For the first time, theoretical physicists from the Institute of Theoretical Physics (IPhT) in Paris-Saclay have completely determined the statistics that can be generated by a system using quantum entanglement. This achievement paves the way for exhaustive test procedures for quantum devices.
The study is published in the journal Nature Physics.
After the advent of transistors, lasers and atomic clocks, the entanglement of quantum objects—as varied as photons, electrons and superconducting circuits—is at the heart of a second quantum revolution, with quantum communication and quantum computing in sight.
What's involved? Two objects prepared together in a quantum state—two horizontally or vertically polarized photons, for example—retain the memory of their common origin, even if they are moved far apart from each other. When the quantum state of the two entangled objects is measured—their polarization, in the proposed example—a distinct correlation is observed between the measurement results.
Measurement obeying quantum statistics
What does this correlation depend on? First, the degree of entanglement between the two objects may vary, depending on the nature of the source of the entangled quantum objects—in the example, horizontally polarized photons may be produced more frequently than vertically polarized ones. Then, a choice of measurement must be made—such as selecting a direction in which to measure the polarization—which may impact its result.
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