Posts belonging to Category quantum



Quantum Satellite Secures Communications

A Chinese quantum satellite has dispatched transmissions over a distance of 1,200 km (746 miles), a dozen times further than the previous record, a breakthrough in a technology that could be used to deliver secure messages, state media said on Friday.

China launched the world’s first quantum satellite last August, to help establish “hack proof” communications between space and the ground, state media said at the time.

The feat opens up “bright prospects” for quantum communications, said Pan Jianwei, the lead scientist of the Chinese team, Quantum Experiments at Space Scale (QUESS), according to the official Xinhua news agency.

The scientists exploited the phenomenon of quantum entanglement, in which a particle can affect a far-off twin instantly, somehow overcoming the long distance separating them, a situation termed “spooky action at a distance” by the Nobel-prize winning physicist Albert Einstein, Xinhua added.

The team had successfully distributed entangled photon pairs over 1,200 km, it said, outstripping the distance of up to 100 km (62 miles) at which entanglement had previously been achieved.

The technology so far is “the only way to establish secure keys between two distant locations on earth without relying on trustful relay,” Pan told Xinhua, referring to encrypted messages.

The new development “illustrates the possibility of a future global quantum communication network” the journal Science, which published the results of the Chinese team, said on its website.

Source: http://www.reuters.com/

NanoCar Race

The NanoCar Race is an event in which molecular machines compete on a nano-sized racetrack. These “NanoCars” or molecule-cars can have real wheels, an actual chassis…and are propelled by the energy of electric pulses! Nothing is visible to the naked eye, however a unique microscope located in Toulouse (France) will make it possible to follow the race. A genuine scientific prowess and international human adventure, the race is a one-off event, and will be broadcast live on the web, as well as at the Quai des Savoirs, science center in Toulouse.

nanocars

The NanoCar race takes place on a very small scale, that of molecules and atoms: the nano scale…as in nanometer! A nanometer is a billionth of a meter, or 0.000000001 meters or 10 -9 m. In short, it is 500,000 times thinner then a line drawn by a ball point pen; 30,000 times thinner than the width of a hair; 100 times smaller than a DNA molecule; 4 atoms of silicon lined up next to one another.

A very powerful microscope is necessary to observe molecules and atoms: the scanning tunneling microscope (STM) makes this possible, and it is also responsible for propelling the NanoCars. The scanning tunneling microscope was invented in 1981 by Gerd Binnig and Heinrich Rohrer, and earned them the Nobel Prize in Physics in 1986. The tunnel effect is a phenomenon in quantum mechanics: using a tip and an electric current, the microscope will use this phenomenon to determine the electric conductance between the tip and the surface, in other words the amount of current that is passing through.

nanocar in movement Screening provides an electronic map of the surface and of each atom or molecule placed on it.At the CNRS‘s Centre d’élaboration de matériaux et d’études structurales (CEMES) in Toulouse, it is the one of a kind STM microscope that makes the race possible: the equivalent of four scanning tunneling microscopes, this device is the only one able to simultaneously and independently map four sections of the track in real time, thanks to its four tungsten tips.

Source: http://nanocar-race.cnrs.fr/

Light Makes OscillatorTo Oscillate Indefinitely

Researchers have designed a device that uses light to manipulate its mechanical properties. The device, which was fabricated using a plasmomechanical metamaterial, operates through a unique mechanism that couples its optical and mechanical resonances, enabling it to oscillate indefinitely using energy absorbed from light.

metamaterialThis work demonstrates a metamaterial-based approach to develop an optically-driven mechanical oscillator. The device can potentially be used as a new frequency reference to accurately keep time in GPS, computers, wristwatches and other devices, researchers said. Other potential applications that could be derived from this metamaterial-based platform include high precision sensors and quantum transducers..

Researchers engineered the metamaterial-based device by integrating tiny light absorbing nanoantennas onto nanomechanical oscillators. The study was led by Ertugrul Cubukcu, a professor of nanoengineering and electrical engineering at the University of California San Diego. The work, which Cubukcu started as a faculty member at the University of Pennsylvania and is continuing at the Jacobs School of Engineering at UC San Diego, demonstrates how efficient light-matter interactions can be utilized for applications in novel nanoscale devices.

