The story

New form of matter created by scientists using light

When we talk about matter we normally have in our minds something of substance that we can touch and hold. However, scientists at Harvard and MIT have questioned our beliefs about matter and the way we perceive light by discovering a way in which photons (a particle representing a quantum of light) can be used to form molecules.

This discovery according to Professor Mikhail Lukin of Harvard University goes against what has been accepted for centuries about the nature of light, which is that photons are elementary particles that do not have mass and do not interact with each other.

The scientific team managed to create a medium where photons interact in such a strong way that they form molecules and create mass.

Such a discovery could have many applications in the future once the mechanics of it are understood in a better way. The first big help will be in quantum computers where they may be able to manipulate photons and perform logical operations at the molecular level. To take it even further in the future it may be possible to create complex three dimensional structures like crystals completely out of light.

There is lots of research to be conducted on this new topic. After all, it is a new form of matter that we have never encountered before. As Professor Lukin said: “We do this for fun, and because we’re pushing the frontiers of science”.

It looks like the light sabre of Star Wars may become a reality after all…

    History of research on light

    Many researchers through the ages have taken up the challenge of finding out &ldquoWhat is Light?&rdquo
    Optics is known as the oldest discipline along with mechanics.
    The progress of the study of light has been made by the great scholars from different fields introduced here while leading other discipline and closely involved with the growth of industry and culture.


    The law of conservation of mass can only be formulated in classical mechanics when the energy scales associated to an isolated system are much smaller than m c 2 > , where m is the mass of a typical object in the system, measured in the frame of reference where the object is at rest, and c is the speed of light.

    The law can be formulated mathematically in the fields of fluid mechanics and continuum mechanics, where the conservation of mass is usually expressed using the continuity equation, given in differential form as

    where ρ < extstyle ho >is the density (mass per unit volume), t < extstyle t>is the time, ∇ ⋅ < extstyle abla cdot >is the divergence, and v < extstyle mathbf > is the flow velocity field. The interpretation of the continuity equation for mass is the following: For a given closed surface in the system, the change in time of the mass enclosed by the surface is equal to the mass that traverses the surface, positive if matter goes in and negative if matter goes out. For the whole isolated system, this condition implies that the total mass M < extstyle M>, sum of the masses of all components in the system, does not change in time, i.e.

    where d V < extstyle < ext>V> is the differential that defines the integral over the whole volume of the system.

    The continuity equation for the mass is part of Euler equations of fluid dynamics. Many other convection–diffusion equations describe the conservation and flow of mass and matter in a given system.

    In chemistry, the calculation of the amount of reactant and products in a chemical reaction, or stoichiometry, is founded on the principle of conservation of mass. The principle implies that during a chemical reaction the total mass of the reactants is equal to the total mass of the products. For example, in the following reaction

    where one molecule of methane ( CH
    4 ) and two oxygen molecules O
    2 are converted into one molecule of carbon dioxide ( CO
    2 ) and two of water ( H
    2 O ). The number of molecules as result from the reaction can be derived from the principle of conservation of mass, as initially four hydrogen atoms, 4 oxygen atoms and one carbon atom are present (as well as in the final state), then the number water molecules produced must be exactly two per molecule of carbon dioxide produced.

    Many engineering problems are solved by following the mass distribution in time of a given system, this practice is known as mass balance.

    An important idea in ancient Greek philosophy was that "Nothing comes from nothing", so that what exists now has always existed: no new matter can come into existence where there was none before. An explicit statement of this, along with the further principle that nothing can pass away into nothing, is found in Empedocles (c. 4th century BC): "For it is impossible for anything to come to be from what is not, and it cannot be brought about or heard of that what is should be utterly destroyed." [4]

    A further principle of conservation was stated by Epicurus around 3rd century BC, who, describing the nature of the Universe, wrote that "the totality of things was always such as it is now, and always will be". [5]

