Lifeboat Foundation

New schemes based on Rydberg superatoms placed in optical cavities can be used to manipulate single photons with high efficiency.

The past decade has witnessed swift progress in the development and application of quantum technologies. Many promising directions involve using photons, the smallest energy packets of light, as carriers of quantum information [1]. Photons at optical wavelengths can be quickly transported through optical fibers over long distances and with negligible noise, even at room temperature. Unfortunately, one drawback is that photons do not normally interact with each other, which makes it challenging to manipulate a photon with another photon. Optical photons also couple weakly with other quantum systems, such as superconducting qubits, which makes it hard to interface these platforms with photons.

A new design based on the quantum capacitance of a silicon quantum dot could enable scalable, high-fidelity qubit readout.

The Facility for Rare Isotope Beams opens its doors to experiments that will study the formation of heavy elements in the Universe and provide critical tests of nuclear theories.

A “forever battery” is much smaller and more energy-dense than lithium-ion. They’ll change the world and unlock a trillion-dollar revolution.

In this week’s episode, Aaron and I discuss what could be the “holy grail” of energy: the solid-state — or forever battery. Obviously, lithium-ion cells are the status quo of today. And they power pretty much everything, like your smartphone, laptop and electric vehicle.

Continue reading “Forever Battery: QuantumScape’s Holy Grail of Energy” »

A researcher from Skoltech has filled in the gaps connecting quantum simulators with more traditional quantum computers, discovering a new computationally universal model of quantum computation, the variational model. The paper was published as a Letter in the journal Physical Review A. The work made the Editors’ Suggestion list.

A quantum simulator is built to share properties with a target quantum system we wish to understand. Early quantum simulators were ‘dedicated’—that means they could not be programmed, tuned or adjusted and so could mimic one or very few target systems. Modern quantum simulators enable some control over their settings, offering more possibilities.

In contrast to quantum simulators, the long-promised quantum computer is a fully programmable quantum system. While building a fully programmable quantum processor remains elusive, noisy quantum processors that can execute short quantum programs and offer limited programmability are now available in leading laboratories around the world. These quantum processors are closer to the more established quantum simulators.

A team of researchers and engineers at Canadian company Xanadu Quantum Technologies Inc., working with the National Institute of Standards and Technology in the U.S., has developed a programmable, scalable photonic quantum chip that can execute multiple algorithms. In their paper published in the journal Nature, the group describes how they made their chip, its characteristics and how it can be used. Ulrik Andersen with the Technical University of Denmark has published a News & Views piece in the same journal issue outlining current research on quantum computers and the work by the team in Canada.

Scientists around the world are working to build a truly useful quantum computer that can perform calculations that would take traditional computers millions of years to carry out. To date, most such efforts have been focused on two main architectures—those based on superconducting electrical circuits and those based on trapped-ion technology. Both have their advantages and disadvantages, and both must operate in a supercooled environment, making them difficult to scale up. Receiving less attention is work using a photonics-based approach to building a quantum computer. Such an approach has been seen as less feasible because of the problems inherent in generating quantum states and also of transforming such states on demand. One big advantage photonics-based systems would have over the other two architectures is that they would not have to be chilled—they could work at room temperature.

In this new effort, the group at Xanadu has overcome some of the problems associated with photonics-based systems and created a working programmable photonic quantum chip that can execute multiple algorithms and can also be scaled up. They have named it the X8 photonic quantum processing unit. During operation, the chip is connected to what the team at Xanadu describe as a “squeezed light” source—infrared laser pulses working with microscopic resonators. This is because the new system performs continuous variable quantum computing rather than using single-photon generators.

Foresight Molecular Machines Group.
Program & apply to join: https://foresight.org/molecular-machines/

Joe Lyding.
Silicon-Based Nanotechnology: There’s Still Plenty of Room at the Bottom.
Joe Lyding is a distinguished professor in Electrical and Computer Engineering at the University of Illinios. His career includes constructing the first atomic resolution scanning tunneling microscope, discovering new industrial uses for deuterium, studying quantum size effects down to 2nm lateral graphene dimensions, and much more. His current research is focused on carbon nanoelectronics. Specifically using carbon nanoelectronics based on carbon nanotubes and graphene for future semiconducting device applications.

Continue reading “J. Lyding & L. Grill | Silicon-Based Nanotechnology & Manipulating Single Molecules on Surfaces” »

We argue in a model-independent way that the Hilbert space of quantum gravity is locally finite-dimensional. In other words, the density operator describing the state corresponding to a small region of space, when such a notion makes sense, is defined on a finite-dimensional factor of a larger Hilbert space. Because quantum gravity potentially describes superpo-sitions of different geometries, it is crucial that we associate Hilbert-space factors with spatial regions only on individual decohered branches of the universal wave function. We discuss some implications of this claim, including the fact that quantum field theory cannot be a fundamental description of Nature.

Quanta of light—photons—form the basis of quantum key distribution in modern cryptographic networks. Before the huge potential of quantum technology is fully realized, however, several challenges remain. A solution to one of these has now been found.

In a paper published in the journal Science, teams led by David Novoa, Nicolas Joly and Philip Russell report a breakthrough in frequency up-conversion of single photons, based on a hollow-core photonic crystal fiber (PCF) filled with hydrogen gas. First a spatio-temporal hologram of molecular vibrations is created in the gas by stimulated Raman scattering. This hologram is then used for highly efficient, correlation-preserving frequency conversion of single photons. The system operates at a pressure-tuneable wavelength, making it potentially interesting for quantum communications, where efficient sources of indistinguishable single-photons are unavailable at wavelengths compatible with existing fiber networks.

The approach combines quantum optics, gas-based nonlinear optics, hollow-core PCF, and the physics of molecular vibrations to form an efficient tool that can operate in any spectral band from the ultraviolet to the mid-infrared—an ultra-broad working range inaccessible to existing technologies. The findings may be used to develop fiber-based tools in technologies such as quantum communications, and quantum-enhanced imaging.

Physicists from Paderborn University have developed a novel concept for generating individual photons—tiny particles of light that make up electromagnetic radiation—with tailored properties, the controlled manipulation of which is of fundamental importance for photonic quantum technologies. The findings have now been published in the journal Nature Communications.

Professor Artur Zrenner, head of the “nanostructure optoelectronics” research group, explains how tailored desired states have so far posed a challenge: “Corresponding sources are usually based on light emissions from individual semiconductor quantum emitters, which generate the photons. Here, the properties of the emitted photons are defined by the fixed properties of the quantum emitter, and can therefore not be controlled with full flexibility.”

To get around the problem, the scientists have developed an all-optical, non-linear method to tailor and control single photon emissions. Based on this concept, they demonstrate laser-guided energy tuning and polarization control of photons (i.e., the light frequency and direction of oscillation of electromagnetic waves).