Lamina Tenuissima...

Illustration of a tungsten disulfide monolayer suspended in air and patterned with a square array of nanoholes. Upon laser excitation, the monolayer emits photoluminescence. A portion of this light couples into the monolayer and is guided along the material. At the nanohole array, periodic modulation in the refractive index causes a small portion of the light to decay out of the plane of the material, allowing the light to be observed as guided mode resonance. Courtesy: E Cubukcu, UCSD

Note: lamina tenuissima = thinnest (Latin)

Topics: Applied Physics, Nanotechnology, Optical Physics, Photonics

Researchers have succeeded in making the thinnest ever optical device in the form of a waveguide just three atomic layers thick. The device could lead to the development of higher density optoelectronic chips.

Optical waveguides are crucial components in data communication technologies but scaling them down to the nanoscale has proved to be no easy task, despite important advances in nano-optics and nanomaterials. Indeed, the thinnest waveguide used in commercial applications today is hundreds of nanometres thick and researchers are studying nanowire waveguides down to 50 nm in the laboratory.

“We have now pushed this limit down to just three atoms thick,” says Ertugrul Cubukcu of the University of California at San Diego, who led this new research effort. “Such a thin waveguide, which is at the ultimate limit for how thin an optical waveguide can be built, might potentially lead to a higher density of waveguides or optical elements on an optoelectronic chip – in the same way that ever smaller transistors have led to a higher density of these devices on an electronic chip.”

Cubukcu and colleagues’ waveguide is just six angstroms thick. This makes it 104 times thinner than a typical optical fiber and about 500 times thinner than on-chip optical waveguides in integrated photonic circuits.

Three-atom-thick optical waveguide is the thinnest ever, Belle Dumé, Physics World

3D Topological Insulators...

Courtesy: H. Chen

Topics: Laser, Optical Physics, Photonics, Materials Science, Nanotechnology, Quantum Mechanics

Reference: Topological Insulators, then the rest of the post.

Researchers in China and Singapore say they have made the first ever 3D photonic topological insulator using a stack of thin plastic sheets embedded with metal nanoantennas. The insulator works at microwave frequencies, but if extended to terahertz or optical wavelengths, it could find use in applications such as high-power lasers, optical diodes and photonic computer chips.

2D topological insulators, also known as 2D quantum spin Hall insulators, are materials that are electrical insulators in the bulk but can conduct electricity extremely well on their edge via special, topologically protected, electronic states. Electrons can only travel in one direction along these states and do not backscatter. This means that they can carry electrical current with near-zero dissipation of energy and so could be used to make energy-efficient electronic devices in the future.

Structures made from photonic crystals

In recent years, researchers have started looking at making topological insulators that work using light rather than electric currents. These structures are made from photonic crystals – materials in which the periodic variation of the refractive index means that only certain wavelengths of light are able to pass through. One of the advantages of these photonic topological insulators is that they can operate at room temperature, unlike their electronic counterparts.

Another is that the space through which photons can travel can be engineered so that it is curved like the surface of a cone. These structures thus mimic a 2D quantum spin Hall insulator that naturally contains so-called surface Dirac cones. These are the sharp single points in a 2D material at which the valence and the conduction bands meet at the Fermi level, and at which electrons behave as though they are relativistic particles with no rest mass.

3D topological insulators go photonic, Belle Dumé, Physics World

Nanophotonics and Darkness...

A finite photonic crystal nanostructure in free space. The photonic crystal consists of periodic arrangements of pores in a semiconductor material such as silicon (shown in grey) that are being fabricated in Twente. Light noise in the surrounding free space is shown as the red wavelets. For a range of colours of light (known as the photonic band gap), the light noise is forbidden from entering the crystal, thus leading to strong darkness. The question solved in Twente is: How fast is absolute darkness reached while making the nanostructure larger and larger? Courtesy: University of Twente

Topics: Applied Physics, Nanotechnology, Optics, Photonics

Just as there is no such thing as a complete vacuum, there is no such thing as complete darkness. This is because there are always continuous fluctuations of light in space, also known as light noise. Theory predicts that this light noise might be completely eliminated in photonic crystals, however, so allowing them to become absolutely dark.

Photonic crystals are nanostructured materials in which a periodic variation of the refractive index on the length scale of visible light produces a photonic “band gap”. This gap affects how photons propagate through the material and is similar to the way in which a periodic potential in semiconductors affects the flow of electrons by defining allowed and forbidden energy bands. In the case of photonic crystals, light of certain wavelength ranges can pass through the photonic band gap while light in other ranges is reflected.

