Quantifying quantumness: A mathematical project 'of immense beauty'

November 17, 2020

WASHINGTON, November 17, 2020 -- Large objects, such as baseballs, vehicles, and planets, behave in accordance with the classical laws of mechanics formulated by Sir Isaac Newton. Small ones, such as atoms and subatomic particles, are governed by quantum mechanics, where an object can behave as both a wave and a particle.

The boundary between the classical and quantum realms has always been of great interest. Research reported in AVS Quantum Science, by AIP Publishing, considers the question of what makes something "more quantum" than another -- is there a way to characterize "quantumness"? The authors report they have found a way to do just that.

The degree of quantumness is important for applications such as quantum computing and quantum sensing, which offer advantages that are not found in their classical counterparts. Understanding these advantages requires, in turn, an understanding of the degree of quantumness of the physical systems involved.

Rather than proposing a scale whose values would be associated with the degree of quantumness, the authors of this study look at extrema, namely those states that are either the most quantum or the least quantum. Author Luis Sanchez-Soto said the idea for the study came from a question posed at a scientific meeting.

"I was giving a seminar on this topic when someone asked me the question: 'You guys in quantum optics always talk about the most classical states, but what about the most quantum states?'" he said.

It has long been understood that so-called coherent states can be described as quasi-classical. Coherent states occur, for example, in a laser, where light from multiple photon sources are in phase making them the least quantum of states.

A quantum system can often be represented mathematically by points on a sphere. This type of representation is called a Majorana constellation, and for coherent states, the constellation is simply a single point. Since these are the least quantum of states, the most quantum ones would have constellations that cover more of the sphere.

The investigators looked at several ways that other scientists have explored quantumness and considered the Majorana constellation for each way. They then asked what the most evenly distributed set of points on a sphere for this approach is.

As Sanchez-Soto and his colleagues considered the question of quantumness, they realized it was a mathematical project "of immense beauty," in addition to being useful.
-end-
The article, "Extremal quantum states," is authored by Aaron Z. Goldberg, Andrei B. Klimov, Markus Grassl, Gerd Leuchs, and Luis L. Sánchez-Soto. The article will appear in AVS Quantum Science on Nov. 17, 2020 (DOI: 10.1116/5.0025819). After that date, it can be accessed at https://aip.scitation.org/doi/10.1116/5.0025819.

ABOUT THE JOURNAL

AVS Quantum Science, co-published by AIP Publishing and AVS, is a truly intradisciplinary journal that reaches from its foundations in quantum science into a breadth of areas from condensed matter and atomic, molecular and optical physics, to biology, chemistry, and materials science, as well as computer science and engineering. The journal places a strong emphasis on focused and comprehensive reviews and features perspectives and original research. https://avs.scitation.org/journal/aqs

ABOUT AVS

AVS is an interdisciplinary, professional society with some 4,500 members worldwide. Founded in 1953, AVS hosts local and international meetings, publishes five journals, serves members through awards, training and career services programs and supports networking among academic, industrial, government, and consulting professionals. Its members come from across the fields of chemistry, physics, biology, mathematics, engineering and business and share a common interest in basic science, technology development and commercialization related to materials, interfaces, and processing. https://www.avs.org

American Institute of Physics

Related Quantum Mechanics Articles from Brightsurf:

Theoreticians show which quantum systems are suitable for quantum simulations
A joint research group led by Prof. Jens Eisert of Freie Universit├Ąt Berlin and Helmholtz-Zentrum Berlin (HZB) has shown a way to simulate the quantum physical properties of complex solid state systems.

A new interpretation of quantum mechanics suggests reality does not depend on the measurer
For 100 years scientists have disagreed on how to interpret quantum mechanics.

New evidence for quantum fluctuations near a quantum critical point in a superconductor
A study has found evidence for quantum fluctuations near a quantum critical point in a superconductor.

Simulating quantum 'time travel' disproves butterfly effect in quantum realm
Using a quantum computer to simulate time travel, researchers have demonstrated that, in the quantum realm, there is no 'butterfly effect.' In the research, information--qubits, or quantum bits--'time travel' into the simulated past.

Orbital engineering of quantum confinement in high-Al-content AlGaN quantum well
Recently, professor Kang's group focus on the limitation of quantum confine band offset model, the hole states delocalization in high-Al-content AlGaN quantum well are understood in terms of orbital intercoupling.

A Metal-like Quantum Gas: A pathbreaking platform for quantum simulation
Coherent and ultrafast laser excitation creates an exotic matter phase with spatially overlapping electronic wave-functions under nanometric control in an artificial micro-crystal of ultracold atoms.

Fluid mechanics mystery solved
An environmental engineering professor has solved a decades-old mystery regarding the behavior of fluids, a field of study with widespread medical, industrial and environmental applications.

Quantum leap: Photon discovery is a major step toward at-scale quantum technologies
A team of physicists at the University of Bristol has developed the first integrated photon source with the potential to deliver large-scale quantum photonics.

USTC realizes the first quantum-entangling-measurements-enhanced quantum orienteering
Researchers enhanced the performance of quantum orienteering with entangling measurements via photonic quantum walks.

A convex-optimization-based quantum process tomography method for reconstructing quantum channels
Researchers from SJTU have developed a convex-optimization-based quantum process tomography method for reconstructing quantum channels, and have shown the validity to seawater channels and general channels, enabling a more precise and robust estimation of the elements of the process matrix with less demands on preliminary resources.

Read More: Quantum Mechanics News and Quantum Mechanics Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.