Quantum Random Number Generator Created Using A Smartphone Camera� — The Physics arXiv Blog — Medium

Quantum Random Number Generator Created Using A Smartphone Camera� — The Physics arXiv Blog — Medium:  It’s straightforward to calculate the average number of electrons this process should produce, given the probabilistic nature of photon emission. But the actual number of electrons should differ by a number that is random. That produces a single random digit. And since a light-sensitive array consists of many pixels working in parallel, it is possible to generate a large quantity of random digits from each image...

So the process of generating random numbers consists of pointing the camera at a green LED that evenly illuminates all the pixels and pressing the shutter button. A simple program then extracts the random digits.

Spy agencies want low-energy system to solve 'interesting problems' - Computerworld

Spy agencies want low-energy system to solve 'interesting problems' - Computerworld: The goal of the government's solicitation is "to demonstrate a small-scale computer based on superconducting logic and cryogenic memory that is energy efficient, scalable, and able to solve interesting problems..."

The U.S. believes superconducting technologies can reduce power demand for one petaflop to 25 kW or even 100 petaflops for about 200 kW, including the cost of cryogenic refrigeration...


The NSA, in particular, has had a long interest in superconducting technology, but "significant technical obstacles prevented exploration of superconducting computing," the government said in its solicitation. Those innovations include cryogenic memory designs that allow operation of memory and logic in close proximity within the cold environment, as well as much faster switching speeds.

Time cloak hides events by splicing them movie style

Time cloak hides events by splicing them movie style: Time cloaks work by slowing down light in an optical fibre, creating a gap in the beam. Any outside light that enters the hole becomes cloaked when the original beam is sped up...

A diffraction grating stretches out a laser beam, producing a series of gaps. Pulses of light sent along the fibre at the same time slot into these. A second grating then closes the holes, hiding the pulses from the intended receiver. There is now no record that the pulses ever traversed the fibre... This string of cloaks can hide up to 1.5 gigabytes per second.

Moving plane exchanges quantum keys with Earth

Moving plane exchanges quantum keys with Earth: Flying at a height of 20 kilometres and a speed of nearly 300 km per hour, the challenge was to tightly align the infrared laser pulses transmitted by the aircraft with the receiving station on the ground. Any deviation would limit the number of photons reaching the target.

The researchers kept the laser on track using moving mirrors both in the aircraft and on the ground. Performing the experiment shortly after sunset avoided interference from sunlight. The transmission lasted for 10 minutes, amounting to a key long enough to encrypt 10 kilobytes of data.

Quantum Teleportation Achieved over Record Distances

Quantum Teleportation Achieved over Record Distances:  In a paper posted May 17 to the physics preprint Web site arXiv.org, just eight days after the Chinese group announced their achievement on the same Web site, a European and Canadian group claims to have teleported information from one of the Canary Islands to another, 143 kilometers away. That paper has not been peer-reviewed but comes from a very reputable research group.

Ghosts in the atom: Unmasking the quantum phantom - physics-math - 02 August 2012 - New Scientist

Ghosts in the atom: Unmasking the quantum phantom:  ...They imagined a hypothetical theory that completely describes a single quantum system such as an atom but, crucially, without an underlying wave telling the particle what to do.

Next they concocted a thought experiment to test their theory, which involved bringing two independent atoms together and making a particular measurement on them. What they found is that the hypothetical wave-less theory predicts an outcome that is different from standard quantum theory. "Since quantum theory is known to be correct, it follows that nothing like our hypothetical theory can be correct..."

The UK trio's work has also received support from Lucien Hardy at the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, Canada. Using slightly different assumptions, he has obtained a similar result indicating the reality of the wave function (arxiv.org/abs/1205.1439)...


...Some point to problems with the team's "benign" assumptions. One is the notion that a quantum system has true properties even before any measurement has been made on it...

Pusey and his colleagues also suppose that the two atoms in their thought experiment are truly independent of each other, so that a measurement made on one does not affect the other. They also take for granted that the laws of cause and effect hold...