Metamaterials are artificial materials that are engineered to exhibit exotic properties not found in nature. For example, metamaterials can be designed to manipulate light, sound and heat waves in ways that can’t typically be done with conventional materials.

Metamaterials are generally considered “lossy” because their metal components absorb light very efficiently. “The lossy trait of metamaterials is considered a nuisance in photonics applications and telecommunications systems, where you have to transmit a lot of power. We’re presenting a unique metamaterials approach by taking advantage of this lossy feature,” Cubukcu said. The researchers also point out that because the plasmomechanical metamaterial can efficiently absorb light, it can function under a broad optical resonance. That means this metamaterial can potentially respond to a light source like an LED and won’t need a strong laser to provide the energy.

Using plasmonic metamaterials, we were able to design and fabricate a device that can utilize light to amplify or dampen microscopic mechanical motion more powerfully than other devices that demonstrate these effects. Even a non-laser light source could still work on this device,” said Hai Zhu, a former graduate student in Cubukcu’s lab and first author of the study.

Optical metamaterials enable the chip-level integration of functionalities such as light-focusing, spectral selectivity and polarization control that are usually performed by conventional optical components such as lenses, optical filters and polarizers. Our particular metamaterial-based approach can extend these effects across the electromagnetic spectrum,” adds Fei Yi, a postdoctoral researcher who worked in Cubukcu’s lab.

The research was published in the journal Nature Photonics.

Source: http://jacobsschool.ucsd.edu/

The First Satellite Using Quantum Cryptography Is Chinese

Congratulations are in order for China: by launching the world’s first quantum communications satellite, the country has achieved an interesting — if somewhat difficult to explain — milestone in space and cryptography.

quantum dots

Quantum Experiments at Space Scale (QUESS), nicknamed Micius after the philosopher, lifted off from Jiuquan Satellite Launch Center at 1:40 AM local time (late yesterday in the U.S.) and is currently maneuvering itself into a sun-synchronous orbit at 500 km.

So what’s in the package that’s so exciting?

QUESS is an experiment in the deployment of quantum cryptography — specifically, a prototype that will test whether it’s possible to perform this delicate science from space. Inside QUESS is a crystal that can be stimulated into producing two photons that are “entangled” at a subatomic, quantum level. Entangled photons have certain aspects — polarization, for example — that are the same for both regardless of distance; if one changes, the other changes. The trouble is that photons are rather finicky things, and tend to be bounced, absorbed, and otherwise interfered with when traveling through fibers, air, and so on. QUESS will test whether sending them through space is easier, and whether one of a pair of entangled photons can be successfully sent to the surface while the other remains aboard the satellite.

If this is possible, the entangled photons can be manipulated in order to send information; the satellite could, for example, send binary code by inverting its photon’s polarization, one way for 1, the other way for 0. The ground station would see its photon switching back and forth and record the resulting data. This process would be excruciatingly slow, but fast enough for, say, key creation and exchange — after which data can be exchanged securely by more ordinary means. The critical thing about this is that there is no transmission involved, or at least not one we understand and can intercept.

Source: https://techcrunch.com/

How To Remove Nanoparticles From Blood

Engineers at the University of California, San Diego developed a new technology that uses an oscillating electric field to easily and quickly isolate drug-delivery nanoparticles from blood. The technology could serve as a general tool to separate and recover nanoparticles from other complex fluids for medical, environmental, and industrial applications.

Nanoparticles, which are generally one thousand times smaller than the width of a human hair, are difficult to separate from plasma, the liquid component of blood, due to their small size and low density. Traditional methods to remove nanoparticles from plasma samples typically involve diluting the plasma, adding a high concentration sugar solution to the plasma and spinning it in a centrifuge, or attaching a targeting agent to the surface of the nanoparticles. These methods either alter the normal behavior of the nanoparticles or cannot be applied to some of the most common nanoparticle types.

nanoparticles in blood

Nanoparticle removal chip developed by researchers in Professor Michael Heller’s lab at the UC San Diego Jacobs School of Engineering. An oscillating electric field (purple arcs) separates drug-delivery nanoparticles (yellow spheres) from blood (red spheres) and pulls them towards rings surrounding the chip’s electrodes.

