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Category: quantum physics

Recent developments in chip-based photonic quantum circuits have radically impacted quantum information processing. However, it is challenging for monolithic photonic platforms to meet the stringent demands of most quantum applications. Hybrid platforms combining different photonic technologies in a single functional unit have great potential to overcome the limitations of monolithic photonic circuits. Our Review summarizes the progress of hybrid quantum photonics integration, discusses important design considerations, including optical connectivity and operation conditions, and highlights several successful realizations of key physical resources for building a quantum teleporter. We conclude by discussing the roadmap for realizing future advanced large-scale hybrid devices, beyond the solid-state platform, which hold great potential for quantum information applications.

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PsiQuantum is a little-known quantum computing startup, however it recently had no trouble raising almost a quarter of a billion dollars from Microsoft’s M12 venture fund and other investors. That is in addition to a whopping $230 million it received last year from a fund formed by Andy Rubin, developer of the Android operating system.

The company was founded in 2016 by British professor Jeremy O’Brien and three other academics, Terry Rudolph, Mark Thompson, and Pete Shadbolt. In just a few years, they have quietly grown the company from a few employees to a robust technical staff of more than 100.

Compared to today’s modest quantum computing capabilities, PsiQuantum’s elevator pitch for investors sounds like a line from a science fiction movie. O’Brien not only says he is going to build a fault-tolerant quantum computer with a staggering one million qubits, he also says he is going to do it within five years. O’Brien’s technology of choice for this claim is silicon photonics, which uses particles of light called photons to perform quantum calculations. Theoretically, photons behave as both waves and particles, but that’s a subject for another article. Quantum computing technologies in use today are primarily superconductors and trapped ion. However, there is plenty of research that shows photonics holds a lot of promise.

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Most quantum computers being developed around the world will only work at fractions of a degree above absolute zero. That requires multi-million-dollar refrigeration and as soon as you plug them into conventional electronic circuits they’ll instantly overheat.

But now researchers led by Professor Andrew Dzurak at UNSW Sydney have addressed this problem.

“Our new results open a path from experimental devices to affordable quantum computers for real world business and government applications,” says Professor Dzurak.

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:oooo.

Metasurfaces are artificial materials designed at the nanoscale, which can control the scattering of light with exceptionally high precision. Over the past decade or so, these materials have been used to create a variety of technological tools ranging from sensors to lenses and imaging techniques.

A research team led by Mikhail Lukin at Harvard University has recently proposed a new type of metasurface that can control both the spatiotemporal and of transmitted and reflected . In a paper published in Nature Physics, the team showed that realizing a quantum metasurface is possible and could be achieved by entangling the macroscopic response of thin atom arrays to light.

“Quantum metasurfaces are an entirely new type of materials designed atom by atom, which enable applications such as quantum computation with photons,” Rivka Bekenstein, the lead author of the recent paper, told Phys.org. “We combined a state-of-the-art technique for manipulating the state of many by (i.e., Rydberg interactions) with a recent discovery of how a single sheet of atoms can reflect light. We identified an architecture that can be realized in the laboratory, in which a single layer of atoms can act as a switchable quantum mirror.”

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When the American physicist Arthur Compton discovered that light waves behave like particles in 1922, and could knock electrons out of atoms during an impact experiment, it was a milestone for quantum mechanics. Five years later, Compton received the Nobel Prize for this discovery. Compton used very shortwave light with high energy for his experiment, which enabled him to neglect the binding energy of the electron to the atomic nucleus. Compton simply assumed for his calculations that the electron rested freely in space.

During the following 90 years up to the present, numerous experiments and calculations have been carried out with regard to Compton scattering that continually revealed asymmetries and posed riddles. For example, it was observed that in certain experiments, seemed to be lost when the motion energy of the electrons and light particles (photons) after the collision were compared with the energy of the photons before the collision. Since energy cannot simply disappear, it was assumed that in these cases, contrary to Compton’s simplified assumption, the influence of the on the photon-electron collision could not be neglected.

For the first time in an impact experiment with photons, a team of physicists led by Professor Reinhard Dörner and doctoral candidate Max Kircher at Goethe University Frankfurt has now simultaneously observed the ejected electrons and the motion of the nucleus. To do so, they irradiated helium atoms with X-rays from the X-ray source PETRA III at the Hamburg accelerator facility DESY. They detected the ejected and the charged rest of the atom (ions) in a COLTRIMS reaction microscope, an apparatus that Dörner helped develop and which is able to make ultrafast reactive processes in atoms and molecules visible.

