Quantum networks are sometimes described as the long run of the web — but as an alternative of transmitting classical information in bits, they send quantum information carried by photons. These networks could enable ultra-secure communication, link together distant quantum computers right into a single, vastly more powerful machine, and create precision sensing systems that may measure time or environmental conditions with unprecedented accuracy.
To make such a network possible, so-called quantum network nodes — that may store quantum information and share it via light particles – are needed. Of their latest work, the Innsbruck team led by Ben Lanyon on the Department of Experimental Physics of the University of Innsbruck demonstrated such a node using a string of ten calcium ions in a prototype quantum computer. By fastidiously adjusting electric fields, the ions were moved one after the other into an optical cavity. There, a finely tuned laser pulse triggered the emission of a single photon whose polarization was entangled with the ion’s state.
The method created a stream of photons; each tied to a distinct ion-qubit within the register. In future the photons could travel to distant nodes and be used to determine entanglement between separate quantum devices. The researchers achieved a median ion-photon entanglement fidelity of 92 percent, a level of precision that underscores the robustness of their method.
“Certainly one of the important thing strengths of this system is its scalability,” says Ben Lanyon. “While earlier experiments managed to link only two or three ion-qubits to individual photons, the Innsbruck setup may be prolonged to much larger registers, potentially containing a whole bunch of ions and more.” This paves the best way for connecting entire quantum processors across laboratories and even continents.
“Our method is a step towards constructing larger and more complex quantum networks,” says Marco Canteri, the primary creator of the study. “It brings us closer to practical applications reminiscent of quantum-secure communication, distributed quantum computing and large-scale distributed quantum sensing.”
Beyond networking, the technology could also advance optical atomic clocks, which keep time so precisely that they might lose lower than a second over the age of the universe. Such clocks might be linked via quantum networks to form a worldwide timekeeping system of unmatched accuracy.
The work, now published in Physical Review Letters, was financially supported by the Austrian Science Fund FWF and the European Union, amongst others, and demonstrates not only a technical milestone but additionally a key constructing block for the subsequent generation of quantum technologies.