This is the first example of isolating a wide range of nanoparticles out of plasma with a minimum amount of manipulation,” said Stuart Ibsen, a postdoctoral fellow in the Department of NanoEngineering at UC San Diego and first author of the study published October in the journal Small.
We’ve designed a very versatile technique that can be used to recover nanoparticles in a lot of different processes.”

Source: http://ucsdnews.ucsd.edu/

How To Manipulate Light

Electrons are so 20th century. In the 21st century, photonic devices, which use light to transport large amounts of information quickly, will enhance or even replace the electronic devices that are ubiquitous in our lives today. But there’s a step needed before optical connections can be integrated into telecommunications systems and computers: researchers need to make it easier to manipulate light at the nanoscale.

Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have done just that, designing the first on-chip metamaterial with a refractive index of zero, meaning that the phase of light can travel infinitely fast.

This new metamaterial was developed in the lab of Eric Mazur, the Balkanski Professor of Physics and Applied Physics and Area Dean for Applied Physics at SEAS, and is described in the journal Nature Photonics.

manipulated light

New zero-index material made of silicon pillar arrays embedded in a polymer matrix and clad in gold film creates a constant phase of light, which stretches out in infinitely long wavelengths

Light doesn’t typically like to be squeezed or manipulated but this metamaterial permits you to manipulate light from one chip to another, to squeeze, bend, twist and reduce diameter of a beam from the macroscale to the nanoscale,” said Mazur. “It’s a remarkable new way to manipulate light.”

Although this infinitely high velocity sounds like it breaks the rule of relativity, it doesn’t. Nothing in the universe travels faster than light carrying information — Einstein is still right about that. But light has another speed, measured by how fast the crests of a wavelength move, known as phase velocity. This speed of light increases or decreases depending on the material it’s moving through.

When light passes through water, for example, its phase velocity is reduced as its wavelengths get squished together. Once it exits the water, its phase velocity increases again as its wavelength elongates. How much the crests of a light wave slow down in a material is expressed as a ratio called the refraction index — the higher the index, the more the material interferes with the propagation of the wave crests of light. Water, for example, has a refraction index of about 1.3.

When the refraction index is reduced to zero, really weird and interesting things start to happen.

Source: https://www.seas.harvard.edu

Teleportation

Mention the word ‘teleportation’ and for many people it conjures up “Beam me up, Scottie” images of Captain James T Kirk.
teleportation2But in the last two decades quantum teleportation – transferring the quantum structure of an object from one place to another without physical transmission — has moved from the realms of Star Trek fantasy to tangible reality.

Quantum teleportation is an important building block for quantum computing, quantum communication and quantum network and, eventually, a quantum Internet. While theoretical proposals for a quantum Internet already exist, the problem for scientists is that there is still debate over which of various technologies provides the most efficient and reliable teleportation system. This is the dilemma which an international team of researchers, led by Dr Stefano Pirandola of the Department of Computer Science at the University of York (UK), set out to resolve.

In a paper published in Nature Photonics, the team, which included scientists from the Freie Universität Berlin and the Universities of Tokyo and Toronto, reviewed the theoretical ideas around quantum teleportation focusing on the main experimental approaches and their attendant advantages and disadvantages. None of the technologies alone provide a perfect solution, so the scientists concluded that a hybridisation of the various protocols and underlying structures would offer the most fruitful approach.

For instance, systems using photonic qubits work over distances up to 143 kilometres, but they are probabilistic in that only 50 per cent of the information can be transported. To resolve this, such photon systems may be used in conjunction with continuous variable systems, which are 100 per cent effective but currently limited to short distances.

