Single photons is a step toward quantum computing

Source: Max Planck Institute of Quantum Optics Summary: The idea to perform data processing with light, without relying on any electronic components, has been around for quite some time. In fact, necessary components such as optical transistors are available. However, up to now they have not gained a lot of attention from computer companies. This could change in the near future as packing densities of electronic devices as well as clock frequencies of electronic computers are about to reach their limits. Optical techniques promise a high bandwidth and low dissipation power, in particular, if only faint light pulses are needed to achieve the effect of switching. The ultimate limit is a gate-pulse that contains one photon only. A team of scientists has now managed to bring this almost utopian task into reality. The scientists succeeded in switching a medium -- a cloud of about 200 ultracold atoms -- from being transparent to being opaque for light pulses. This "single-photon-switch" could be the first step in the development of a quantum logic gate, an essential component in the field of quantum information processing.

The idea to perform data processing with light, without relying on any electronic components, has been around for quite some time. In fact, necessary components such as optical transistors are available. However, up to now they have not gained a lot of attention from computer companies. This could change in the near future as packing densities of electronic devices as well as clock frequencies of electronic computers are about to reach their limits. Optical techniques promise a high bandwidth and low dissipation power, in particular, if only faint light pulses are needed to achieve the effect of switching. The ultimate limit is a gate-pulse that contains one photon only. A team of scientists around Professor Gerhard Rempe, director of the Quantum Dynamics Division at the Max-Planck-Institute of Quantum Optics, has now managed to bring this almost utopian task into reality. The scientists succeeded in switching a medium -- a cloud of about 200,000 ultracold atoms -- from being transparent to being opaque for light pulses. This "single-photon-switch" could be the first step in the development of a quantum logic gate, an essential component in the field of quantum information processing. The experiment starts with cooling a cloud of about 200,000 rubidium atoms down to a temperature of 0.43 micro-Kelvin (this is just above absolute zero, which corresponds to minus 273 degree Celsius). The atoms are held in an optical dipole trap created by the crosswise superposition of two laser beams. The cloud is irradiated by two light pulses separated by 0.15 micro-seconds. The pulses are extremely weak, they contain on average one or even less photons. The first pulse -- the so-called gate-pulse -- gets absorbed inside the cloud. To be precise, it is stored as an atomic excitation, as it brings one of the atoms into a highly excited Rydberg state. The mere presence of the Rydberg atom leads to a shift of the corresponding energy levels of the other atoms in the cloud. Hence, the wavelength of the second pulse -- the target pulse -no longer meets the requirements for excitation and gets blocked. In other words, the cloud of atoms acts as a medium which, on capturing one single photon, switches from being transparent to opaque. The storage of the photon can be maintained as long as the Rydberg state survives, i.e. for about 60 micro-seconds. The whole procedure is based on a sophisticated combination of a number of experimental measures. For example, the transparency of the cloud is achieved by the application of a control laser. "In order to trap the gate-photon we use the so-called slow-light technique," Dr Stephan Dürr, leader of the experiment, explains. "When the photon is traversing the cloud it polarizes the surrounding medium and is slowed down to a velocity of 1000 km/h. As a consequence, the pulse length shrinks to a couple of tens of micrometres, such that it is completely contained inside the cloud during a certain time window. If the control laser is switch off exactly in this time period, the pulse comes to a halt and is completely converted into an atomic excitation." The second pulse is prepared with a polarization that cannot couple to the atomic excitation that has been stored before. This prevents the target pulse from reading out the stored photon. "Subsequently, we switch the control laser back on. A photon with the right polarization can retrieve the gate-photon from the cloud. We repeat this cycle every 100 micro-seconds," says Simon Baur, who works at the experiment as a doctoral candidate. In a series of measurements the scientists were able to prove that the number of transmitted target photons was reduced by a factor of 20 if a gate-photon had been stored in the cloud before. "Our experiment opens new perspectives in the field of quantum information," Professor Rempe resumes. "A single-photon switch could herald the successful storage of quantum information. That way, storage times could be improved. Last but not least, the new device could be the first step in the development of a quantum logic gate, a key element in quantum information processing." Story Source: The above story is based on materials provided by Max Planck Institute of Quantum Optics. The original article was written by Olivia Meyer-Streng. Note: Materials may be edited for content and length.

Simulations back up theory that Universe is a hologram

A team of physicists has provided some of the clearest evidence yet that our Universe could be just one big projection.

