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Showing posts with label Computer Science. Show all posts
Showing posts with label Computer Science. Show all posts

Friday, 14 February 2020

New record: researchers have tangled quantum memory for more than 50 kilometers


Chinese scientists have succeeded in obtaining two quantum memories entangled on 50 kilometers of fiber optic cables, almost 40 times the previous record! This feat makes the idea of ​​an ultra-fast and ultra-secure quantum Internet much more plausible.

You should know that quantum communication is based on quantum entanglement : where two particles become inextricably linked and depend on each other, even if they are not in the same place. Indeed, in quantum mechanics, quantum entanglement is a phenomenon in which two particles (or groups of particles) form a linked system and have quantum states dependent on each other whatever the distance between them.

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In other words, quantum memory is the quantum equivalent of conventional computer memory:  to store information for later use, and if we ever want to develop and use practical and useful quantum computers, we must understand how to use this memory.

"The main purpose of this article is to extend the entanglement distance in [optical] fiber between quantum memories across the city," said Jian-Wei Pan, of the University of Science and Technology of China, head of the research team. The study was published in the journal Nature.



Quantum entanglement over a long distance

With regard to the entanglement of photon particles (light), scientists today know how to manage it in an empty space as well as at great distances. However, adding quantum memory to this equation makes the process much more complicated. Therefore, the researchers suggest that another type of approach might be preferable for this: the entanglement between atoms and photons on successive nodes (where the atoms are the nodes and the photons transmit the messages).

In other words, it is entanglement of photons with a twist, where atomic matter is added to the mixture to obtain a gain of efficiency, reliability and stability. According to scientists, with a good network of such nodes, we could create better basic technology for a future quantum Internet than with quantum entanglement using only photons.

During the experiment, the team used two storage units for quantum memory, which concretely were rubidium atoms cooled to a low energy state. Associated with entangled photons, they are then each part of an entangled system. Unfortunately, the more the photons have to travel by moving between the atoms, the more risks there are for the system to be disturbed. This is why this new record is so impressive.

According to the researchers, the key to this improvement and this record distance lies in a technique called “cavity improvement”, which reduces the loss of photon coupling during entanglement. The method involves placing the atoms of quantum memory in special rings, which reduces random noise that could interfere and destroy memory. The cavity has the additional advantage of improving the recovery of quantum information.

Thus, the coupled atoms and the photons produced by the improvement of the cavity constitute the node. Then, the photons are brought to a frequency suitable for transmission, through telecommunications networks (in this specific case, a network the size of a city).

You should know that Pan's scientific team has already established a quantum entanglement record, transmitting entangled photons between a satellite and the Earth over a distance of 1200 km, in 2017. This satellite system works well in space, but in the Earth's atmosphere, with all the interference present, it is less efficient and results in a loss of signal.