Most importantly, teleportation-based optical communication needs an interface with suitable matter-based quantum memories where quantum information can be stored and further processed.

Dr Pirandola, who is also a member of the York Centre for Quantum Technologies, said: “We don’t have an ideal or universal technology for quantum teleportation. The field has developed a lot but we seem to need to rely on a hybrid approach to get the best from each available technology.

teleportation

The use of quantum teleportation as a building block for a quantum network depends on its integration with quantum memories. The development of good quantum memories would allow us to build quantum repeaters, therefore extending the range of teleportation. They would also give us the ability to store and process the transmitted quantum information at local quantum computers.
“This could ultimately form the backbone of a quantum Internet. The revised hybrid architecture will likely rely on teleportation-based long-distance quantum optical communication, interfaced with solid state devices for quantum information processing.

Source: https://www.york.ac.uk/

Solar Cells Collect 30 Times More From Sun’s Photons

By combining designer quantum dot light-emitters with spectrally matched photonic mirrors, a team of scientists with Berkeley Lab and the University of Illinois created solar cells that collect blue photons at 30 times the concentration of conventional solar cells, the highest luminescent concentration factor ever recorded. This breakthrough paves the way for the future development of low-cost solar cells that efficiently utilize the high-energy part of the solar spectrum.

sun

 Solar (or photovoltaic) cells convert the sun’s energy into electricity. Whether they’re adorning your calculator or orbiting our planet on satellites, they rely on the the photoelectric effect: the ability of matter to emit electrons when a light is shone on it. Silicon is what is known as a semi-conductor, meaning that it shares some of the properties of metals and some of those of an electrical insulator, making it a key ingredient in solar cells. Let’s take a closer look at what happens when the sun shines onto a solar cell.
Sunlight is composed of miniscule particles called photons, which radiate from the sun. As these hit the silicon atoms of the solar cell, they transfer their energy to loose electrons, knocking them clean off the atoms. The photons could be compared to the white ball in a game of pool, which passes on its energy to the coloured balls it strikes. Freeing up electrons is however only half the work of a solar cell: it then needs to herd these stray electrons into an electric current. This involves creating an electrical imbalance within the cell, which acts a bit like a slope down which the electrons will flow in the same direction. Creating this imbalance is made possible by the internal organisation of silicon.

Source: http://newscenter.lbl.gov/

How To Store Solar Energy Up To Several Weeks

The materials in most of today’s residential rooftop solar panels can store energy from the sun for only a few microseconds at a time. A new technology developed by chemists at UCLA is capable of storing solar energy for up to several weeks — an advance that could change the way scientists think about designing solar cells.

The new design is inspired by the way that plants generate energy through photosynthesis.
bundle of polymers

The scientists devised a new arrangement of solar cell ingredients, with bundles of polymer donors (green rods) and neatly organized fullerene acceptors (purple, tan).
Biology does a very good job of creating energy from sunlight,” said Sarah Tolbert, a UCLA professor of chemistry and one of the senior authors of the research. “Plants do this through photosynthesis with extremely high efficiency.” “In photosynthesis, plants that are exposed to sunlight use carefully organized nanoscale structures within their cells to rapidly separate charges — pulling electrons away from the positively charged molecule that is left behind, and keeping positive and negative charges separated,” Tolbert said. “That separation is the key to making the process so efficient.

To capture energy from sunlight, conventional rooftop solar cells use silicon, a fairly expensive material.  There is currently a big push to make lower-cost solar cells using plastics, rather than silicon, but today’s plastic solar cells are relatively inefficient, in large part because the separated positive and negative electric charges often recombine before they can become electrical energy.

Modern plastic solar cells don’t have well-defined structures like plants do because we never knew how to make them before,” Tolbert said. “But this new system pulls charges apart and keeps them separated for days, or even weeks. Once you make the right structure, you can vastly improve the retention of energy.”

The findings are published June 19 in the journal Science.

 

Source: http://newsroom.ucla.edu/

Super-Efficient Light-Based Nanocomputers

Stanford electrical engineer Jelena Vuckovic wants to make computers faster and more efficient by reinventing how they send data back and forth between chips, where the work is done.