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You really can not make this up The Bill and Melinda Gates Foundation has donated more than $21 million towards developing a vaccine technology that uses a tattoo-like mechanism which injects invisible nanoparticles under the skin that is now being tested in a vaccine against the virus that causes COVID-19.

Another study funded by the Bill and Melinda Gates Foundation and published in December, 2019 by researchers from the Massachusetts Institute of Technology, the Institute of Chemistry of the Chinese Academy of Sciences in Beijing and the Global Good, Intellectual Ventures Laboratory in Bellevue, WA, describes how “near-infrared quantum dots” can be implanted under the skin along with a vaccine to encode information for “decentralized data storage and bio-sensing.”

“To maximize the utility of this technology for vaccination campaigns, we aimed to create a platform compatible with microneedle-delivered vaccines that could reliably encode data on an individual for at least five years after administration,” said the MIT paper, titled Biocompatible near-infrared quantum dots delivered to the skin by microneedle patches record vaccination. “In addition, this system also needed to be highly biocompatible, deliver a sufficient amount of dye after an application time of 2 min or less, and be detectable using a minimally adapted smartphone.”

Fridrik Laurusson, an author of the microchip study, is from The Global Good, Intellectual Ventures Labarotory . Its website features Microsoft founder Bill Gates on its front page and describes itself as a “collaboration between Bill Gates and Intellectual Ventures” a company founded by Nathan Myhrvold and Edward Jung of Microsoft. Wikipedia describes Intellectual Ventures in Gates’ home state as a private American company that “centers on the development and licensing of intellectual property” and “one of the top-five owners of U.S. patents, as of 2011.

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VTT researchers have successfully demonstrated a new electronic refrigeration technology that could enable major leaps in the development of quantum computers. Present quantum computers require extremely complicated and large cooling infrastructure that is based on mixture of isotopes of helium. The new electronic cooling technology could replace these cryogenic liquid mixtures and enable miniaturization of quantum computers.

In this purely electrical refrigeration method, and thermal isolation operate effectively through the same point like junction. In the experiment the researchers suspended a piece of silicon from such junctions and refrigerated the object by feeding electrical current from one junction to another through the piece. The current lowered the thermodynamic temperature of the silicon object as much as 40% from that of the surroundings. This could lead to the miniaturization of future quantum computers, as it can simplify the required cooling infrastructure significantly. The discovery has been published in Science Advances.

“We expect that this newly discovered electronic cooling method could be used in several applications from the miniaturization of quantum computers to ultra-sensitive radiation sensors of the security field,” says Research Professor Mika Prunnila from VTT Technical Research Centre of Finland.

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:oooo circa 2009.

The portrait of Peter Higgs is on display at the University of Edinburgh’s School of Informatics. Photograph: Ken Currie.

It seems that Peter Higgs, despite his known aversion to publicity is turning up everywhere. Of course the potential discovery of the particle in the next few years by either/both of the Large Hadron Collider at CERN and the Tevatron at Fermilab is bringing a lot more attention to him, and a little to the other theorists, such as Guralnik, Hagen, Kibble, Brout, and Englert, who also developed the ideas behind a mass-giving spontaneously symmetry broken quantum field and its manifestation as a particle, now known as the Higgs boson. (Yep, that sounds scary because it gets technical.)

But Higgs the man seems to turn up in all kinds of places and lots of people have stories about where and how they met the man. I ran into him in at a function in a museum in the Hunterian Museum at the University of Glasgow over a decade ago, while Lauren, one of the symmetry interns, used to make him his sandwich in a cafe most days when she spent time in Glasgow. (Tell us your story of meeting Higgs in the comments below.)

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Ions trapped nanoscale optical cavities could be used to distribute entangled quantum particles over large distances. That is the conclusion of Jonathan Kindem and colleagues at Caltech in the US, who showed that a trapped ion of ytterbium can remain entangled with a photon for long periods of time. Furthermore, the team showed that the ion’s quantum state can be read out when manipulated by laser and microwave pulses. Their achievement could lay the foundations for a future quantum internet.

Quantum computers are becoming a reality as research labs and companies roll out nascent devices. An important next step in this quantum revolution is creating a “quantum internet” across which quantum information can be shared. The delicate nature of quantum information, however, means that it is very difficult to connect quantum computers over long distances.

Most quantum computers encode quantum bits (qubits) of information into the quantum states of matter – trapped atoms or superconducting circuits, for example. However, the best way to transmit quantum information over long distances is to encode it into a photon of light. An important challenge is how to transfer quantum information from stationary matter-based qubits to photon-based “flying” qubits and then back again.

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