    Jain philosophy, a non-creationist philosophy based on the teachings of Mahavira (6th century BC), [6] states that the universe and its constituents such as matter cannot be destroyed or created. The Jain text Tattvarthasutra (2nd century AD) states that a substance is permanent, but its modes are characterised by creation and destruction. [7] A principle of the conservation of matter was also stated by Nasīr al-Dīn al-Tūsī (around 13th century AD). He wrote that "A body of matter cannot disappear completely. It only changes its form, condition, composition, color and other properties and turns into a different complex or elementary matter". [8]

    Discoveries in chemistry Edit

    By the 18th century the principle of conservation of mass during chemical reactions was widely used and was an important assumption during experiments, even before a definition was formally established, [9] as can be seen in the works of Joseph Black, Henry Cavendish, and Jean Rey. [10] The first to outline the principle was Mikhail Lomonosov in 1756. He might have demonstrated it by experiments and certainly had discussed the principle in 1748 in correspondence with Leonhard Euler, [11] though his claim on the subject is sometimes challenged. [12] [13] According to the soviet physicist Yakov Dorfman:

    The universal law was formulated by Lomonosov on the basis of general philosophical materialistic considerations, it was never questioned or tested by him, but on the contrary, served him as a solid starting position in all research throughout his life. [14]

    A more refined series of experiments were later carried out by Antoine Lavoisier who expressed his conclusion in 1773 and popularized the principle of conservation of mass. The demonstrations of the principle disproved the then-popular phlogiston theory that claimed mass could be gained or lost in combustion and heat processes.

    The conservation of mass was obscure for millennia because of the buoyancy effect of the Earth's atmosphere on the weight of gases. For example, a piece of wood weighs less after burning this seemed to suggest that some of its mass disappears, or is transformed or lost. This was not disproved until careful experiments were performed in which chemical reactions such as rusting were allowed to take place in sealed glass ampoules it was found that the chemical reaction did not change the weight of the sealed container and its contents. Weighing of gases using scales was not possible until the invention of the vacuum pump in 17th century.

    Once understood, the conservation of mass was of great importance in progressing from alchemy to modern chemistry. Once early chemists realized that chemical substances never disappeared but were only transformed into other substances with the same weight, these scientists could for the first time embark on quantitative studies of the transformations of substances. The idea of mass conservation plus a surmise that certain "elemental substances" also could not be transformed into others by chemical reactions, in turn led to an understanding of chemical elements, as well as the idea that all chemical processes and transformations (such as burning and metabolic reactions) are reactions between invariant amounts or weights of these chemical elements.

    Following the pioneering work of Lavoisier, the exhaustive experiments of Jean Stas supported the consistency of this law in chemical reactions, [15] even though they were carried out with other intentions. His research [16] [17] indicated that in certain reactions the loss or gain could not have been more than from 2 to 4 parts in 100,000. [18] The difference in the accuracy aimed at and attained by Lavoisier on the one hand, and by Morley and Stas on the other, is enormous. [19]

    Modern physics Edit

    The law of conservation of mass was challenged with the advent of special relativity. In one of the Annus Mirabilis papers of Albert Einstein in 1905, he suggested an equivalence between mass and energy. This theory implied several assertions, like the idea that internal energy of a system could contribute to the mass of the whole system, or that mass could be converted into electromagnetic radiation. However, as Max Planck pointed out, a change in mass as a result of extraction or addition of chemical energy, as predicted by Einstein's theory, is so small that it could not be measured with the available instruments and could not be presented as a test to the special relativity. Einstein speculated that the energies associated with newly discovered radioactivity were significant enough, compared with the mass of systems producing them, to enable their mass-change to be measured, once the energy of the reaction had been removed from the system. This later indeed proved to be possible, although it was eventually to be the first artificial nuclear transmutation reaction in 1932, demonstrated by Cockcroft and Walton, that proved the first successful test of Einstein's theory regarding mass-loss with energy-loss.

    The law conservation of mass and the analogous law of conservation of energy were finally overruled by a more general principle known as the mass–energy equivalence. Special relativity also redefines the concept of mass and energy, which can be used interchangeably and are relative to the frame of reference. Several definitions had to be defined for consistency like rest mass of a particle (mass in the rest frame of the particle) and relativistic mass (in another frame). The latter term is usually less frequently used.