Diagram of the system for generating remote entanglement between atomic sets. Two distant quantum memory nodes are connected by a fiber optic channel and an intermediate station for photon measurement. In node A (B), an atomic set of 87Rb is placed inside a ring cavity. All atoms are first prepared in the basic state. A local entanglement is first created between the atomic set and a writing photon by applying a writing pulse (blue arrow). Then, the writing photon is collected clockwise (reverse) from the cavity and sent to the QFC module. Using a PPLN waveguide chip (PPLN-WG) and a 1950 nm pump laser (green arrow), the 795 nm (wavelength) writing photon is converted in O telecommunications band. After filtering the noise, two write photons are transmitted through long fibers, interfering in a base station and detected by two devices (SNSPD), with an efficiency of around 50%. The effective interference in the central station announces the entanglement of two sets. Fiber polarization controllers (PC) and polarization beam splitters (PBS) before interference from the base station are designed to actively compensate for polarization offset in long fiber. To recover the state of the atom, the researchers apply a read pulse (red arrow) in counter-propagation to the write pulse. Thanks to the phase correspondence between the spin wave and the improvement of the cavity, the atomic state is effectively recovered in a counter-clockwise direction from the ring cavity. Credits: Jian-Wei Pan / University of Science and Technology of China Fiber polarization controllers (PC) and polarization beam splitters (PBS) before interference from the base station are designed to actively compensate for polarization offset in long fiber. To recover the state of the atom, the researchers apply a read pulse (red arrow) in counter-propagation to the write pulse. Thanks to the phase correspondence between the spin wave and the improvement of the cavity, the atomic state is effectively recovered in a counter-clockwise direction from the ring cavity. Credits: Jian-Wei Pan / University of Science and Technology of China Fiber polarization controllers (PC) and polarization beam splitters (PBS) before interference from the base station are designed to actively compensate for polarization offset in long fiber. To recover the state of the atom, the researchers apply a read pulse (red arrow) in counter-propagation to the write pulse. Thanks to the phase correspondence between the spin wave and the improvement of the cavity, the atomic state is effectively recovered in a counter-clockwise direction from the ring cavity. Credits: Jian-Wei Pan / University of Science and Technology of China researchers apply a read pulse (red arrow) in counter-propagation to the write pulse. Thanks to the phase correspondence between the spin wave and the improvement of the cavity, the atomic state is effectively recovered in a counter-clockwise direction from the ring cavity. Credits: Jian-Wei Pan / University of Science and Technology of China researchers apply a read pulse (red arrow) in counter-propagation to the write pulse. Thanks to the phase correspondence between the spin wave and the improvement of the cavity, the atomic state is effectively recovered in a counter-clockwise direction from the ring cavity. Credits: Jian-Wei Pan / University of Science and Technology of China



During this experiment, the nodes of the atoms were in the same laboratory, but the photons still had to travel through cables extending over 50 kilometers. It is difficult to separate atoms more, but the proof of concept is there: "Despite enormous progress, at present, the maximum physical separation achieved between two nodes is 1.3 km, and challenges for longer distances remain,” explain the researchers.

"Our experiment could be extended to nodes physically separated by similar distances, which would thus form a functional segment of the atomic quantum network, opening the way to the establishment of an atomic entanglement on many nodes and on much longer distances.», They add.

Towards a quantum Internet?

This is where things get really interesting: while quantum memories could be the equivalent of computer memory in classical physics, the quantum version should be able to do a lot more, like for example processing more information in less time, or even solve problems that go far beyond those handled by our current computers.



When it comes to data communication, quantum technology promises to improve transmission speeds and secure data transfers thanks to the laws of quantum physics, provided we can make them work reliably over long distances.

According to the researchers, a quantum Internet that would connect remote quantum processors should allow a number of revolutionary applications, such as globalized quantum computing. "Its realization will be based on the entanglement of quantum memories over long distances", concluded the researchers.

Bibliography:


Entanglement of two quantum memories via fibres over dozens of kilometres.

Nature 578, 240–245 (2020).

https://doi.org/10.1038/s41586-020-1976-7

Monday, 10 February 2020

A bereaved mother finds her deceased child in Virtual Reality (+ VIDEO)


Jang Ji-sung lost his daughter when she was only seven years old. It was in 2016 that everything changed for her, when her little Nayeon died of an incurable disease. Three years later, the bereaved South Korean mother was able to find her daughter in some way, in a virtual world created for a television documentary.

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Last Thursday, the Munhwa Broadcasting Corporation shared on its YouTube channel an extract from a special documentary entitled "I Met You", showing a moving sequence linking the real world to the virtual.

In the first scene, Jang stands in front of a large green screen with a VR headset and haptic gloves. In the second scene, we can see the young mother chatting with her daughter. They hold hands and even plan a birthday party.



The VR meeting is, as you can imagine, extremely moving. Jang begins to cry as soon as she sees the virtual version of her daughter Nayeon, while the rest of the family - Nayeon's father, brother and sister - witness the reunion between dark emotions and occasional tears.

