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Category: quantum physics – Page 1,169

Quantum processor for single photons

“Nothing is impossible!” In line with this motto, physicists from the Quantum Dynamics Division of Professor Gerhard Rempe (director at the Max Planck Institute of Quantum Optics) managed to realise a quantum logic gate in which two light quanta are the main actors. The difficulty of such an endeavour is that photons usually do not interact at all but pass each other undisturbed. This makes them ideal for the transmission of quantum information, but less suited for its processing. The scientists overcame this steep hurdle by bringing an ancillary third particle into play: a single atom trapped inside an optical resonator that takes on the role of a mediator. “The distinct feature of our gate implementation is that the interaction between the photons is deterministic”, explains Dr. Stephan Ritter. “This is essential for future, more complex applications like scalable quantum computers or global quantum networks.”

In all modern computers, data processing is based on information being binary-coded and then processed using logical operations. This is done using so-called which assign predefined output values to each input via deterministic protocols. Likewise, for the information processing in computers, quantum logic gates are the key elements. To realise a universal quantum computer, it is necessary that every input quantum bit can cause a maximal change of the other quantum bits. The practical difficulty lies in the special nature of quantum information: in contrast to classical bits, it cannot be copied. Therefore, classical methods for error correction cannot be applied, and the gate must function for every single photon that carries information.

Because of the special importance of photons as information carriers – for example, for communicating quantum information in extended quantum networks – the realisation of a deterministic photon-photon gate has been a long-standing goal. One of several possibilities to encode photonic quantum bits is the use of polarisation states of single photons. Then the states “0” and “1” of a classical bit correspond to two orthogonal polarisation states. In the two-photon gate, the polarisation of each photon can influence the polarisation of the other photon. As in the classical logic gate it is specified beforehand which input polarisation leads to which output polarisation. For example, a linear polarisation of the second photon is rotated by 90° if the first one is in the logic state “1”, and remains unchanged if the first one is in “0”.

Probing Quantum Phenomena in Tiny Transistors

Nearly 1,000 times thinner than a human hair, nanowires can only be understood with quantum mechanics. Using quantum models, physicists from Michigan Technological University have figured out what drives the efficiency of a silicon-germanium (Si-Ge) core-shell nanowire transistor.

Core-Shell Nanowires

The study, published last week in Nano Letters, focuses on the quantum tunneling in a core-shell nanowire structure. Ranjit Pati, a professor of physics at Michigan Tech, led the work along with his graduate students Kamal Dhungana and Meghnath Jaishi.

Quantum fingerprinting surpasses classical limit

Nice.

(Phys.org)—As the saying goes, no two fingerprints are alike, and the same is true for quantum fingerprints. Just as a human fingerprint is only a fraction of the size of a person, yet can be used to distinguish between any two people (at least in theory), quantum fingerprints are exponentially smaller than the string of information they represent, yet they can be used to distinguish between any two strings.

Ever since quantum fingerprinting was first proposed in 2001, it has for the most part remained an interesting theoretical concept, with only a handful of protocols having managed to experimentally demonstrate the idea.

Now in a new study, researchers have experimentally demonstrated a quantum fingerprinting protocol and shown that it can surpass the classical limit for solving communication complexity problems. In these problems, two parties each have a message, and they both share some of their message with a referee, who has to decide whether the two messages are the same or not. The classical limit requires that a minimum amount of must be transmitted between each party and the referee in order for the referee to make this decision.

Bowtie-shaped nanostructures may advance the development of quantum devices

Bowtie-shaped nanoparticles made of silver may help bring the dream of quantum computing and quantum information processing closer to reality. These nanostructures, created at the Weizmann Institute of Science and described recently in Nature Communications, greatly simplify the experimental conditions for studying quantum phenomena and may one day be developed into crucial components of quantum devices.