    Special relativity Edit

    In special relativity, the conservation of mass does not apply if the system is open and energy escapes. However, it does continue to apply to totally closed (isolated) systems. If energy cannot escape a system, its mass cannot decrease. In relativity theory, so long as any type of energy is retained within a system, this energy exhibits mass.

    Also, mass must be differentiated from matter, since matter may not be perfectly conserved in isolated systems, even though mass is always conserved in such systems. However, matter is so nearly conserved in chemistry that violations of matter conservation were not measured until the nuclear age, and the assumption of matter conservation remains an important practical concept in most systems in chemistry and other studies that do not involve the high energies typical of radioactivity and nuclear reactions.

    The mass associated with chemical amounts of energy is too small to measure Edit

    The change in mass of certain kinds of open systems where atoms or massive particles are not allowed to escape, but other types of energy (such as light or heat) are allowed to enter, escape or be merged, went unnoticed during the 19th century, because the change in mass associated with addition or loss of small quantities of thermal or radiant energy in chemical reactions is very small. (In theory, mass would not change at all for experiments conducted in isolated systems where heat and work were not allowed in or out.)

    Mass conservation remains correct if energy is not lost Edit

    The conservation of relativistic mass implies the viewpoint of a single observer (or the view from a single inertial frame) since changing inertial frames may result in a change of the total energy (relativistic energy) for systems, and this quantity determines the relativistic mass.

    The principle that the mass of a system of particles must be equal to the sum of their rest masses, even though true in classical physics, may be false in special relativity. The reason that rest masses cannot be simply added is that this does not take into account other forms of energy, such as kinetic and potential energy, and massless particles such as photons, all of which may (or may not) affect the total mass of systems.

    For moving massive particles in a system, examining the rest masses of the various particles also amounts to introducing many different inertial observation frames (which is prohibited if total system energy and momentum are to be conserved), and also when in the rest frame of one particle, this procedure ignores the momenta of other particles, which affect the system mass if the other particles are in motion in this frame.

    For the special type of mass called invariant mass, changing the inertial frame of observation for a whole closed system has no effect on the measure of invariant mass of the system, which remains both conserved and invariant (unchanging), even for different observers who view the entire system. Invariant mass is a system combination of energy and momentum, which is invariant for any observer, because in any inertial frame, the energies and momenta of the various particles always add to the same quantity (the momentum may be negative, so the addition amounts to a subtraction). The invariant mass is the relativistic mass of the system when viewed in the center of momentum frame. It is the minimum mass which a system may exhibit, as viewed from all possible inertial frames.

    The conservation of both relativistic and invariant mass applies even to systems of particles created by pair production, where energy for new particles may come from kinetic energy of other particles, or from one or more photons as part of a system that includes other particles besides a photon. Again, neither the relativistic nor the invariant mass of totally closed (that is, isolated) systems changes when new particles are created. However, different inertial observers will disagree on the value of this conserved mass, if it is the relativistic mass (i.e., relativistic mass is conserved but not invariant). However, all observers agree on the value of the conserved mass if the mass being measured is the invariant mass (i.e., invariant mass is both conserved and invariant).

    The mass-energy equivalence formula gives a different prediction in non-isolated systems, since if energy is allowed to escape a system, both relativistic mass and invariant mass will escape also. In this case, the mass-energy equivalence formula predicts that the change in mass of a system is associated with the change in its energy due to energy being added or subtracted: Δ m = Δ E / c 2 . .> This form involving changes was the form in which this famous equation was originally presented by Einstein. In this sense, mass changes in any system are explained simply if the mass of the energy added or removed from the system, are taken into account.

    The formula implies that bound systems have an invariant mass (rest mass for the system) less than the sum of their parts, if the binding energy has been allowed to escape the system after the system has been bound. This may happen by converting system potential energy into some other kind of active energy, such as kinetic energy or photons, which easily escape a bound system. The difference in system masses, called a mass defect, is a measure of the binding energy in bound systems – in other words, the energy needed to break the system apart. The greater the mass defect, the larger the binding energy. The binding energy (which itself has mass) must be released (as light or heat) when the parts combine to form the bound system, and this is the reason the mass of the bound system decreases when the energy leaves the system. [20] The total invariant mass is actually conserved, when the mass of the binding energy that has escaped, is taken into account.