"It may be a real paradise," said Jang of his RV reunion. “I met Nayeon, who called me with a smile. It was very short, but very joyful. I think I had the waking dream that I always wanted.”


Eight months of development

According to Aju Business Daily , the production team spent eight months on the project. The developers designed the virtual park after a real place that Jang had gone with his daughter. They then used motion capture technology to record the movements of a child actor, which they could then use as a model for the virtual Nayeon.

The process may not be simple and the end product may not be perfect, but it has resulted in technology that can recreate real people in VR, convincingly enough to move their relatives. And the implications are simply impossible to predict.

It took a whole team of experts to produce "I Met You", but we're clearly getting closer to a platform that one day would allow anyone to easily download images of a deceased loved one and interact then with a virtual version of it.

What impact will this technology have on the grieving process? Will being able to meet a loved one in VR help loved ones to pass the course and move forward after a death? Will some people become addicted to this virtual world?

Besides, with the evolution of robotics, we could also imagine that such applications could one day extend to humanoid robots. So is this a first step towards androids designed to imitate our deceased loved ones both in appearance and in personality, as in the episode of the Black Mirror series “Be Right Back”?

Several startups have already prepared the ground for this future, in particular by compiling data on living and deceased people in order to produce real “digital avatars”. Other companies are already producing robot clones of real people .

The Black Mirror episode “Be Right Back”:


A therapeutic framework?

Nevertheless, it is obvious that the reunion in VR could constitute positive experiences. We could also see this as a 21st century version of a photo album.

"Since you know the person is gone, you accept the virtual equivalent for what they are - a 'comforting remnant'," Princeton neuroscientist Michael Graziano told Dell Technology. "There is nothing wrong or unethical."



However, perhaps regulation would be necessary. Rather than allowing startups to freely offer the public the opportunity to interact with virtual versions of their deceased loved ones, perhaps we could make the technology available only to people who have undergone an assessment with a psychologist, for example.

Interacting with a convincing version of the deceased in virtual reality is unexplored territory, and now that we have officially entered this era, many questions arise. We will therefore have to respond as quickly as possible in order to best introduce this technology.

Source

Thursday, 31 October 2019

The US military has finally stopped using floppy disks to control its nuclear weapons


Do you know what a floppy disk is? You should probably be surprised by the title of this article. You do not know what a floppy disk is? Know that our lives depend on it, literally.

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Fortunately for all of us, the future of humanity is no longer at the mercy of this obsolete data storage medium. Indeed, now the US military has finally stopped using this technological relic to control its arsenal of nuclear weapons.

Developed in the 1960s, floppy disks disappeared from common use in the late 1990s, especially since the use of compact discs and the Internet, both of which have gradually replaced some uses of floppy disks. Then, during the 2000s , USB sticks and memory cards give the coup de grace floppy disks, on new personal computers. And it is finally in March 2011 that Sony permanently stops the manufacture of 3.5-inch floppies (the latest floppy disk still existing, created 30 years ago).

Floppies survive in our memories as save button icons, in some programs. Credits: PublicDomainPictures / Pixabay

However, they remained the main data storage system of the Strategic Automated Command and Control System (SACCS), which coordinates the operations of US nuclear missiles and bombers.

But now Lieutenant-Colonel Jason Rossi of 595 Strategic Communications Squadron of the US Air Force, who oversees the day-to-day operations of SACCS, said the diskettes were finally removed in June of this year. Few details about the upgrade have been made public, but Rossi said the old drives have been replaced by a " highly secure solid state digital storage solution ."

The SACCS elements seen here are subjected to diagnostic tests by the 595th Airborne Strategic Communications Squadron. Credits: Valerie Insinna / Staff

Despite the many limitations of using technology dating back half a century, Rossi also said that the continued use of floppy disks has actually helped to make the world safer because "  you can not hack something that does not have an IP address ...  "

However, maintenance problems eventually led to the need for modernization. Indeed, it is often impossible to find replacement parts for defective components, which means that they must all be repaired, a process that takes a lot of time and usually requires re-wiring and soldering the circuits to the using a microscope. Note that modern technicians are not trained in this.


