Lifeboat Foundation

Information and gravity may seem like completely different things, but one thing they have in common is that they can both be described in the framework of geometry. Building on this connection, a new paper suggests that the rules for optimal quantum computation are set by gravity.

Physicists Paweł Caputa at Kyoto University and Javier Magan at the Instituto Balseiro, Centro Atómico de Bariloche in Argentina have published their paper on the link between quantum computing and gravity in a recent issue of Physical Review Letters.

In the field of computational complexity, one of the main ideas is minimizing the cost (in terms of computational resources) to solve a problem. In 2006, Michael Nielsen demonstrated that, when viewed in the context of differential geometry, computational costs can be estimated by distances. This means that minimizing computational costs is equivalent to finding minimal “geodesics,” which are the shortest possible distances between two points on a curved surface.

The super-thin ’wonder material’ graphene has been shaking up science for years with its amazing properties, but things get really interesting when you stack this 2D nanomaterial up against itself.

In new experiments, physicists in the US have found that when graphene is assembled in a double-layer vertical stack – with two adjacent sheets of the material that are almost touching – the proximity produces quantum states that haven’t been observed before.

These newly measured states, resulting from complex interactions of electrons between the two graphene layers, are examples of what’s called the fractional quantum Hall effect – and it’s just the latest example of how physical science gets weird when materials effectively only occupy two dimensions.

The discovery could help overcome a major quantum computing hurdle.

Physicists at the National Institute of Standards and Technology (NIST) have teleported a computer circuit instruction known as a quantum logic operation between two separated ions (electrically charged atoms), showcasing how quantum computer programs could carry out tasks in future large-scale quantum networks.

Quantum teleportation transfers data from one quantum system (such as an ion) to another (such as a second ion), even if the two are completely isolated from each other, like two books in the basements of separate buildings. In this real-life form of teleportation, only quantum information, not matter, is transported, as opposed to the Star Trek version of “beaming” entire human beings from, say, a spaceship to a planet.

Teleportation of quantum data has been demonstrated previously with ions and a variety of other quantum systems. But the new work is the first to teleport a complete quantum logic operation using ions, a leading candidate for the architecture of future quantum computers. The experiments are described in the May 31 issue of Science.

Photography measures how much light of different color hits the photographic film. However, light is also a wave, and is therefore characterized by the phase. Phase specifies the position of a point within the wave cycle and correlates to depth of information, meaning that recording the phase of light scattered by an object can retrieve its full 3D shape, which cannot be obtained with a simple photograph. This is the basis of optical holography, popularized by fancy holograms in sci-fi movies like Star Wars.

But the problem is that the spatial resolution of the photo/hologram is limited by the wavelength of light, around or just-below 1 μm (0.001 mm). That’s fine for macroscopic objects, but it starts to fail when entering the realm of nanotechnology.

Continue reading “New holographic technique opens the way for quantum computation” »

Heat flows from hot to cold objects. When a hot and a cold body are in thermal contact, they exchange heat energy until they reach thermal equilibrium, with the hot body cooling down and the cold body warming up. This is a natural phenomenon we experience all the time. It is explained by the second law of thermodynamics, which states that the total entropy of an isolated system always tends to increase over time until it reaches a maximum. Entropy is a quantitative measure of the disorder in a system. Isolated systems evolve spontaneously toward increasingly disordered states and lack of differentiation.

An experiment conducted by researchers at the Brazilian Center for Research in Physics (CBPF) and the Federal University of the ABC (UFABC), as well as collaborators at other institutions in Brazil and elsewhere, has shown that quantum correlations affect the way entropy is distributed among parts in thermal contact, reversing the direction of the so-called “thermodynamic arrow of time.”

In other words, heat can flow spontaneously from a cold object to a hot object without the need to invest energy in the process, as is required by a domestic fridge. An article describing the experiment with theoretical considerations has just been published in Nature Communications.

In conventional imaging methods, a beam of photons (or other particles) is reflected off the object to be imaged. After the beam travels to a detector, the information gathered there is used to create a photograph or other type of image. In an alternative imaging technique called “ghost imaging,” the process works a little differently: an image is reconstructed from information that is detected from a beam that never actually interacts with the object.

The key to ghost imaging is to use two or more correlated beams of particles. While one beam interacts with the object, the second beam is detected and used to reconstruct the image, even though the second beam never interacts with the object. The only aspect of the first beam that is detected is the arrival time of each photon on a separate detector. But because the two beams are correlated, the image of the object can be fully reconstructed.

While two beams are usually used in ghost imaging, recent research has demonstrated higher-order correlations—that is, correlations among three, four, or five beams. Higher-order ghost imaging can lead to improvements in image visibility, but it comes with the drawback that higher-order correlated events have a lower probability of detection, which causes lower resolution.

Researchers at MIT have developed a system for converting the molecular structures of proteins, the basic building blocks of all living beings, into audible sound that resembles musical passages. Then, reversing the process, they can introduce some variations into the music and convert it back into new proteins never before seen in nature. Credit: Zhao Qin and Francisco Martin-Martinez.

Want to create a brand new type of protein that might have useful properties? No problem. Just hum a few bars.

Continue reading “By turning molecular structures into sounds, researchers gain insight into protein structures and create new variations” »

Mechanical systems facilitate the development of a hybrid quantum technology comprising electrical, optical, atomic and acoustic degrees of freedom, and entanglement is essential to realize quantum-enabled devices. Continuous-variable entangled fields—known as Einstein–Podolsky–Rosen (EPR) states—are spatially separated two-mode squeezed states that can be used for quantum teleportation and quantum communication. In the optical domain, EPR states are typically generated using nondegenerate optical amplifiers, and at microwave frequencies Josephson circuits can serve as a nonlinear medium^4,5,6. An outstanding goal is to deterministically generate and distribute entangled states with a mechanical oscillator, which requires a carefully arranged balance between excitation, cooling and dissipation in an ultralow noise environment. Here we observe stationary emission of path-entangled microwave radiation from a parametrically driven 30-micrometre-long silicon nanostring oscillator, squeezing the joint field operators of two thermal modes by 3.40 decibels below the vacuum level. The motion of this micromechanical system correlates up to 50 photons per second per hertz, giving rise to a quantum discord that is robust with respect to microwave noise. Such generalized quantum correlations of separable states are important for quantum-enhanced detection and provide direct evidence of the non-classical nature of the mechanical oscillator without directly measuring its state. This noninvasive measurement scheme allows to infer information about otherwise inaccessible objects, with potential implications for sensing, open-system dynamics and fundamental tests of quantum gravity. In the future, similar on-chip devices could be used to entangle subsystems on very different energy scales, such as microwave and optical photons.