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Category: quantum physics – Page 487

The equations of quantum mechanics provide a roadmap to predicting the properties of chemicals starting from basic scientific theories. However, these equations quickly become too expensive in terms of computer time and power when used to predict behavior in large systems. Machine learning offers a promising approach to accelerating such large-scale simulations.

Researchers have shown that machine learning models can mimic the basic structure of the fundamental laws of nature. These laws can be very difficult to simulate directly. The machine learning approach enables predictions that are easy to compute and are accurate in a wide range of chemical systems.

The improved machine learning model can quickly and accurately predict a wide range of properties of molecules (Proceedings of the National Academy of Sciences, “Deep Learning of Dynamically Responsive Chemical Hamiltonians with Semi-Empirical Quantum Mechanics”). These approaches score very well on important benchmarks in computational chemistry and show how deep learning methods can continue to improve by incorporating more data from experiments. The model can also succeed at challenging tasks such as predicting excited state dynamics—how systems behave with elevated energy levels.

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Two big players in computing and research are trying to lay the groundwork for a future quantum internet.

Amazon Web Services (AWS) is teaming up with Harvard University to test and develop strategies for networking together quantum technologies. Their partnership was announced today, and is a continuation of AWS’ goals to create a communications channel between the quantum computers that it is also working on in parallel.

During the three-year research alliance, funding from Amazon will support research projects at Harvard that focus on quantum memory, integrated photonics, and quantum materials, and help upgrade infrastructure in Harvard’s Center for Nanoscale Systems.

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American physicist, professor of theoretical physics at Stanford University, and founding director of the Stanford Institute for Theoretical Physics, Leonard Susskind, explains black holes, quantum physics, general relativity and how they are intertwined.

Knowing how the laws of physics behave at the extremes of space and time, near a black hole, is an important piece of the puzzle we must obtain if we are to understand how the universe works. Leonard Susskind explains how general relativity and quantum mechanics are related.

There are four fundamental forces at work in the universe: the strong force, the weak force, the electromagnetic force, and the gravitational force. They work over different ranges and have different strengths. Gravity is the weakest but it has an infinite range.

Three of the four fundamental forces of physics are described within the framework of quantum mechanics and quantum field theory. The current understanding of the fourth force, gravity, is based on Albert Einstein’s general theory of relativity, which is formulated within the entirely different framework of classical physics. However, that description is incomplete.

According to Susskind, quantum gravitational effects are extremely weak and therefore difficult to test.

Leonard Susskind and his colleges of theoretical physicists have forged a connection between wormholes in spacetime and a quantum phenomenon called entanglement. This could help physicists reconcile Einstein’s general theory of relativity and quantum mechanics.

Continue reading “Leonard Susskind Marrying Quantum Physics & General Relativity” | >

A team of researchers from the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory and Stony Brook University have devised a new quantum algorithm to compute the lowest energies of molecules at specific configurations during chemical reactions, including when their chemical bonds are broken. As described in Physical Review Research, compared to similar existing algorithms, including the team’s previous method, the new algorithm will significantly improve scientists’ ability to accurately and reliably calculate the potential energy surface in reacting molecules.

For this work, Deyu Lu, a Center for Functional Nanomaterials (CFN) physicist at Brookhaven Lab, worked with Tzu-Chieh Wei, an associate professor specializing in at the C.N. Yang Institute for Theoretical Physics at Stony Brook University, Qin Wu, a theorist at CFN, and Hongye Yu, a Ph.D. student at Stony Brook.

“Understanding the quantum mechanics of a molecule, how it behaves at an atomic level, can provide key insight into its chemical properties, like its stability and reactivity,” said Lu.

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Few things in the Universe keep the beat as reliably as an atom’s pulse.

Yet even the most advanced ‘atomic’ clocks based on variations of these quantum timekeepers lose count when pushed to their limits.

Physicists have known for some time that entangling atoms can help tie particles down enough to squeeze a little more tick from every tock, yet most experiments have only been able to demonstrate this on the smallest of scales.

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Not everything needs to be seen to be believed; certain things are more readily heard, like a train approaching its station. In a recent paper, published in Physical Review Letters, researchers have put their ears to the rail, discovering a new property of scattering amplitudes based on their study of sound waves through solid matter.

Be it light or sound, physicists consider the likelihood of particle interactions (yes, sound can behave like a particle) in terms of probability curves or scattering amplitudes. It is common lore that when the momentum or energy of one of the scattered particles goes to zero, scattering amplitudes should always scale with integer powers of momentum (i.e., p1, p2, p3, etc.). What the research team found however, was that the can be proportional to a fractional power (i.e., p1/2, p1/3, p1/4, etc.).

Why does this matter? While quantum field theories, such as the Standard Model, allow researchers to make predictions about particle interactions with extreme accuracy, it is still possible to improve upon current foundations of fundamental physics. When a new behavior is demonstrated—such as fractional-power scaling—scientists are given an opportunity to revisit or revise existing theories.

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A new device has been fabricated that can demonstrate the quantum anomalous Hall effect, in which tiny, discrete voltage steps are generated by an external magnetic field. This work may enable extremely low-power electronics, as well as future quantum computers.

If you take an ordinary wire with running through it, you can create a new electrical voltage perpendicular to the flow of current by applying an . This so-called Hall effect has been used as part of a simple magnetic sensor, but the sensitivity can be low.

There is a corresponding quantum version, called the quantum anomalous Hall effect that comes in defined increments, or quanta. This has raised the possibility of using the quantum anomalous Hall effect for the purpose of constructing new highly conductive wires or even quantum computers. However, the physics that leads to this phenomenon is still not completely understood.

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