(Press-News.org) Researchers from Skoltech and the University of Cambridge have shown that polaritons, the quirky particles that may end up running the quantum supercomputers of the future, can form structures behaving like molecules - and these "artificial molecules" can potentially be engineered on demand. The paper outlining these results was published in the journal Physical Review B Letters.
Polaritons are quantum particles that consist of a photon and an exciton, another quasiparticle, marrying light and matter in a curious union that opens up a multitude of possibilities in next-generation polaritonic devices. Alexander Johnston, Kirill Kalinin and Natalia Berloff, professor at the Skoltech Center for Photonics and Quantum Materials and University of Cambridge, have shown that geometrically coupled polariton condensates, which appear in semiconductor devices, are capable of simulating molecules with various properties.
Ordinary molecules are groups of atoms bound together with molecular bonds, and their physical properties differ from those of their constituent atoms quite drastically: consider the water molecule, H2O, and elemental hydrogen and oxygen. "In our work, we show that clusters of interacting polaritonic and photonic condensates can form a range of exotic and entirely distinct entities - "molecules" - that can be manipulated artificially. These "artificial molecules" possess new energy states, optical properties, and vibrational modes from those of the condensates comprising them," Johnston, of the University of Cambridge Department of Applied Mathematics and Theoretical Physics, explains.
When researchers were running numerical simulations of two, three, and four interacting polariton condensates, they noticed some curious asymmetric stationary states in which not all of the condensates have the same density in their ground state. "Upon further investigation, we found that such states came in a wide variety of different forms, which could be controlled by manipulating certain physical parameters of the system. This led us to propose such phenomena as "artificial polariton molecules" and to investigate their potential uses in quantum information systems," Johnston says.
In particular, the team focused on an "asymmetric dyad", which consists of two interacting condensates with unequal occupations. When two of those dyads are combined into a tetrad structure, the latter is, in some sense, analogous to a homonuclear molecule - for instance, to molecular hydrogen H2. Furthermore, artificial polariton molecules can also form more elaborate structures, which could be thought of as "artificial polariton compounds."
"There is nothing preventing more complex structures from being created. Indeed, in our work we have found that there is a wide range of exotic, asymmetric states possible in tetrad configurations. In some of these, all condensates have different densities (despite all of the couplings being of equal strength), inviting an analogy with chemical compounds," Alexander Johnston notes.
In specific tetrad structures, each asymmetric dyad can be viewed as an individual "spin," defined by the orientation of the density asymmetry. This has interesting consequences for the system's degrees of freedom (the independent physical parameters required to define states); the "spins" introduce a discrete degree of freedom, in addition to the continuous degrees of freedom given by the condensate phases.
The relative orientation of each of the dyads can be controlled by varying the coupling strength between them. Since quantum information systems can potentially have increased accuracy and efficiency if they utilize some kind of hybrid discrete-continuous system, the team therefore proposed this hybrid tetrad structure as a potential basis for such a system.
"In addition, we have discovered a plethora of exotic asymmetric states in triad and tetrad systems. It is possible to seamlessly transition between such states simply by varying the pumping strength used to form the condensates. This property suggests that such states could form the basis of a polaritonic multi-valued logic system, which could enable the development of polaritonic devices that dissipate significantly less power than traditional methods and, potentially, operate orders of magnitude faster," Professor Berloff says.
INFORMATION:
Skoltech is a private international university located in Russia. Established in 2011 in collaboration with the Massachusetts Institute of Technology (MIT), Skoltech is cultivating a new generation of leaders in the fields of science, technology and business, is conducting research in breakthrough fields, and is promoting technological innovation with the goal of solving critical problems that face Russia and the world. Skoltech is focusing on six priority areas: data science and artificial intelligence, life sciences, advanced materials and modern design methods, energy efficiency, photonics and quantum technologies, and advanced research. Web: https://www.skoltech.ru/.
A group of researchers representing four countries summed up the results of the Supertest, a large-scale study of the academic performance of engineering students in Russia, China, India, and the United States. It is the first study to track the progress of students in computer science and electrical engineering over the course of their studies with regard to their abilities in physics, mathematics, and critical thinking and compare the results among four countries. The article about study in Nature Human Behavior.
The HSE Institute of Education played a key role not only in collecting and analyzing data from Russia, ...