Best evidence yet that our Universe is a hologram Whole protein hormone made from scratch in a testube Water gushes seasonally on Mars In 1997, theoretical physicist Juan Maldacena proposed1 that an audacious model of the Universe in which gravity arises from infinitesimally thin, vibrating strings could be reinterpreted in terms of well-established physics. The mathematically intricate world of strings, which exist in nine dimensions of space plus one of time, would be merely a hologram: the real action would play out in a simpler, flatter cosmos where there is no gravity. Maldacena's idea thrilled physicists because it offered a way to put the popular but still unproven theory of strings on solid footing — and because it solved apparent inconsistencies between quantum physics and Einstein's theory of gravity. It provided physicists with a mathematical Rosetta stone, a 'duality', that allowed them to translate back and forth between the two languages, and solve problems in one model that seemed intractable in the other and vice versa. But although the validity of Maldacena's ideas has pretty much been taken for granted ever since, a rigorous proof has been elusive. Related stories Black holes shrink but endure How to see quantum gravity in Big Bang traces Theoretical physics: The origins of space and time More related stories In two papers posted on the arXiv repository, Yoshifumi Hyakutake of Ibaraki University in Japan and his colleagues now provide, if not an actual proof, at least compelling evidence that Maldacena’s conjecture is true. In one paper2, Hyakutake computes the internal energy of a black hole, the position of its event horizon (the boundary between the black hole and the rest of the Universe), its entropy and other properties based on the predictions of string theory as well as the effects of so-called virtual particles that continuously pop into and out of existence. In the other3, he and his collaborators calculate the internal energy of the corresponding lower-dimensional cosmos with no gravity. The two computer calculations match. “It seems to be a correct computation,” says Maldacena, who is now at the Institute for Advanced Study in Princeton, New Jersey and who did not contribute to the team's work. Regime change The findings “are an interesting way to test many ideas in quantum gravity and string theory”, Maldacena adds. The two papers, he notes, are the culmination of a series of articles contributed by the Japanese team over the past few years. “The whole sequence of papers is very nice because it tests the dual [nature of the universes] in regimes where there are no analytic tests.” “They have numerically confirmed, perhaps for the first time, something we were fairly sure had to be true, but was still a conjecture — namely that the thermodynamics of certain black holes can be reproduced from a lower-dimensional universe,” says Leonard Susskind, a theoretical physicist at Stanford University in California who was among the first theoreticians to explore the idea of holographic universes. Neither of the model universes explored by the Japanese team resembles our own, Maldacena notes. The cosmos with a black hole has ten dimensions, with eight of them forming an eight-dimensional sphere. The lower-dimensional, gravity-free one has but a single dimension, and its menagerie of quantum particles resembles a group of idealized springs, or harmonic oscillators, attached to one another. Nevertheless, says Maldacena, the numerical proof that these two seemingly disparate worlds are actually identical gives hope that the gravitational properties of our Universe can one day be explained by a simpler cosmos purely in terms of quantum theory. Nature doi:10.1038/nature.2013.14328 References Maldacena, J. M. Adv. Theor. Math. Phys. 2, 231–252 (1998). Show context Hyakutake, Y. Preprint available at http://arxiv.org/abs/1311.7526 (2013). PubMedISI Show context Hanada, M., Hyakutake, Y., Ishiki, G. & Nishimura, J. Preprint available at http://arxiv.org/abs/1311.5607 (2013).