    General relativity Edit

    In general relativity, the total invariant mass of photons in an expanding volume of space will decrease, due to the red shift of such an expansion. The conservation of both mass and energy therefore depends on various corrections made to energy in the theory, due to the changing gravitational potential energy of such systems.

    Scientists discover how to turn light into matter after 80-year quest

    Imperial physicists have discovered how to create matter from light - a feat thought impossible when the idea was first theorised 80 years ago.

    In just one day over several cups of coffee in a tiny office in Imperial&rsquos Blackett Physics Laboratory, three physicists worked out a relatively simple way to physically prove a theory first devised by scientists Breit and Wheeler in 1934.

    Breit and Wheeler suggested that it should be possible to turn light into matter by smashing together only two particles of light (photons), to create an electron and a positron &ndash the simplest method of turning light into matter ever predicted. The calculation was found to be theoretically sound but Breit and Wheeler said that they never expected anybody to physically demonstrate their prediction. It has never been observed in the laboratory and past experiments to test it have required the addition of massive high-energy particles.

    The new research, published in Nature Photonics, shows for the first time how Breit and Wheeler&rsquos theory could be proven in practice. This &lsquophoton-photon collider&rsquo, which would convert light directly into matter using technology that is already available, would be a new type of high-energy physics experiment. This experiment would recreate a process that was important in the first 100 seconds of the universe and that is also seen in gamma ray bursts, which are the biggest explosions in the universe and one of physics&rsquo greatest unsolved mysteries.

    The scientists had been investigating unrelated problems in fusion energy when they realised what they were working on could be applied to the Breit-Wheeler theory. The breakthrough was achieved in collaboration with a fellow theoretical physicist from the Max Planck Institute for Nuclear Physics, who happened to be visiting Imperial.

    Demonstrating the Breit-Wheeler theory would provide the final jigsaw piece of a physics puzzle which describes the simplest ways in which light and matter interact (see image). The six other pieces in that puzzle, including Dirac&rsquos 1930 theory on the annihilation of electrons and positrons and Einstein&rsquos 1905 theory on the photoelectric effect, are all associated with Nobel Prize-winning research (see image).

    Professor Steve Rose from the Department of Physics at Imperial College London said: &ldquoDespite all physicists accepting the theory to be true, when Breit and Wheeler first proposed the theory, they said that they never expected it be shown in the laboratory. Today, nearly 80 years later, we prove them wrong. What was so surprising to us was the discovery of how we can create matter directly from light using the technology that we have today in the UK. As we are theorists we are now talking to others who can use our ideas to undertake this landmark experiment.&rdquo

    Theories describing light and matter interactions. Credit: Oliver Pike, Imperial College London

    The collider experiment that the scientists have proposed involves two key steps. First, the scientists would use an extremely powerful high-intensity laser to speed up electrons to just below the speed of light. They would then fire these electrons into a slab of gold to create a beam of photons a billion times more energetic than visible light.

    The next stage of the experiment involves a tiny gold can called a hohlraum (German for &lsquoempty room&rsquo). Scientists would fire a high-energy laser at the inner surface of this gold can, to create a thermal radiation field, generating light similar to the light emitted by stars.

    They would then direct the photon beam from the first stage of the experiment through the centre of the can, causing the photons from the two sources to collide and form electrons and positrons. It would then be possible to detect the formation of the electrons and positrons when they exited the can.

    Lead researcher Oliver Pike who is currently completing his PhD in plasma physics, said: &ldquoAlthough the theory is conceptually simple, it has been very difficult to verify experimentally. We were able to develop the idea for the collider very quickly, but the experimental design we propose can be carried out with relative ease and with existing technology. Within a few hours of looking for applications of hohlraums outside their traditional role in fusion energy research, we were astonished to find they provided the perfect conditions for creating a photon collider. The race to carry out and complete the experiment is on!&rdquo

    Reference: Pike, O, J. et al. 2014. &lsquoA photon&ndashphoton collider in a vacuum hohlraum&rsquo. Nature Photonics, 18 May 2014.

