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Category: quantum physics

Quantum Microscope May Be Able to See Inside Living Cells

By combining quantum mechanical quirks of light with a technique called photonic force microscopy, scientists can now probe detailed structures inside living cells like never before. This ability could bring into focus previously invisible processes and help biologists better understand how cells work.

Photonic force microscopy is similar to atomic force microscopy, where a fine-tipped needle is used to scan the surface of something extremely small such as DNA. Rather than a needle, researchers used extremely tiny fat granules about 300 nanometers in diameter to map out the flow of cytoplasm inside yeast cells with high precision.

To see where these miniscule fat particles were, they shined a laser on them. Here, the researchers had to rely on what’s known as squeezed light. Photons of light are inherently noisy and because of this, a laser beam’s light particles won’t all hit a detector at the same time. There is a slight randomness to their arrival that makes for a fuzzy picture. But squeezed light uses quantum mechanical tricks to reduce this noise and clear up the fuzziness.

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Congressional Science Committee Leaders Introduce Bill to Advance Quantum

WASHINGTON – U.S. Reps. Lamar Smith (R-Texas) and Eddie Bernice Johnson (D-Texas), who serve as the chairman and ranking member of the House Committee on Science, Space, and Technology, and U.Sens. John Thune (R-S.D.) and Bill Nelson (D-Fla.), who serve as the chairman and ranking member of the Senate Committee on Commerce, Science, and Transportation, today announced the introduction of House and Senate companions of the National Quantum Initiative Act. The legislation would accelerate and coordinate public and private quantum science research, standards, and workforce development to give the United States a competitive advantage as China and Europe vie to achieve technological breakthroughs in this field.

Chairman Smith: “The National Quantum Initiative Act will accelerate the development of quantum information science in the United States and secure our leadership in the quantum sector. As other nations are rapidly developing their own quantum programs, the U.S. faces the risk of falling behind. This legislation provides a path forward to ensure that the U.S. secures its influence in the next generation of science and technology. I am glad that Senator John Thune has joined me in introducing this legislation, along with our respective Ranking Democrat Committee Members Rep. Eddie Bernice Johnson and Senator Bill Nelson.

”The bill creates a 10-year federal program that will significantly develop our quantum knowledge. It will bring a whole of government approach to advance QIS to the next level of research and development, while also creating public-private partnerships, leveraging the resources and expertise of government, industry and academia. Through new research facilities and a strong workforce pipeline, students and researchers will have greater resources and opportunities to develop their quantum skills and create the next great computing innovation. There is no doubt quantum technology will revolutionize our world to come. This bill secures American leadership in quantum science and guarantees a first place finish in the great quantum race.”

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Scale-invariant magnetoresistance in a cuprate superconductor

Cuprate superconductors have many unusual properties even in the “normal” (nonsuperconducting) regions of their phase diagram. In the so-called “strange metal” phase, these materials have resistivity that scales linearly with temperature, in contrast to the usual quadratic dependence of ordinary metals. Giraldo-Gallo et al. now find that at very high magnetic fields—up to 80 tesla—the resistivity of the thin films of a lanthanum-based cuprate scales linearly with magnetic field as well, again in contrast to the expected quadratic law. This dual linear dependence presents a challenge for theories of the normal state of the cuprates.

Science, this issue p. 479

The anomalous metallic state in the high-temperature superconducting cuprates is masked by superconductivity near a quantum critical point. Applying high magnetic fields to suppress superconductivity has enabled detailed studies of the normal state, yet the direct effect of strong magnetic fields on the metallic state is poorly understood. We report the high-field magnetoresistance of thin-film La2–xSrxCuO4 cuprate in the vicinity of the critical doping, 0.161 ≤ p ≤ 0.190. We find that the metallic state exposed by suppressing superconductivity is characterized by magnetoresistance that is linear in magnetic fields up to 80 tesla. The magnitude of the linear-in-field resistivity mirrors the magnitude and doping evolution of the well-known linear-in-temperature resistivity that has been associated with quantum criticality in high-temperature superconductors.

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Black hole hologram appears in a graphene flake

Much research on black holes is theoretical since it is difficult to make actual measurements on real black holes. Such experiments also need to be undertaken over decades or longer. Physicists are therefore keen to create laboratory systems that are analogous to these cosmic entities. New theoretical calculations by a team in Canada, the US, UK and Israel have now revealed that a material as simple as a graphene flake with an irregular boundary subjected to an intense external magnetic field can be used to create a quantum hologram that faithfully reproduces some of the signature characteristics of a black hole. This is because the electrons in the carbon material behave according to the Sachdev-Ye-Kitaev model.

Some of the most important unresolved mysteries in modern physics come from the “incompatibility” between Einstein’s theory of general relativity and the theory of quantum mechanics. General relativity describes the physics of the very big (the force of gravity and all that it affects: spacetime, planets, galaxies and the expansion of the Universe). The theory of quantum mechanics is the physics of the very small – and the other three forces, electromagnetism and the two nuclear forces.

“In recent years, physicists have gleaned important new insights into these questions through the study of the SYK model,” explains Marcel Franz of the University of British Columbia in Canada, who led this research effort. “This model is an illustration of a type of ‘holographic duality’ in which a lower-dimensional system can be represented by a higher dimensional one. In our calculations, the former is N graphene electrons in (0+1) dimensions and the latter the dilation gravity of a black hole in (1+1) dimensional anti-de Sitter (AdS2) space.

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