In computers today, data is pushed through wires as a stream of electrons. That takes a lot of power, which helps explain why laptops get so warm.

Several years ago, my colleague David Miller carefully analyzed power consumption in computers, and the results were striking,” said Vuckovic, referring to David Miller, the W.M. Keck Foundation Professor of Electrical Engineering. “Up to 80 percent of the microprocessor power is consumed by sending data over the wires – so-called interconnects.”

In a Nature Photonics article whose lead author is Stanford graduate student Alexander Piggott, Vuckovic, a professor of electrical engineering, and her team explain a process that could revolutionize computing by making it practical to use light instead of electricity to carry data inside computers.

infrared lightIn essence, the Stanford engineers want to miniaturize the proven technology of the Internet, which moves data by beaming photons of light through fiber optic threads

Optical transport uses far less energy than sending electrons through wires,” Piggott said. “For chip-scale links, light can carry more than 20 times as much data.”

Theoretically, this is doable because silicon is transparent to infrared light – the way glass is transparent to visible light. So wires could be replaced by optical interconnects: silicon structures designed to carry infrared light.
Source: http://engineering.stanford.edu/

Black Silicon Solar Cells Efficiency Jump

Researchers from Aalto University (Finland) together with colleagues from Universitat Politècnica de Catalunya (Spain) have obtained the record-breaking efficiency of 22.1% on nanostructured silicon solar cells as certified by Fraunhofer ISE CalLab. An almost 4% absolute increase to their previous record is achieved by applying a thin passivating film on the nanostructures by Atomic Layer Deposition, and by integrating all metal contacts on the back side of the cell.black_silicon_solar_cell_hele_savin_aalto_university_en

The surface recombination has long been the bottleneck of black silicon solar cells and has so far limited the cell efficiencies to only modest values. The new record cells consists of a thick back-contacted structure that is known to be highly sensitive to the front surface recombination. The certified external quantum efficiency of 96% at 300nm wavelength demonstrates that the increased surface recombination problem no longer exists and for the first time the black silicon is not limiting the final energy conversion efficiency. The energy conversion efficiency is not the only parameter that we should look at, explains Professor Hele Savin from Aalto University, who coordinated the study. Due to the ability of black cells to capture solar radiation from low angles, they generate more electricity already over the duration of one day as compared to the traditional cells.

The results were published online 18.5.2015 in Nature Nanotechnology.
Source: http://www.aalto.fi/

Solar Cell: How To Boost Perovskites Performance

One of the fastest-growing areas of solar energy research is with materials called perovskites. These promising light harvesters could revolutionize the solar and electronics industries because they show potential to convert sunlight into electricity more efficiently and less expensively than today’s silicon-based semiconductors. These superefficient crystal structures have taken the scientific community by storm in the past few years because they can be processed very inexpensively and can be used in applications ranging from solar cells to light-emitting diodes (LEDs) found in phones and computer monitors.
A new study published online in the journal Science by University of Washington (UW) and University of Oxford researchers demonstrates that perovskite materials, generally believed to be uniform in composition, actually contain flaws that can be engineered to improve solar devices even further.
peroskite solar cell
Perovskites are the fastest-growing class of photovoltaic material over the past four years,” said lead author Dane deQuilettes, a UW doctoral student working with David Ginger, professor of chemistry and associate director of the UW Clean Energy Institute.

In that short amount of time, the ability of these materials to convert sunlight directly into electricity is approaching that of today’s silicon-based solar cells, rivaling technology that took 50 years to develop,” deQuilettes said. “But we also suspect there is room for improvement.”

Perovskite solar cells have so far have achieved efficiencies of roughly 20 percent, compared to about 25 percent for silicon-based solar cells. The team found “dark” or poorly performing regions of the perovskite material at intersections of the crystals. In addition, they discovered that they could “turn on” some of the dark areas by using a simple chemical treatment.
Source: http://www.washington.edu/