The research team led by Prof. Gilad Haran of Weizmann’s Chemical Physics Department — postdoctoral fellow Dr. Kotni Santhosh, Dr. Ora Bitton of Chemical Research Support and Prof. Lev Chuntonov of the Technion-Israel Institute of Technology — manufactured two-dimensional bowtie-shaped silver nanoparticles with a minuscule gap of about 20 nanometers (billionths of a meter) in the center. The researchers then dipped the “bowties” in a solution containing quantum dots, tiny semiconductor particles that can absorb and emit light, each measuring six to eight nanometers across. In the course of the dipping, some of the quantum dots became trapped in the bowtie gaps.

Under exposure to light, the trapped dots became “coupled” with the bowties — a scientific term referring to the formation of a mixed state, in which a photon in the bowtie is shared, so to speak, with the quantum dot. The coupling was sufficiently strong to be observed even when the gaps contained a single quantum dot, as opposed to several. The bowtie nanoparticles could thus be prompted to switch from one state to another: from a state without coupling to quantum dots, before exposure to light, to the mixed state characterized by strong coupling, following such exposure.

Quantum physics meets IT security

Nice that they are trying to ensure this. However, as we integrate more tech into Biocomputing space and our efforts in achieving singularity; you will need some level of a medical/ or bio background.

It’s hard enough for IT security managers to keep with the latest in conventional computing. Cloud Security Alliance and the US government are trying to make sure you don’t need a physics degree, too.

China to launch ‘hack-proof’ quantum satellite next month

Get ready.

China will launch the world’s first quantum satellite next month to demonstrate a series of advanced technologies such as hacker-proof communications and quantum teleportation.

Ground testing and quality checks on the satellite had finished at the Chinese Academy of Sciences, and it would depart for the Jiuquan Satellite Launch Centre in Inner Mongolia early this month for a launch aboard a Long March 2D rocket in the middle of next month, according to a report on the central government’s website posted on Friday.

The project has drawn attention from scientists and governments around the world because it could provide solutions to some significant problems. With the rapid advancement of quantum technology in recent years, it is widely believed that quantum computers will soon be available but such a computer would be so powerful, it could crack every encryption method currently in use.

Proof Beyond a Reasonable Doubt That Majorana Fermions Exist

Not only could they transform quantum computing, they’re a candidate for dark matter.

A team of Chinese physicists from Shanghai’s Jiaotong University have proof beyond a reasonable doubt of the existence of the Majorana fermion — a special particle that could potentially revolutionize quantum computing.

“The search for this particle is for condensed-matter physicists what the Higgs boson search was for high-energy particle physicists,” said Leonid Rokhinson, an associate professor of physics at Purdue University, who was the first to detect the signature of the fermion in 2012 but was not involved in this study, in a 2012 press release. “It is a very peculiar object because it is a fermion yet it is its own antiparticle with zero mass and zero charge.”

Quantum technologies to revolutionise 21st century — Nobel Laureates discuss at Lindau

Nice read.

Is quantum technology the future of the 21st century? On the occasion of the 66th Lindau Nobel Laureate Meeting, this is the key question to be explored today in a panel discussion with the Nobel Laureates Serge Haroche, Gerardus ’t Hooft, William Phillips and David Wineland. In the following interview, Council Member Professor Rainer Blatt, internationally renowned quantum physicist, recipient of numerous honours, and Scientific Co-Chairman of the 66th Lindau Meeting, talks about what we can expect from the “second quantum revolution”.

Blatt has no doubt: quantum technologies are driving forward a technological revolution, the future impact of which is still unclear. Nothing stands in the way of these technologies becoming the engine of innovations in science, economics and society in the 21st century. Early laboratory prototypes have shown just how vast the potential of quantum technologies is. Specific applications are expected in the fields of metrology, computing and simulations. However, substantial funding is required to advance from the development stage.

Professor Blatt, the first quantum revolution laid the physical foundations for trailblazing developments such as computer chips, lasers, magnetic resonance imaging and modern communications technology. In the Quantum Manifest published in mid-May, researchers now talk about the advent of a second quantum revolution. What exactly does this mean?

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