March 1, 2021 - Benign bone tumors may be present in nearly 20 percent of healthy children, based on a review of historical radiographs in The Journal of Bone & Joint Surgery. The journal is published in the Lippincott portfolio in partnership with Wolters Kluwer.
Although that may sound frightening, non-ossifying fibromas and other common benign bone tumors in symptom-free children are harmless and may resolve over time, reports the new study by Christopher D. Collier, MD, of Indiana University School of Medicine and colleagues. "These findings provide unique evidence to answer many commonly encountered questions when counseling patients and their families on benign bone tumors," the researchers write.
Study offers reassurance that benign ...
Blocking cell receptors for glucagon, the counter-hormone to insulin, cured mouse models of diabetes by converting glucagon-producing cells into insulin producers instead, a team led by UT Southwestern reports in a new study. The END ...
Boston, MA--Most pregnant women and mothers of children younger than 18 years old say they would receive a COVID-19 vaccine and vaccinate their children, according to a survey conducted by researchers at Harvard T.H. Chan School of Public Health. The research indicated that vaccine acceptance was highest in India, the Philippines, and all sampled countries in Latin America, and it was lowest in Russia, the U.S., and Australia.
The results will be published online on March 1, 2021 in the European Journal of Epidemiology.
Vaccines for COVID-19 are being distributed around the world, but until ...
SILVER SPRING, Md. - A recent preclinical study by U.S. Military HIV Research Program (MHRP) researchers showed that an experimental therapy combining a TLR7 agonist and two broadly neutralizing antibodies delayed viral rebound in SHIV-infected macaques after antiretroviral therapy (ART) interruption.
The experimental combination therapy consisted of TLR7 agonist GS-986 and two broadly neutralizing antibodies (bnAbs), N6-LS and PGT121, targeting different regions of the HIV envelope. The rhesus macaques were initiated on viral suppressive antiretroviral therapy 14 days post infection, a timespan from infection to treatment which mirrors what is feasible in acute HIV infection. Researchers then administered the experimental combination ...
NEW YORK, NY (March 1, 2021)--By harnessing the immune system against cancer, immunotherapies have revolutionized the way some types of cancer are treated. But most patients--across cancer types--do not respond, and in most cases, scientists are at a loss as to why.
Researchers at Columbia and MIT have created a new technique that can uncover nearly all of the tricks cancer cells use to evade immunotherapies, which could lead to the development of more effective treatments.
The researchers tested their new technique with cancer cells and matching immune cells from melanoma patients and identified previously unknown resistance mechanisms to immune checkpoint ...
Black Americans have a high level of vaccine hesitancy and mistrust of COVID-19 vaccines, including among Black health care workers, according to a new RAND Corporation survey.
Those who expressed vaccine hesitancy also showed high levels of overall mistrust in the vaccine, concerns about potential harm and side effects, and lack of confidence in vaccine effectiveness and safety.
Participants in the RAND survey reported higher trust in COVID-19 information from health care providers and public health officials than from elected local and federal officials.
The findings are based on a survey ...
Tissue engineering has long-depended on geometrically static scaffolds seeded with cells in the lab to create new tissues and even organs. The scaffolding material -- usually a biodegradable polymer structure -- is supplied with cells and the cells, if supplied with the right nutrients, then develop into tissue as the underlying scaffold biodegrades. But this model ignores the extraordinarily dynamic morphological processes that underlie the natural development of tissues.
Now, researchers at the END ...
A team of international researchers led by a Florida State University assistant professor has analyzed reams of data from the Neolithic to Late Roman period looking at migration patterns across the Mediterranean and found that despite evidence of cultural connections, there's little evidence of massive migration across the region.
"Because of the prevailing scholarly attitude of the 'connected' Mediterranean -- one with high degrees of mobility and migration that drive the archaeological patterns we see -- we'd imagined we'd see comparatively high levels of migration reflected in the strontium isotope data," said Thomas Leppard, assistant professor of anthropology at Florida State. "That instead ...
Invasive alien species, defined as animals and plants that breed and disperse in a landscape beyond their native range, have negative environmental, social, and economic impacts. One example among many is the forage grass genus Brachiaria, originally African and introduced to Brazil to form cattle pasture. It has become a major threat to the survival of native species and biodiversity at several spatial scales.
Complete eradication of invasive species is often impracticable. Attempts to do so have had undesirable consequences and even been damaging because merely withdrawing an invasive ...