Photonic crystals follow a straight path to absolute darkness, Belle Dumé, Physics World

58 Years to the Blue Ray...

Bright prospect: the first International Day of Light will be celebrated on 16 May. (Courtesy: iStock/RichLegg)

Topics: Applied Physics, Laser, Optical Physics, Photonics

This month sees the first International Day of Light. Wednesday 16 May was chosen because it is the anniversary of the first successful operation of the laser, as demonstrated by the American engineer and physicist Ted Maiman in 1960.

It’s a good choice, because the laser is a perfect example of how a scientific discovery can yield revolutionary benefits to society in all sorts of areas, including communications, healthcare and manufacturing. However, when I read the words “first successful operation of the laser” on the International Day of Light website (lightday.org), I had to look further, as it sounded like there might be more to the story.

I have spent most of my career working in photonics, optical communications and lighting, so I was already somewhat familiar with the laser’s history. However, the details still interested me. It turns out that although Maiman did indeed demonstrate the first working laser on 16 May 1960, he is not the only person with a reasonable claim to have “invented” the laser. The other is Gordon Gould, another US physicist who described “Some rough calculations on the feasibility of a LASER: Light Amplification by Stimulated Emission of Radiation” in his lab notebook in November 1957.

A day of light, James McKenzie, Physics World

Quantum Light on a Chip...

A laser (green) excites the quantum dot (red) in this diagram of the chip. The ring, which is tuned via applying voltage to the yellow contacts, manipulates the characteristics of individual photons (ellipsoids).

Topics: Laser, Nanotechnology, Photonics, Quantum Dots, Quantum Mechanics, Solid State Physics

Ideally, optical circuits would generate and shuttle light so well that researchers could use them to transmit encoded information, sense chemical species, and perform quantum computations. But because the components for each circuit—light sources, mirrors, splitters, filters, and waveguides—occupy several feet of table space, they cannot manipulate light down to the nanoscale. In an effort to downsize components and produce practical quantum photonic devices, researchers have been tinkering with nonlinear materials, atomic defects, and traditional semiconductors at the nanoscale.

Now Ali Elshaari at KTH Stockholm and his colleagues have taken a major stride by embedding circuit components on a CMOS-compatible chip that takes up a millionth the area of a tabletop apparatus. The key innovation was implementing precise control over quantum dot light sources, which emit photons in specific quantum states, including entangled ones, when excited by lasers. Scientists had struggled to control the dots’ emission and integrate the dots with waveguides for on-chip applications. Elshaari’s team devised a special geometry that optimized the alignment of the dots’ light emission with the fundamental waveguide mode, which resulted in high coupling efficiencies. To control the emission, an electrically tunable device acted as a spectral filter that could fine-tune the photon characteristics.

Manipulating quantum light on a chip, Katyayani Seal, Physics Today

Abracadabra...

Figure 1: Scheme of the setup used by Jennewein and co-workers [1]. A pump laser generates a three-photon entangled state through a cascade of frequency conversion processes in a nonlinear crystal. The oscillations in the rate of three-photon coincidence measured by the detectors provide the signature of genuine three-photon interference.

Topics: Applied Physics, Optical Physics, Photonics, Quantum Mechanics

Quantum interference effects lie at the heart of technologies that promise radically new capabilities for sensors, secure communications, and computing. Most existing experiments and applications rely on one photon interfering with itself, or two photons interfering with each other. However, the interference of a larger number of particles leads to a richer variety of phenomena, and may enable more sophisticated applications. Now, two independent groups, the first led by Thomas Jennewein at the University of Waterloo, in Canada [1], the second by Ian Walmsley at the University of Oxford, in the UK [2], have been able to isolate and observe, for the first time, “genuine” interference between three photons, that is, an effect deriving from the quantum interference of three photons that does not originate from two-photon or single-photon interference. The two studies provide new tools for controlling multiphoton interference, which may help researchers design new fundamental tests of quantum mechanics, quantum-communication protocols, and powerful quantum simulators.

The quintessential example of multiphoton quantum interference is the Hong-Ou-Mandel (HOM) effect, first observed in 1987. In an HOM experiment [3], two independent photons coming from different directions impinge on a 50:50 beam splitter. If the two incoming photons are distinguishable, the outgoing photons will split equally between the two exit ports of the splitter. However, if the two photons are identical and arrive simultaneously, the quantum-mechanical wave functions will interfere, and the two photons will always exit through the same port, even though each of them has an equal probability of exiting through both ports.

APS Physics Viewpoint: Photonic Hat Trick
Robert Sewell, The Institute of Photonic Sciences, Av. Carl Friedrich Gauss, 3, 08860 Castelldefels (Barcelona), Spain
April 10, 2017• Physics 10, 38

ET, FRBs and Light Sails...