This is why the military relies mainly on relatively old civilian technicians to repair floppy disks, as new recruits simply do not have the skills to maintain this equipment.

A 2016 report by the US Government Accountability Office (USGAO) indicated that SACCS was still running on a 1970s IBM Series / 1 computer, and that $ 61 billion was spent on maintaining the system every year.

The USGAO also pointed out that the Ministry of Defense is considering " updating its data storage solutions, port expansion processors, handheld devices and desktop terminals ", thus permanently ending the age of floppy disk ...

Source

Friday, 25 October 2019

Quantum Supremacy: Quantum Computing Passes Another Critical Milestone


In recent years, physicists have taken the concept of quantum computer science fiction to reality by developing functional prototypes demonstrating all the potential power of this new technology. Researchers even say today they have reached an important milestone in achieving "quantum supremacy". Indeed, recently, a quantum computer called Sycamore solved a mathematical problem in 3.5 minutes, while the world's most powerful supercomputer Summit, it would have taken more than 10'000 years of work to achieve the same result.

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For the first time, a quantum computer has solved a problem that a traditional computer can not solve, reports a team of researchers in the journal Nature . " A calculation that would take 10'000 years on a conventional supercomputer took 200 seconds on our quantum computer, " says Brooks Foxen, physicist at the Google AI Quantum and at the University of California.

" It is likely that the typical simulation time of 10,000 years will be reduced by the improvement of conventional hardware and algorithms, but since we are currently 1.5 million million times faster, we are proud of to affirm this success "adds Foxen.

Sycamore: the quantum computer with 53 qubits

Due to the superposition principle, quantum computers can store and manipulate much more information per unit of volume than traditional computers, which encode information in a binary way using 0 and 1. The research team directed by Frank Arute of the Google AI Quantum , used a quantum computer called Sycamore, which has 53 functional qubits.

(a) The 54 qubits (53 functional and 1 dysfunctional) of Sycamore, connected to each other via couplers. (b) The Sycamore processor. Credits: Frank Arute et al. 2019

Physicists placed these 53 qubits in a complex overlay state, then asked Sycamore to perform a task similar to generating random numbers. The results were then compared to simulations performed on the Summit supercomputer at the Oak Ridge National Laboratory.

The Sycamore quantum computer, contained in its cryostructure. Credits: Eric Lucero / Google

Summit is currently the most powerful supercomputer in the world, able to perform about 200 million billion operations per second, " said William Oliver, a physicist at MIT. " It includes about 40,000 processing units, each containing billions of transistors, and has 250 million gigabytes of storage. Approximately 99% of Summit's resources were used for conventional sampling . "

A demonstration of quantum supremacy on classical computers

Sycamore completed the operation in about 3.5 minutes, and the results suggested that even the most powerful traditional supercomputer would have to tackle the problem for about 10,000 years.

Graph showing the performance results of Sycamore against the Summit supercomputer. For the latter, the resolution of the problem studied would have required 10'000 years of calculation. Credits: Frank Arute et al. 2019
This demonstration of quantum supremacy over the current classical algorithms on the fastest supercomputers in the world is truly a remarkable achievement and milestone for quantum computing. This shows that quantum computers represent a computer model that is fundamentally different from that of conventional computers. It also combats critics of the controllability and viability of quantum computing in an extraordinarily large computing space (containing at least the 253 states used here) . "

Oliver also pointed out, however, that there is still a long way to go before quantum computers can be democratized. For example, researchers will need to develop new algorithms that can work with error-prone quantum processors, which will be available in the near future. And, to make the technology commercially viable in the long run, scientists will have to design robust protocols to correct quantum errors.

Source

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