    What would be the significance of the creation of a black hole at the LHC?

    The creation of a black hole at the LHC would confirm theories that our universe is not 4 dimensional (3 space plus 1 time dimensions), but indeed hosts other dimensions. It would be quite a spectacular philosophical outcome! In the same way that the theory of relativity or of quantum mechanics revolutionized our way of thinking, discovering the existence of extra dimensions would be a major new milestone in our understanding of the Universe.

    There is no obvious application for knowing this. Many people will start speculating about using these extra dimensions for space and time travel, or as a source of clean energy, and who knows what else. [CERN]

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    New form of matter created by scientists using light - History

    Louis de Broglie, Matter and Light: The New Physics, trans. W. H. Johnston (Allen & Unwin, 1937) presented in Heisenberg, The Physicist’s Conception of Nature, 176-178.

    . laboratory research during the last few years has led to results of the utmost interest almost each day. But theoretical Physics, too, whose function it is to provide a guiding light for experimental Physics, has not remained idle.

    In the history of theoretical Physics, then, during the last thirty years, there are two great landmarks: the Theory of Relativity and the Quantum Theory, two doctrines of the widest scope and while the Theory of Relativity is less closely connected with the advancement of atomic Physics, it is the more familiar to the man in the street. Its origin lies in certain phenomena of the propagation of Light which could not be explained by the older theories but by an intellectual effort which will always hold an eminent place in the annals of Science, Einstein removed the difficulty by the introduction of entirely novel ideas on the nature of Space and Time and their interrelation. Hence the origin of that remarkable Theory of Relativity, which later achieved an even more general scope by providing us with an entirely new conception of Gravitation. It is true that certain of the experimental verifications of the Theory have been, and still remain, in debate but it is quite certain that it provides us with extremely novel and fertile points of view. For it has shown how the removal of certain preconceived ideas, adopted through habit rather than logic, made it possible to overcome obstacles regarded as insuperable and thus to discover unexpected horizons and for physicists the Theory of Relativity has been a marvellous exercise in overcoming mental rigidity.

    The Quantum Theory and its developments, if less generally familiar, are certainly at least equally important, since by means of this Theory it has been possible to make use of the discoveries of experimental Physics to form a science of atomic phenomena. When a more precise description of these phenomena was felt to be necessary, the fundamental fact which became apparent was that it was imperative to introduce completely novel concepts which had been entirely unknown to classical Physics. For in order to describe the atomic world it is not enough to transport the methods and images which are valid on the human, or on the astronomical scale, to another and very much smaller scale. We saw that, following Bohr, scientists succeeded in imagining atoms to be miniature solar systems in which the electrons played the part of the planets, and in tracing their orbits round a central sun bearing a positive charge. But if this image was to give really valuable results, it became necessary to assume, still further, that the atomic solar system obeyed Quantum Laws and these were entirely different from the Laws governing the systems with which Astronomy deals. The more carefully this difference was considered, again, the more its wide scope and fundamental significance began to be appreciated for the intervention of quanta brought about the introduction of discontinuity in atomic Physics, and this introduction is of essential importance, since without it atoms would be unstable and Matter could not exist.

    We saw that the discovery of the double nature of electrons, as at once corpuscular and undulatory, was followed by a change in the Quantum Theory, so that this was given a new form, some years ago, called Wave Mechanics. The new form has met with manifold success, and Wave Mechanics has brought about a better understanding and prediction of those phenomena which depend upon the existence of quantized stationary states for atoms. Every branch of Science, including Chemistry, has benefited from the impetus due to the new theory, because this has brought with it an entirely novel and interesting manner of interpreting chemical combinations.

    The development of Wave Mechanics, then, has compelled physicists to give an ever wider and wider scope to their concepts. For according to the new principles, the Laws of Nature no longer have the strict character which they bear in classical Physics: phenomena (in other terms) are no longer subject to a rigorous Determinism they only obey the Laws of Probability. The famous Principle of Uncertainty advanced by Heisenberg gives an exact formulation to this fact. Even the notions of Causality and of Individuality have had to undergo a fresh scrutiny, and it seems certain that this major crisis, affecting the guiding principles of our physical concepts, will be the source of philosophical consequences which cannot yet be clearly perceived.