Physicists bang the drum for quantum memory

Physicists in the US say they are the first to store – and then retrieve – quantum information in a mechanical oscillator. Their device consists of an extremely thin disc of aluminium that is connected to a microwave circuit. Quantum information encoded in a microwave signal is transferred to the disc, which vibrates much like a drumhead. This information can then be retrieved by converting the mechanical oscillations back into microwaves. Built by Konrad Lehnert and colleagues at the National Institute of Standards and Technology in Boulder and the neighbouring University of Colorado, the team says the device can store quantum information for long enough to make it a potential candidate for a future quantum computer. Such machines could, in principle, outperform conventional computers at certain tasks, but require quantum bits (or qubits) that can store and transfer quantum information without it being destroyed by interacting with the outside world. Cool stuff Like many attempts to make "quantum memory", the qubits built by Lehnert and colleagues are "mesoscopic" objects – small enough to behave as quantum systems, yet large enough to fabricate on a chip and connect to other qubits. Weighing just 48 pg, their drumhead is a circular sheet of aluminium 15 μm in diameter and 100 nm thick. The entire device was chilled to 25 mK and the drum itself is put into its lowest-energy vibrational state (its ground state) using a microwave cooling technique. Quantum information is first encoded in the amplitude and phase of a microwave pulse. This pulse is then sent along a waveguide that sits next to a spiral-like resonant circuit that includes the drum (see figure; click to enlarge). The circuit is designed such that the pulse is completely absorbed by the circuit and the microwave energy is converted to vibrational energy stored in the drum. "At the end of the process, the mechanical oscillator quivers with a particular amplitude and phase, which is the amplitude and phase that the microwave signal had before it was absorbed," explains Lehnert. Towards improved efficiency This absorption process is controlled using a second microwave signal, with the presence or absence of this "transfer field" determining whether the pulse can move from the waveguide to the resonant circuit and vice versa. To read out the quantum information, the transfer field is adjusted so that the vibration of the drum is converted back to a microwave pulse, which can then jump into the waveguide and be measured by Lehnert and colleagues. In a typical experiment the team was able to store quantum information for about 25 μs without it degrading significantly. The team was also able to successfully store and retrieve the pulses in about 65% of attempts. According to Lehnert, this inefficiency arises because the microwave circuit is not perfect and some of the microwave signal is lost. But he is confident that smaller circuits will improve the performance. "We believe the prospects for improving this number are quite good, as other researchers have recently demonstrated microwave circuits with loss about 100 times smaller than we achieved," says Lehnert. Lehnert told physicsworld.com that his team's drums could be used in conjunction with superconducting qubits, which also operate at low temperatures and microwave frequencies. While mechanical oscillators cannot easily be connected with each other to create logic devices, they could be used to store quantum information that is then processed in superconducting devices. In particular, Lehnert points out that the linear nature of the device means that it could be used to store more than one qubit at the same time. Optical boost Another possible application in quantum information is using mechanical oscillators as quantum transducers, which convert quantum information from one form to another. "We are working on using mechanical oscillators to convert quantum information encoded in microwave electrical signals into information encoded as an optical field [light]," Lehnert says. Converting qubits from microwave to optical signals could play an important role in large-scale quantum information systems of the future. Although microwaves are very well suited for transferring quantum information in small ultracold devices, they cannot carry information over large distances. Optical signals, on the other hand, can travel tens or even hundreds of kilometres without losing their quantum nature.

Quantum simulation targets particle physics

A major challenge for physics in the last century was connecting two of its leading theories – quantum physics and special relativity. Researchers are still grappling with the relativistic quantum theories that resulted. Writing in Physical Review Letters, CQT researchers propose a solution to one outstanding problem: how to make predictions from the Thirring Model. The Thirring Model, which dates back to the 1950s, describes the interactions of relativistic fermions. Such particles are moving at speeds close enough to the speed of light to significantly experience time slowing and length contracting, as predicted by special relativity. Weird effects occur when the particles interact, such as the 'dressing' or changing of the particle's mass. Fermions are particles having the quantum property of half-integer spin. But researchers only know exactly what the Thirring Model predicts for fermions that have no mass. In this case, an exact solution to the equation of motion exists. However, when the model needs a mass term – for example, to describe the interactions of electrons or quarks – the mathematical solutions are cumbersome. Predictions for the behaviour of matter at these regimes are then hard or impossible to make. In their new paper, CQT's Dimitris Angelakis and his collaborators suggest a way to make predictions by quantum simulation. Over the past few years, Dimitris and his team have pioneered the idea of simulating quantum systems using photons. This approach was initially surprising because photons do not easily interact, making them apparently poor candidates to simulate interacting particles. The proposed simulations use techniques from nonlinear optics to create the effect of interactions between the photons. The team has previously shown that such photon-based quantum simulators could recreate phenomena such as the 'Luttinger liquid', an elusive state predicted in condensed matter physics, and the Cooper pairing of fermions in a superconductor. A collaboration with mathematical physicist Vladimir Korepin of the State University of New York at Stony Brook, US, who visited CQT in 2012, has now helped Dimitris and his collaborators show that the same kind of simulator system can mimic the Thirring Model, offering a way to tackled the unsolved cases. "He spoke maths and we spoke physics, but we managed to get something that makes sense from our collaboration," jokes Dimitris. The team proposes that polarised photons are confined in a one-dimensional system such as an optical fibre or waveguide, together with atoms that act as a nonlinear medium. Dimitris' student MingXia Huo, a co-author on the paper, performed calculations and simulations to show how the effective interactions could be controlled by outside lasers to make the photons behave like fermions. A photon with vertical polarisation simulates a fermion with spin 'up' and one with horizontal polarisation a fermion with spin 'down'. The proposal could point the way to simulations for other exotic fields theories, such as those describing the interaction of quarks in quantum chromodynamics. The photon-based simulator would be implementable in a table-top set-up, and Dimitris says some groups are close to having the kind of system required to test the simulation proposals. Handily, the fact that the Thirring model has already been solved for massless particles provides a way to test the simulator's output. The unknown solutions for massive particles can then be probed by tuning optical parameters such as the photon-atom interactions which give mass to the particles.. Dimitris is a Principal Investigator at CQT and faculty at the Science Department, Technical University of Crete in Greece. He, MingXia and Vladimir carried out the work with CQT PI Leong Chuan Kwek and Darrick Chang from the Institut de Ciencies Fotoniques (ICFO) near Barcelona, Spain. MingXia is a final-year PhD student co-supervised by Dimitris and Kwek. For more details, see the research article "Mimicking interacting relativistic theories with stationary pulses of light", Phys. Rev. Lett. 110, 100502 (2013); arXiv: 1207.727