Quantum Cryptography Outperformed By Classical Technique

Quantum Cryptography Outperformed By Classical Technique: Once again the secrecy is guaranteed by the laws of physics but instead of quantum mechanics, Kish and co say the second law of thermodynamics provides the necessary underwriting...


Alice wants to send Bob a message via an ordinary wire. At each end of the wire, there are two different resistors that correspond to a 0 or 1.

Alice encodes her message by connecting these two resistors to the wire in the required sequence.

Bob, on the other hand, connects his resistors to the wire at random.

The crucial part of this set up is that the actual current and voltage through the wire is random, ideally Johnson noise. The essential features of this noise are determined by the combination of resistors at each end. This noise is public--anybody can see or measure it.

Now here's the clever bit. Bob knows which resistor he connected to the wire and so can work out which resistor Alice must have connected.

But  Eve, who is listening in to the publicly available noise, does not know which resistor was connected at each end and cannot work it out either because the laws of thermodynamics prevent the extraction of this information from this kind of signal.

What's more, any kind of active attack that might interrogate the resistors at each end always introduces energy into  the system that Alice and Bob can easily spot. That allows them to guarantee the secrecy, even when they send only a single bit.

Chinese Physicists Smash Distance Record For Teleportation

Chinese Physicists Smash Distance Record For Teleportation: Juan Yin at the University of Science and Technology of China in Shanghai, and a bunch of mates say they have teleported entangled photons over a distance of 97 kilometres across a lake in China...


So the most important advance these guys have made is to develop a steering mechanism using a guide laser that keeps the beam precisely on target. As a result, they were able to teleport more than 1100 photons in 4 hours over a distance of 97 kilometres.

That's interesting because it's the same channel attenuation that you'd have to cope with when beaming photons to a satellite with, say, 20 centimetre optics orbiting at about 500 kilometres. "The successful quantum teleportation over such channel losses in combination with our high-frequency and high-accuracy [aiming] technique show the feasibility of satellite-based ultra-long-distance quantum teleportation," say Juan and co.

Physicists Go Totally Random - Science News

Physicists Go Totally Random - Science News: In the new work, the scientists have calculated what might happen to a stream of partially random information, in which some of the bits are correlated with other variables, thus making the bits not random. By using these bits to choose measurements on pairs of entangled particles sent down two separate paths, a final outcome can be produced that is independent of any other variables, Colbeck and Renner showed. In other words, perfectly random bits are produced.

Quantum Rainbow Photon Gun Unveiled

Quantum Rainbow Photon Gun Unveiled: One of the significant weaknesses of current quantum cryptographic systems is the finite possibility that today's lasers emit photons in bunches rather than one at a time. When this happens, an eavesdropper can use these extra photons to extract information about the data being transmitted...

The gun is a disc-shaped crystal of lithium niobate zapped with 582nm light from a neodymium-doped yttrium aluminium garnet (Nd:YAG) laser. Lithium niobate is a nonlinear material that causes single photons to spontaneously convert into photon pairs.
So the 582nm photons ricochet around inside the disc and eventually emerge either as unchanged 582nm photons or as a pair of entangled photons with about twice the wavelength (about 1060nm). This entangled pair don't have quite the same wavelength and so all three types of photon can be easily separated...
These guys can also change the wavelength of the photons the gun emits by heating or cooling the crystal and thereby changing its size.

Physicists Create First Long-Distance Quantum Link

Physicists Create First Long-Distance Quantum Link: "In the past, we have built networks that can communicate quantum information, but convert it into classical form at the network switching points. [The researchers] report preliminary experiments towards forming a network in which the information remains in quantum form..."

As simple as this may sound, the researchers still needed a complete lab room full of lasers, optical elements, and other equipment for each node. Each atom sat between two highly reflective mirrors 0.5 mm apart, which form an "optical cavity." By applying an external laser to atom A, Ritter's team caused a photon emitted by that atom to escape from its cavity and travel through a 60-meter-long optical fiber to the cavity across the street. When the photon was absorbed by atom B, the original quantum information from the first atom was transferred to the second. By starting with just the right state of the first atom, the researchers could entangle the two atoms. According to the researchers, the entanglement could in principle be extended to a third atom, which makes the system scalable to more than two nodes.

