Feb 25, 2022

Physicists test real quantum theory in an optical quantum network

Posted by in category: quantum physics

Quantum theory was originally formulated using complex numbers. Nonetheless, when replying to a letter by Hendrik Lorenz, Erwin Schrödinger (one of its founding fathers), wrote: “Using complex numbers in quantum theory is unpleasant and should be objected to. The wave function is surely fundamentally a real function.”

In recent years, scientists successfully ruled out any local hidden variable explanation of quantum using Bell tests. Later, such tests were generalized to a network with multiple independent hidden variables. In such a quantum network, quantum theory with only real numbers, or “real quantum theory,” and standard quantum theory make quantitatively different predictions in some scenarios, enabling experimental tests of the validity of real quantum theory.

Researchers at Southern University of Science and Technology in China, the Austrian Academy of Sciences and other institutes worldwide have recently adapted one of these tests so that they could be implemented in state-of-the-art photonic systems. Their paper, published in Physical Review Letters, experimentally demonstrates the existence of quantum correlations in an optical network that cannot be explained by real quantum theory.

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