Quantum darwinism, The reality of reality?

An electron, atom, or other quantum system can be many places at once. It collapses into a single location when an observer pinpoints it, but what happens when an object is not being measured? Can it choose a location on its own, or must it wait for an observer? SFI External Professor Wojciech Zurek might have an answer. His Theory of Quantum Darwinism applies natural selection to our quantum universe. It builds on the theory of decoherence, which shows that a quantum particle can no longer be in many places at once not only at the moment it’s measured, but also when it interacts with its environment, which can be a de facto observer. (For a particle, common environments are photons and air molecules. Scaling up to a more tangible level, our world persists in its classical state only because large objects can never be fully isolated from their surroundings.) Quantum Darwinism goes beyond decoherence by studying imprints left by the system on the environment, he says. Drawing from natural selection, where the fittest survive and proliferate, Quantum Darwinism shows that certain states are selected because they survive better than others in a given environment. Surviving states then proliferate by spreading information about themselves, and we discover them indirectly by intercepting tiny fractions of the environment. This is how consensus about the fittest states -- the “objective classical reality” we take for granted -- arises in our quantum universe, Zurek says, and how effectively classical states that exist objectively, immune to measurement, emerge from a quantum substrate. Recent studies have offered evidence in support of Zurek’s theory. Now, with his newly awarded grant from the John Templeton Foundation, he will examine how quantum information propagates, and how the classical world of our everyday experience emerges from the quantum ingredients.

