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A secure quantum internet is one step closer thanks to a quantum memory made from a crystal, which could form a crucial part of a device able to transmit entangled photons over a distance of 5 kilometres. Crucially, it is entirely compatible with existing communication networks, making it suitable for real-world use.

There has long been a vision of a quantum version of the internet, which would allow quantum computers to communicate across long distances by exchanging particles of light called photons that have been linked together with quantum entanglement, allowing them to transmit quantum states.

The problem is that photons get lost when they are transmitted through long lengths of fibre-optic cable. For normal photons, this isn’t an issue, because networking equipment can simply measure and retransmit them after a certain distance, which is how normal fibre data connections work. But for entangled photons, any attempt to measure or amplify them changes their state.

D-Wave’s newest offering, available in mid-2020, offers two and a half times more connectivity between qubits than the 2000Q quantum computer.

Just as microelectronics transformed the modern world through the creation of the integrated circuit, which is now at the heart of most electronic devices, quantum photonics needs an equivalent platform to fulfil its application potential. In this special focus issue of Nature Photonics, we report on the progress in making this a reality with the developments in integrated quantum photonics (IQP).

In a Review Article, Jianwei Wang and colleagues provide a general overview and introduction to IQP circuits and summarize the present development of quantum hardware based on IQP chips. They remark that the challenge for measurement-based quantum computation may shift from the need for deterministic gates to constructing a generic entangled cluster-state, on which any quantum computation could be mapped by a sequence of measurements.

IQP circuits are also a desirable platform for chip-based quantum communications. However, fully integrated chip-based quantum communication has not yet been realized, largely because of the integration difficulties between silicon wafers that feature optical waveguides and other passive components and light sources and photodetectors that are made from different semiconductors. Key components such as transmitters and receivers for quantum key distribution and quantum random number generators are instead individually fabricated.

The creation, transfer, and stabilization of localized excitations are studied in a donor–acceptor Frenkel exciton model in an atomistic treatment of reduced-size double quantum dots (QDs) of various sizes. The explicit time-dependent dynamics simulations carried out by hybrid time-dependent density functional theory/configuration interaction show that laser-controlled hole trapping in stacked, coupled germanium/silicon quantum dots can be achieved by a UV/IR pump–dump pulse sequence. The first UV excitation creates an exciton localized on the topmost QD and after some coherent transfer time, an IR pulse dumps and localizes an exciton in the bottom QD. While hole trapping is observed in each excitation step, we show that the stability of the localized electron depends on its multiexcitonic character.

Featureless “cost functions” prevent quantum machine learning algorithms from reconstructing scrambled information.

A team of scientists at the University of Sussex have for the first time built a modular quantum brain scanner, and used it to record a brain signal. This is the first time a brain signal has been detected using a modular quantum brain sensor anywhere in the world. It’s a major milestone for all researchers working on quantum brain imaging technology because modular sensors can be scaled up, like Lego bricks. The team have also connected two sensors like Lego bricks, proving that whole-brain scanning using this method is within reach—as detailed in their paper, which is published today in pre-print. This has not been possible with the currently commercially available quantum brain sensors from the United States.

These modular devices work like play bricks in that they can be connected together. This opens up the potential for whole–brain scanning using quantum technology, and potential advances for neurodegenerative diseases like Alzheimer’s.

The device, which was built at the Quantum Systems and Devices laboratory at the university, uses ultra-sensitive quantum sensors to pick up these tiniest of magnetic fields to see inside the brain in order to map the neural activity.

Using an ultrafast transmission electron microscope, researchers from the Technion—Israel Institute of Technology have, for the first time, recorded the propagation of combined sound and light waves in atomically thin materials.

The experiments were performed in the Robert and Ruth Magid Electron Beam Quantum Dynamics Laboratory headed by Professor Ido Kaminer, of the Andrew and Erna Viterbi Faculty of Electrical & Computer Engineering and the Solid State Institute.

Continue reading “Researchers observe sound-light pulses in 2D materials for the first time” »

Two novel demonstrations bring the backbone of the quantum internet, quantum repeaters, a little closer.

TAMPA, Fla. — Seraphim Capital plans to trade stakes it has amassed in space technology startups on the public market through an investment trust.

The Seraphim Space Investment Trust will eventually comprise bets in 19 international startups, including satellite data specialist Spire Global, quantum encryption firm Arqit and space-based cellular network operator AST Space Mobile.

Those three recently got valuations of more than $1 billion in mergers with special purpose acquisition companies (SPACs), investment vehicles that offer another route to public markets.