in the ions would have shifted with a 12-hour period. (Hartmut Haeffner image)
As the Earth rotates every 24 hours, the orientation of the ions in the quantum computer/detector changes with respect to the Sun’s rest frame. If space were squeezed in one direction and not another, the energies of the electrons in the ions would have shifted with a 12-hour period. (Hartmut Haeffner image)

If space were squeezed in one or more directions, the energy of the electrons would change with a 12-hour period. It didn’t, showing that space is in fact isotropic to one part in a billion billion (1018), 100 times better than previous experiments involving electrons, and five times better than experiments like Michelson and Morley’s that used light.

The results disprove at least one theory that extends the Standard Model by assuming some anisotropy of space, he said.

Häffner and his colleagues, including former graduate student Thaned Pruttivarasin, now at the Quantum Metrology Laboratory in Saitama, Japan, will report their findings in the Jan. 29 issue of the journal Nature.

Entangled qubits

Häffner came up with the idea of using entangled ions to test the isotropy of space while building quantum computers, which involve using ionized atoms as quantum bits, or qubits, entangling their electron wave functions, and forcing them to evolve to do calculations not possible with today’s digital computers. It occurred to him that two entangled qubits could serve as sensitive detectors of slight disturbances in space.

“I wanted to do the experiment because I thought it was elegant and that it would be a cool thing to apply our quantum computers to a completely different field of physics,” he said. “But I didn’t think we would be competitive with experiments being performed by people working in this field. That was completely out of the blue.”

He hopes to make more sensitive quantum computer detectors using other ions, such as ytterbium, to gain another 10,000-fold increase in the precision measurement of Lorentz symmetry. He is also exploring with colleagues future experiments to detect the spatial distortions caused by the effects of dark matter particles, which are a complete mystery despite comprising 27 percent of the mass of the universe.

“For the first time we have used tools from quantum information to perform a test of fundamental symmetries, that is, we engineered a quantum state which is immune to the prevalent noise but sensitive to the Lorentz-violating effects,” Häffner said. “We were surprised the experiment just worked, and now we have a fantastic new method at hand which can be used to make very precise measurements of perturbations of space.”

Other co-authors are UC Berkeley graduate student Michael Ramm, former UC Berkeley postdoc Michael Hohensee of Lawrence Livermore National Laboratory, and colleagues from the University of Delaware and Maryland and institutions in Russia. The work was supported by the National Science Foundation.

Source: UC Berkeley