Timing glitches dog neutrino claim

BY EUGENIE SAMUEL REICH

Is it an epic blunder or a textbook demonstration of how science should work? To some physicists, the OPERA (Oscillation Project with Emulsion-tracking Apparatus) collaboration deserves credit for disclosing possible errors in its paradigm-challenging measurement of neutrinos travelling faster than light. “I think we did the right thing to continue to investigate,” says Dario Autiero of the Institute of Nuclear Physics of Lyons in France, who presented the original results and notes that the collaboration had spent six months checking its result before its announcement last September. To others, the revelation shows that the OPERA team went public too soon with its claim that neutrinos from CERN, the European particle-physics laboratory near Geneva in Switzerland, were flouting Albert Einstein’s absolute limit on the speed of light as they travelled the 730 kilometres to the OPERA detector at the underground Gran Sasso National Laboratory near L’Aquila, Italy. “I find it embarrassing,” says Luca Stanco of the National Institute of Nuclear Physics in Padova, Italy, an OPERA member who initially refused to sign a paper about the result. “Maybe we should have been more cautious and done more checks.”
On 23 February, OPERA team members reported two possible sources of error in the experiment. The initial result suggested that the neutrinos were reaching the detector 60 nanoseconds faster than the speed of light would allow. Both potential errors would affect the neutrinos’ arrival time, as measured by OPERA’s master clock (see ‘Timing trouble’). The first is a faulty connection at the point at which the light from a fibre-optic cable brings a synchronizing Global Positioning System (GPS) signal into the master clock. The fault could have delayed the GPS signal, causing the master clock to run slow and thus causing the neutrinos’ travel time to appear shorter than it actually was.
“It’s a subtle effect,” says Autiero, and one that was evident only when the team examined many measurements of signals passing through the connection. Tests of the timing system turned up a second, opposing effect: an oscillator within the master clock that keeps time between the arrivals of synchronization signals was running fast. That would have made the neutrinos’ travel time seem longer.
The collaboration says that it has not yet worked out the magnitude of these effects. Autiero says that because of the high profile of the result and the possibility of rumours and leaks, the collaboration wanted to disclose the potential errors promptly. The OPERA team plans to correct the faults and repeat the experiment after CERN’s neutrino beam is switched on again in March, following a winter break. Two independent checks of the measurement are also being considered. One, at Japan’s Tokai to Kamioka (T2K) neutrino experiment, would still be valuable despite the doubt cast on the OPERA data, but may now prove harder to fund, says international co-spokesman Chang Kee Jung, a physicist at Stony Brook University in New York. But another, the Main Injector Neutrino Oscillation Search (MINOS) experiment, which fires neutrinos from Fermilab in Batavia, Illinois, to an underground detector in northern Minnesota, will proceed, at a cost of about US$500,000. “It’s never a bad idea to have multiple measurements,” says MINOS
co-spokesman Rob Plunkett.
Jorge Páramos, a physicist at the Higher Technical Institute in Lisbon, says that the admissions by OPERA point to an honest mistake, albeit one that should have been avoided. “The putative origin of the systematic error reflects the innards of the experiment — something that should have been checked exhaustively before any public announcement,” he says.

Source: Nature Physics
By Shabir Barzanjeh.

10 Tops topics which will shake our scientific notion

The two physics stories that dominated the news in 2011 were questions rather than solid scientific results, namely "Do neutrinos travel faster than light?" and "Has the Higgs boson been found?". However, there have also been some fantastic bona fide research discoveries over the last 12 months, which made it difficult to decide on the Physics World 2011 Breakthrough of the Year. But after much debate among the Physics World editorial team, this year's honour goes to Aephraim Steinberg and colleagues from the University of Toronto in Canada for their experimental work on the fundamentals of quantum mechanics. Using an emerging technique called "weak measurement", the team is the first to track the average paths of single photons passing through a Young's double-slit experiment – something that Steinberg says physicists had been "brainwashed" into thinking is impossible. We have also awarded nine runners-up (see below). The choice between first and second place was particularly close this year because the number-two finding also involves weak measurement – this time to map the wavefunction of a bunch of photons. But we felt that Steinberg's finding edged it. Other breakthroughs in the list include the first "space–time" cloak, a laser made from a living cell and a new way to measure cosmic distances.

1st place: Shifting the morals of quantum measurement
Steinberg's work stood out because it challenges the widely held notion that quantum mechanics forbids us any knowledge of the paths taken by individual photons as they travel through two closely spaced slits to create an interference pattern. This interference is exactly what one would expect if we think of light as an electromagnetic wave. But quantum mechanics also allows us to think of the light as photons – although with the weird consequence that if we determine which slit individual photons travel through, then the interference pattern vanishes. By using weak measurements Steinberg and his team have been able to gain some information about the paths taken by the photons without destroying the pattern. In the experiment, the double slit is replaced by a beamsplitter and a pair of optical fibres. A single photon strikes the beamsplitter and travels along either the right or the left fibre. After emerging from the closely spaced ends of the parallel fibres, it creates an interference pattern on a detector screen. The weak measurement is performed by passing the emerging photons through a piece of calcite, which imparts a tiny rotation in the polarization of the photon. The amount of rotation depends on the direction of travel of the photon – in other words, its momentum. The photons are then "post-selected" according to where they strike the screen, which allows the researchers to determine the average direction of travel of photons that arrive there. The experiment reveals, for example, that a photon detected on the right-hand side of the diffraction pattern is more likely to have emerged from the optical fibre on the right than from the optical fibre on the left. While this knowledge is not forbidden by quantum mechanics, Steinberg says that physicists have been taught that "asking where a photon is before it is detected is somehow immoral". "Little by little, people are asking forbidden questions," says Steinberg, who adds that his team's experiment will "push [physicists] to change how they think about things".