    'Einstein Was Right: You Can Turn Energy Into Matter'

    Essentially, the equation says that mass and energy are intimately related. Atom bombs and nuclear reactors are practical examples of the formula working in one direction, turning matter into energy.

    But until now there has been no way to do the reverse, turn energy into matter. What makes it particularly hard is that c 2 term, the speed of light squared. It accounts for the huge amounts of energy released in nuclear reactions, and the huge amount you’d need to inject to turn energy into matter.

    Previous experiments have always required a little bit of mass, even if it was only an electron’s worth.

    Albert Einstein's famous formula triumphs again (Photo credit: DonkeyHotey)

    But scientists at Imperial College London (including a visiting physicist from Germany's Max Planck Institute for Nuclear Physics) think they’ve figured out how to turn energy directly into matter.

    Oliver Pike, Felix Mackenroth, Edward Hill and Steve Rose have suggested a way to turn a pair of photons, particles of light, into an electron and its antiparticle, a positron.

    They came up with the idea in less than a day, over several cups of coffee at Imperial’s Blackett Physics Laboratory.

    They started off talking about fusion, but realised their work could be applied to an earlier problem, an idea proposed by two US scientists, Gregory Breit and John Wheeler, in 1934.

    Breit and Wheeler, who went on to work on America’s Manhattan Project to build the first A-bomb, thought it was theoretically possible to smash two photons together to produce an electron and a positron.

    “Despite all physicists accepting the theory to be true, when Breit and Wheeler first proposed the theory, they said that they never expected it be shown in the laboratory,” said Professor Rose. “Today, nearly 80 years later, we prove them wrong.”

    Their article in Nature Photonics proposes that a new kind of collider be built, one that smashes photons instead of protons, as at the Large Hadron Collider at CERN where the Higgs boson was discovered last year.

    Their accomplishment has huge implications, not only does it yet again prove an aspect of Einstein’s theories, it recreates a “process that was important in the first 100 seconds of the universe and that is also seen in gamma ray bursts, which are the biggest explosions in the universe,” said Imperial.

    The first step would be to accelerate electrons with a high-energy laser to just below the speed of light (300,000km/s) and smash them into a slab of gold, which would create a beam of light a billion times more intense than the light from the Sun.

    This would be aimed into a hollow gold shell called a hohlraum (German for empty room). The shell would be excited by another laser to create a thermal radiation field that emits light akin to starlight.

    When the two sources of light cross, some will collide and create electrons and their corresponding antimatter particles, positrons, which could be detected as they left the hohlraum. They calculate that the experiment should produce 100,000 pairs of particles.

    “What was so surprising to us was the discovery of how we can create matter directly from light using the technology that we have today,” said Rose. “As we are theorists we are now talking to others who can use our ideas to undertake this landmark experiment.”

    Pike, the lead author on the paper, said: "Although the theory is conceptually simple, it has been very difficult to verify experimentally. We were able to develop the idea for the collider very quickly, but the experimental design we propose can be carried out with relative ease and with existing technology. Within a few hours of looking for applications of hohlraums outside their traditional role in fusion energy research, we were astonished to find they provided the perfect conditions for creating a photon collider. The race to carry out and complete the experiment is on."

    Among candidate locations for the experiment are the Omega laser in Rochester, New York and the Orion laser at Aldermaston, the UK atomic weapons facility in Berkshire.

    Artificial life breakthrough after scientists create new living organism using synthetic DNA

    In a major step toward creating artificial life, US researchers have developed a living organism that incorporates both natural and artificial DNA and is capable of creating entirely new, synthetic proteins.

    The work, published in the journal Nature, brings scientists closer to the development of designer proteins made to order in a laboratory.

    Previous work by Floyd Romesberg, a chemical biologist at the Scripps Research Institute in La Jolla, California, showed that it was possible to expand the genetic alphabet of natural DNA beyond its current four letters: adenine(A), cytosine(C), guanine (G) and thymine(T).

    In 2014, Romesberg and colleagues created a strain of E. coli bacteria that contained two unnatural letters, X and Y.


