A new theorem shows that no universal entanglement purification protocol exists for all two-qubit entangled states if one is limited to just standard local operations and classical communication.
Category: quantum physics – Page 62
Researchers establish fundamental limit on how light bosonic dark matter can be
In a new study published in Physical Review Letters, scientists have estimated a new lower bound on the mass of ultra-lightweight bosonic dark matter particles.
Purported to make up about 85% of the matter content in the universe, dark matter has eluded direct observation. Its existence is only inferred by its gravitational effects on cosmic structures.
Because of this, scientists have been unable to identify the nature of dark matter and, therefore, its mass. According to our current model of quantum mechanics, all fundamental particles must be either fermions or bosons.
Electro-optic sampling research unlocks new insights into quantum physics
Konstantin Vodopyanov, a professor at the College of Sciences and CREOL, the College of Optics and Photonics, recently co-authored a study published in the journal Optica. This research examines electro-optic sampling (EOS), a technique that advances fields such as quantum physics, molecular spectroscopy and biomedical sensing.
As a professor at the two colleges, Vodopyanov shows how working across different fields can lead to new ideas. The Optica Fellow’s research, which combines interdisciplinary work, is shaping the future of quantum physics and other areas of science.
His new study explores how EOS transmits ultrashort laser pulses through crystals that change in response to an applied electric field. This technique allows researchers to accurately capture the shape and timing of electric fields across a broad range of frequencies.
A superconducting diode: Researchers successfully control the direction of current in a superconductor
What would happen if you combined the unparalleled efficiency of a superconductor with the flexibility and controllability of a semiconductor? Thanks to a new breakthrough in quantum materials, we may be getting an answer soon.
In an article published in Communications Physics, a multi-institutional research team led by The University of Osaka announces the successful observation of the so-called superconducting diode effect in an Fe(Se, Te)/FeTe heterostructure. The paper is titled “A scaling relation of vortex-induced rectification effects in a superconducting thin-film heterostructure.”
The article describes a series of experiments in which the material developed a preference for current to flow in a particular direction, a phenomenon known as rectification, under a broad range of temperature and magnetic fields.
Applicability of a key quantum law extended to simulation conditions for systems with long-range interactions
The findings are published in the journal Physical Review Letters.
Compared with their classical counterparts, systems made up of many quantum particles—such as quantum computers—are horrendously complex to analyze and simulate. This complexity is due in part to the strong correlations between particles, which can act over long distances.
Naturally occurring clay material has sought-after properties for use in quantum technology
In the future, quantum technology will become the standard for extremely fast computers. These kinds of machines will be important in everything from space technology to mineral exploration and the development of new medicines.
“Quantum technology is often associated with synthetic materials that have been developed in advanced, completely clean environments,” says Professor Jon Otto Fossum from NTNU’s Department of Physics.
But Fossum and colleagues have good news.
Bismuth’s mask uncovered: Implications for quantum computing and spintronics materials
Whether bismuth is part of a class of materials highly suitable for quantum computing and spintronics was a long‑standing issue. Kobe University research has now revealed that the true nature of bismuth was masked by its surface, and in doing so uncovered a new phenomenon relevant to all such materials.
The team have published their results in a letter in the journal Physical Review B.
There is a class of materials that are insulators in their bulk, but robustly conductive at their surface. As this conductivity does not suffer from defects or impurities, such “topological materials,” as they are called, are expected to be highly suitable for use in quantum computers, spintronics and other advanced electronic applications.
Superconductivity Inspires New Dark Matter Contender
As searches for the leading dark matter candidates—weakly interacting massive particles, axions, and primordial black holes—continue to deliver null results, the door opens on the exploration of more exotic alternatives. Guanming Liang and Robert Caldwell of Dartmouth College in New Hampshire have now proposed a dark matter candidate that is analogous with a superconducting state [1]. Their proposal involves interacting fermions that could exist in a condensate similar to that formed by Cooper pairs in the Bardeen-Cooper-Schrieffer theory of superconductivity.
The novel fermions considered by Liang and Caldwell emerge in the Nambu–Jona-Lasinio model, which can be regarded as a low-energy approximation of the quantum chromodynamics theory that describes the strong interaction. The duo considers a scenario where, in the early Universe, the fermions behave like radiation, reaching thermal equilibrium with standard photons. As the Universe expands and the temperature drops below a certain threshold, however, the fermions undergo a phase transition that leads them to pair up and form a massive condensate.
The proposed scenario has several appealing features, say Liang and Caldwell. The fermions’ behavior would be consistent with that of the cold dark matter considered by the current standard model of cosmology. Further, the scenario implies a slight imbalance between fermions with different chiralities (left-and right-handed). Such an imbalance might be related to the yet-to-be-explained matter–antimatter asymmetry seen in the Universe. What’s more, the model predicts that the fermions obey a time-dependent equation of state that would produce unique, potentially observable signatures in the cosmic microwave background (CMB) radiation. The researchers suggest that next-generation CMB measurements—by the Simons Observatory and by so-called stage 4 CMB telescopes—might reach sufficient precision to vet their idea.
Light is the science of the future: The Africans using it to solve local challenges
Light is all around us, essential for one of our primary senses (sight) as well as life on Earth itself. It underpins many technologies that affect our daily lives, including energy harvesting with solar cells, light-emitting-diode (LED) displays and telecommunications through fiber optic networks.
The smartphone is a great example of the power of light. Inside the box, its electronic functionality works because of quantum mechanics. The front screen is an entirely photonic device: liquid crystals controlling light. The back too: white light-emitting diodes for a flash, and lenses to capture images.
We use the word photonics, and sometimes optics, to capture the harnessing of light for new applications and technologies. Their importance in modern life is celebrated every year on 16 May with the International Day of Light.