Image Source: Science Alert

Topics: Astrophysics, Photonics, SETI, Solar Sail, Space Exploration

It's not the first time I've discussed Fast Radio Burst (FRBs): I had posts in 2013, 2015 and just last year in 2016. I first read this in Science Alert, then followed the links to arXiv. Although I've posted from physics arXiv before, some things I should give as a caveat emptor:

- The arXiv is a pre-print journal, i.e. it precedes publication in peer-reviewed, scientific journals.

- As such, it's a good way to "get an idea out there." The first stringent peer reviews should be from your own research team. You can also in subsequent submission to scholarly publications correct previous conclusions, especially after peer challenge.

- You can submit your paper here, if you're a registered author.

What took me aback was a Harvard astrophysicist* submitting it, and it's apparently not as the colloquial phrase goes, his first rodeo (see #P4TC related link below). I was a little thrilled and a little worried if the hypothesis falls flat.

However, it does work on physics that we know, or at least think we know: we haven't built a functional solar sail YET, but it's a little more practical on our humble 0.7 Kardashev Scale than warp drive (to the chagrin of my inner Trekkie), but within the realm of reasonable relativistic speeds, a fraction of light speed, but doable.

If we're receiving these fast radio bursts, the question are: is this just stellar phenomena, a lucky observation break, or are we in a flight path? And if the latter, for what purpose?

* Loeb admits that this work is speculative. When asked whether he really believes that any fast radio bursts are due to aliens, he replied, "Science isn't a matter of belief, it's a matter of evidence. Deciding what’s likely ahead of time limits the possibilities. It's worth putting ideas out there and letting the data be the judge.”

Abstract

We examine the possibility that Fast Radio Bursts (FRBs) originate from the activity of extragalactic civilizations. Our analysis shows that beams used for powering large light sails could yield parameters that are consistent with FRBs. The characteristic diameter of the beam emitter is estimated through a combination of energetic and engineering constraints, and both approaches intriguingly yield a similar result which is on the scale of a large rocky planet. Moreover, the optimal frequency for powering the light sail is shown to be similar to the detected FRB frequencies. These `coincidences' lend some credence to the possibility that FRBs might be artificial in origin. Other relevant quantities, such as the characteristic mass of the light sail, and the angular velocity of the beam, are also derived. By using the FRB occurrence rate, we infer upper bounds on the rate of FRBs from extragalactic civilizations in a typical galaxy. The possibility of detecting fainter signals is briefly discussed, and the wait time for an exceptionally bright FRB event in the Milky Way is estimated.

Physics arXiv: Fast Radio Bursts from Extragalactic Light Sails
Manasvi Lingam, Abraham Loeb

#P4TC:

Light Sails Leakage, September 9, 2015

Sustaining Qubits...

Image Source: Link below

Topics: Computer Science, Photonics, Quantum Computer, Quantum Mechanics

When the quantum computer was imagined 30 years ago, it was revered for its potential to quickly and accurately complete practical tasks often considered impossible for mere humans and for conventional computers. But, there was one big catch: Tiny-scale quantum effects fall apart too easily to be practical for reliably powering computers.

Now, a team of scientists in Japan may have overcome this obstacle. Using laser light, they have developed a precise, continuous control technology giving 60 times more success than previous efforts in sustaining the lifetime of "qubits," the unit that quantum computers encode. In particular, the researchers have shown that they can continue to create a quantum behavior known as the entangled state—entangling more than one million different physical systems, a world record that was only limited in their investigation by data storage space.

This feat is important because entangled quantum particles, such as atoms, electrons and photons, are a resource of quantum information processing created by the behaviors that emerge at the tiny quantum scale. Harnessing them ushers in a new era of information technology. From such behaviors as superposition and entanglement, quantum particles can perform enormous calculations simultaneously. The report of their investigation appears this week in the journal APL Photonics.

Phys.org: Quantum computing advances with control of entanglement

Omid Kokabee...

Image Source: Second Link below

Topics: Laser, Optical Physics, Photonics, Physics, Politics, Research

Omid Kokabee was a PhD student and researcher at the University of Texas, Austin in Laser Physics until his capture in 2011 during a family visit to Iran, and wrongful conviction by an authoritarian Iranian court. His health is fading; cancer claiming his right kidney. It was removed finally, but he's still in considerable pain and in real danger of dying. Instead of thinking of his scientific contributions to the US and the world at large, I fear our letting him languish this long is due to his being "other."

