In a revolutionary experiment, physicists have created a single particle of light, or photon, that exists in 37 dimensions at once, extending the limits of quantum mechanics well beyond classical physics. The success, reported in Science Advances, is the most dramatic demonstration to date of quantum nonlocality, the effect in which particles affect one another at a distance in a manner that classical theory cannot describe.
The work is based on the Greenberger–Horne–Zeilinger (GHZ) paradox, a quantum puzzle that demonstrates how some entangled states can yield outcomes that are counterintuitive in classical logic, including equations in which 1 = -1. Using a variant of the GHZ paradox on photons, scientists were hoping to find out how far quantum behavior could deviate in relation to classical physics.
The team, headed by Zhenghao Liu of the Technical University of Denmark, controlled the photons with coherent light that was engineered to suit particular wavelengths and colors. This enabled them to manipulate and quantify quantum states in 37 distinct dimensions, a sharp contrast to the three spatial dimensions and time that we are used to.
According to Liu, this experiment demonstrates that quantum physics is more nonclassical than many of us believed. It may be [that] 100 years after its discovery, we are just seeing the tip of the iceberg.
The consequences are enormous. Demonstrating that photons can be in such high-dimensional states could open up new possibilities in quantum computing, cryptography, and information processing, which rely on the ability to take advantage of quantum weirdness.
Liu and his colleagues think that their results may result in even more powerful quantum advantages in high-dimensional systems, providing a hint of a more complex and richer reality than ever before. And, should this be the tip of the iceberg, then the quantum world lurking beneath the surface may be stranger and more potent than science ever imagined.
