In probability theory, the multi-armed bandit problem (sometimes called the K- or N-armed bandit problem) is a problem in which a gambler at a row of slot machines (sometimes known as “one-armed bandits”) has to decide which machines to play, how many times to play each machine and in which order to play them. When played, each machine provides a random reward from a distribution specific to that machine. The objective of the gambler is to maximize the sum of rewards earned through a sequence of lever pulls.
(Phys.org)—A combined team of researchers from France and Japan has created a decision-making device that is based on basic properties of quantum mechanics. In their paper published in Scientific Reports (and uploaded to the arXiv preprint server), the team describes the idea behind their device and how it works.
There is a classic decision-making problem that is known as the exploration-exploitation dilemma—it is typically described by suggesting a scenario where a gambler faced with a floor full of slot machines must decide which offers the best payout on a regular basis. In real life, the solution involves feeding all of the machines coins until a discernible pattern emerges. Computer algorithms have been developed to run essentially the same process. Now, however, that approach appears to be ready for an update, as the researchers with this new effort have come up with a way to run the same sort of algorithm without using any kind of computer. Instead, they use a laser, a photon detector and feedback device. The idea is based on the fact that quantum mechanics laws are probabilistic in nature.
The device is based on prior research that has shown that if photons are fired from a proton gun at a 45 degree angle, they will each have an equal chance of being vertically or horizontally polarized when they strike a detector—thus a stream will have equal numbers of both. But, if the filter on the gun is changed slightly, to say fire at 44 or 46 degree angles, that increase the odds of the associated polarization. The team used that fact by adding a feedback loop to the system—data sent back representing a “win” on a slot machine caused the filter to move in one direction, while a loss moved it in the other. Over time, the preponderance of wins (indicating a learning process) from one virtual machine would drive the device towards indicating it was the winning choice.
One of the most confounding implications of quantum physics is that light can behave as both a particle (photon) and a wave, depending on the nature of the observation. This is called wave-particle duality, and it has been extremely difficult to picture, let alone observe in both stages simultaneously. Now, physicists publishing in Nature Communications report that they have been able to capture a photograph of wave/particle duality ‘in action’, so to speak. This TED video explains the nature of the effect:
Right now, the most powerful physics machine ever constructed by man is running at maximum power after a major upgrade that took two years to complete.
And recently, two different experiments reported that they may have discovered a particle that behaves in ways that cannot be explained with any existing physical laws, as Scientific American reports.
Shown below is one of four major detectors that are crucial to the machine’s purpose:
China is set to complete the installation of the world’s longest quantum communication network stretching 2,000km (1,240miles) from Beijing to Shanghai by 2016, say scientists leading the project. Quantum communications technology is considered to be “unhackable” and allows data to be transferred at the speed of light.
By 2030, the Chinese network would be extended worldwide, the South China Morning Post reported. It would make the country the first major power to publish a detailed schedule to put the technology into extensive, large-scale use.
The development of quantum communications technology has accelerated in the last five years. The technology works by two people sharing a message which is encrypted by a secret key made up of quantum particles, such as polarized photons. If a third person tries to intercept the photons by copying the secret key as it travels through the network, then the eavesdropper will be revealed by virtue of the laws of quantum mechanics – which dictate that the act of interfering with the network affects the behaviour of the key in an unpredictable manner.
A study led by researchers from the U.S. Department of Energy’s (DOE) SLAC National Accelerator Laboratory and the University of California, Los Angeles has demonstrated a new, efficient way to accelerate positrons, the antimatter opposites of electrons. The method may help boost the energy and shrink the size of future linear particle colliders — powerful accelerators that could be used to unravel the properties of nature’s fundamental building blocks.
The scientists had previously shown that boosting the energy of charged particles by having them “surf” a wave of ionized gas, or plasma, works well for electrons. While this method by itself could lead to smaller accelerators, electrons are only half the equation for future colliders. Now the researchers have hit another milestone by applying the technique to positrons at SLAC’s Facility for Advanced Accelerator Experimental Tests (FACET), a DOE Office of Science User Facility.