As much as I think the Iranian nuclear arms deal is a good thing - avoiding species extinction always is - an individual like Omid Kokabee is going through his own personal extinction albeit in a kind of psychopathic slow-motion.

Omid Kokabee was awarded the Andrei Sakharov Prize from the American Physical Society for “his courage in refusing to use his physics knowledge to work on projects that he deemed harmful to humanity, in the face of extreme physical and psychological pressure.” He has also been suffering from a number of serious health problems that have not been treated.

The timing of the petition delivery is critical: following a concerted effort on his behalf by a number of organizations and thousands of activists around the world, Iran’s Supreme Court recently vacated the ten-year sentence and is now going to review the case against Omid Kokabee. October 28 also marks the official presentation to the United Nations of the report of the UN Special Rapporteur on the Situation of Human Rights in Iran, Dr. Ahmed Shaheed. Iran’s human rights record will also be closely scrutinized when its Universal Periodic Review in the UN Human Rights Council in Geneva is conducted starting October 31.

The delegation delivering the petitions to the Iran UN Mission is calling for Omid Kokabee to be immediately and unconditionally released so that he can receive urgent medical treatment for his numerous and severe health problems.

The letter to Iran’s Supreme Leader calling for the release of Omid Kokabee is endorsed by the following 31 Nobel laureates in physics: Leon Neil Cooper (1972), Brian David Josephson (1973), Anthony Hewish (1974), Burton Richter (1976), Samuel Chao Chung Ting (1976), Philip W. Anderson (1977), Arno Allan Penzias (1978), Sheldon Lee Glashow (1979), James Cronin (1980), Nicolaas Bloembergen (1981), Klaus von Klitzing (1985), Jack Steinberger (1988), David. M. Lee (1996), Douglas D. Osheroff (1996), Claude Cohen-Tannoudji (1997), William D. Phillips (1997), Daniel Tsui (1998), Eric A. Cornell (2001), Wolfgang Ketterle (2001), Masatoshi Koshiba (2002), Alexei Abrikosov (2003), Anthony Leggett (2003), David Politzer (2004), David J. Gross (2004), John Hall (2005), John Mather (2006), Toshihide Maskawa (2008), Konstantin Novoselov (2010), Andre Geim (2010), David J. Wineland (2012) and Peter W. Higgs (2013).

This is grand and noble, but it's also from an entry on Iranian Human Rights' site in  2014.

To remind what exactly authoritarianism is and why it's so destructive, I give this Eric Fromm ("Escape From Freedom") primer:

Authoritarianism: Fromm characterizes the authoritarian personality as containing a sadist element and a masochist element. The authoritarian wishes to gain control over other people in a bid to impose some kind of order on the world, they also wish to submit to the control of some superior force which may come in the guise of a person or an abstract idea.

Destructiveness: Although this bears a similarity to sadism, Fromm argues that the sadist wishes to gain control over something. A destructive personality wishes to destroy something it cannot bring under its control.

Conformity: This process is seen when people unconsciously incorporate the normative beliefs and thought processes of their society and experience them as their own. This allows them to avoid genuine free thinking, which is likely to provoke anxiety.

We're seeing this the world over: Iran, Europe and especially the United States. There is and always has been a war on science by authoritarian regimes be they religious or secular (fossil fuels has no cathedral I'm aware of, but they and other business interests control a considerable amount of news media and therefore modulate consent). Science tends to report what "is," not what business interests, the liturgical or the state wishes reality to be. It is this reason why we can't get any action on Climate Change in the United States and therefore adversely affecting the planet elsewhere with no "plan B." It is a formula for species extinction. Homo Sapiens literally translates from Latin to "wise man": this clearly is NOT.

I've created a White House Petition: http://wh.gov/ioO5v. There are others out there, I know, but 100,000 signatures in 30 days with social media makes me confident we can reach that simple milestone, and get our physicist home.

We are all Omid: those of us that support and participate in any level of science, K-12 and post secondary education or industry can suddenly find ourselves in a virtual or real gulag for being ourselves; for researching, advancing academically - thinking. Thoughtcrime is not so Orwellian anymore, refer to the Fromm primer above.

This is an election year, and in the off possibilty republicans take back the White House, I feel Dr. Kokabee's chances of returning to Austin and Physics research exponentially reduce from slim to nil.

I would attend the rally were I still living in Austin. I complete this post with tears for Omid, and a swelling of hope in my chest at this activism for a fellow scientist.

I've never been prouder being a physicist.