    In the latest work, Romesberg’s team has shown that this partially synthetic form of E. coli can take instructions from this hybrid genetic alphabet to make new proteins.

    “This is the first time ever a cell has translated a protein using something other than G, C, A or T,” Romesberg said.

    Although the actual changes to the organism were small, the feat is significant, he said in a telephone interview. “It’s the first change to life ever made.”

    It’s a goal Romesberg has been working toward for the past 20 years. Creating new forms of life, however, is not the main point. Romesberg is interested in using this expanded genetic alphabet to create new types of proteins that can be used to treat disease.

    In 2014, he formed a company called Synthorx Inc, which is working on developing new protein-based treatments.


    “A lot of proteins that you want to use as drugs get cleared in the kidney very quickly,” Romesberg said. The new system would allow scientists to attach fat molecules to drugs to keep them in the body longer.

    Romesberg is aware that the creation of semi-synthetic organisms might raise concerns of hybrid life forms spreading beyond the lab, but the system they used makes such an escape unlikely.

    For example, in natural DNA, base pairs are attracted to each other through the bonding of hydrogen atoms. Romesberg’s X and Y bases are attracted through an entirely different process, which prevents them from accidentally bonding with natural bases.

    Scientists Create Solid Light

    On a late summer afternoon it can seem like sunlight has turned to honey,਋ut could liquid—or even solid—light be more than a piece of poetry? Princeton University electrical engineers say not only is it possible, they’ve already made it happen.

    In Physical Review X, the researchers reveal that they have locked individual photons together so that they become like a solid object.

    "It&aposs something that we have never seen before," says Dr. Andrew Houck, an associate professor of electrical engineering and one of the researchers. "This is a new behavior for light."

    The researchers constructed what they call an 𠇊rtificial atom” made of 100 billion atoms engineered to act like a single unit. They then brought this close to a superconducting wire carrying photons. In one of the almost incomprehensible behaviors unique to the quantum world, the atom and the photons became entangled so that properties passed between the 𠇊tom” and the photons in the wire. The photons started to behave like atoms, correlating with each other to produce a single oscillating system.

    As some of the photons leaked into the surrounding environment, the oscillations slowed and at a critical point started producing quantum divergent behavior. In other words, like Schroedinger&aposs Cat, the correlated photons could be in two states at once.

    "Here we set up a situation where light effectively behaves like a particle in the sense that two photons can interact very strongly," said co-author Dr. Darius Sadri. "In one mode of operation, light sloshes back and forth like a liquid in the other, it freezes."

    As cool as it is to produce solidified light, the team was not acting out of curiosity alone. When connected together the photons of light behave like subatomic particles, but are in some ways easier to study. Consequently, the team is hoping to use the solid light to simulate subatomic behavior.

    Attempts to model the behavior of large numbers of particles usually use statistical mechanics, and often simplify by assuming no interaction between particles and a system at equilibrium. However, in a point we can all relate to, Houck and his colleagues note, “The world around us is rarely in equilibrium.” The solidified light offers a chance to observe a subatomic system as it starts to diverge from equilibrium, with potential for a basic understanding of how these systems operate.

    The system created so far is very simple, with the light entangled with the atom at two points. However, it should be possible to increase this, greatly expanding the complexity and range of possibilities of what is being constructed.

    As well as providing an easy-to-study model of atomic systems that actually exist, Houck and his team hope the frozen light could be made to behave like materials that do not exist, but have been hypothesised by physicists, allowing them to explore how these things would react if they were real.

    Something from Nothing? A Vacuum Can Yield Flashes of Light

    A vacuum might seem like empty space, but scientists have discovered a new way to seemingly get something from that nothingness, such as light. And the finding could ultimately help scientists build incredibly powerful quantum computers or shed light on the earliest moments in the universe's history.

    Quantum physics explains that there are limits to how precisely one can know the properties of the most basic units of matter&mdashfor instance, one can never absolutely know a particle's position and momentum at the same time. One bizarre consequence of this uncertainty is that a vacuum is never completely empty, but instead buzzes with so-called &ldquovirtual particles&rdquo that constantly wink into and out of existence.