“Together with our previous achievement, the new study is a very important step toward making smaller, less expensive next-generation electron-positron colliders,” said SLAC’s Mark Hogan, co-author of the study published today in Nature. “FACET is the only place in the world where we can accelerate positrons and electrons with this method.”
July, 2015; as you know.. was the all systems go for the CERNs Large Hadron Collider (LHC). On a Saturday evening, proton collisions resumed at the LHC and the experiments began collecting data once again. With the observation of the Higgs already in our back pocket — It was time to turn up the dial and push the LHC into double digit (TeV) energy levels. From a personal standpoint, I didn’t blink an eye hearing that large amounts of Data was being collected at every turn. BUT, I was quite surprised to learn at the ‘Amount’ being collected and processed each day — About One Petabyte.
Approximately 600 million times per second, particles collide within the (LHC). The digitized summary is recorded as a “collision event”. Physicists must then sift through the 30 petabytes or so of data produced annually to determine if the collisions have thrown up any interesting physics. Needless to say — The Hunt is On!
The Data Center processes about one Petabyte of data every day — the equivalent of around 210,000 DVDs. The center hosts 11,000 servers with 100,000 processor cores. Some 6000 changes in the database are performed every second.
With experiments at CERN generating such colossal amounts of data. The Data Center stores it, and then sends it around the world for analysis. CERN simply does not have the computing or financial resources to crunch all of the data on site, so in 2002 it turned to grid computing to share the burden with computer centres around the world. The Worldwide LHC Computing Grid (WLCG) – a distributed computing infrastructure arranged in tiers – gives a community of over 8000 physicists near real-time access to LHC data. The Grid runs more than two million jobs per day. At peak rates, 10 gigabytes of data may be transferred from its servers every second.
By early 2013 CERN had increased the power capacity of the centre from 2.9 MW to 3.5 MW, allowing the installation of more computers. In parallel, improvements in energy-efficiency implemented in 2011 have led to an estimated energy saving of 4.5 GWh per year.
Image: CERN
PROCESSING THE DATA (processing info via CERN)> Subsequently hundreds of thousands of computers from around the world come into action: harnessed in a distributed computing service, they form the Worldwide LHC Computing Grid (WLCG), which provides the resources to store, distribute, and process the LHC data. WLCG combines the power of more than 170 collaborating centres in 36 countries around the world, which are linked to CERN. Every day WLCG processes more than 1.5 million ‘jobs’, corresponding to a single computer running for more than 600 years.
CERN DATA CENTER: The server farm in the 1450 m2 main room of the DC (pictured) forms Tier 0, the first point of contact between experimental data from the LHC and the Grid. As well as servers and data storage systems for Tier 0 and further physics analysis, the DC houses systems critical to the daily functioning of the laboratory. (Image: CERN)
The data flow from all four experiments for Run 2 is anticipated to be about 25 GB/s (gigabyte per second)
ALICE: 4 GB/s (Pb-Pb running)
ATLAS: 800 MB/s – 1 GB/s
CMS: 600 MB/s
LHCb: 750 MB/s
In July, the LHCb experiment reported observation of an entire new class of particles: Exotic Pentaquark Particles (Image: CERN)
Possible layout of the quarks in a pentaquark particle. The five quarks might be tightly bound (left). The five quarks might be tightly bound. They might also be assembled into a meson (one quark and one anti quark) and a baryon (three quarks), weakly bound together.
The LHCb experiment at CERN’s LHC has reported the discovery of a class of particles known as pentaquarks. In short, “The pentaquark is not just any new particle,” said LHCb spokesperson Guy Wilkinson. “It represents a way to aggregate quarks, namely the fundamental constituents of ordinary protons and neutrons, in a pattern that has never been observed before in over 50 years of experimental searches. Studying its properties may allow us to understand better how ordinary matter, the protons and neutrons from which we’re all made, is constituted.”