Related sites:

Free Omid

Imprisoned Iranian Physicist Loses Kidney to Cancer, Must Be Released Permanently

University Of Texas-Austin Students, Faculty To Rally For Imprisoned Physicist

Free Omid Kokabee; A Rally To Be Held At University of Texas-Austin

Staircase Avalanche Photodiode...

Fig. 1

Conceptual band diagrams of a staircase APD unbiased (top) and under reverse bias (bottom). The arrows below the valance band indicate that holes do not impact ionize.

Citation: Appl. Phys. Lett. 108, 081101 (2016); http://dx.doi.org/10.1063/1.4942370

Topics: Electronics, Photonics, Semiconductor Technology, Quantum Mechanics

An avalanche photodiode is a semiconductor-based photodetector (photodiode) which is operated with a relatively high reverse voltage (typically tens or even hundreds of volts), sometimes just below breakdown. In this regime, carriers (electrons and holes) excited by absorbed photons are strongly accelerated in the strong internal electric field, so that they can generate secondary carriers, as it also occurs in photomultipliers. The avalanche process, which may take place over a distance of only a few micrometers, for example, effectively amplifies the photocurrent by a significant factor. Therefore, avalanche photodiodes can be used for very sensitive detectors, which need less electronic signal amplification and are thus less susceptible to electronic noise. However, the avalanche process itself is subject to quantum noise and amplification noise, which can offset the mentioned advantage. The excess noise is quantified with the excess noise factor F, which is the factor by which the electronic noise power is increased compared with that of an ideal photodetector. *

* Encyclopedia of Laser Physics and Technology: Avalanche Photodiodes

Abstract

Over 30 years ago, Capasso and co-workers [IEEE Trans. Electron Devices 30, 381 (1982)] proposed the staircase avalanche photodetector (APD) as a solid-state analog of the photomultiplier tube. In this structure, electron multiplication occurs deterministically at steps in the conduction band profile, which function as the dynodes of a photomultiplier tube, leading to low excess multiplication noise. Unlike traditional APDs, the origin of staircase gain is band engineering rather than large applied electric fields. Unfortunately, the materials available at the time, principally AlxGa1−xAs/GaAs, did not offer sufficiently large conduction band offsets and energy separations between the direct and indirect valleys to realize the full potential of the staircase gain mechanism. Here, we report a true staircase APD operation using alloys of a rather underexplored material,AlxIn1−xAsySb1−y, lattice-matched to GaSb. Single step “staircase” devices exhibited a constant gain of ∼2×, over a broad range of applied bias, operating temperature, and excitation wavelengths/intensities, consistent with Monte Carlo calculations.

Applied Physics Letters: AlInAsSb/GaSb staircase avalanche photodiode
Min Ren, Scott Maddox, Yaojia Chen1, Madison Woodson1, Joe C. Campbell1 and Seth Bank

Bubble Pen Lithography...

Schematic illustration of the pattern-writing process using an optically controlled microbubble on a plasmonic substrate and the logo of “UT-AUSTIN” written with 60 nm polystyrene beads. Courtesy: M Yogeesh

Topics: Biology, Carbon Nanotubes, Medical Physics, Nanotechnology, Photonics, Semiconductor Technology

A new “bubble-pen” lithography technique can be used to pattern colloidal and biological particles on solid-state substrates according to researchers at the University of Texas at Austin. The technique, which works by using laser-controlled microbubbles to create the patterns, will find a wide range of applications in microelectronics, nanophotonics and nanomedicine.

Photolithography is one of the main techniques available today to make micro- and nano-scale components for semiconductor devices. However, the problem is that these methods have inherent disadvantages. “Far-field" optical lithography, for example, is limited by the so-called diffraction limit of light, which means that it is extremely difficult to create features smaller than several hundred nanometres across. Techniques based on "near-field" scanning optical microscopy can overcome the diffraction limit by bringing the light source very near to the surface, but they are low-throughput and can only scan small areas at a time. Electron-beam lithography, although able to produce much smaller features, is also limited by the choice of working materials and substrates that can survive exposure to an electron beam.

The new bubble-pen lithography technique invented by Yuebing Zheng's team in collaboration with Deji Akinwande's and Andrew Dunn's groups in Texas uses a single low-power laser beam to generate a microbubble at the interface of a colloidal suspension of nanoparticles and a plasmonic substrate containing a network of metallic nanoparticles that interact strongly with light via localized surface plasmons (collective oscillations of electrons on a metal's surface). These metal particles act as efficient optical nanoantennas and can focus light to wavelengths dramatically below the diffraction limit. The microbubble produced captures and immobilizes the colloidal particles on the substrate and by directing the laser beam to move the bubble, the researchers can create different patterns from the colloidal particles with varying sizes and architectures.

