Quantum Networking Using Discrete Variables and Continuous Variables Demonstrated

‘Hybrid’ Quantum Networking Demonstrated for First Time

Key points…

+  In a world’s first, researchers in France and the U.S. have performed a pioneering experiment demonstrating “hybrid” quantum networking. The approach, which unites two distinct methods of encoding information in particles of light called photons, could eventually allow for more capable and robust communications and computing.

“DV and CV encoding have distinct advantages and drawbacks,” says Hugues de Riedmatten of the Institute of Photonic Sciences in Barcelona, who was not a part of the research. CV systems encode information in the varying intensity, or phasing, of light waves. They tend to be more efficient than DV approaches but are also more delicate, exhibiting stronger sensitivity to signal losses. Systems using DVs, which transmit information by the counting of photons, are harder to pair with conventional information technologies than CV techniques. They are also less error-prone and more fault-tolerant, however. Combining the two, de Riedmatten says, could offer “the best of both worlds.”

+  Similar to how classical electronics can represent information as digital or analog signals, quantum systems can encode information as either discrete variables (DVs) in particles or continuous variables (CVs) in waves. Researchers have historically used one approach or the other—but not both—in any given system.

+  Now scientists at the Kastler Brossel Laboratory in Paris and the U.S. National Institute of Standards and Technology have successfully united both techniques by establishing and distributing entanglement between DV- and CV-encoded states of light within a single quantum network.

+  Using a complicated assembly of optical components, the team successfully produced photons in two highly entangled states. One of them arose from splitting a single photon between two different paths. The other—a so-called hybrid-entangled state—emerged from entangling a DV optical qubit with a CV qubit, which was held in a superposition of two different phases of light. “By using a special procedure called Bell-state measurement between these two separately entangled states, the entanglement was transferred or ‘teleported’ to the two systems, [which] never interacted with each other,” says Julien Laurat, a professor at Sorbonne University in Paris and senior author of the study. This transference allowed the conversion of the qubits’ quantum information from one encoding method to the other, paving the way for incorporating both DV and CV approaches into a single, scalable quantum network.

Source:  Scientific American.  Dhananjay Khadikar,  ‘Hybrid’ Quantum Networking Demonstrated for First Time…

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