    These virtual particles often appear in pairs that near-instantaneously cancel themselves out. Still, before they vanish, they can have very real effects on their surroundings. For instance, photons&mdashpackets of light&mdashcan pop in and out of a vacuum. When two mirrors are placed facing each other in a vacuum, more virtual photons can exist around the outside of the mirrors than between them, generating a seemingly mysterious force that pushes the mirrors together.

    This phenomenon, predicted in 1948 by the Dutch physicist Hendrick Casimir and known as the Casimir effect, was first seen with mirrors held still . Researchers also predicted a dynamical Casimir effect that can result when mirrors are moved, or objects otherwise undergo change. Now quantum physicist Pasi Lähteenmäki at Aalto University in Finland and his colleagues reveal that by varying the speed at which light can travel, they can make light appear from nothing.

    The speed of light in a vacuum is constant, according to Einstein's theory of relativity, but its speed passing through any given material depends on a property of that substance known as its index of refraction. By varying a material's index of refraction, researchers can influence the speed at which both real and virtual photons travel within it. Lähteenmäki says one can think of this system as being much like a mirror, and if its thickness changes fast enough, virtual photons reflecting off it can receive enough energy from the bounce to turn into real photons. "Imagine you stay in a very dark room and suddenly the index of refraction of light [of the room] changes," Lähteenmäki says. "The room will start to glow."

    The researchers began with an array of 250 superconducting quantum-interference devices, or SQUIDs&mdashcircuits that are extraordinarily sensitive to magnetic fields. They inserted the array inside a refrigerator. By carefully exerting magnetic fields on this array, they could vary the speed at which microwave photons traveled through it by a few percent. The researchers then cooled this array to 50 thousandths of a degree Celsius above absolute zero. Because this environment is supercold, it should not emit any radiation, essentially behaving as a vacuum. "We were simply studying these circuits for the purpose of developing an amplifier, which we did," says researcher Sorin Paraoanu, a theoretical physicist at Aalto University. "But then we asked ourselves&mdashwhat if there is no signal to amplify? What happens if the vacuum is the signal?"

    The researchers detected photons that matched predictions from the dynamical Casimir effect. For instance, such photons should display the strange property of quantum entanglement&mdashthat is, by measuring the details of one, scientists could in principle know exactly what its counterpart is like, no matter where it is in the universe, a phenomenon Einstein referred to as "spooky action at a distance." The scientists detailed their findings online February 11 in Proceedings of the National Academy of Sciences.

    "This work and a number of other recent works demonstrate that the vacuum is not empty but full of virtual photons," says theoretical physicist Steven Girvin at Yale University, who did not take part in the Aalto study.

    Another study from physicist Christopher Wilson and his colleagues recently demonstrated the dynamical Casimir effect in a system mimicking a mirror moving at nearly 5 percent of the speed of light. "It's nice to see further confirmation of this effect and see this area of research continuing," says Wilson, now at the University of Waterloo in Ontario, who also did not participate in the Aalto study. "Only recently has technology advanced into a new technical regime of experiments where we can start to look at very fast changes that can have dramatic effects on electromagnetic fields," he adds.

    The investigators caution that such experiments do not constitute a magical way to get more energy out of a system than what is input. For instance, it takes energy to change a material's index of refraction.

    Instead, such research could help scientists learn more about the mysteries of quantum entanglement, which lies at the heart of quantum computers&mdashadvanced machines that could in principle run more calculations in an instant than there are atoms in the universe. The entangled microwave photons the experimental array generated "can be used for a form of quantum computation known as 'continuous variable' quantum information processing,&rdquo Girvin says. &ldquoThis is a direction which is just beginning to open up.&rdquo

    Wilson adds that these systems &ldquomight be used to simulate some interesting scenarios. For instance, there are predictions that during cosmic inflation in the early universe, the boundaries of the universe were expanding nearly at light-speed or faster than the speed of light. We might predict there'd be some dynamical Casimir radiation produced then, and we can try and do tabletop simulations of this."

    So the static Casimir effect involves mirrors held still the dynamical Casimir effect can for instance involve mirrors that move.

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