2nd place: Measuring the wavefunction
Second place goes to another group that has asked a "forbidden question". Led by Jeff Lundeen at the National Research Council of Canada in Ottawa – a former colleague of Steinberg – a team has used weak measurement to map out the wavefunction of an ensemble of identical photons without actually destroying any of them. Quantum tomography, in contrast, maps out the wavefunction at the expense of destroying the state. As well as boosting our understanding of the fundamentals of quantum mechanics, the technique could prove useful in cases where tomography cannot be used.

3rd place: Cloaking in space and time
Coming in at third place are two teams – one at Cornell University in the US led by Alexander Gaeta, and the other at Imperial College London headed by Martin McCall. In early 2011 McCall's team published a theoretical analysis of how an event in space and time could be cloaked, which he later described in a special Physics World feature. A few months later, Gaeta and colleagues built a device that uses two "split time lenses" to do just that. As well as changing our ideas about what can and cannot be cloaked, space–time cloaking could also be used in the perfect bank heist – at least in theory.

4th place: Measuring the universe using black holes
Fourth spot on the list goes to Darach Watson and colleagues at the University of Copenhagen, Denmark, and the University of Queensland, Australia, who have worked out a way of using supermassive black holes – which power active galactic nuclei (AGNs) – as "standard candles" for making accurate measurements of cosmic distances. The work is important because AGNs can be found just about everywhere in the universe, and unlike the supernovae currently used as standard candles, the light from AGNs endures for long periods of time.

5th place: Turning darkness into light
Christopher Wilson and colleagues of Chalmers University of Technology in Sweden together with physicists in Japan, Australia and the US have bagged fifth place because they are the first to see the dynamical Casimir effect in the lab. The effect arises when a mirror is moving so quickly through a vacuum that pairs of virtual photons – which are always appearing and then annihilating – are pulled apart to create real photons that can then be detected. As well as shedding new light on the Casimir effect, the team's use of a superconducting quantum interference device (SQUID) as the mirror make this an extremely clever experiment.

6th place: Taking the temperature of the early universe
Just after the Big Bang, the universe was a complicated soup of free quarks and gluons that eventually condensed to form the protons and neutrons we see today. Sixth place in our top 10 goes to a team of physicists in the US, India and China that has made the best calculation yet of this condensation temperature: two trillion degrees Kelvin. As well as providing important insights into the early universe, the work also advances our understanding of quantum chromodynamics, which describes the properties of neutrons, protons and other hadrons.

7th place: Catching the flavour of a neutrino oscillation
Seventh place is awarded to the international team of physicists working on the Tokai-to-Kamioka (T2K) experiment in Japan. The researchers fired a beam of muon neutrinos 300 km underground to a detector, where they found that six neutrinos had changed, or "oscillated", into electron neutrinos. While the measurement is not good enough to claim the discovery of the muon-to-electron neutrino oscillation, it is the best evidence yet that one "flavour" of neutrino can oscillate into another.

8th place: Living laser brought to life
In a fascinating bit of biophysics, Malte Gather and Seok Hyun Yun at Harvard Medical School in the US share eighth place for being the first to make a laser from a living biological cell. By shining intense blue light onto green fluorescent protein molecules inside an embryonic kidney cell, the molecules generate light that is intense, monochromatic and directional. The cells survive the ordeal and this amazing phenomenon could potentially be used to distinguish cancerous cells from healthy ones.

9th place: Complete quantum computer made on a single chip
Ninth place goes to Matteo Mariantoni and colleagues at the University of California, Santa Barbara for being the first to implement a quantum version of the "Von Neumann" architecture found in PCs. Based on superconducting circuits and integrated on a single chip, the new device has been used to perform two important quantum-computing algorithms. Its development moves us closer to the creation of practical quantum computers that solve real-life problems.

10th place: Seeing pure relics from the Big Bang
Michele Fumagalli and Xavier Prochaska of the University of California, Santa Cruz and John O'Meara of Saint Michael's College in Vermont take 10th spot for being the first to catch sight of clouds of gas that are pure relics of the Big Bang. Unlike other clouds in the distant universe – which appear to contain elements created by stars – these clouds contain just the hydrogen, helium and lithium created by the Big Bang. As well as confirming predictions of the Big Bang theory, the clouds provide a unique insight into the materials from which the first stars and galaxies were born.

Source:physicsworld
Shabir. Barzanjeh