Nanotechweb: Bubble-pen lithography patterns nanodevices, Belle Dumé

CMOS and SET...

(a) SEM image of the e-beam patterned nanoelectrodes (scale bar 20 μm); inset: nanoelectrode structure with 12 nm gap. (b) Room temperature I-V measurements with drain voltage sweeping from 0.1 V to 0.7 V at gate voltage of -12.2V.

Topics: Nanotechnology, Photonics, Semiconductor Technology, Quantum Mechanics

As complementary metal-oxide semiconductor (CMOS) devices shrink to sub 5 nm, interference due to quantum size effects becomes unavoidable. Single-electron tunnelling (SET) devices provide a promising alternative for low-power integrated circuits due to their operation at the single electron level. Reporting in Nanotechnology, researchers aim to address this need by fabricating monodisperse ultra-small gold nanoparticles (AuNPs) deposited by a CMOS-compatible tilted-target sputtering technique.

Fabrication and integration of monodisperse ~1 nm metal nanoparticles as charge transport islands in a device configuration remains a major challenge in the progress of SET device technology. Here, the researchers deposit AuNPs into 12 nm nanogaps between electrodes, fabricated using high-resolution e-beam lithography. The ~1 nm AuNP functions as a charge transport island within a transistor configuration and the resultant device can explore the AuNP’s quantum coulomb blockade and quantized energy level spacings at room temperature (300 K).

Nanotechweb:

CMOS-Integrable room-temperature operational single-electron transistors

Haisheng Zheng is a PhD candidate supervised by Shubhra Gangopadhyay at the University of Missouri-Columbia in the department of Electrical and Computer Engineering.

Pig Fat Laser...

Technology Review: A piece of pig skin glows with laser light after being stimulated by an optical fiber.

Topics: Biomedicine, Humor, Laser, Modern Physics, Optical Physics, Photonics, Research

Yes, you read the post title right, and it's referenced in the title of the article at Technology Review. The technique has also apparently been done with human samples. I could only grin as I know a few of my Jewish and Muslim friends and family members who probably wouldn't think of such a device as "kosher."

Researchers have made pig-skin lasers. Yes, pig laser beams.

The technology, outlined in a paper published today in Nature Photonics, showed that pumping light into fat cells could turn them into tiny, self-contained lasers.

The microlaser technique could afford scientists new ways to study and use cells, but mostly it’s just “very cool,” says Russ Algar, an assistant professor at the University of British Columbia in Vancouver, Canada, who wasn’t involved in the work.

MIT Technology Review: Making Pig Fat into a Laser, Karen Weintraub

Weyl Fermions...

The surface of the double-gyroid photonic crystal used by Marin Soljačić and colleagues. A US dime is shown for scale. (Courtesy: Ling Lu)

Topics: Consumer Electronics, Particle Physics, Photonics, Quantum Computer, Theoretical Physics

Evidence for the existence of particles called Weyl fermions in two very different solid materials has been found by three independent groups of physicists. First predicted in 1929, Weyl fermions also have unique properties that could make them useful for creating high-speed electronic circuits and quantum computers.

In 1928 Paul Dirac derived his eponymous equation, which describes the physics of spin-1/2 fundamental particles called fermions. For particles with charge and mass, he found that the Dirac equation predicts the existence of the electron and its antiparticle the positron, the latter being discovered in 1932.

However, there are other solutions of the Dirac equation that suggest the existence of more exotic particles than the familiar electron. In 1937 Ettore Majorana discovered a solution of the equation that describes a neutral particle that is its own antiparticle: the Majorana fermion. Although there is no evidence that Majorana fermions exist as fundamental particles, Majorana-like collective excitations (or quasiparticles) have been detected in condensed-matter systems. Another solution of the Dirac equation – this time for massless particles – was derived in 1929 by the German mathematician Hermann Weyl. For some time it was thought that neutrinos were Weyl fermions, but now it looks almost certain that neutrinos have mass and are therefore not Weyl particles.

Now, a group headed by Zahid Hasan at Princeton University has found evidence that Weyl fermions exist as quasiparticles – collective excitations of electrons – in the semimetal tanatalum arsenide (TaAs).

Physics World: Weyl fermions are spotted at long last, Hamish Johnston

Smooth Operator...

Illustration of the programmable photonic circuit. Photons enter from the left, are processed and exit to the right. The connector at the centre top of the circuit is to the external control system. (Courtesy: Jacques Carolan et al./Science).

Topics: Consumer Electronics, Electrical Engineering, Nanotechnology, Optics, Photonics, Quantum Computer, Semiconductor Technology

Note: "Smooth operator" is in the link title of the above photo in the article. No insult or creative infringement to Helen Folasade Adu (the singer Sade) was intended.