Our understanding of the structure of matter was revolutionized in 1964 when American physicist Murray Gell-Mann proposed that a category of particles known as baryons, which includes protons and neutrons, are comprised of three fractionally charged objects called quarks, and that another category, mesons, are formed of quark-antiquark pairs. This quark model also allows the existence of other quark composite states, such as pentaquarks composed of four quarks and an antiquark.
Until now, however, no conclusive evidence for pentaquarks had been seen. Earlier experiments that have searched for pentaquarks have proved inconclusive. The next step in the analysis will be to study how the quarks are bound together within the pentaquarks.
“The quarks could be tightly bound,” said LHCb physicist Liming Zhang of Tsinghua University, “or they could be loosely bound in a sort of meson-baryon molecule, in which the meson and baryon feel a residual strong force similar to the one binding protons and neutrons to form nuclei.” More studies will be needed to distinguish between these possibilities, and to see what else pentaquarks can teach us!
August 18th, 2015 CERN Experiment Confirms Matter-Antimatter CPT Symmetry For Light Nuclei, Antinuclei (Image: CERN)
Days after scientists at CERN’s Baryon-Antibaryon Symmetry Experiment (BASE) measured the mass-to-charge ratio of a proton and its antimatter particle, the antiproton, the ALICE experiment at the European organization reported similar measurements for light nuclei and antinuclei.
The measurements, made with unprecedented precision, add to growing scientific data confirming that matter and antimatter are true mirror images.
Antimatter shares the same mass as its matter counterpart, but has opposite electric charge. The electron, for instance, has a positively charged antimatter equivalent called positron. Scientists believe that the Big Bang created equal quantities of matter and antimatter 13.8 billion years ago. However, for reasons yet unknown, matter prevailed, creating everything we see around us today — from the smallest microbe on Earth to the largest galaxy in the universe.
Last week, in a paper published in the journal Nature, researchers reported a significant step toward solving this long-standing mystery of the universe. According to the study, 13,000 measurements over a 35-day period show — with unparalleled precision – that protons and antiprotons have identical mass-to-charge ratios.
The experiment tested a central tenet of the Standard Model of particle physics, known as the Charge, Parity, and Time Reversal (CPT) symmetry. If CPT symmetry is true, a system remains unchanged if three fundamental properties — charge, parity, which refers to a 180-degree flip in spatial configuration, and time — are reversed.
The latest study takes the research over this symmetry further. The ALICE measurements show that CPT symmetry holds true for light nuclei such as deuterons — a hydrogen nucleus with an additional neutron — and antideuterons, as well as for helium-3 nuclei — two protons plus a neutron — and antihelium-3 nuclei. The experiment, which also analyzed the curvature of these particles’ tracks in ALICE detector’s magnetic field and their time of flight, improve on the existing measurements by a factor of up to 100.
IN CLOSING..
A violation of CPT would not only hint at the existence of physics beyond the Standard Model — which isn’t complete yet — it would also help us understand why the universe, as we know it, is completely devoid of antimatter.
Physicists have discovered a jewel-shaped geometric object that challenges the notion that space, time and particles are fundamental constituents of nature.
Matter and antimatter appear to be perfect mirror images of each other as far as anyone can see, scientists have discovered with unprecedented precision, foiling hope of solving the mystery as to why there is far more matter than antimatter in the universe.
Everyday matter is made up of protons, neutrons or electrons. These particles have counterparts known as antiparticles — antiprotons, antineutrons and positrons, respectively — that have the same mass but the opposite electric charge. (Although neutrons and antineutrons are both neutrally charged, they are each made of particles known as quarks that possess fractional electrical charges, and the charges of these quarks are equal and opposite to one another in neutrons and antineutrons.)
The known universe is composed of everyday matter. The profound mystery is, why the universe is not made up of equal parts antimatter, since the Big Bang that is thought to have created the universe 13.7 billion years ago produced equal amounts of both. And if matter and antimatter appear to be mirror images of each other in every respect save their electrical charge, there might not be much any of either type of matter left — matter and antimatter annihilate when they encounter each other. [The 9 Biggest Unsolved Mysteries in Physics].
