Communications of the ACM
Peeking Into Schrodinger's Box
Using direct measurement to determine quantum state "is sort of like peeking into the box to see if Schrodinger's cat is alive, without fully opening the box," according to one of the researchers.
Credit: TGDaily
University of Rochester researchers have used the direct measurement method to measure a 27-dimensional quantum state in a single experiment with no post-processing. Previously, the process would have required quantum tomography in multiple, time-consuming stages.
Improved methods for characterizing high-dimensional states could advance the development of high security quantum communications systems, and increase fundamental knowledge of quantum mechanics. "Our work shows that direct measurement offers an exciting alternative to quantum tomography," says Rochester professor Robert Boyd. "As the field of quantum information continues to advance, we expect direct measurement to play an increasingly important role in this."
Direct measurement, developed in 2011 by scientists at the National Research Council Canada, directly assesses the state of a quantum system. Ordinarily in quantum mechanics, measuring a quantum state causes irreversible damage known as collapse of the wavefunction. However, direct measurement relies on first a weak measurement that mildly disturbs the quantum system without collapsing the wavefunction, followed by a strong measurement. The weak and strong measurements are then repeated for multiple identically prepared quantum systems, until the wave function can be determined with the desired level of accuracy.
From TG Daily
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