The Transition Space Between Quantum and Classical Worlds Studied with New Consistent-histories Algorithm

**Using Quantum Computers to Test the Fundamentals of Physics**

Excerpts and salient points ~

+ A quantum-computing algorithm, developed by scientists at Los Alamos National Laboratory and the University of California, Davis—including both of us—opens a new window on the connection between the quantum and classical worlds and the transition that must occur as we zoom out from the smallest scales.

*To study the quantum-to-classical transition, physicists need to evaluate how close a quantum system is to acting classically. Among other effects, physicists must consider the fact that quantum objects are subject to wave-particle duality. Things we often think of as particles, such electrons, can act like waves in some circumstances. And things we think of as waves, such as light, can act like particles, which are called photons. In a quantum system, the wavelike states of particles can interfere with one another in much the same way that ocean waves can sometimes add together or cancel one another out.*

+ For systems of a few atoms, finding consistent histories is fairly trivial. For systems made up of many pieces, however, quantum-to-classical transition calculations are notoriously difficult to solve. The number of equations involved grows drastically with each added atom. In fact, for systems of more than just a few atoms, calculations rapidly become intractable on even the most powerful supercomputers.

+ Appropriately enough, the new consistent-histories algorithm relies on a quantum computer to overcome the computational explosion and gauge how close to classical a quantum system is behaving. Unlike conventional computers that manipulate data made up of 1s and 0s, quantum computers store and manipulate data as quantum combinations of numbers. Similar to how an atom exists as a quantum cloud rather than at a single point, data in a quantum computer is not a single number but a superposition of many numbers.

Source:* SCIENTIFIC AMERICAN. Andrew Sornborger, Using Quantum Computers to Test the Fundamentals of Physics… *

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