A group of physicists in the UK has made a programmable photonic circuit that can be used to carry out any kind of linear optics operation. The researchers say that the device provides experimental proof of a long-standing theory in quantum information, and could help speed the development of photonic quantum computers, as well as establishing whether quantum computers are fundamentally different from their classical counterparts.

The research builds on work carried out back in 1897 by German mathematician Adolf Hurwitz, who showed how a matrix of complex numbers known as a unitary operator can be built up from smaller 2 × 2 matrices. A unitary operator provides a mathematical description of a linear optical circuit. This is any circuit that uses fairly standard optical components – such as mirrors, half-silvered mirrors and phase shifters – to route photons and cause them to interfere with one other. The operator has as many rows as there are output ports in the circuit and as many columns as there are input ports. With only one photon in the circuit, the probability that it travels from a particular input to a particular output is given by the square of the corresponding matrix entry.

Physics World: Physicists build universal optics chip, Edwin Cartlidge

NIST News...

NIST Director Willie E. May
Credit: NIST

Topics: Chemistry, Diversity in Science, Optics, National Institute of Science and Technology, Photonics

Washington, D.C. – On May 4, 2015, the U.S. Senate confirmed Willie E. May as the second Under Secretary of Commerce for Standards and Technology and the 15th director of the National Institute of Standards and Technology (NIST). May has been serving as acting director since June 2014. He has worked at NIST since 1971, leading research activities in chemical and biological measurement science activities prior to serving as associate director for laboratory programs and principal deputy to the NIST director.

“Willie has been a partner and champion in our efforts to strengthen America’s manufacturing sector and promote innovation, key drivers to spurring economic growth, and core pillars of the Department’s ‘Open for Business Agenda.’ In addition to serving as a world-class research institute, NIST has taken the lead on several major Department of Commerce and Obama Administration priorities, including implementing a national network of manufacturing institutes and working with industry and other stakeholders to develop the NIST Cybersecurity Framework,” said U.S. Secretary of Commerce Penny Pritzker.

Among many other awards and honors, May was elected a Fellow of the American Chemical Society in 2011. He has been recognized with the Department of Commerce's Bronze (1981), Silver (1985) and Gold (1992) medals. The National Organization for the Professional Advancement of Black Chemists and Chemical Engineers (NOBCChE) has recognized him with both the Percy Julian Award for outstanding research in organic analytical chemistry and the Henry Hill Award for exemplary work and leadership in the field of chemistry. May received the 2007 Alumnus of the Year Award from the College of Chemical and Life Sciences at the University of Maryland, and in 2010 he was among the first class of inductees into the Knoxville College Alumni Hall of Fame. He was the keynote speaker for the 2002 winter commencement ceremonies for the University of Maryland's College of Life Sciences, and for Wake Forest University's Graduate School of Arts and Sciences commencement exercises in 2012. [1]

* * * * *

The science and technology of light are essential to a multitude of applications that have transformed our society, and there is much promise that optics and photonics will remain at the forefront of the world’s innovations well into this century.

Moreover, the general excitement in and impact of optics and photonics is growing dramatically. This presentation will highlight: (a) past breakthroughs, present advances and potential future growth in the science and technology of light, (b) the convergence of the International Year of Light, the Nobel Prizes based on light and the various U.S. government initiatives in photonics, and (c) the critical nature of metrology to harnessing the exquisite capabilities of high-frequency, coherent light for different industries. This talk is part of an afternoon NIST program celebrating World Metrology Day. [2]

1. Senate Confirms May as 15th NIST Director, Jennifer Huergo
2. Optics and Photonics: Essential for Our World, May 20, 2015

Quantum Mazes...

The quickest way to solve a maze exploits both quantum and classical processes, say physicists who have demonstrated the effect for the first time.

Topics: Biology, Photonics, Quantum Biology, Quantum Mechanics

TECHNOLOGY REVIEW: The emerging discipline of quantum biology is attempting to understand the role quantum mechanics plays in the processes of life, such as photosynthesis—the capture of sunlight by plants and its conversion into stored energy.

One phenomenon that physicists have observed is the transfer of energy across giant protein matrices that appears to occur extremely rapidly with close to 100 percent efficiency. These matrices are like giant mazes so the question is how energy can find its way across the structures before it dissipates.

The classical solution to this problem is to explore the maze with a series of random hops. But this process would take so long that most of the energy would be lost.