Serious Flaw Emerges In Device-Independent Quantum Cryptography - Technology Review

Serious Flaw Emerges In Device-Independent Quantum Cryptography - Technology Review:  Some groups claim to have made progress in developing  device-independent protocols but Barrett and co have found an issue that all others appear to have overlooked. These protocols all treat quantum cryptography as a single-shot process, as if the equipment is used only once.

Laser's Quantum Fluctuations Provide a Better, Faster Source of Random Numbers

Laser's Quantum Fluctuations Provide a Better, Faster Source of Random Numbers: Ben Sussman at the National Research Council in Ottawa works with a laser pulse lasting a few trillionths of a second, and shines it at a 3-mm piece of diamond crystal. The interactions with vacuum fluctuations changes the incoming photons, whose signals are amplified and converted into binary to generate random bit sequences...
Other researchers have tapped quantum uncertainty to build truly random sequences, including a Chinese team that used quantum noise last year to introduce small frequency changes in laser light. Their method achieved 300 megabits per second of random data, pretty fast but still not great compared to modern bit-rate requirements. Sussman says his method is much faster, capable of producing gigabit-per-second random data.

Quantum Mechanics Braces for the Ultimate Test

Quantum Mechanics Braces for the Ultimate Test: The now-celebrated Aspect experiment, along with similar ones, helped to write nonlocality into physics textbooks. But there is another loophole that those experiments did not close. The trouble is that photons are slippery customers: small, fast, and notoriously hard to detect. Typically, if five photons are hurled at a detector, it will register only one. That means that physicists can trust that Bell's bound has been violated only if they assume that the photons caught provide a fair representation of how all the photons in the experiment behaved—much the way exit polls at voting booths predict election results.

Most physicists accept that the fair-sampling assumption is a good one. “It's unlikely that nature is so malicious that it conspires with the apparatus to hold back particular photons just to fool us into thinking that quantum mechanics works,” Gisin says.
Nonetheless, physicists hate loose ends, so the chase to find a perfect, loophole-free test has continued over the past decade. “Until the test is done, we can't honestly say that hidden variables have been ruled out—even if the consensus is they don't make sense—because we haven't proved it,” says Harald Weinfurter of the Ludwig Maximilian University in Munich, Germany...
Building on Wineland's experiment, Weinfurter's group is attempting to tie up both loopholes at once, by weaving photons together with atoms to reap the benefits of both. The idea is to start with two initially unentangled atoms in separate laboratories—ideally more than 100 meters apart, so that the atoms cannot influence each other over the course of the test. Each atom emits a photon; the two photons are captured and transmitted along optical fibers to a third location, where they are entangled. “The magic is that as soon as the photons are entangled, their parent atoms automatically become entangled, too...”

Technology Review: Blogs: arXiv blog: 1978 Cryptosystem Resists Quantum Attack

Technology Review: Blogs: arXiv blog: 1978 Cryptosystem Resists Quantum Attack: "The McEliese cryptosystem is different. It too is asymmetric but its security is based not on factorisation but on a version of a conundrum that mathematicians call the hidden supgroup problem. What Dinh and buddies have shown is that this problem cannot be solved using quantum fourier analysis. In other words it is immune to attack by Shor's algorithm. In fact, it is immune to any attack based on quantum fourier sampling.

That's a big deal. It means that anything encoded in this way will be safe when the next generation of quantum computers start chomping away at the more conventional public key cryptosystems. One such system is Entropy, a peer-to-peer communications network designed to resist censorship based on the McEliese cryptosystem.

But Entropy is little used and there are good reasons why others have resisted the McEliese encryption system. The main problem is that both the public and private keys are somewhat unwieldy: a standard public key is a large matrix described by no fewer than 2^19 bits."