Tag Archives: Hamid Ohadi

Ancient Namibian gemstone could be key to new light-based quantum computers

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Researchers in Scotland, the US, Australia, and Denmark have a found a solution to a problem with creating light-based computers according to an April 15, 2022 news item on phys.org,

A special form of light made using an ancient Namibian gemstone could be the key to new light-based quantum computers, which could solve long-held scientific mysteries, according to new research led by the University of St Andrews.

The research, conducted in collaboration with scientists at Harvard University in the US, Macquarie University in Australia and Aarhus University in Denmark and published in Nature Materials, used a naturally mined cuprous oxide (Cu2O) gemstone from Namibia to produce Rydberg polaritons, the largest hybrid particles of light and matter ever created.

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Cuprous oxide – the mined crystal from Namibia used for making Rydberg polaritons. Courtesy: University of St. Andrews

An April 15, 2022 University of St. Andrews press release, which originated the news item, describes Rydberg polaritons and explains why they could be the key to light-based quantum computing,

Rydberg polaritons switch continually from light to matter and back again. In Rydberg polaritons, light and matter are like two sides of a coin, and the matter side is what makes polaritons interact with each other.

This interaction is crucial because this is what allows the creation of quantum simulators, a special type of quantum computer, where information is stored in quantum bits. These quantum bits [qubits], unlike the binary bits in classical computers that can only be 0 or 1, can take any value between 0 and 1. They can therefore store much more information and perform several processes simultaneously.

This capability could allow quantum simulators to solve important mysteries of physics, chemistry and biology, for example, how to make high-temperature superconductors for highspeed trains, how cheaper fertilisers could be made potentially solving global hunger, or how proteins fold making it easier to produce more effective drugs.

Project lead Dr Hamid Ohadi, of the School of Physics and Astronomy at the University of St Andrews, said: “Making a quantum simulator with light is the holy grail of science. We have taken a huge leap towards this by creating Rydberg polaritons, the key ingredient of it.”

To create Rydberg polaritons, the researchers trapped light between two highly reflective mirrors. A cuprous oxide crystal from a stone mined in Namibia was then thinned and polished to a 30-micrometer thick slab (thinner than a strand of human hair) and sandwiched between the two mirrors to make Rydberg polaritons 100 times larger than ever demonstrated before.

One of the leading authors Dr Sai Kiran Rajendran, of the School of Physics and Astronomy at the University of St Andrews, said: “Purchasing the stone on eBay was easy. The challenge was to make Rydberg polaritons that exist in an extremely narrow colour range.”

The team is currently further refining these methods in order to explore the possibility of making quantum circuits, which are the next ingredient for quantum simulators.

The research was funded by UK Engineering and Physical Sciences Research Council (EPSRC).

Here’s a link to and a citation for the paper,

Rydberg exciton–polaritons in a Cu2O microcavity by Konstantinos Orfanakis, Sai Kiran Rajendran, Valentin Walther, Thomas Volz, Thomas Pohl & Hamid Ohadi. Nature Materials (2022) DOI: DOIhttps://doi.org/10.1038/s41563-022-01230-4 Published: 14 April 2022

This paper is behind a paywall.

Gold nanoparticles concentrate light so atomic bonds can be viewed

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Artist's impression light waves capable of revealing atomic bonds Credit: NanoPhotonics Cambridge/Bart deNijs

Artist’s impression light waves capable of revealing atomic bonds Credit: NanoPhotonics Cambridge/Bart deNijs

This research upends centuries of scientific thought according to a Nov. 10, 2016 news item on ScienceDaily,

For centuries, scientists believed that light, like all waves, couldn’t be focused down smaller than its wavelength, just under a millionth of a metre. Now, researchers led by the University of Cambridge have created the world’s smallest magnifying glass, which focuses light a billion times more tightly, down to the scale of single atoms.

If they’ve created is a ‘magnifying glass’ as they call it in the news item, then I suppose you could call the ‘pico-cavity’ mentioned in the following press release, a lens.

A Nov. 10, 2016 University of Cambridge press release (also on EurekAlert), which originated the news item, describes the research in more detail,

In collaboration with European colleagues, the team used highly conductive gold nanoparticles to make the world’s tiniest optical cavity, so small that only a single molecule can fit within it. The cavity – called a ‘pico-cavity’ by the researchers – consists of a bump in a gold nanostructure the size of a single atom, and confines light to less than a billionth of a metre. The results, reported in the journal Science, open up new ways to study the interaction of light and matter, including the possibility of making the molecules in the cavity undergo new sorts of chemical reactions, which could enable the development of entirely new types of sensors.

According to the researchers, building nanostructures with single atom control was extremely challenging. “We had to cool our samples to -260°C in order to freeze the scurrying gold atoms,” said Felix Benz, lead author of the study. The researchers shone laser light on the sample to build the pico-cavities, allowing them to watch single atom movement in real time.

“Our models suggested that individual atoms sticking out might act as tiny lightning rods, but focusing light instead of electricity,” said Professor Javier Aizpurua from the Center for Materials Physics in San Sebastian in Spain, who led the theoretical section of this work.

“Even single gold atoms behave just like tiny metallic ball bearings in our experiments, with conducting electrons roaming around, which is very different from their quantum life where electrons are bound to their nucleus,” said Professor Jeremy Baumberg of the NanoPhotonics Centre at Cambridge’s Cavendish Laboratory, who led the research.

The findings have the potential to open a whole new field of light-catalysed chemical reactions, allowing complex molecules to be built from smaller components. Additionally, there is the possibility of new opto-mechanical data storage devices, allowing information to be written and read by light and stored in the form of molecular vibrations.

Here’s a link to and a citation for the paper,

Single-molecule optomechanics in “picocavities” by Felix Benz, Mikolaj K. Schmidt, Alexander Dreismann, Rohit Chikkaraddy, Yao Zhang, Angela Demetriadou, Cloudy Carnegie, Hamid Ohadi, Bart de Nijs, Ruben Esteban, Javier Aizpurua, Jeremy J. Baumberg. Science  11 Nov 2016: Vol. 354, Issue 6313, pp. 726-729 DOI: 10.1126/science.aah5243

This paper is behind a paywall.