That’s why physicists think that quantum processes must somehow be involved. Their initial thinking was that the quantum process of energy transfer might work by exploring many routes through the maze at the same time. This superposition of states would then collapse when the solution was found. In this way, the maze can be solved rapidly and the energy transferred efficiently.

Abstract

Escaping from a complex maze, by exploring different paths with several decision-making branches in order to reach the exit, has always been a very challenging and fascinating task. Wave field and quantum objects may explore a complex structure in parallel by interference effects, but without necessarily leading to more efficient transport. Here, inspired by recent observations in biological energy transport phenomena, we demonstrate how a quantum walker can efficiently reach the output of a maze by partially suppressing the presence of interference. In particular, we show theoretically an unprecedented improvement in transport efficiency for increasing maze size with respect to purely quantum and classical approaches. In addition, we investigate experimentally these hybrid transport phenomena, by mapping the maze problem in an integrated waveguide array, probed by coherent light, hence successfully testing our theoretical results. These achievements may lead towards future bio-inspired photonics technologies for more efficient transport and computation.

Physics arXiv: Fast Escape from Quantum Mazes in Integrated Photonics
Filippo Caruso, Andrea Crespi, Anna Gabriella Ciriolo, Fabio Sciarrino, Roberto Osellame

Quantum Hall Effect...

False-colour scanning-electron-microscope image of the edge of the JQI optical lattice showing the ring-shaped waveguides. A waveguide at the centre of the image is missing and the light is seen detouring around it. (Courtesy: Emily Edwards/JQI)

A version of the quantum Hall effect (QHE) involving light rather than electrons has been created by physicists in the US. The team believes the demonstration could boost understanding of the QHE and perhaps lead to the development of better photonic circuits that use light to process information.

The QHE is a well-known phenomenon that occurs when a voltage is applied along a thin conducting sheet and a magnetic field is applied perpendicular to the sheet's surface. Throughout most of the sheet, the magnetic field makes conduction electrons travel in circular orbits that are quantized. At the edge of the sheet, however, the electrons cannot travel in circles because they would have to leave the sheet and re-enter it. Instead, these electrons hop along the edge in repeated semicircles. Crucially, they will travel along the edge regardless of its shape, following any dents or bulges.

These "topologically protected" paths and other aspects of the QHE have proven to be a rich seam of physics research that has led to two Nobel prizes. However, certain key predictions of QHE theory, such as the presence of bound electron states called anyons, remain unproven. This is because QHE experiments require pure samples, cryogenic temperatures and an ultra-high magnetic field – making measurements difficult to do.

Physics World: Quantum Hall effect created using light

High-Speed Measurements...

Scientists have discovered how to measure greenhouse gases 200,000 times faster as the result research by an award-winning PhD student from The University of Western Australia and a US team.

The discovery - which is already being used by NASA scientists in Space - has major implications for global warming research, breath analysis (to detect illness), explosives detection, chemical process monitoring and a range of other applications, including fundamental quantum theory.

UWA physics graduate Gar-Wing Truong used highly-sensitive rapid laser scanning technology to help lead US scientists from National Institute of Standards and Technology (NIST) in Maryland to build new gas measurement equipment with unparalleled speed, accuracy, precision and spectral coverage.

NASA's Jet Propulsion Laboratory in California has begun using data from Mr Truong's research to calibrate carbon monitoring satellites in orbit around Earth and better understand carbon dioxide molecules.

University of Western Australia:
High-speed discovery helps measure greenhouse gases from space.

Local Realism...

Quantum optical setup used in this experiment - IQOQI Vienna, Jacqueline Godany 2012

In everyday life it is only natural that the properties of objects exist independent of being observed or not. The quantum world on the other hand is ruled by other laws: the property of a particle may be defined not until the instant it is being measured, and two entangled particles seem to be connected in a non-local way over large distances.

Various experiments worldwide have proven this fundament of quantum theory. However, up to now last doubts could not be ruled out completely. Advocates of “local realism,” by which the classical world is governed, refer to several “loopholes” which have been identified in order to save their world view. Now, physicists from the group of Prof. Anton Zeilinger at the Institute of Quantum Optics and Quantum Information (IQOQI) in Vienna, Austria, have closed an important loophole in photonic experiments which use quantum entanglement to rule out a local realistic explanation of nature.

The work got theoretical support from Dr. Johannes Kofler from the group of Prof. Ignacio Cirac at the Max Planck Institute of Quantum Optics (MPQ) in Garching, Germany, and experimental assistance from researchers at the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig Germany, as well as the National Institute of Standards (NIST) in Boulder, USA. The results are published this week in Nature.

R&D Mag: Physicists close loophole for entangled photonic systems